If you are interested in rucking, aka tabbing (in British English, although this is commonly rucking at speed), it can be worthwhile to read some the studies behind the activity. Not surprisingly, much of the the data comes from various military studies. Be sure to read the papers, especially the detailed Discussion sections, rather than simply the (limited) Conclusions, as shared below.
If you are interested in other rucking related articles: how to start, the gear required, hydration etc, please read here.
Please note, these resources are shared for information purposes only. Always exercise within your limits. If you are considering changing your diet, exercise or lifestyle practices, plans with your primary medical practitioner before making any changes; especially if you are under treatment.
In our home base of Singapore, all men have to complete National Service. Army recruits finalise their training with a 24km (15 mile) loaded march. We have found 1 local study related to this subject, entitled: Thermal strain and fluid balance during a 72-km military route march in a field setting.
Stay Healthy,
Alastair
The following articles might also be of interest:
Studies 2024
Baur DA, Baur KG, Buchanan BK, Ortiz MJ, Doody AG. Load carriage physiology in normoxia and hypoxia. Eur J Appl Physiol. 2024 Mar;124(3):925-943. doi: 10.1007/s00421-023-05320-2. Epub 2023 Sep 23. PMID: 37740748; PMCID: PMC10879375.
"Conclusion: Load carriage reduces cardiorespiratory efficiency and increases physiological strain, particularly in hypoxic environments. Potential load carriage-induced alterations in cerebral blood flow may increase the risk for altitude illnesses and requires further study."
Looney DP, Lavoie EM, Notley SR, Holden LD, Arcidiacono DM, Potter AW, Silder A, Pasiakos SM, Arellano CJ, Karis AJ, Pryor JL, Santee WR, Friedl KE. Metabolic Costs of Walking with Weighted Vests. Med Sci Sports Exerc. 2024 Jun 1;56(6):1177-1185. doi: 10.1249/MSS.0000000000003400. Epub 2024 Jan 30. PMID: 38291646.
"Conclusions: The updated Load Carriage Decision Aid (LCDA) metabolic model calculates accurate predictions of metabolic rate when carrying heavy backpack and vest-borne loads. Tactical populations and recreational athletes that train with weighted vests can confidently use the simplified LCDA metabolic calculator provided as Supplemental Digital Content to estimate metabolic rates for work/rest guidance, training periodization, and nutritional interventions."
2023
Armstrong NC, Smith SJR, Risius D, Doyle D, Wardle SL, Greeves JP, House JR, Tipton M, Lomax M. Cognitive performance of military men and women during prolonged load carriage. BMJ Mil Health. 2023 Feb;169(1):37-45. doi: 10.1136/bmjmilitary-2021-002000. Epub 2022 Apr 7. PMID: 35393357; PMCID: PMC9887367.
"Conclusion: These data provide further evidence that cognitive performance of military personnel can be affected during long duration loaded marching. Women reported discomfort from equipment more frequently than men, which may make them more susceptible to declines in cognitive performance. These findings highlight important considerations for equipment procurement."
Gill N, Roberts A, O'Leary TJ, Liu A, Hollands K, Walker D, Greeves JP, Jones R. Role of sex and stature on the biomechanics of normal and loaded walking: implications for injury risk in the military. BMJ Mil Health. 2023 Feb;169(1):89-93. doi: 10.1136/bmjmilitary-2020-001645. Epub 2021 Jan 21. PMID: 33478981.
"Conclusion n/a"
Armstrong NC, Smith SJR, Risius D, Doyle D, Wardle SL, Greeves JP, House JR, Tipton M, Lomax M. Cognitive performance of military men and women during prolonged load carriage. BMJ Mil Health. 2023 Feb;169(1):37-45. doi: 10.1136/bmjmilitary-2021-002000. Epub 2022 Apr 7. PMID: 35393357; PMCID: PMC9887367.
"Conclusion: These data provide further evidence that cognitive performance of military personnel can be affected during long duration loaded marching. Women reported discomfort from equipment more frequently than men, which may make them more susceptible to declines in cognitive performance. These findings highlight important considerations for equipment procurement."
2022
Oeschger R, Roos L, Wyss T, Buller MJ, Veenstra BJ, Gilgen-Ammann R. Influence of Soldiers' Cardiorespiratory Fitness on Physiological Responses and Dropouts During a Loaded Long-distance March. Mil Med. 2022 Jan 7;188(7-8):e1903–9. doi: 10.1093/milmed/usab540. Epub ahead of print. PMID: 35015894; PMCID: PMC10363014.
"Conclusion: Soldiers with a high $\dot{\rm{V}}$O2peak showed a lower mean heart rate and peak body core temperature throughout the long-distance march, as well as higher performance motivation, no dropouts, and lower energy deficit. All soldiers showed an enormous energy deficit; therefore, corresponding nutritional strategies are recommended."
Poon BH, Prakaash S, Teo YS, Fan PW, Wei Lee JK. Thermal strain and fluid balance during a 72-km military route march in a field setting. Singapore Med J. 2022 Sep;63(9):497-502. doi: 10.11622/smedj.2021053. Epub 2021 Apr 19. PMID: 34005849; PMCID: PMC9678143
"Conclusion: Our study found low thermal strain heat-acclimatised individuals during a 72-km route march. However, there was an overall decrease in serum sodium levels, even when the participants were allowed to drink ad libitum. Challenges of exercise-associated hyponatraemia during prolonged activities remain to be addressed."
2021
Orr R, Pope R, Lopes TJA, Leyk D, Blacker S, Bustillo-Aguirre BS, Knapik JJ. Soldier Load Carriage, Injuries, Rehabilitation and Physical Conditioning: An International Approach. Int J Environ Res Public Health. 2021 Apr 11;18(8):4010. doi: 10.3390/ijerph18084010. PMID: 33920426; PMCID: PMC8069713.
"Optimal conditioning and reconditioning practices include load carriage sessions with a frequency of one session every 10-14 days in conjunction with a program of both resistance and aerobic training. Speed of march and grade and type of terrain covered are factors that can be adjusted to manipulate load carriage intensity, limiting the need to adjust load weight alone. Factors external to the load carriage program, such as other military duties, can also impart physical loading and must be considered as part of any load carriage conditioning/reconditioning program."
2020
Godhe M, Helge T, Mattsson CM, Ekblom Ö, Ekblom B. Physiological Factors of Importance for Load Carriage in Experienced and Inexperienced Men and Women. Mil Med. 2020 Aug 14;185(7-8):e1168-e1174. doi: 10.1093/milmed/usaa050. PMID: 32248224.
"Conclusion: The study showed that body mass, without sex differences, and experience of carrying heavy loads are the dominant factors for the ability to carry heavy loads. Even though the effect of experience alludes to the need for extensive carrying training, no causality can be proven. Load carry training intervention studies is suggested for future investigations."
Ohlsson C, Gidestrand E, Bellman J, Larsson C, Palsdottir V, Hägg D, Jansson PA, Jansson JO. Increased weight loading reduces body weight and body fat in obese subjects - A proof of concept randomized clinical trial. EClinicalMedicine. 2020 Apr 30;22:100338. doi: 10.1016/j.eclinm.2020.100338. PMID: 32510046; PMCID: PMC7264953.
"Discussion: The main finding was that high load treatment reduced body weight compared to low load treatment and that this was the result of a reduction in fat mass while fat-free mas was unaffected. Our interpretation of these results is that there is a weight loading dependent homeostatic regulation of body weight, the gravitostat, also in humans."
2019
Coakley SL, Myers SD, Walker EF, Hale B, Jackson S, Greeves JP, Roberts R, Blacker SD. 1.5mile run time and body mass predict 8mile loaded march performance, irrespective of sex. J Sci Med Sport. 2019 Feb;22(2):217-221. doi: 10.1016/j.jsams.2018.07.007. Epub 2018 Jul 20. PMID: 30249459.
"Conclusion: 1.5mile run time and body mass predict 8mile LM performance with no further improvement gained in the model by including sex as a variable."
Wills JA, Saxby DJ, Glassbrook DJ, Doyle TLA. Load-Carriage Conditioning Elicits Task-Specific Physical and Psychophysical Improvements in Males. J Strength Cond Res. 2019 Sep;33(9):2338-2343. doi: 10.1519/JSC.0000000000003243. PMID: 31269002.
"The training program resulted in significant increases in squat jump maximal force, push-ups, sit-ups (p < 0.05), and estimated maximal oxygen uptake (p < 0.05). Physical performance improvements and positive physiological adaptations to a load-carriage task were elicited in males after completing a 10-week training program. Military organizations could use this evidence-based training program to efficiently train soldiers to improve their load-carriage capacity."
David Boffey, Idan Harat, Yftach Gepner, Cheyanne L Frosti, Shany Funk, Jay R Hoffman, The Physiology and Biomechanics of Load Carriage Performance, Military Medicine, Volume 184, Issue 1-2, January-February 2019, Pages e83–e90, https://doi.org/10.1093/milmed/usy218
"The literature recommends that load and speed should be managed in order to maintain an exercise intensity ~45% VO2 max to delay time to fatigue during prolonged marches, and the Load–Speed Index corroborated this finding, identifying 47% VO2 max as a threshold above which intensity increases at a greater rate with increases in load and speed."
Wills JA, Saxby DJ, Glassbrook DJ, Doyle TLA. Load-Carriage Conditioning Elicits Task-Specific Physical and Psychophysical Improvements in Males. J Strength Cond Res. 2019 Sep;33(9):2338-2343. doi: 10.1519/JSC.0000000000003243. PMID: 31269002.
"The training program resulted in significant increases in squat jump maximal force, push-ups, sit-ups (p < 0.05), and estimated maximal oxygen uptake (p < 0.05). Physical performance improvements and positive physiological adaptations to a load-carriage task were elicited in males after completing a 10-week training program."
Faghy MA, Brown PI. Functional training of the inspiratory muscles improves load carriage performance. Ergonomics. 2019 Nov;62(11):1439-1449. doi: 10.1080/00140139.2019.1652352. Epub 2019 Aug 16. PMID: 31389759.
"Practitioner Summary: We confirmed the ergogenic benefit of Inspiratory Muscle Training (IMT) upon load carriage performance. Furthermore, we demonstrate that functional IMT methods provide a greater performance benefit during exercise with thoracic loads."
Coakley SL, Myers SD, Walker EF, Hale B, Jackson S, Greeves JP, Roberts R, Blacker SD. 1.5mile run time and body mass predict 8mile loaded march performance, irrespective of sex. J Sci Med Sport. 2019 Feb;22(2):217-221. doi: 10.1016/j.jsams.2018.07.007. Epub 2018 Jul 20. PMID: 30249459.
"This study showed that 8mile loaded march performance to the British Army Infantry standard can be predicted from an individual’s 1.5mile run time and body mass, irrespective of sex. Compared to women, men had faster 1.5mile run and 8mile loaded march performance times, greater body mass, fat free mass, single lift (SL) and water can carry (WCC) scores. Although the mean women physical performance scores were lower, some women test scores were above the men test scores in the 1.5mile run, SL, WCC, and loaded march with the least overlap in SL (measure of muscular strength). A greater proportion of men compared to women achieved the Infantry pass standard for WCC (150m standard; 99 vs. 50%), SL (40kg standard; 97 vs 15%) and loaded march (<120min standard; 100 vs. 69%). Whereas, only 6 of the 48 women participants (13%) achieved the Infantry standard across all three representative military tasks"
2018 and Before
Schram B, Orr R, Pope R. A Profile of Knee Injuries Suffered by Australian Army Reserve Soldiers. Int J Environ Res Public Health. 2018 Dec 20;16(1):12. doi: 10.3390/ijerph16010012. PMID: 30577566; PMCID: PMC6339105.
"Among the 1434 injuries reported by ARES personnel, the knee was the most common injury site (n = 228, 16%). Soft tissue injury due to trauma or unknown causes was the most common nature of knee injury (n = 177, 78%). Combat training was the most common activity being performed when soft tissue injuries occurred at the knee (n = 73, 42%), with physical training the second most common (n = 51, 30%), due to muscular stress (n = 36, 71%) and falls (n = 8, 16%). Targeted intrinsic and extrinsic approaches to injury minimization strategies for soft tissue knee injuries during combat and physical training should be designed."
Chatterjee T, Bhattacharyya D, Pramanik A, Pal M, Majumdar D, Majumdar D. Soldiers' load carriage performance in high mountains: a physiological study. Mil Med Res. 2017 Feb 17;4:6. doi: 10.1186/s40779-017-0113-x. PMID: 28239483; PMCID: PMC5316174.
"Conclusions: Considering the physiological responses, expressions of perceived exertion and changes in relative work load at both of the high altitudes Indian soldiers are advised to walk slowly with adequate rest in between their schedules and to carry not more than 32% of their body weight."
Faghy MA, Brown PI. Whole-body active warm-up and inspiratory muscle warm-up do not improve running performance when carrying thoracic loads. Appl Physiol Nutr Metab. 2017 Aug;42(8):810-815. doi: 10.1139/apnm-2016-0711. Epub 2017 Mar 13. PMID: 28288302.
"Whole-body AWU and IMW performed alone or combination have no ergogenic effect upon high-intensity, short-duration performance when carrying a 25-kg load in a backpack."
Kenefick RW, Heavens KR, Luippold AJ, Charkoudian N, Schwartz SA, Cheuvront SN. Effect of Physical Load on Aerobic Exercise Performance during Heat Stress. Med Sci Sports Exerc. 2017 Dec;49(12):2570-2577. doi: 10.1249/MSS.0000000000001392. PMID: 28767522.
"Conclusions: In regard to performance, we observed the following: 1) load itself (20%, 30%, and 50% of BM) impaired 5-km TT performance when compared with unloaded performance in a temperate environment); 2) the time penalty of the 20% load was <50% load and was not different from that of the 30% load in a temperate environment, nor were the lines of best fit; 3) the addition of heat exposure impaired 5-km TT performance beyond the penalty of load; 4) the addition of heat exposure to 20%–30% load increased the time penalty equivalent to that of 50% load in a temperate environment; 5) and lastly, the combination of heat and 50% load resulted in a substantial penalty such that continuous work was not sustainable for all of the volunteers."
Orr RM, Pope R. Gender differences in load carriage injuries of Australian army soldiers. BMC Musculoskelet Disord. 2016 Nov 25;17(1):488. doi: 10.1186/s12891-016-1340-0. PMID: 27884191; PMCID: PMC5123228.
"Conclusions: While both genders similarly have the lower back as the leading site of injury while carrying load, female soldiers have more injuries to the foot as the second leading site of injury, as opposed to ankle injuries in males. The typically smaller statures of female soldiers may have predisposed them to their observed higher risk of suffering SPI while carrying loads."
Hunt AP, Billing DC, Patterson MJ, Caldwell JN. Heat strain during military training activities: The dilemma of balancing force protection and operational capability. Temperature (Austin). 2016 Feb 26;3(2):307-317. doi: 10.1080/23328940.2016.1156801. PMID: 27857960; PMCID: PMC4965006.
"The present study provides evidence to show that the force protection provided by the Work Table may be preventing the majority of personnel from conducting activities in hot environments and thereby constraining a commander's mandate to develop a resilient and optimised military force."
Other
Undated document "Load Carriage in Military Operations, A Review of Physiological, Historical, Biomechanical and Medical Aspects" Joseph Knapick SCD and Katy Reynolds MD (Note: .pdf 78 pages)
US Army "Foot Marches" documentation, April 2022 (Note: pdf. 160 pages)
Training protocols: Julia Coyle , Rodney Pope and Robin M Orr In Review Article Issue Volume 18 No. 3 Doi No https://doi-ds.org/doilink/11.2021-49313873/JMVH Vol 18 No 3 Load carriage: minimising soldier injuries through physical conditioning – a narrative review
Mair JL, De Vito G, Boreham CA. Low Volume, Home-Based Weighted Step Exercise Training Can Improve Lower Limb Muscle Power and Functional Ability in Community-Dwelling Older Women. J Clin Med. 2019 Jan 4;8(1):41. doi: 10.3390/jcm8010041. PMID: 30621121; PMCID: PMC6352105.
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