NSCA’s Coaching Podcast, Episode 117: Dr. John McMahon

by Eric McMahon, MEd, CSCS, RSCC*D and Dr. John McMahon, CSCS
Coaching Podcast February 2022


Take a deep dive into force plate research and trends with “Force Plate Coach”,  Dr. John McMahon from the University of Salford in England. In this episode, John discusses his path from Royal Marine Commando into strength and conditioning and biomechanics teaching and research. Listen in as John connects with NSCA Coaching and Sport Science Program Manager, Eric McMahon, on the past, present, and future of force plates in sport and the ways we can improve our testing and evaluation of athletes.  

This episode mentions the following paper from NSCA’s Strength and Conditioning Journal: 
McMahon, JJ, Suchomel, TJ; Lake, JP, and Comfort, P. Understanding the Key Phases of the Countermovement Jump Force-Time Curve, Strength and Conditioning Journal 40(4):  96-106, 2018  
Find John on Instagram: @forceplatecoach, on Twitter: @ForcePlateCoach, and on YouTube: @ForcePlateCoach| Find Eric on Instagram: @ericmcmahoncscs or Twitter: @ericmcmahoncscs

Show Notes

“Some more of your fast stretch shortening cycle tests, like the drop jump and the multi-rebound jumps, as well as the countermovement jump test, just to try and map the way in which practitioners would like to use their force plates with their athletes to get more of a holistic overview of what their neuromuscular status is at any given time.” 13:55

“So those two mechanisms were raised as red flag flags and in the effect sizes they were considered moderate to large changes in countermovement depth and body weight that we saw immediately post-match. Now, if we didn't have a force plate, we wouldn't know that those changes had occurred, or we would say is that the jump height was the same post-match.” 22:21

“And because we tend to use jump height as the key outcome variable that was displayed on the screen in the scoreboards. Those athletes will see that there's no improvement to their previous period. But if they're 5 kilos heavier that means that they've applied a greater impulse in total to their body center of mass.” 24:50

“I assessed the PhD student earlier this year that's effectively been involved in the British Army, saw a different regimen that they now use the isometric mid-thigh pull to inform the job roles that they can apply for when they commence their training, believe it or not. So they've got certain key performance indicators like, in terms of peak force relative to body mass, that people must be able to pull, or push I should say.” 49:41


[00:00:00.77] Welcome to the NSCA Coaching Podcast, episode 117.

[00:00:05.24] Some more of you fast stretch shortening cycle tests like the drop jump and the multi-rebound jumps, as well as the countermovement jump test, just to try and map the way in which practitioners would like to use their force plates with their athletes to get more of a holistic overview of what their muscular status is at any given time.

[00:00:20.78] This is the NSCA's Coaching Podcast, where we talk to strength and conditioning coaches about what you really need to know but probably didn't learn in school. There's strength and conditioning, and then there's everything else.

[00:00:32.01] Welcome to the NSCA Coaching Podcast. I'm Eric McMahon. Today, we're joined by Dr. John McMahon, a lecturer in biomechanics and strength and conditioning at the University of Salford in the UK. John, welcome.

[00:00:46.45] Thank you, Eric. Thanks for having me. It's a pleasure to talk to you today.

[00:00:49.60] Always great having some international guests on the podcast and learning a little bit about strength and conditioning around the world. I think that's been one of the real positives that this podcast has taken away from COVID, COVID-19 and the pandemic, has been that we've been able to branch out on Zoom and record some of these episodes. So ready to dive in here and excited to learn a little bit more about your background.

[00:01:19.21] Thank you very much. Yeah so I've been at Salford now for 14 years I was reflecting on my career prior to coming to talk to you today and I can't quite believe that it's been 14 years to be honest. But before that, I was in the Marines. I was in the Marines for four years serving at a commando unit and decided that I was going to take a different path because it was difficult to maintain a relationship, I suppose, whilst traveling the world. So it was one of those things that I was looking for opportunities to do something that would hopefully lead down a career path.

[00:01:50.20] And I am from Manchester, which is in the Northwest of England. And Salford University's literally six miles from where I grew up. And so at the time I was interested in training and didn't really give it too much thought in terms of the topic that I was going to pursue for a degree, but I just knew that I was interested in training. I was really fit. I was only 22 back then. It's not the same case now.

[00:02:12.65] And so I just wanted to learn more for myself, really, like, how I could apply some of the principles from science to my own training. And then throughout that time, I was lucky enough to do quite a lot of placements. They weren't quite termed internships back then. They were more work placements that I was doing concurrent to-- it was called the applied sport science degree back then.

[00:02:32.80] And I got really lucky to get some experience with UK athletics and the English Institute of Sport with British cycling and taekwondo, lots of different football clubs and rugby clubs. And I suppose looking back, about 2007-2008 in the UK, that's when-- I know we're going to get onto the topic of forced plates later-- but that's when, at that point, force plates weren't actually as prevalent in the institutions that we were doing the testing with. It was more that they used to outsource to universities like ours to come and do the testing with their athletes.

[00:03:05.05] So for example, the local football clubs would send their players to our institution, or we would go out and test with the force plates that we had that were portable at their institution. So I've got very much involved in the testing of athletes from an earlier on, well, early period while doing my bachelor's degree and then by the time I hit the end of that I was kind of in a position whereby I think like most Bachelor students are in the final year deciding what they're going to do next.

[00:03:29.03] And I was really lucky that a guy called Dr. Phil Graham-Smith, who happened to be one of the co-founders of four steps in the end this was prior to then, and he was able to secure a funded PhD for me at Salford and coincidentally, Paul Comfort, who had just begun his tenure at the University as well about 18 months prior. So I ended up in a situation where I was able to do a biomechanics focused PhD that was funded. I also got them paid to become Paul Comfort's teaching assistant.

[00:03:57.05] So Paul really had a vision for strength and conditioning in our institution to formulate a master's degree in a defined pathway for our undergrad students. And just at that time was when I was literally embarking on this PhD and was able to basically facilitate those practical sessions as you would imagine a key focus on Olympic weightlifting but obviously other pertinent topics strength and conditioning as well whilst also building upon my own professional expertise consulting and working mainly in football and rugby back then and then later on in netball

[00:04:30.07] So I was in a situation from 2010 where I was working as a teaching assistant, doing a PhD, and working part time as a strength coach. I did that for three years in which time Phil Graham-Smith went to go and work at Aspire, which is out in Qatar. And so there was a vacancy for a biomechanist and strength conditioning lecturer role in 2013 which I applied for, and I was successful and I've been there ever since.

[00:04:54.05] So I've always been conscious that being at one institution can be a bit limiting and I've heard people speak about that. You sometimes can only get a one-dimensional view of strength and conditioning and education and strength conditioning by being at one place, but I think one thing that we've always done well at Salford is staying in contacts with local sports teams. We really look in the Northwest that we've got so many professional and semi-professional sports teams that are in a 10-mile radius, like I'm talking maybe 10 or 12 professional football clubs, for example, that are all within about a 10-mile radius of our university and then we've got rugby union, rugby league netball.

[00:05:29.23] And I know the system here is a little bit different in the States, not least because your country is so big compared to ours. You don't have to drive too far to hit a professional sports club around here. And we've always been able to take our research out to the field and work and consult with practitioners who are working with athletes on a day-to-day basis, so I suppose we've got more of a vicarious experience of strength coaching through being an outside party that ends up consulting with those different clubs. But that's been great because it allows myself and Paul Jones who also works on our master's degree to make sure that the content that we're teaching our undergraduate and graduate students is relevant to the field. And then we've also got one mind always on developments of the NSCA and the UKSCA to make sure that we map our modules and our research to the expectations and requirements that employers are looking for in our graduates basically.

[00:06:18.23] So that's kind of where I started out and for the last seven years, I've been lucky enough to-- or eight years now, actually-- work in that role. Paul and I have tried to produce as much research as we can with the time that we've had available. It's ended up becoming for me more of a focus on force plate use in sport, just trying to tidy that up a bit and try and go practitioners who now have force plates, unlike in 2007 and 8 when I first started it didn't really have too much hands-on experience with that. And just try and fill that education gap that I think does exist around inheriting a force plate system, but then really understanding the biomechanics of it and able to take away the practical applications to advise on an athlete program and things like that.

[00:07:02.60] Yeah, I'm really interested just in the evolution of the strength and conditioning profession. And that's something I get to think about in this role and speak to quite a bit. You know I think back to being educated in the field and a lot of what we learned was based on endocrinology, exercise physiology, but biomechanics and evaluating movement-- looking at movement in a more scientific way-- this is a very relevant conversation right now.

[00:07:31.56] And I think your work with force plates-- I can think of a number of papers that you've put out in the Strength and Conditioning Journal and the JSCR that have really gained a lot of traction in the field. And I wanted to give you a chance to share a little bit about your research area, but in particular, the increase in accessibility of force plates within strength and conditioning environments, in weight room environments. And that's something we see now-- and you alluded to it-- is that you don't have to go to a university, a local university, to access a force plate anymore. There's a lot more products available for coaches to get information day to day or as part of their workouts. Speak to your work with force plates, and just where you see that going and helping our field.

[00:08:27.33] Yeah, sure. Thanks. So I published an article in the Strength and Conditioning Journal called Understanding the Key Phases of the Countermovement Jump Force-time Curve, and at that time it was more for I wrote that with my students in mind mostly. Because we were using force plates quite a lot, but they were laboratory grade force plates. So your typical-- if you go back maybe even five years actually-- your typical laboratory grade force plates would be like your AMTIs and your Kistlers and things. And we would take them out to different venues to test athletes so rugby athletes and football athletes, as in soccer football I'm talking about here. And they would have a lot of [? tables. ?] We would have to do the analysis through our own programs. And our students would use those as part of their research projects but not really understand the different phases of the force-time curve to be able to split that down into a bit more detail than just looking at outcome variables like jump height so we can look at what we like to call the strategy that led to the jump height that was achieved or whichever outcome variable is chosen. And so I literally just wrote that with that in mind. And I submitted it as a Strength and Conditioning Journal article because I thought it might be relevant to practitioners as well, just at the time where commercial force plate systems were really starting to take off especially here in the UK.

[00:09:44.50] So all of a sudden now I was speaking to more practitioners. And lots of our master's degree students do the master's degree part time. They're full-time practitioners working in sport and then they just do a small commitment of time for the master's degree at Salford. And so, I was getting more and more conversations with those students around what they'll do with the data once I've collected it. How do we interpret their countermovement jump force data because everyone seems to be calculating or measuring countermovement jumps as part of their test? And it seems to be that one universal test that's done on a force plate across any sport that I've come into contact with so far. And I couldn't believe how much that took off in terms of the reads and social media hits and things. I kind of wrote it thinking it was relatively basic. I didn't think it was going to end up being the paper that ended up almost defining where I took my research and the subsequent three years really. But I suppose as soon as I realized that there was a demand for more information around how to understand and process force-time curves, particularly in jump-based tests.

[00:10:39.96] That was almost a catalyst for me deciding on what I was going to spend my time conducting research on because the way the contract works for me in my institution is at that time, I only had about half a day a week to do research. So you're talking maybe four hours and trying to then spread that out across teaching and supervision of PhDs and things. It ends up taking a long time to achieve any output just because by the time I get to the following week I can barely remember what I was thinking the previous week when I left off. But that's kind of evolved over that time so I've got more time now to spend doing research.

[00:11:12.88] And so what I'm really interested in is trying to help guide practitioners on how they can more effectively use their force place in sport. And we kind of know through not just my research but some of the other research that's been done that jump height on its own only tells part of the story. We can see the same jump height at different time points when we test our athletes for their strategy to achieve that jump height could have changed quite substantially.

[00:11:36.73] And so if you're using some of the alternative systems like contact maps or electronic systems or even like the really user-friendly iPhone apps and things and Android apps which estimate jump height from flight time. That's a good tool if that's all you've got in your budget to be able to use and if that's all you're able to use then great, but the force plates give us so much more, especially if we can understand how to analyze it in more detail.

[00:12:03.49] So I love that practitioners have got more force plates that are accessible to them. I think what I've seen though, and this is more anecdotal than it is anything else, is almost a time lag between the force plates being used and the research actually catching up with that force plate used to try and help guide practitioners with variable selection and interpretation, and applications, training programs or monitoring interventions and things. And I suppose that's true of any topic area really, but I just happen to notice it because, obviously, that's the route that I've gone there.

[00:12:34.02] But the last two years, I suppose, there's been much more of a shift in commercial software being pretty good these days as well. In fact, that's exceptional in some circumstances. And so practitioners can be pretty confident that the variables that they're getting from their software, providing that the software providers open with the way in which those calculations have been done, by the way. They can take confidence from that and most of the calculations now seem to be mapping against the calculations that we would use when we're doing our research projects through MATLAB or Microsoft Excel or whatever of a platform we've decided to use.

[00:13:10.82] So that's great but I suppose what's still missing for me is there's a lot of variables that you can get from a force plate test. If we take into account a movement jump on its own like some of the software providers will produce over 100 variables that you could take from that one countermovement jump test for that athlete. And so trying to navigate which variables actually mean something, which variables might establish cause and effect between strategy and outcome, is probably where we want to take it next and really understand how we can benchmark athletes performances. Not just from the countermovement jump, which I suppose has been the main focus for me, but across a plethora of force plate tests that include multi-joint asymmetric assessments, some more of your fast stretch shortening cycle tests, like the drop jump and the multi-rebound jumps, as well as the countermovement jump test, just to try and map the way in which practitioners would like to use their force plates with their athletes to get more of a holistic overview of what their neuromuscular status is at any given time. And how that changes in response to different phases of the season or acutely even, sort of pre and post-match, for example, and that recovery profile afterwards.

[00:14:12.89] So we've got a big project that we're working on right now that's been funded externally. So we've got Hawkin Dynamics that-- so Hawkin Dynamics have been great, and they funded a project that we've got a student called Andrew [? Bobby ?] working on at the minute, and I really feel like over the next few years, you're going to see a lot coming from Salford through Andy's PhD that supervised by myself and Paul Comfort to really try and fill some of the gaps that are currently present in the force plate domain.

[00:14:41.13] And in fact, it's more there's more research coming out that I've seen even in the last few days in Journal of Strength and Conditioning research that seems to all be trying to work towards the same goal, which is great. So it used to just be one or two research groups that were kind of working away at full-time analysis. But it seems to have opened up across the globe a lot more which is nice. And so it'd be good to get more of a collective kind of effort to drive the industry forward because a lot of athletes are being tested in individual clubs with slightly different protocols to the club that's two miles down the road.

[00:15:13.66] And even though they compete in the same sport, the fact that they've got different systems and the collecting of force data in a slightly different way, and it's being analyzed in a slightly different way, doesn't help us to try and pool that data together to really understand larger data sets in those sports that can then be used to generate benchmarks for athletes and to guide return-to-play criteria, for example, with injured athletes. Or which are your fatigue-based variables are more likely to be sensitive acutely sort of pre and post--match versus those that might reflect more of a chronic either de-training or fatigue effect that might occur during periods of fixture congestion, for example.

[00:15:48.14] And so it's kind of a double-edged sword for me. I think it's great that people have got access to force plates, but still, it's a tendency, even in the research world I come from, for people to work in silos. And so what I'm trying to do at the minute is reach out to all the people that are like minded to try and really pull together our resources, just for the benefit of the strength and conditioning profession mainly.

[00:16:06.49] Because, otherwise, we all end up kind of missing just tiny little tricks here and there that otherwise could have made for a fantastic research project. You end up just doing a little bit of something to progress the field, rather than a collective effort to try and really, really progress it. We've really large data sets that have been collected in the field by the practitioners that use them on a day-to-day basis.

[00:16:27.67] It's really interesting to hear that from the practitioner side, where there's so much complexity when you add a device like a force plate. And you mentioned it, the number of variables that you have at your disposal. But I think coaches-- the struggle is you have so much information what do you, what do you do with it? How do you apply that information on a day-to-day level? And I think we're getting better as a field at looking, or I guess thinking of this more as a monitoring approach versus a we're just going to test at the beginning and end of the season and see how things progress.

[00:17:04.27] But it's daily monitoring and force plates are part of that, and I think what you're talking about connects with that vision in a way of getting a steady flow of information. And then being better with decision making around that information, and that's really where that gap is. We look at force plates as a performance tool-- how high can someone jump, for example, and how much force can they create, and how they're creating that. But do you see force plates also as a readiness tool or recovery tool in looking at the data acutely on a day-to-day basis? Do you think there's capability in that space?

[00:17:52.22] Yeah, that's a really good question. I think certainly there is. I mean just a touch on like more of the performance piece, the outcome variables, and by that, I mean the jump height. It could be the impulse that created that jump height. The takeoff velocity, which will be derived from the impulse, which will feed into the jump height calculation. That they really-- we've had the same with things like RSI and RSI-mod from account of movement jump or RSI from a drop jump. We kind of know where those variables are, that a higher score is better.

[00:18:27.36] So for example, if we benchmark in athletes and try to advise what they might focus on in their programs. We can say with certainty that if you've jumped higher, that's a good thing. If you've got higher RSI that's a good thing. And whether you use takeoff velocity or jump height as your monitoring tool is a decision to be made by practitioners. But I feel like there's utility potentially in having a different set of variables that we report to athletes and sports coaches versus what others sport scientists and strength and conditioning coaches use to monitor our athletes.

[00:18:59.40] So with the example of the takeoff velocity, basically, the more speed that we leave the ground with, the higher we're going to jump, irrespective of our body mass. So if we all left the floor at the same speed or the same takeoff velocity, we would all achieve the same jump height. That jump height is a noisier variable, like the measurement error is double what it is for takeoff velocity.

[00:19:21.18] So when you mentioned about using force plates as a monitoring tool the first thing is obviously to try and navigate which variables are sensitive enough to allow us to detect changes, certainly over an acute period like pre and post-match and then that recovery period may be up to two or three days after that match. And so it might be that takeoff velocity is a variable that is going to better show fluctuations in performance versus the jump height because when we square the takeoff velocity to feed it into our jump height calculation, we end up squaring the measurement error as well.

[00:19:50.67] So we could report jump heights to our coaches and our athletes because that's something tangible that they can kind of relate to. Nobody really understands what a takeoff velocity of 2.5 meters per second looks like. But we can certainly have that in our minds as sport science and S&C coaches as a monitoring variable. But even that takeoff velocity is going to be achieved in slightly different ways, even if it remains the same pre and post-match.

[00:20:15.47] So for example, we've been working on something a minute where we see in immediately post a soccer match. The jump height is the same and therefore the takeoff velocity was the same. But what's happened is this during those matches the athletes have actually lost body weight through dehydration for example. So their body weight might have dropped 2% or 3%.

[00:20:35.75] So in theory, having a lighter body mass should allow those athletes to achieve a greater takeoff velocity, and therefore, jump height, but that wasn't the case. The jump height was the same. So even that change in body weight on its own should be enough to prompt an increase in outcome variable, but that isn't. So just on that one layer that's like potentially showing us a mechanism of fatigue that's been caused by that much through the fact that the athletes are lighter, but they can't apply a greater force to accelerate that lighter mass. Coupled with that, we see changes in countermovement depth and so that's one of the key strategy variables. For me the strategy variables, just to clarify for the people listening, I interpret it as being the times over which the forces were produced in each phase, and also the positional changes of the body center of mass.

[00:21:23.81] So usually, we take the countermovement depth. The difference in countermovement jumps from when we stood up, before we commenced the jump down to our deepest position, and then we can look at the proportion, like the older way of saying that I suppose in my mind, is concentric phase, which is from that bottom position through to the period where we take off. So if we've got a shallower countermovement depth, we have given ourselves a shorter distance over which we can apply force.

[00:21:49.34] And so if, in that example, athletes go through a larger range of motion after a football match, in theory they should be able to achieve a higher takeoff velocity. It's a bit like doing a linear sprint test. We need that distance to be able to achieve a higher speed. It's the same principle when we talk about countermovement jumps, but instead of dealing in meters or yards we're talking like centimeter differences here. So in that example where the athlete has lost body weight, which meant that it should have been able to jump higher. They also went through a greater countermovement depth, which again should have meant that you should have been able to jump higher.

[00:22:21.33] So those two mechanisms were raised as red flag flags and in the effect sizes they were considered moderate to large changes in countermovement depth and body weight that we saw immediately post-match. Now, if we didn't have a force plate, we wouldn't know that those changes had occurred, or we would say is that the jump height was the same post-match. And it was the same when we followed up at 24 and 48 hours afterwards.

[00:22:42.56] But actually, the profile was different immediately after the match. And then at 24 to 48 hours, it covered back to the body weight being the same it was prior to the match and the countermovement strategy in terms of the depth and the timing has been the same. So it's just those subtle differences that we can detect through a force plate that just aren't afforded to us from using some of the alternative systems that are available in the market.

[00:23:06.86] The other thing is that if we were to look at any change over time, over longer periods of time that is, we do need to consider some of the conceptual factors as well, in my opinion, alongside that countermovement jump or drop jump or asymmetric [? type ?] or whatever it is that you're doing. And they mainly for me are, especially for youth athletes, any changes in standing height that have occurred between tests and occasions. And because, again, like I said before, we need the displacement, a greater displacement to achieve a higher takeoff velocity. And we're constrained anatomically in terms of the amount of depth that we can squat to and jump back out of, right? Right so I'm only 5 feet 9 inches tall so I'm fairly limited in terms of my ability to kind of dip down and drive back up again.

[00:23:48.91] But if you've got athletes that change their standing height over time that's worthwhile those monitoring alongside the force plates that the force plates actually don't give you. Obviously, you need to input that and then collect it separately as a coach. That might help to explain any changes that we see in performances over a longer period of time.

[00:24:04.24] And the body weight is a big one, like if an athlete is heavier. So if an athlete gains 5 kilos, say at the end of that pre-season training versus the beginning. But they can jump the same height. Again, the jump height alone would show no change.

[00:24:17.98] Therefore, potentially that might be interpreted as no improvement. The athletes might feel pretty rubbish about that. If you tell them that they can still jump 40 centimeters after six weeks of intense training, compared to what you could at the start then they might not feel particularly great and I suppose that's one thing.

[00:24:33.88] Actually, just as a side note from the commercial software now you can create leaderboards. You can have real time feedback when you're doing the testing. So the athletes can see usually through if you've got the computer screen up or a TV monitor. They can see their scores last time and what they're getting this time? And because we tend to use jump height as the key outcome variable that was displayed on the screen in the scoreboards. Those athletes will see that there's no improvement to their previous period. But if they're 5 kilos heavier that means that they've applied a greater impulse in total to their body center of mass.

[00:25:04.12] It's just the fact that they're heavier means that takeoff velocity, which is where we take the impulse in that propulsion phase, we divide it by body mass and then that's what it takes. Jump height just hasn't shown any change. But for me that's what I like to call an interim adaptation, that's like a short-term adaptation.

[00:25:19.36] It's a positive thing in my mind because I didn't separate that and report that back to my athletes and say, well actually you can jump the same height as last time despite being five kilos heavier. That's a good thing. That means that you're able to accelerate your mass at the same speed as you could before. But you're actually five kilos heavier. And now next time over this next four- or six-week block or whatever training kind of system you're working off, we're expecting to surpass that 40 centimeters that you could achieve at the start of the preseason. So I think it's more about setting that context.

[00:25:50.17] And things like jump momentum, which is identical in number to the propulsion than impulse, but is probably a more familiar term than propulsion than impulse is, even if not used in the right context, I suppose. Momentum shows this idea of progression or an accumulation of something that tends to be considered good.

[00:26:10.03] That can be something that discerns and distinguishes performance across a longer period of time as athletes mature. Or even if you take any athlete that's gone through hypertrophy or like a higher volume strength training block where hypertrophy might occur as a byproduct of that training. If they've gained body mass, we need to interpret those changes in jump performances alongside the actual body mass increases as well.

[00:26:33.32] And then lastly before I move on, the other thing for me is that the jump height actually is as an outcome variable that we use to determine which athletes have scored top, middle, and bottom or whichever way you want to think of it. It depends on the cues that we actually give to the athletes in the first place. We tend to cue athletes to jump as fast and as high as possible. So we're putting a time constraint on that commencement of the counter movement through to takeoff.

[00:26:59.45] So we're going to naturally make them adjust the range of motion that they move through. And so for me the RSI mod is probably the best variable to report if you're going to rank athletes on some sort of scoreboard system because that metric is the jump height divided by the time to takeoff. And so it better reflects the actual instructions that be given the athletes that do the test because we're saying we want you to jump high but we want you to do it in a shorter time as possible. Now, time to take off in the countermovement jump obviously includes the countermovement phase, which is the unweighting and braking phase combined, and the propulsion phase as well.

[00:27:32.95] If that was just a squat jump, then I would say the mean power is the best metric to include, because again it's the same kind of idea. It's the work done divided by the time. So the jump height divided by the time it took you to perform that jump. So I would go mean power for a squat jump, if you're cueing them to do it as fast and the highest possible. RSI mod for a countermovement jump. And then for any drop or intensified repeated jump or a countermovement rebound jump or whatever rebound jump you might be doing that's meant to be more [? fast rep showing ?] on cycle based.

[00:28:05.34] Now, I would say the reactive strength index which is jump height divided by the contact time on the ground is again going to be probably your best metric to rank athletes or to put up as a scoreboard. Because again we're never going to be able to jump as high as we can if we focus on constraining a time over which we produce that impulse. Because we're always going to end up going through a situation where we're almost cutting off the range of motion we can move through, because we're focusing more on getting in and out the ground quick than we are actually really making use of the displacement that we can be afforded through the height that we are. So I suppose it's just it's about the context. I suppose that's the big thing for me.

[00:28:41.97] And then lastly like for monitoring with-- I suppose longer periods of time like the-- It tends to be that the jumps that involve a break in or countermovement movement phase tend to be more sensitive to detecting neuromuscular changes over time. Athletes seem to be able to mask more so the proportional concentric phase variables but it's the counter movement or eccentric variables if you want to call it that seems to be more illuminated. So if you're doing any drop jump testing things or you tend to find repeated jump test. Then trying to split that up into the braking phase could be an interesting area of future research because there's not that much that's been done actually with the fast stretch-shortening cycle exercises as a monitoring tool for fatigue, or just seasonal changes in performance.

[00:29:30.79] And I think that's partly because, again, with force plates we have to think about how we can actually take that, if we take a drop jump for example. If we take that drop jump force time curve and we want to be able to split it up into the eccentric braking phase and the concentric propulsion phase then really, we need to know when you transition from that kind of bottom position in their center of mass position and then start to propel themselves upwards. The only way we can really do that is by getting them to stand still at the end for a second. And all we do is we integrate the data but backwards.

[00:30:01.41] So I'll just clarify that a bit further for anyone that's not following what I'm saying. When we do a drop jump, we're obviously falling from whatever height that we stood on. But the height that we actually fall is always different to the box height. There's very rarely an occurrence where an athlete is actually falling from the same height of the box that they stood on.

[00:30:17.32] And if you look at the literature that can range typically anywhere from being 29% lower than the box height to 39% above the box height for a range of athletes or a huge variance. The problem is with a lot of the commercial software is what they want you to put in is the height of the box when you do a drop jump test so you might stick in 40 centimeters. And then the assumption is then is that just like I said before irrespective of our mass if we've jumped a certain height, we've all left the floor at the same speed.

[00:30:44.25] This is the same principle but in reverse. If we all dropped from 40 centimeters as if we actually really did drop from 40 centimeters then we would all hit the ground at the same speed. The problem is then is that initial speed of velocity when the athlete hits the ground is what's used to then go through and split that drop jump force time curve up into the braking or eccentric and the proportional concentric phases. So any discrepancy between the box height and the fall height if that's the system that's being used, is going to lead to a disproportionate amount of emphasis being assumed to be braking or assumed to be propulsion.

[00:31:17.04] So unless we get the athletes to stand still for the final seconds to account for that and do the integration backwards it's basically the opposite to a countermovement jump basically the way we treat the data. Then we can never really be confident of any changes in drop or fall height prior to them performing that rebound portion of the drop jump. And the reason that's important is that if we're only focusing on RSI and then maybe the jump height and the contact time and the drop jump that led to the RSI, but not considering how fall height, might change and every single time we test our athletes. What we might see is improvements in RSI but not know that that's because that they've lowered themselves by centimeters in this test versus when we tested them six weeks ago.

[00:31:56.79] And so it ends up leading to some false interpretations of the data whereas what we want to see is an athlete ideally that's dropped from the same height or even higher. I would accept who has then in spite of that being able to reduce their contact time and increase the jump height to increase their RSI if all those factors kind of coincide. Then I'm fairly confident that that's a positive neuromuscular adaptation during that test and not something that's gone amiss because they've lowered their center of mass prior to stepping off the box.

[00:32:24.54] Some big takeaways there that I hear are force plates give us a deeper understanding of the why behind vertical jump height and take it one step further so that you have a more clear window of trainability to work with your players or your athletes. Considerations around the athlete's body and developmental stage and also technique of which assessments you're implementing may give you different information. And I think that's really valuable insight for coaches because like we talked about before there's just so many variables there's so much complexity around force plates in the research.

[00:33:08.79] And one thing I just want to-- do all our listeners share-- understanding the key phases of countermovement jump force time curve paper. If you go into the Strength and Conditioning Journal on the NSCA website and search John McMahon there's a number of great papers in there that really dive into these concepts and allow you to further your knowledge of what's best for your program. How do you implement force plates with your athletes on a daily basis and help drive the decision making at the researcher level? And so that you can bring questions that can get looked at further in the research.

[00:33:52.31] I think that's really what we try to do at the NSCA is we educate our professionals to serve the athletes in the field but we have to give back to the educator and researcher side of things. I think that's a huge perspective that gets overlooked at times and it comes through loud and clear and what you're saying John so I appreciate that. I want to ask you about strength and conditioning education and I know being in the UK you might have a little bit different perspective than what we hear often in the US. How are we doing in terms of educating strength and conditioning professionals to serve athletes and what's your thoughts on that?

[00:34:37.65] In terms of the way the education system is in the UK?

[00:34:41.07] Yeah, absolutely.

[00:34:42.39] Yeah, I think we're doing a good job I mean obviously it's been a difficult 18 months to do and deliver strength and conditioning education. I don't know. I assume that's been the same internationally. We've certainly felt at Salford we've had to switch to a lot of online based learning over the last 18 months in particular. But in fact, what that's done is it's allowed us to actually think about-- like you said at the start of this conversation actually, ways in which we can engage with audiences, not just immediately on our doorstep in our face-to-face environment but across the world.

[00:35:17.83] So we've had some really good and insightful talks with our students, especially our master's strength conditioning students around how they've had to adapt as practitioners to still deliver their provisions of S&C to their athletes during the lockdowns that we've had in the UK. Using technology to actually remotely assess their athletes even if they're not in a situation where they can coach them face to face.

[00:35:43.29] And actually, I know I have to bring it back to force plates. I'm sorry if I'm going on like a broken record like. There's a reason people call me countermovement John at work. But effectively the way the force plant systems work just to touch on it one last time. With the software that's available now, because a lot of it's cloud-based, we can actually go and send force plates out to different places. And I can be sat at home drinking a coffee in my nice warm house actually seeing that data come in and providing the reports and flipping it back to athletes, which is something that I've never been able to do before.

[00:36:12.76] So what we tried to do with our-- we always try and keep with our particular MSC program the education that Paul Comfort, Paul Jones, and I deliver to be reflective of the state, not just as strength and conditioning more broadly in the world, but also the actual real-life practical constraints that people work within. And the biggest one that springs to mind right now is the fact that actually there's a lot of uncertainty around accessibility to face-to-face scenarios when we're coaching athletes.

[00:36:41.01] So it's pushed us to actually produce more resources for our students, but also for the students to produce more resources that their athletes can actually access, which I think ultimately will remain with us going forward just like using Zoom, I suppose, for podcasts and things. I think we've kind of taken a step forward with technology in the way in which we apply it within our profession that we'll probably never go back to the way it was. Now, don't get me wrong, there's no substitute for face-to-face delivery when it comes to learning those key coaching practical skills.

[00:37:12.42] And thankfully, this trimester of our university year so far-- touch wood-- we've only got a week and a half to go. We've managed to come in and deliver face-to-face sessions and every single time that we've had it scheduled this year. So we've been literally making the most of being in that environment in the weight room and teaching Olympic weightlifting. We've been out on the 3G artificial pitches to do speed and change direction work, plyometric training and all those things we've managed to deliver a whole battery of stuff that we would deliver to our students that we just haven't been able to do previously.

[00:37:46.65] But I do think that the wearable technology to allow indirect monitoring of athletes if you like when you're not actually in that face-to-face situation with them has the potential to be a huge growth area. I mean you can see anywhere within the actual research domain. Certainly, if you look on social media around or even on the special interest group actually that Tim kind of chairs there's a lot of technology.

[00:38:11.26] Now, sports tech is a huge growth area which I think just like with the force plates is a good thing in general but it takes a little bit of time to really understand the validity and reliability of those devices to really try and help coach athletes not just remotely but also in that face-to-face environment as well. In the UK, there's plenty of job opportunities actually I don't think this year has been any different to-- not last year but certainly all the years that came before-- in terms of strength and conditioning roles being available.

[00:38:39.84] But it seems to be from my perspective still very much more of a football, rugby, cricket, and maybe Olympic sport focus to strength and conditioning still in the UK in terms of the jobs that are available for students to then go and pursue and try and apply for. But I think these, as the technology develops and the strength and conditioning professional's role kind of expands. There's roles to tap into more of the health market. I think people are valuing more the personal training application of strength and conditioning more so now in the UK than I've seen before.

[00:39:14.86] And I think part that's been borne through, unfortunately, people have had it tough in terms of income generation over the previous 18 months. And the fact it's quite commendable how much people have actually managed to use their time to carve other opportunities that they probably otherwise wouldn't have done. So we've got lots of students now that are doing remote personal training to supplement their income while they try and do internships or placement opportunities to get the S&C role that they desire. But they can take all those skills and apply them to any remote conditioning that might take place with their athletes.

[00:39:48.74] I think one of the downsides of being remote and feeding into a program that is remotely driven is that in the UK there tends to be-- certainly at a national level-- regional splits. You might be similar in the States where you might have a coach that's say, in netball for example, an S&C coach that's in charge for the northwest region, the northeast region, the southwest, and the southeast region of England, for example. And sometimes there isn't an alignment of the technology that's being used to set those athletes and all of those different places.

[00:40:19.31] That was one of the reasons that I pursued the force plate research in the first place. I used to be the northwest regional lead strength and conditioning coach for England netball. So I had Under 14s, Under 16s, and Under 19-year-old group-- about 60 athletes in total. And that's still similar now, not just in netball, but in sort of other major sports in the UK as well, where they'll have kind of regional lead strength conditioning coaches that will get together on training camps, that will test athletes, provide some input into their training programs and then they will disperse back into their individual clubs.

[00:40:50.93] But what I've seen in terms of sports technology is that each of those different regions might have a different device that they're assessing their athletes with, but all that data is being pooled back together by the sports coaches to inform team selection and things. Which has been a huge, I suppose, red flag for me as somebody who's is quite sensitive to understanding the requirements of sports technology and how delicate you have to be to make sure that you can compare data accurately. So I would say that that's kind of one thing that I think sports technology is. It can be both a good, and a bad, or not bad. Bad's probably quite a strong word for it but certainly it can be a benefit and a limitation depending on how it's applied.

[00:41:28.92] But I think the similarity is in the way the UK have approached the response in terms of higher education. I've got colleagues that teach out in the States. So researchers that I collaborate with that also teach and conduct research out at universities in America. My general impression is that everybody is now, where possible, back doing face-to-face delivery. And same with colleagues out in Spain and Australia as well, which I think is a really positive thing, because like I said before, there's no substitution for actually getting in the gym environment or the field environment and really kind of immersing yourself in that. But I do feel like a blended approach of trying to learn some of these remote skills and certainly the technology that might guide those decision-making criteria when we're working remotely can certainly be something that we keep in our program going forward.

[00:42:17.65] I think there's like you're saying there's high and low resource programs everywhere you go that's something we worked through here in the US depending on where you're getting started in the field, who you have as a mentor, what school you go to. One of the themes that comes through in strength and conditioning education today is the need to continually up-skill and technology is a good example of that. I want to give you a chance to share a little bit about your new YouTube channel. Came across that recently and we keep looping it back to force plates, but talk about your YouTube experience.

[00:42:56.59] Yeah. Cheers for that. You know what, the YouTube channel seem like a really good idea at the time so I was figuring like-- I've got a six-year-old son and I've got a one-year-old daughter and my one-year-old daughter just started nursery in September. So I was like brilliant I can eventually get some time where I can create a resource because I keep on getting the same questions being asked to me on social media and my students always ask me the same questions. Just like the basics of force plate set up. Like, how do you calculate impulse, how does that feed into jump height?

[00:43:25.96] So my plan was to do these small, maybe 5 to 10-minute videos that kind of start. I started basic. I've only done six videos so far. You're probably going to give me the motivation now to continue that now that you've mentioned it. My idea was is to keep that running. And then, I think because we had a daughter during a global pandemic who was very much sheltered from the outside world. She started nursery, bless her, and she's literally picked up every book going at nursery since she started in September.

[00:43:53.36] So in terms of best laid plans, they've all kind of fallen by the wayside. Like I will get back to it. And I think maybe at some point over Christmas and into January I'll be able to really kick off because I've got lots of ideas for videos that should be fairly sequential with the way in which I put them out. It's literally just finding the time when you're kind of working from home. I said at the start before we came to actually talk where it was recorded that I haven't got an office in my house either.

[00:44:18.16] So I'm trying to find-- in between stepping on dinosaurs and superhero toys-- like a space in my house to actually record the videos that isn't going to be too disruptive for the people watching it. But now I will pick that back up and I kind of feel like it's just an opportunity for me just to signpost people to the answer to a question that I don't have to give maybe another 1,000 times over the course of my career, basically. It's just like you're asking that question. Brilliant. I've got a video that I can signpost you to that should hopefully answer that question for you. But my plan with that is to also invite some other people as well like John Harry, Jason Lake, you also, have really kind of in touch with force plate research to maybe come on I haven't told them this. So this is probably the first time they're going to hear it.

[00:45:01.61] Make sure I'll make sure they get word.

[00:45:04.21] To come on and do stuff and same goes for practitioners as well, I suppose. It's not just about my interpretation of force plate tests and how we can analyze and handle that data like I said earlier on it's I think the only way we really will progress the field in terms of guiding people and how they might select different variables and implement them into their athletes training program, in terms of decision-making is to have more of a universal approach and a universal agreement. I think we still need to do some research before we produce a position stand on force plate testing in sport.

[00:45:34.87] I think there's probably another three- or four-years worth of stuff to do before we get that point. But I think that'd be great to kind of get to, at some point, if we get some agreement between different hardware and software providers with the way in which they will analyze data, just so it allows that kind of larger data set studies to be done that we usually struggle to do in our field. And the funded PhD by Hawkin Dynamics has opened opportunities for me and my students to try and influence like the variables that they might report with their protocols, which should then feed out to everybody that uses their system.

[00:46:14.45] I want to go back to the beginning. You said you were in the Marines.

[00:46:17.62] I was.

[00:46:18.02] And tactical strength and conditioning is something here in the US that is really growing quickly. Talk about your military experience and just the role that strength and conditioning, physical fitness played and some of the areas that you see that could benefit from strength conditioning. And just I'm excited to hear a little different side of you.

[00:46:44.16] I'm really glad that you asked me that question because I still, in my mind, feel like I was in the Marines about one year ago. I mean, it was a long time ago now. It was 2007 was when I left, and like I said at the start, I was in-- I was a Royal Marine Commando. So I was at a commando unit. I was based down in the southwest of England, but at 40 Commando unit, and then traveling around the globe, as well. And it's got a very traditional, or it certainly did when I was in it, anyway, a very traditional approach to military training. And I think keeping those traditions is important.

[00:47:17.51] A lot of it wasn't to do with maximal strength, which was probably good for me at the time and more to do with muscular endurance and aerobic fitness, and just generally being resilient to injury, I think that was the thing that carried me through. So, for example, the way it works is that you've got 30 weeks of basic training. It's like the longest basic training from civilians and military. I think in the world actually, not just the UK. I could be wrong there.

[00:47:44.24] And I was 18 years old, and so I took my resilience for granted, I think. Looking back on it, I was just one of those kids that was just fit. I wasn't the best at any sport, but I was kind of good at most. I was kind of average, I suppose. I could run, I could jump, I could sprint, I could keep going for a long time without getting too tired, and so that kind of lent itself quite well to doing all the commando training that I had to do, which like I said, is very much focused on muscular endurance, repeated bouts and aerobic fitness. The only load, really, that I ever lifted was the kind of packs that we used to carry.

[00:48:19.58] So it wasn't necessarily something that we focused on in the gym, like say maximal strength training as we would view it today to prepare ourselves to do those load carrying-based activities. It was more just, more mental than anything else, I think, it was more having that mental resilience to be able to carry your pack for a 30-mile jog, and still be there at the end of it. But there were 46 athletes-- look at me now talking in my current profession-- 46 recruits that started with me and only nine of us got to the end and all of those ones that fell out throughout that 30-week process were either because they decided it wasn't for them. But for the majority actually, it was injuries that they sustained.

[00:49:01.40] So there's a lot of shin splints, lots of tendon-based injuries, certainly around the Achilles tendon issues. And then they would go into a rehabilitation section of training and they might spend up to a year in there to try and get fit again before they would come back in. So I suppose it's like return to play for athletes now, like post-ACL reconstruction or something. It was like a similar approach. They would go into a rehabilitation center, and they would only be entered back into the point where they terminated their training when the medical professionals felt that they were at a point where it could.

[00:49:36.23] Now, at that time, there were no performance assessments in terms of what we view as performance assessments now using sports technology that was involved in my career at all. But interestingly enough, I assessed the PhD student earlier this year that's effectively been involved in the British Army, saw a different regimen that they now use the isometric mid-thigh pull to inform the job roles that they can apply for when they commence their training, believe it or not. So they've got certain key performance indicators like, in terms of peak force relative to body mass, that people must be able to pull, or push I should say. We call that an [? ISO pull ?] but it's a push through the feet. I suppose I'll use that opportunity just to make that clear, through the force plates.

[00:50:17.45] And they're using force plate technology to screen recruits when they start training and then also dictate which job roles they're eligible to apply for when they go through that basic training process which I just found fascinating because like I said before my training was very much entrenched in tradition. The training that I did was similar to the training for the Marines as it would have been in the 1940s and 1950s, like traditional running, packs on, going through tunnels, getting soaking wet on the water, jumping out of helicopters, like all these really cool things that I really wish I could do on a day-to-day basis now. But never really in the gym did I pick up a weight and do a back squat.

[00:50:57.70] I certainly didn't do any assessments other than how many sit ups could I do in a minute, how many push-ups I do in a minute. What stage could I get on the [? multi-shuttle ?] test? Like, that was kind of the only gym-based repetition counts, if you like, really, that I would do in that environment.

[00:51:15.11] So it would be really interesting to kind of look further in the Marines in particular actually in the UK and see where that's kind of at. I've still got some guys that are serving now so they're there, believe it or not, approaching retirement now because you only do 22 years in the UK. And then, you can retire with full pension, which sounds crazy to me now that these guys are 40 years old in like one or two years, and they're going to be set to retire. And I suppose rethink what they do next. But maybe I'll reach out and try and figure out what it is that they do now from a performance test standpoint because my understanding is that in the Army it's something that's definitely prevalent now. And I wouldn't be surprised at all if it's similar in the Navy, the Air Force, and the Marines as well.

[00:51:54.65] It's really interesting, and what I've heard just through this conversation there's a lot of alignment just we're all strength and conditioning professionals. It's a global community, and wherever you come from. We've talked about high and low resource programs. We've talked about performance technology. We've talked about tactical strength and conditioning and just the evolution or the pendulum shift from traditional endurance training towards strength and now towards more power, as in how we generate power. And I think it's-- I mean these are a lot of the same conversations we're having here in the US. I know just from colleagues in Australia and different parts of the world that these are global conversations.

[00:52:40.52] And it's valuable as professionals to expand your network beyond your borders because there's so much great insight to gain just from good conversation. And one great thing, kind of go back to how we were talking about COVID-- the world's a lot smaller today. It's easier to get on the phone or on a Zoom call and connect with professionals around the world. Really great insight. Deep dive into force plates for this episode and you know I think it really uncovers the deeper need for understanding around, really what's become a strong paradigm in our field, of vertical jump as a-- vertical jump testing as a performance indicator. This is well established in pretty much every field sport here in North America but also internationally when we look at the international sports and the Olympic sports. So John, I just really appreciate you taking the time to share with us today.

[00:53:43.68] I really appreciate it, Eric. Thank you so much

[00:53:45.98] We talked about your YouTube channel. What are some other ways to get in contact with you for anyone listening in?

[00:53:52.75] So I'm on Instagram and Twitter. I don't feel like I'm cool enough for Instagram, but I suppose some of the stuff that is easier to share in pictures form than it is in text. So you can look for me at @forceplatecoach That's the same name for the YouTube channel as well. I only changed it when I changed the YouTube channel and I will start producing more content on that, like I say. But obviously I appreciate that people listening might struggle to visualize some of the things I was talking about when I'm on about different metrics that you can get from a force plate.

[00:54:23.70] So my plan with the YouTube channel and just isolated infographics which I think has been a real-- again another real, really great I suppose productive use of time over the last 18 months. The infographics that people are producing to summarize complex topics or research outcomes are fantastic. So my plan is to populate some of those on Twitter and Instagram as well, which will hopefully help to complement some of the things that I've discussed with you today.

[00:54:49.40] Great, thanks again. To all our listeners, we appreciate you taking the time to listen to the NSCA Coaching Podcast. We'd also like to thank Sorinex Exercise Equipment. We appreciate their support. From the NSCA thank you for listening to the NSCA Coaching Podcast. We serve you the coaching community. So follow, subscribe, and download for future episodes. We look forward to connecting with you again soon and hope you'll join us at an upcoming NSCA event or in one of our special interest groups. For more information, go to nsca.com

[00:55:23.84] This was the NSCA's Coaching Podcast the National Strength and Conditioning Association was founded in 1978 by strength and conditioning coaches to share information, resources, and help advance the profession. Serving coaches for over 40 years, the NSCA is the trusted source for strength and conditioning professionals. Be sure to join us next time.

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Eric L. McMahon, MEd, CSCS,*D, TSAC-F,*D, RSCC*E

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Eric McMahon is the Coaching and Sport Science Program Manager at the NSCA Headquarters in Colorado Springs. He joined the NSCA Staff in 2020 with ove ...

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