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TSAC Report 47 Research Review

by Rod Pope, PhD
TSAC Report June 2017

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This article is the 11th in a continuing series of tactical strength and conditioning (TSAC) research reviews. It is designed to bring awareness to new research findings of relevance to tactical strength and conditioning communities.

Firefighter Recruits Become More Fit during Initial Training but Lose Fitness Gains during First Six Months of Active Duty

 

Cornell and colleagues recently tracked the fitness levels of firefighter recruits through initial training and the first six months of active duty to demonstrate how fitness levels changed over time (1). Twenty-seven male firefighters participated in the study and the researchers assessed body composition, aerobic capacity, muscular power, muscular strength and muscular endurance. Testing was performed during the first week of academy training, the last week (week 14) of academy training, and 6 months after commencement of subsequent probationary period of active duty (1).

Body mass (mean = -2.6 kg), waist-to-hip ratio (mean = -0.02) and estimated body fat percentage (mean = -5.5%) of the recruits all decreased significantly across the 14 weeks of initial training and estimated fat-free mass increased significantly (mean = +2.6 kg) (1). However, during the subsequent 6-month period of probationary active duty, average body mass increased to pre-training levels, average body mass index increased slightly, waist-to-hip ratio increased beyond pre-training levels, and estimated percentage body fat increased significantly again such that they regained half of the reduction they had achieved in percentage body fat during initial training (1). Nevertheless, estimated fat-free mass was maintained during the 6-month probationary period following training (1). Measures of aerobic fitness (assessed as estimated relative VO2max from a step test, mean change of +10.2 mL•kg-1•min-1), arm strength (assessed as estimated 1-repetition maximum [1RM] bench press, mean change of +5.7 kg), leg strength (assessed as estimated 1RM squat, mean change of +26.0 kg) and muscular endurance (assessed as maximum push-ups and maximum plank hold time, mean changes of 12 reps and 51 s, respectively) also improved significantly following initial training. However, they again declined somewhat during the 6-month period of probationary active duty, though mostly not back to pre-training levels (approximately 20% of aerobic fitness gains, 43% of arm strength gains, 0% of leg strength gains, 63% of push-up gains, and 100% of plank time gains were lost) (1).

Cornell and colleagues noted, based on previous research findings, the importance of physical conditioning for firefighters to mitigate heightened cardiovascular and musculoskeletal injury risks relative to the general population and viewed the training effects that they observed during initial training as very positive (1). However, the detraining effects observed in this study during the 6-month period of probationary active duty in firefighters was a concern, as they note, it would leave the firefighters again at heightened risk of adverse events (1). The authors recommended that attention be paid to maintenance of health and fitness among firefighters throughout their career.

For the tactical strength and conditioning facilitator, the study may serve as a further reminder of the importance of tactical personnel maintaining fitness levels through regular and appropriately designed exercise across the career-span. For firefighters, levels of physical conditioning may mean the difference between either suffering a cardiovascular event or musculoskeletal injury due to overexertion while undertaking work tasks or completing the tasks without incident.

Physical Performance Capacity is Lower in Older Age Groups of Law Enforcement Officers

Lockie and colleagues recently published a study involving 362 male and 21 female law enforcement officers, in which they assessed differences between the age groups in flexibility (sit and reach test), muscular endurance (maximum push-ups and sit-ups, each in 1 min), lower body power (vertical jump test) and aerobic capacity (2.4-km run time) (2). The age groups examined for male officers were 20 – 29, 30 – 39, 40 – 49 and 50 – 59 years of age, and there were no women in the 50 – 59 group (2).

Within the cohort of male officers, those aged 40 – 49 or 50 – 59 years performed significantly less well, on average, when compared to those aged 20 – 29 years, in a vertical jump test (average difference of 8 cm and 9 cm, respectively), 1-min sit-up test (average difference of 5 sit-ups and 6 sit-ups, respectively) and 2.4-km run time (average difference of 2 min) (2). Within the cohort of female officers, those aged 30 – 39 or 40 – 49 years performed significantly less well, on average, when compared to those aged 20 – 29 years, in a 1-min push-up test (average difference of 15 push-ups and 16 push-ups, respectively) (2). Female officers in these older age groups also performed less well than their 20 – 29 year old counterparts in the vertical jump test (average difference of 3 cm and 7 cm, respectively) and 2.4-km run time (average difference of 3 min and 4 min, respectively) (2). However, these differences did not reach statistical significance, possibly because of the low number of female participants in the study, which is a limitation of the study.

The authors noted that law enforcement can be physically demanding and officers must possess sufficient physical capacity to enable them to safely and efficiently complete assigned tasks (2). Based on findings in this study and results of research by others, the authors therefore recommended that attention be given to ensuring training for older officers includes adequate physical conditioning, with emphasis on lower-body power, muscular endurance, and aerobic capacity (2). Of importance to the tactical strength and conditioning facilitator, the authors further noted that such training will often have to be adapted from traditional periodization models, since these can be difficult to accommodate within an operational context, due to work demands (2). They recommended that training in such contexts be efficient and diverse in nature, working around scheduling constraints and taking advantage of any available opportunities to undertake training (2).

36 Hours of Military Survival Training and Sleep Deprivation Reduced Grip Strength, Grip Control, Balance, and Heart Rate Responses but not Reaction Times, Running Agility, or Marksmanship

In a recently published study involving 15 Polish Air Force Cadets, Tomczak and colleagues investigated the effects of 36 hr of military survival training, involving exercise and sleep deprivation, on physical and mental functioning (5). The cadets (age = 19.6±0.3 years [mean±SE]; height 178.7±1.7 cm, bodyweight 72.0±2.1 kg, and BMI 22.5±0.4 kg/m2) had just commenced military education at the Polish Air Force Academy (5). It was summertime, and ambient temperatures ranged 14 – 22 degrees Celsius (57 to 72 degrees Fahrenheit) (5).  The cadets carried a rucksack and firearm, weighing 10 – 12 kg, and traversed a total of 30 km during 36 hr of wakefulness (5). In this time, they undertook a sequence of activities that included basic combat skills, drills following combat alarms, camouflaged regrouping, reconnaissance, patrolling, shelter preparation, transport of wounded soldiers, and obstacle courses (5).

Measurements of physical and mental functioning were taken at the following time points: prior to the survival training; after 24 hr of survival training; after 36 hr of survival training (i.e., at the conclusion of the training activity); and the day after completion of the training, following a full night of rest (5). These measurements included: maximum hand grip strength; ability to estimate and apply a grip at 50% of maximum capacity; time to complete a multi-component running agility course; reaction times and error rates when using buttons and a keyboard to correctly respond to presentation of stimuli; accuracy of landing in a balanced manner on a line following a jump with 360 degree rotation while in the air; heart rate response and time to complete a 1-mi walk test; and shooting accuracy (5).

Tomczak and colleagues found that maximum grip strength (approximate 15% reduction), ability to moderate grip strength to apply 50% of maximum capacity, and rotating jump balance ability (deteriorated from 3 to 6 on an 18-point scale, where higher scores indicated poorer control) all deteriorated significantly in the participants, after the first 24 hr of the survival training (5). This deterioration persisted even after a night of rest, after the training concluded. Heart rate elevation following the walk test was significantly less pronounced (on average 16 beats per minute lower) after 36 hr of survival training, indicating the cardiovascular system was less responsive in meeting exercise demands (5). Marksmanship was unaffected following the survival training and both running agility and reaction times were also unaffected overall, although one element of the multi-element running agility test was observed to deteriorate significantly—speed of movement slowed by 2% after 24 hr of survival training (5).

These results demonstrate the combined effects on physical and mental functioning of military personnel that arise from sleep deprivation and sustained exercise under load, causing fatigue. These findings are important, as they indicate areas of risk that may occur following sustained exercise and sleep deprivation and highlight potential opportunities for training enhancement.

For the tactical strength and conditioning facilitator, these findings highlight the importance of strength, control, balance, and aerobic training for tactical personnel, to enable them to develop an adequate conditioning “buffer” to enable them to continue to function adequately even after sustained periods of exercise and sleep deprivation. They also highlight the fact that training staff must manage risks that arise from fatigue and sleep deprivation in sustained training activities like the survival training reported in this study. For example, tactical personnel required to carry a stretcher loaded with an injured person when sleep deprived and physically fatigued will possess less grip strength and less ability to control grip, and this may create risks for them and the injured person they are carrying (5). While Tomczak and colleagues suggest that more endurance strength training should be conducted in combination with sleep deprivation, the response to this recommendation should perhaps be tempered by a recognition that any such training should be subject to rigorous evaluation to ensure it delivers the intended benefits and that associated risks can be well managed.

Participation in a Sleep Health Program Can Substantially Reduce Disability Days and Injury Rates in Firefighters

In an interesting and recently published randomized controlled study, Sullivan and colleagues from the Harvard Work Hours, Health and Safety Group examined the impact of a sleep health program on firefighter injury and disability (4). The authors began by noting that firefighters typically work demanding schedules, under high levels of stress, and in extended and varying shifts (4). As a result, they said, firefighters frequently experience sleep deficiency and circadian rhythm disturbances which can lead to undiagnosed sleep disorders and fatigue which, in turn, can contribute to risk of injury and time off work due to disability (4).

On this basis, the research team conducted a study involving 1,189 firefighters (98.7% males) in which roughly half of the participating firefighters attended a 30-min sleep health education session and the other half did not (4). The sleep health education session was described by the authors as follows: “the session provided information on firefighter mortality, fatigue-related health hazards, and the physiological importance of sleep. The sleep health education also included strategies to improve sleep hygiene and tips on how to use caffeine and naps effectively to promote alertness. Eye masks and ear plugs were distributed to aid with sleep hygiene. This information was supplemented by distribution of brochures on various sleep health topics…” (4).

Of those who attended the education session, most (77%) then underwent a voluntary screening for sleep disorders and were referred for clinical follow-up if the screening suggested they should be (4). Prior to the intervention, firefighters reported an average of 45 hr of sleep per week, or 6.4 hr per day, and this increased slightly but not statistically significantly to 47 hr per week (6.7 hr per day) following the intervention (4). Although the frequencies with which firefighters fell asleep while in meetings, on the phone, driving and stopped in traffic reduced substantially (20 – 50%) following the intervention, these differences again did not reach statistical significance, likely due to their low frequencies of occurrence at baseline (4). Nevertheless, perhaps in part reflecting this reduction in frequency of falling asleep on the job, analysis of departmental records relating to the participants for the 12-month period that followed the education and screening interventions showed that those participants who received the education and screening opportunity reported 46% less disability days and were 24% less likely to file at least one injury report during the study than those who did not receive these interventions (4).

These substantial differences in numbers of disability days and injury rates between those who did and those who did not receive the sleep health interventions are instructive, as they indicate firstly that a key contributor to firefighter disability (or ill-health) and injury risk is poor sleep patterns and secondly that this issue can be addressed relatively easily by fire departments (4). For the tactical strength and conditioning facilitator, this information is valuable because it means that if a particular group of firefighters is observed to be experiencing higher-than-usual rates of disability and injury, the primary reasons may not always be training deficiencies, occupational tasks, or preceding levels of physical conditioning. While these factors should always be considered as possible contributors to any observed high rates of disability and injury, the sleep health of firefighters should also be considered and acted upon by those in command, if potential issues are identified.

Reflex-Based Self-Defense Training Improves Police Performance in Simulated High Pressure Arrests More than Regular Police Arrest and Self-Defense Skills Training

Renden and colleagues recently published the results of a randomized crossover trial conducted in the Netherlands, which involved 11 experienced police officers and examined whether a program of reflex-based self-defense training (FIRST) was more effective than regular arrest and self-defense skills (ASDS) training (3). The outcome of interest was subsequent police performance in simulated high pressure arrests. Both forms of training took 90 min to complete, noting that these were experienced police officers and so the training was designed in each case to “refresh” their skills. Six participants undertook the FIRST training first, and the other 5 participants undertook the ASDS training first, with all completing both types of training and being tested after each (3).

The ASDS training was conducted in a training room and involved practicing key skills that were examined each year, including kick and punch actions on a foam object, various control exercises, handcuff exercises with varying levels of resistance, transition from pepper spray to handgun, and effective use of both of these options (3). The FIRST training began with a classroom session and then progressed to physical practice of skills in a training room. In the classroom, FIRST trainees received an explanation of how people’s behavior could be analyzed to assist in deescalating a situation and this was reinforced and further demonstrated by use of video clips of real situations, where trainees analyzed the behavior of the people in the clips and considered how specific actions could help deescalate the situation (3). In addition, the trainer explained the “flinch” reflex and how this could be used to advantage by police in a violent situation, through attention to positioning of self-relative to offender, for example (3). Further details are provided in the article. In the training room, the FIRST trainees physically practiced what they had learned in the classroom, in realistic scenarios.

The participants rated both types of training as entertaining, useful, and applicable to their police duties, but they rated the FIRST training slightly more entertaining and useful (3). Perhaps most interesting, however, is the finding that the ASDS training did not result in any change from pre-training to post-training in scores for ASDS performance, when both were assessed via video footage by an experienced independent assessor who did not know which video footage was taken pre-training and which was taken post-training (3). However, the FIRST training resulted in a significant improvement (average 20%) of ASDS performance, when this was assessed and scored in the same manner, by the same independent assessor (3).

The authors noted that a key difference between the FIRST and regular ASDS training was that the FIRST training involved practice of skills in realistic scenarios, whereas the regular ASDS training involved practice of key skills in relative isolation from realistic scenarios (3). For the tactical strength and conditioning facilitator, this is a further reminder of the importance of specificity and realism in tactical skills training. In addition, as the authors note, the results provide insights to ways to optimize training in arrest and self-defense skills, and potentially also some other types of tactical skills (3). Specifically, the FIRST training, which achieved better results than the regular ASDS training and appeared to be a better approach, required the police officers who were undergoing training to first attend to and analyze people’s behaviors and signals, before any physical contact occurred, so that they could then apply appropriate de-escalation techniques right from the start of the interaction (3). Secondly, the FIRST training also taught the police officers to act to ensure their own natural physical reflexes could be used to their advantage if the situation was, or became violent, for example by positioning themselves optimally relative to the offender (3).

Levels of Trait Anxiety and Sensation-Seeking, and Some Pre-Week Mood States Predict Injury Risk in Navy Diving Training

Some of the preceding sections highlight the contributions that disordered sleep, sleep deprivation, and physical fatigue can make to determining injury risk for tactical personnel. In a similar vein, a study published recently by Van Wijk and Fourie investigated the extent to which pre-course levels of trait anxiety and sensation-seeking, as well as weekly measures of transient mood states, predict levels of injury risk across and within each week of a navy diving training course (6). The diving training course was conducted over 6 weeks by the South African Navy and was physically-demanding, involving swimming, running, and strength training (6). Forty-one trainee divers (6 women and 35 men) participated in the study and completed pre-course psychological and mood state measures, as well as weekly measures of mood states (6). Injuries resulting in at least one lost day of training and occurring to the participants across the diving course were recorded each week of training.

The authors found that divers who were injured during the diving training course were assessed to have significantly higher average pre-course trait anxiety (1.9 points on a 10-point scale) and significantly lower average pre-course levels of sensation seeking (2.3 points on a 40-point scale) than their uninjured peers (6). These findings are interesting, first because they indicate that trainees who were by nature more anxious were also more likely to be injured, and the authors hypothesize that this may be because more anxious trainee divers were more likely to panic and thereby become injured than their less anxious peers (6). The findings are also interesting because they suggest that at least a moderate sensation-seeking attitude may help to protect trainee divers from injury, as noted by the authors (6). The findings also raise the possibility that these factors might play similar roles in other tactical populations, and this possibility warrants further research.

Van Wijk and Fourie also found that injuries were more likely to occur each week in trainee divers who, prior to the start of the week, scored higher on tension, depression, or confusion (6). This finding is again interesting, as it suggests that the risk of injury for any trainee may be affected by their pre-training mood state, and that life events or circumstances that cause tension, depression, or confusion may increase trainee risk of injury (6).

For the tactical strength and conditioning facilitator, this information is useful, similar to the information regarding disordered sleep, sleep deprivation, and physical fatigue provided in preceding sections. As noted in those preceding sections, knowledge of these factors enables the tactical strength and conditioning facilitator to consider a wider range of possible contributors to higher-than-usual rates of injury, where higher rates are observed, rather than assuming some combination of the training program, occupational tasks, or prior physical conditioning of the trainees must be responsible. Being aware of the behavior and moods of individual trainees may also enable the tactical strength and conditioning facilitator to identify possible concerns so that these can be raised with appropriate professionals and command staff and so addressed, if confirmed, to help mitigate risks.

This article originally appeared in TSAC Report, the NSCA’s quarterly, online-only publication geared toward the training of tactical athletes, operators, and facilitators. It provides research-based articles, performance drills, and conditioning techniques for operational, tactical athletes. The TSAC Report is only available for NSCA Members. Read more articles from TSAC Report 

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References 

1. Cornell, D, Gnacinski, S, Meyer, B, and Ebersole, K. Changes in health and fitness in firefighter recruits: An observational cohort study. Medicine and Science in Sports and Exercise Publish Ahead of Print, 2017. DOI: 10.1249/MSS.0000000000001356

2. Lockie, R, Dawes, J, Kornhauser, C, and Holmes, R. A crosssectional and retrospective cohort analysis of the effects of age on flexibility, strength endurance, lower-body power, and aerobic fitness in law enforcement officers. The Journal of Strength and Conditioning Research Publish Ahead of Print, 2017. DOI: 10.1519/ JSC.0000000000001937

3. Renden, P, Savelsbergh G, and Oudejans, R. Effects of reflexbased self-defence training on police performance in simulated high-pressure arrest situations. Ergonomics 60(5): 669-679, 2017.

4. Sullivan, J, O’Brien, C, Barger, L, Rajaratnam, S, Czeisler, C, and Lockley, S, for the Harvard Work Hours, Health and Safety Group. Randomized, prospective study of the impact of a sleep health program on firefighter injury and disability. SLEEP 40(1): 2017. http://dx.doi.org/10.1093/sleep/zsw001

5. Tomczak, A, Dąbrowski, J, and Mikulski, T. Psychomotor performance of Polish Air Force cadets after 36 hours of survival training. Annals of Agricultural and Environmental Medicine: 2017. DOI: 10.5604/12321966.1232762

6. Van Wijk, C, and Fourie, M. Using psychological markers of sport injuries for navy diving training. International Journal of Sport and Exercise Psychology 15(1): 1-11, 2017.

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Rod Pope is currently a Professor of Physiotherapy at Charles Sturt University and co-leads the Tactical Research Unit headquartered at Bond Universit...

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