• Hot Topic: Physical Training to Optimize Load Carriage in the Tactical Operator
    Load carriage can be defined as the external load comprising items critical to tactical and operational mission success. This article reviews the impact of load carriage on physical performance and provides evidence-based guidelines for physical training strategies.
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  • A firefighter using a water hose on a fireIntroduction
    Load carriage can be defined as the external load comprising items critical to tactical and operational mission success (e.g., protective equipment, weapons, ammunition, foodstuffs, communications equipment, etc.). 

    Load carriage is one of the most physically demanding occupational tasks that a tactical operator must perform, and it can be a decisive factor during emergency situations and military conflicts. The consequences of overloading a tactical operator include excessive fatigue, diminished physical performance, impaired mobility, and the potential of sustaining overuse and musculoskeletal injuries.

    Tactical strength and conditioning (TSAC) facilitators should employ evidence-based research when prescribing strength and conditioning programs for the purpose of optimizing and improving load carriage performance. The purpose of this article is to review the impact of load carriage on physical performance and to provide evidence-based guidelines for physical training strategies that aim to improve load carriage performance.

    These training guidelines can be extrapolated and utilized by all tactical operators in which load carriage is an essential occupational task (e.g., firefighters wearing personal protective equipment, police officers wearing body armor, military personnel carrying heavy equipment on their backs, etc.).

    Physiological Demands of Load CarriageThe job requirement of almost any tactical operator is to be able to complete a mission successfully—the undertaking of which is often physically laborious and conducted in austere environments while wearing protective clothing and gear. Performing a mission wearing an additional load incurs substantial physiological demands. Previous research has demonstrated a substantial impact of load carriage on physiological, metabolic, and performance variables.

    For example, Quesada et al. conducted a simulated road march with loads of 0, 30, and 50% of body mass and demonstrated that heart rate (HR) and oxygen consumption (VO2) increased linearly with heavier loads (14). Beekley et al. assessed HR, VO2, respiratory exchange ratio (RER), rating of perceived exertion (RPE), and ventilation (VE) following 30 minutes of road marching at 6 km/hr with loads of 30, 50, and 70% of lean body mass (LBM) (1). Results showed that HR, VO2, RER, and VE increased progressively as loads got heavier.

    Another study examined physical work performance, energy cost, and physiological fatigue in military personnel walking on a treadmill for 30 minutes with body armor (~32 lb). Results demonstrated that subjects wearing body armor had significantly greater increases in VO2, blood lactate, HR, and RPE (16). Moreover, wearing body armor caused an increase in the metabolic cost of walking at both slow (42 kcal/hr) and moderate (126 kcal/hr) paces.

    Physical performance was significantly affected by body armor as demonstrated by 61% fewer pull-ups in men, a 63% decrease in women’s hang time, and a 16% decrement for both men and women in stair stepping (16). The authors of this study concluded that wearing body armor increases the potential for physical exhaustion and impairs the performance of physical tasks during sustained operations (16).

    In a study examining explosive, anaerobic power during a military task, Treloar et al. sought to assess explosive, anaerobic performance while simulating a defensive withdrawal under fire (break contact drill) with 21.6 kg of equipment (18). The authors concluded that this load significantly affected soldiers’ mobility during the performance of explosive, anaerobic military tasks. They stressed that a soldier’s strength and conditioning program should target these specific occupational requirements.

    Research clearly demonstrates that load carriage significantly increases the stress of both the physiology and physical performance of tactical operators. The following section will review current literature on strength and conditioning considerations for load carriage and provide recommendations to enhance the tactical operator’s ability to maneuver successfully under loaded conditions.

    Improving the Tactical Operator’s Mobility during Load CarriageOver the last 20 – 25 years, research has focused on physical training strategies aimed at conditioning soldiers to endure load carriage tasks. The outcome of research in this area has broadened our understanding of the physiological demands of performing occupational tasks with load carriage. Evidence on strength and conditioning for load carriage over the last two decades has demonstrated that programs that incorporate a combination of resistance training, aerobic, and load-specific carriage exercises are most effective for improving load carriage performance (2,3,6,9,11,20,21).

    Task-Specific TrainingThere are numerous studies in the literature that have examined the influence of different types of exercise training programs on load carriage performance. One of the most important concepts for improving load carriage performance is the principle of specificity. Therefore, load carriage tasks should be included in a conditioning program designed for improving load carriage ability (8,22). Appropriate application of the principle of specificity in load carriage physical training was revealed in a study by Patterson et al. who examined the effects of a 12-week conditioning program that included circuit and resistance training, running, and load carriage marches on performance outcomes in soldiers (13).

    Although soldiers increased strength and aerobic capacity during this study, load carriage performance did not change significantly.

    This may be due to two reasons:
    1. To minimize any observable effect of training, load carriage was limited to only two sessions throughout the study (week three and five). 
    2. The longest load carriage march in the study was 30 min which is much shorter than a 15-km event (165 min) normally used to assess performance in the U.S. Army. 
    A meta analysis conducted by Knapik et al. (7) showed that the largest overall improvements in load carriage performance occurred when once weekly progressive load carriage was included as part of the training regimen (4,7,20). This specific training likely involves the skills, energy systems, and muscle groups required for performing this task. It is evident that prescribing progressive load carriage exercise in a strength and conditioning program will develop the skills, and condition the muscle groups and energy systems required to enhance performance of this specific task (15). 

    Visser et al. examined the impact of different training doses on load carriage capacity by comparing a high-intensity (load) and low-volume (distance) training routine to a lower intensity and higher volume routine with a constant speed (19). The training dose combinations were analyzed against the effects of training frequency (number of sessions per week). Results demonstrated that all training groups improved in measures of strength, aerobic endurance, marching speed, and progressive load march performance.

    However, the higher intensity, lower volume groups improved the greatest in the progressive load march test compared to the lower intensity, higher volume groups. In addition, the higher frequency (once per week) training groups made significantly greater improvements in the physical performance outcome measures than the lower frequency (bimonthly) groups. These findings suggest that improvement in load carriage performance is highly dependent on training intensity (load), followed by training frequency (sessions per week), and then by training volume (distance) (19).

    Another study examined two different 11-week conditioning programs in recruits where one group (run) comprised endurance running, load carriage, and other conditioning activities while the other group replaced all running sessions with weight load marching (17). Both groups made similar gains in aerobic fitness, but only the weight load marching group demonstrated improvements in aerobic fitness together with an increase in walking speed and loads carried. These results suggest that the load carriage regimen needs to have sufficient intensity (load and speed) to stimulate improvements in aerobic fitness and load carriage ability. It is evident that when designing strength and conditioning programs for the purpose of enhancing load carriage performance, the training intensity (load and speed) of load carriage is a key factor.

    Concurrent TrainingConcurrent training involves training for more than one physiological response (e.g., strength and aerobic) at the same time. To examine the effects of concurrent training, Harman et al. compared standardized Army physical training (i.e., weight load marching, stretching, calisthenics, sprints, shuttle runs, and medium-distance runs) to a weight-based training program (weight load marching, full-body resistance, longer distance, ability-based runs, sprinting, and agility training) (4).

    Since both groups included weight load marching into their programs, both groups made significant improvements in load carriage performance providing further evidence of the importance of specificity of training. Performing physical training programs that exclude load carriage tasks have also been successful at improving load carriage performance. The fact that load carriage performance has been enhanced with resistance/aerobic training suggests that combining strength and cardiorespiratory endurance are important fitness components of an overall training regimen directed toward improving load carriage performance (7).

    In 2001, Kraemer et al. examined the influence of periodized resistance training programs on strength, power, endurance, and military occupational performance (9). The study selected 93 untrained women who were divided into six groups: total strength/power resistance (TP), total strength/hypertrophy resistance (TH), upper strength/power resistance (UP), upper strength/hypertrophy resistance (UH), field exercises with minimal equipment (FLD), and aerobic training (AER).

    The TP, TH, UP, and UH groups emphasized both resistance training and 25 – 35 min of running, cycling, or stair climbing for three days a week. The FLD group emphasized calisthenics, dumbbell and partner-resisted exercises, and ballistic plyometrics. The AER group conducted 25 – 30 min of running/aerobic exercise three days a week and low-volume resistance band exercises (<5 kg). The load carriage task for all groups was a two-mile time to completion event while wearing a 75-lb load. Results revealed that all groups enhanced performance on the load carriage task except the AER group.

    The addition of strength training improved load carriage performance in this study, thus clearly underscoring the importance of prescribing strength and conditioning for those personnel in physically demanding occupations. As such, the TSAC facilitator should prescribe a strength and conditioning program that includes exercises specific to all three energy systems since both studies conducted by Kraemer et al. demonstrated that programs employing either resistance training or aerobic training in isolation failed to make significant improvements in load carriage performance (9,10).

    An important caveat to consider when examining studies that suggest load carriage performance can be improved with a concurrent training program that excludes a specific load carriage training component is that subjects with lower initial fitness levels tend to make greater initial gains regardless of mode of training used; after which specified training is needed to make improvements (22).

    Practical Applications for the Enhancement of Load Carriage PerformanceThe TSAC facilitator has the responsibility of prescribing strength and conditioning programs designed with the specific intensity requirements that mirror the tactical operator’s respective tasks regarding the distance (or time) of prescribed load carriage tasks against both intensity and outcome requirements. For example, tactical operators may require short-duration, high-intensity sessions to develop explosive, anaerobic ability (i.e., as needed under direct fire or climbing a flight of stairs) in addition to physical training sessions that are longer in duration to optimize the physical and mental endurance needed for dismounted patrols (12).

    TSAC facilitators are charged with the responsibility of designing effective, evidence-based strength and conditioning programs that facilitate all aspects of physical adaptation including progressive overload, injury prehabilitation and mitigation, and recovery. The following practical guidelines are an evidence-based summary of research that demonstrates improvements in load carriage, and are provided to the TSAC facilitator to be used as a reference when designing and prescribing strength and conditioning programs for the purpose of improving load carriage performance.
    1. Once weekly progressive load carriage included in the program design (7).  
    2. A progressive increase in the weight/intensity of loads carried over time to meet tactical requirements (12). 
    3. A progressive increase in load carriage volume (duration and/or distance) to meet tactical requirements (12). 
    4. Resistance training performed with free weights and machines at least three days per week moving from high repetitions (10 – 12 reps) with less weight (muscular endurance) to lower repetitions (5 – 7 reps) with heavier weight (strength) and working up to three sets per exercise (9,10). 
    5. Aerobic training with progressive increases in distance (running 20 – 30 min based on heart rate, two times per week) and interval training with progressive decreases in rest (~once per week) (5). 
    Summary and ConclusionsA unit’s mission success is based entirely on the performance of their tactical operators who often have to react and maneuver in austere environments while under loaded conditions. TSAC facilitators are charged with ensuring that the strength and conditioning programs they prescribe are based on sound research and are appropriate for the personnel they are coaching. The principles and guidelines set forth in this article will prepare the TSAC facilitator with evidence-based knowledge ensuring they develop sound strength and conditioning programs for tactical operators. 
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    About the Author:

    CPT Paul C. Henning, PhD, CSCS

    CPT Henning is a research physiologist in the Military Performance Division at the United States Army Research Institute of Environmental Medicine (USARIEM), Natick, MA, the Army’s premier research organization for warfighter performance and environmental medicine. CPT Henning’s research supports Medical Research and Material Command Task Area: Physiological Mechanisms of Musculoskeletal Injuries. CPT Henning received his doctorate degree in exercise physiology from The Florida State University in December 2010. His research at Florida State focused on the cellular and molecular mechanisms regulating myofiber size in response to aging, catabolic stress and nutritional interventions. CPT Henning’s prior active duty experience was as a field medical officer while assigned to the First Cavalry Division at Fort Hood, Texas. He completed various assignments with the Cavalry and completed two combat tours in support of Operation Iraqi Freedom: (2004-2005) and (2006-2008).

    REFERENCES →


    1. Beekley MD, Alt J, Buckley CM, Duffey M, and Crowder TA. Effects of heavy load carriage during constant-speed, simulated, road marching. Mil Med 172: 592-595, 2007.
    2. Gerber Ka. Influence of physical fitness training on the manual material handling capability and road marching performance of female soldiers. Aberdeen Proving Ground, MD: Human Research and Engineering Directorate, U.S. Army Research Laboratory, 1996.
    3. Harman EA FP, Palmer C, Lammi E, Reynolds K, and Backus V. Effects of a specifically designed physical conditioning program on the load carriage and lifting performance of female soldiers. Natick MA: US Army Research Institute of Environmental Medicine 1997.
    4. Harman EA, Gutekunst DJ, Frykman PN, Nindl BC, Alemany JA, Mello RP, and Sharp MA. Effects of two different eight-week training programs on military physical performance. J Strength Cond Res 22: 524-534, 2008.
    5. Hendrickson NR, Sharp MA, Alemany JA, Walker LA, Harman EA, Spiering BA, Hatfield DL, Yamamoto LM, Maresh CM, Kraemer WJ, and Nindl BC. Combined resistance and endurance training improves physical capacity and performance on tactical occupational tasks. Eur J Appl Physiol, 2010.
    6. Knapik J. Bahrke M SJ, Reynolds K. Vogel J, O'Connor J. Frequency of loaded road march training and performance on a loaded road march. Natick, MA: U.S. Army Research Institute of Environmental Medicine, 1990.
    7. Knapik JJ, Harman EA, Steelman RA, and Graham BS. A systematic review of the effects of physical training on load carriage performance. J Strength Cond Res 26: 585-597, 2012.
    8. Knapik JJ, Reynolds KL, and Harman E. Soldier load carriage: historical, physiological, biomechanical, and medical aspects. Mil Med 169: 45-56, 2004.
    9. Kraemer WJ, Mazzetti SA, Nindl BC, Gotshalk LA, Volek JS, Bush JA, Marx JO, Dohi K, Gomez AL, Miles M, Fleck SJ, Newton RU, and Hakkinen K. Effect of resistance training on women's strength/power and occupational performances. Med Sci Sports Exerc 33: 1011-1025, 2001.
    10. Kraemer WJ, Vescovi JD, Volek JS, Nindl BC, Newton RU, Patton JF, Dziados JE, French DN, and Hakkinen K. Effects of concurrent resistance and aerobic training on load-bearing performance and the Army physical fitness test. Mil Med 169: 994-999, 2004.
    11. Kramer WJ VJ, Patton JF, Dziados JE, Reynolds KL; . The effects of various physical training programs on short duration, high intensity load bearing performance and the Army Physical Fitness Test. Natick, MA: U.S. Army Research Instituture of Environmental Medicine, 1987.
    12. Orr RM PR, Johnston V and Coyle J. Load carriage: minimising soldier injuries through physical conditioning – a narrative review. Journal of Military and Veterans’ Health 18: 31-38, 2010.
    13. Patterson MJ RW LW, et al. . Gender and Physical Training Effects on Soldier Physical Competencies and Physiological Strain. Defence Science and Technology Organisation, 2005.
    14. Quesada PM, Mengelkoch LJ, Hale RC, and Simon SR. Biomechanical and metabolic effects of varying backpack loading on simulated marching. Ergonomics 43: 293-309, 2000.
    15. Reilly T, Morris T, and Whyte G. The specificity of training prescription and physiological assessment: a review. J Sports Sci 27: 575-589, 2009.
    16. Ricciardi R, Deuster PA, and Talbot LA. Metabolic demands of body armor on physical performance in simulated conditions. Mil Med 173: 817-824, 2008.
    17. Rudzki SJ. Weight-load marching as a method of conditioning Australian Army recruits. Mil Med 154: 201-205, 1989.
    18. Treloar AK and Billing DC. Effect of load carriage on performance of an explosive, anaerobic military task. Mil Med 176: 1027-1031, 2011.
    19. Visser T vDM CT, et al. Is intensity of duration the key factor in march training?, in: International Congress on Soldier’s Performance. Finland, 2005.
    20. Williams AG, Rayson MP, and Jones DA. Effects of basic training on material handling ability and physical fitness of British Army recruits. Ergonomics 42: 1114-1124, 1999.
    21. Williams AG, Rayson MP, and Jones DA. Resistance training and the enhancement of the gains in material-handling ability and physical fitness of British Army recruits during basic training. Ergonomics 45: 267-279, 2002.
    22. Williams AG, Rayson MP, and Jones DA. Training diagnosis for a load carriage task. J Strength Cond Res 18: 30-34, 2004.

  • Disclaimer: The National Strength and Conditioning Association (NSCA) encourages the exchange of diverse opinions. The ideas, comments, and materials presented herein do not necessarily reflect the NSCA’s official position on an issue. The NSCA assumes no responsibility for any statements made by authors, whether as fact, opinion, or otherwise. 
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