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Rosbrook P, Sweet D, Qiao J, Looney DP, Margolis LM, Hostler D, Pryor RR, Pryor JL. Heat stress increases carbohydrate oxidation rates and oxygen uptake during prolonged load carriage exercise. Temperature (Austin) 2024; 11:170-181. [PMID: 38846526 PMCID: PMC11152092 DOI: 10.1080/23328940.2024.2322920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 02/19/2024] [Indexed: 06/09/2024] Open
Abstract
Military missions are conducted in a multitude of environments including heat and may involve walking under load following severe exertion, the metabolic demands of which may have nutritional implications for fueling and recovery planning. Ten males equipped a military pack loaded to 30% of their body mass and walked in 20°C/40% relative humidity (RH) (TEMP) or 37°C/20% RH (HOT) either continuously (CW) for 90 min at the first ventilatory threshold or mixed walking (MW) with unloaded running intervals above the second ventilatory threshold between min 35 and 55 of the 90 min bout. Pulmonary gas, thermoregulatory, and cardiovascular variables were analyzed following running intervals. Final rectal temperature (MW: p < 0.001, g = 3.81, CW: p < 0.001, g = 4.04), oxygen uptake, cardiovascular strain, and energy expenditure were higher during HOT trials (p ≤ 0.05) regardless of exercise type. Both HOT trials elicited higher final carbohydrate oxidation (CHOox) than TEMP CW at min 90 (HOT MW: p < 0.001, g = 1.45, HOT CW: p = 0.009, g = 0.67) and HOT MW CHOox exceeded TEMP MW at min 80 and 90 (p = 0.049, g = 0.60 and p = 0.024, g = 0.73, respectively). There were no within-environment differences in substrate oxidation indicating that severe exertion work cycles did not produce a carryover effect during subsequent loaded walking. The rate of CHOox during 90 minutes of load carriage in the heat appears to be primarily affected by accumulated thermal load.
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Affiliation(s)
- Paul Rosbrook
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
| | - Daniel Sweet
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
| | - JianBo Qiao
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
| | - David P. Looney
- Military Performance Division, United States Army Research Institute of Environmental Medicine, Natick, USA
| | - Lee M. Margolis
- Military Nutrition Division, United States Army Research Institute of Environmental Medicine, Natick, USA
| | - David Hostler
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
| | - Riana R. Pryor
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
| | - J. Luke Pryor
- Center for Research & Education in Special Environments, University at Buffalo, Buffalo, USA
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Baur DA, Baur KG, Buchanan BK, Ortiz MJ, Doody AG. Load carriage physiology in normoxia and hypoxia. Eur J Appl Physiol 2024; 124:925-943. [PMID: 37740748 PMCID: PMC10879375 DOI: 10.1007/s00421-023-05320-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 09/08/2023] [Indexed: 09/25/2023]
Abstract
PURPOSE To determine the effects of load carriage in normoxia and normobaric hypoxia on ventilatory responses, hemodynamics, tissue oxygenation, and metabolism. METHODS Healthy males (n = 12) completed 3 randomly ordered baseline graded exercise tests in the following conditions: (1) unloaded normoxic (U: FIO2 = 20.93%), (2) loaded (~ 30 kg) normoxic (LN), and (3) loaded hypoxic simulating ~ 3650 m (LH: FIO2 = ~ 13%). Thereafter, experimental exercise trials were completed in quasi-randomized order (i.e., U completed first) consisting of 3 × 10 min of walking (separated by 5 min seated rest) with stages matched with the U condition (in ascending order) for relative intensity, absolute oxygen consumption ([VO2]; 1.7 L min-1), and walking speed (1.45 ± 0.15 m s-1). RESULTS Load carriage increased perceived exertion and reduced VO2max (LN: - 7%; LH: - 32%; p < 0.05). At matched VO2, stroke volume and tidal volume were reduced and maintained with LN and LH vs. U, respectively (p < 0.05). Increases in cardiac output and minute ventilation at matched VO2 (with LH) and speed (with LN and LH), were primarily accomplished via increases in heart rate and breathing frequency (p < 0.05). Cerebral oxygenated hemoglobin (O2HHb) was increased at all intensities with LN, but deoxygenated hemoglobin and total hemoglobin were increased with LH (p < 0.05). Muscle oxygen kinetics and substrate utilization were similar between LN and U, but LH increased CHO dependence and reduced muscle O2HHb at matched speed (p < 0.05). 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.
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Affiliation(s)
- Daniel A Baur
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA.
| | - Katherine G Baur
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA
| | - Beverley K Buchanan
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA
| | - Miles J Ortiz
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA
| | - Abaigeal G Doody
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA
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Bordonie NC, Saunders MJ, de Zevallos JO, Kurti SP, Luden ND, Crance JH, Baur DA. Dietary nitrate supplementation enhances heavy load carriage performance in military cadets. Eur J Appl Physiol 2023; 123:91-102. [PMID: 36175576 DOI: 10.1007/s00421-022-05056-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 09/20/2022] [Indexed: 01/07/2023]
Abstract
PURPOSE To determine the effects of dietary nitrate (NO3-) supplementation on physiological responses, cognitive function, and performance during heavy load carriage in military cadets. METHODS Ten healthy males (81.0 ± 6.5 kg; 180.0 ± 4.5 cm; 56.2 ± 3.7 ml·kg·min-1 VO2max) consumed 140 mL·d-1 of beetroot juice (BRJ; 12.8 mmol NO3-) or placebo (PL) for six d preceding an exercise trial, which consisted of 45 min of load carriage (55% body mass) at 4.83 km·h-1 and 1.5% grade, followed by a 1.6-km time-trial (TT) at 4% grade. Gas exchange, heart rate, and perceptual responses were assessed during constant-load exercise and the TT. Cognitive function was assessed immediately prior to, during, and post-exercise via the psychomotor vigilance test (PVT). RESULTS Post-TT HR (188 ± 7.1 vs. 185 ± 7.4; d = 0.40; p = 0.03), mean tidal volume (2.15 ± 0.27 vs. 2.04 ± 0.23; p = 0.02; d = 0.47), and performance (770.9 ± 78.2 s vs. 809.8 ± 61.4 s; p = 0.03; d = 0.63) were increased during the TT with BRJ versus PL. There were no effects of BRJ on constant-load gas exchange or perceptual responses, and cognitive function was unchanged at all time points. CONCLUSION BRJ supplementation improves heavy load carriage performance in military cadets possibly as a result of attenuated respiratory muscle fatigue, rather than enhanced exercise economy.
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Affiliation(s)
- Nicholas C Bordonie
- Department of Kinesiology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Michael J Saunders
- Department of Kinesiology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Joaquin Ortiz de Zevallos
- Department of Kinesiology, School of Health and Human Development, University of Virginia, Charlottesville, VA, 22904, USA
| | - Stephanie P Kurti
- Department of Kinesiology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Nicholas D Luden
- Department of Kinesiology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Jenny H Crance
- Infirmary, Virginia Military Institute, Lexington, VA, 24450, USA
| | - Daniel A Baur
- Department of Human Performance and Wellness, Virginia Military Institute, 208 Cormack Hall, Lexington, VA, 24450, USA.
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Faghy MA, Shei R, Armstrong NCD, White M, Lomax M. Physiological impact of load carriage exercise: Current understanding and future research directions. Physiol Rep 2022; 10:e15502. [PMID: 36324291 PMCID: PMC9630762 DOI: 10.14814/phy2.15502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 09/18/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022] Open
Abstract
Load carriage (LC) refers to the use of personal protective equipment (PPE) and/or load-bearing apparatus that is mostly worn over the thoracic cavity. A commonplace task across various physically demanding occupational groups, the mass being carried during LC duties can approach the wearer's body mass. When compared to unloaded exercise, LC imposes additional physiological stress that negatively impacts the respiratory system by restricting chest wall movement and altering ventilatory mechanics as well as circulatory responses. Consequently, LC activities accelerate the development of fatigue in the respiratory muscles and reduce exercise performance in occupational tasks. Therefore, understanding the implications of LC and the effects specific factors have on physiological capacities during LC activity are important to the implementation of effective mitigation strategies to ameliorate the detrimental effects of thoracic LC. Accordingly, this review highlights the current physiological understanding of LC activities and outlines the knowledge and efficacy of current interventions and research that have attempted to improve LC performance, whilst also highlighting pertinent knowledge gaps that must be explored via future research activities.
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Affiliation(s)
- Mark A. Faghy
- Biomedical Research Theme, School of Human SciencesUniversity of DerbyDerbyUK
| | - Ren‐Jay Shei
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of MedicineUniversity of Alabama at BirminghamBirminghamAlabamaUSA
| | - Nicola C. D. Armstrong
- Defence Science and Technology LaboratorySalisburyUK
- Extreme Environments Laboratory, School of Sport, Health and Exercise ScienceUniversity of PortsmouthPortsmouthUK
| | - Mark White
- Rocky Mountain University of Health ProfessionsProvoUtahUSA
| | - Mitch Lomax
- Extreme Environments Laboratory, School of Sport, Health and Exercise ScienceUniversity of PortsmouthPortsmouthUK
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Del Vecchio AR, Matthews EL, Sullivan W, Hosick PA. Oxygen Consumption and Blood Pressure Are Not Influenced by Use of a Backpack Hip Strap. Wilderness Environ Med 2022; 33:290-295. [PMID: 35778332 DOI: 10.1016/j.wem.2022.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 04/25/2022] [Accepted: 05/05/2022] [Indexed: 11/15/2022]
Abstract
INTRODUCTION Several studies have explored the effect of backpack carriage on physiologic responses while walking, but few have focused specifically on the influence of the use of a hip strap on these responses. The aim of this study was to investigate the effect of a backpack hip strap on physiologic responses when walking at a moderate intensity while carrying a backpack with a standardized relative load of 30% of the wearer's body mass. METHODS Twenty-three healthy, active participants carrying backpacks walked on a treadmill at a speed and grade that elicited 40-50% of their heart rate reserve. Participants completed 2 counterbalanced 30-min trials, one with the hip strap in the strapped condition and one with the hip strap unfastened. Metabolic, heart rate, blood pressure, and muscle oxygen saturation (SmO2) responses were recorded during both trials. For each variable, 5-min intervals were averaged at baseline, 5, 10, 15, 20, 25, and 30 min. A repeated measures ANOVA test was used to evaluate the differences between the conditions at each time point. Data reported are the values from the final 5-min interval (30 min) and are reported as mean±SD. RESULTS No differences were found between strapped and unstrapped trials for oxygen consumption (strapped 21.9±4.2 mL·kg-1·min-1; unstrapped 22.0±4.4 mL·kg-1·min-1, P=0.842), Δmean arterial pressure (strapped +5±17 Δmm Hg; unstrapped +12±14 Δmm Hg, P=0.128) or muscle oxygen saturation of the quadriceps (strapped 86±15%; unstrapped 90±12%, P=0.359) and calf (strapped 73±19%; unstrapped 81±12%, P=0.888). CONCLUSIONS These results suggest that wearing a hip strap does not influence physiologic responses up to 30 min of moderate intensity walking while carrying 30% of the wearer's mass.
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Affiliation(s)
- Angelica R Del Vecchio
- Department of Exercise Science and Physical Education. Montclair State University, Montclair, New Jersey
| | - Evan L Matthews
- Department of Exercise Science and Physical Education. Montclair State University, Montclair, New Jersey
| | - William Sullivan
- Department of Exercise Science and Physical Education. Montclair State University, Montclair, New Jersey
| | - Peter A Hosick
- Department of Exercise Science and Physical Education. Montclair State University, Montclair, New Jersey.
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Scales J, Coleman D, Brown M. Multiday load carriage decreases ability to mitigate ground reaction force through reduction of ankle torque production. APPLIED ERGONOMICS 2022; 101:103717. [PMID: 35202961 DOI: 10.1016/j.apergo.2022.103717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 01/20/2022] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
The aim of this study was to examine the impact of backpack load carriage on lower limb strength and loading rate change in a cohort that match military recruit profiles. Twenty-six participants walked on a treadmill either carrying a military load carriage system (32 kg) or unloaded for 2 h on two consecutive days. Participants ground reaction forces and strength measures were assessed using a force platform and dynamometry, respectively. Testing included assessments before and after treadmill walking on days one and two, and 24 h following day 2. When assessed by mixed methods ANOVA (alpha: 0.05) statistically significant interaction effects were observed for loading peak (p = 0.031), loading rate (p = 0.035) and plantarflexor torque dynamometry variables at 60°s-1 (p = 0.011) and 120°s-1 (p = 0.024). Repeated measures correlation highlighted associations between plantarflexor torque at 60°s-1 and loading rate (r = -0.901, p < 0.001). Load carriage reduced lower limb torque which did not recover between days. Plantarflexor torque reductions were associated with increases in loading rate. Practitioners should consider that load bearers are more likely to experience lower limb injury during multi-day load carriage. Future work should develop protocols to reduce plantarflexor torque loss in order to reduce ground reaction force change.
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Affiliation(s)
- James Scales
- Canterbury Christ Church University, North Holmes Road, Canterbury Kent, CT1 1QU, UK.
| | - Damian Coleman
- Canterbury Christ Church University, North Holmes Road, Canterbury Kent, CT1 1QU, UK
| | - Mathew Brown
- Canterbury Christ Church University, North Holmes Road, Canterbury Kent, CT1 1QU, UK
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7
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Vine CAJ, Coakley SL, Blacker SD, Doherty J, Hale BJ, Walker EF, Rue CA, Lee BJ, Flood TR, Knapik JJ, Jackson S, Greeves JP, Myers SD. Accuracy of Metabolic Cost Predictive Equations During Military Load Carriage. J Strength Cond Res 2022; 36:1297-1303. [PMID: 32398631 DOI: 10.1519/jsc.0000000000003644] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
ABSTRACT Vine, CA, Coakley, SL, Blacker, SD, Doherty, J, Hale, B, Walker, EF, Rue, CA, Lee, BJ, Flood, TR, Knapik, JJ, Jackson, S, Greeves, JP, and Myers, SD. Accuracy of metabolic cost predictive equations during military load carriage. J Strength Cond Res 36(5): 1297-1303, 2022-To quantify the accuracy of 5 equations to predict the metabolic cost of load carriage under ecologically valid military speed and load combinations. Thirty-nine male serving infantry soldiers completed thirteen 20-minute bouts of overground load carriage comprising 2 speeds (2.5 and 4.8 km·h-1) and 6 carried equipment load combinations (25, 30, 40, 50, 60, and 70 kg), with 22 also completing a bout at 5.5 km·h-1 carrying 40 kg. For each speed-load combination, the metabolic cost was measured using the Douglas bag technique and compared with the metabolic cost predicted from 5 equations; Givoni and Goldman, 1971 (GG), Pandolf et al. 1997 (PAN), Santee et al. 2001 (SAN), American College of Sports Medicine 2013 (ACSM), and the Minimum-Mechanics Model (MMM) by Ludlow and Weyand, 2017. Comparisons between measured and predicted metabolic cost were made using repeated-measures analysis of variance and limits of agreement. All predictive equations, except for PAN, underpredicted the metabolic cost for all speed-load combinations (p < 0.001). The PAN equation accurately predicted metabolic cost for 40 and 50 kg at 4.8 km·h-1 (p > 0.05), underpredicted metabolic cost for all 2.5 km·h-1 speed-load combinations as well as 25 and 30 kg at 4.8 km·h-1, and overpredicted metabolic cost for 60 and 70 kg at 4.8 km·h-1 (p < 0.001). Most equations (GG, SAN, ACSM, and MMM) underpredicted metabolic cost while one (PAN) accurately predicted at moderate loads and speeds, but overpredicted or underpredicted at other speed-load combinations. Our findings indicate that caution should be applied when using these predictive equations to model military load carriage tasks.
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Affiliation(s)
- Christopher A J Vine
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Sarah L Coakley
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Sam D Blacker
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Julianne Doherty
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Beverley J Hale
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Ella F Walker
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Carla A Rue
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Ben J Lee
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Tessa R Flood
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
| | - Joseph J Knapik
- Fitness, Injury, and Performance Analysis, Peach Bottom, Pennsylvania, United States of America
| | - Sarah Jackson
- Army Personnel Research Capability, Army HQ, Andover, United Kingdom ; and
| | - Julie P Greeves
- Norwich Medical School, University of East Anglia, Norwich, United Kingdom
| | - Stephen D Myers
- Occupational Performance Research Group, Institute of Sport, University of Chichester, Chichester, United Kingdom
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James S, Damian C, Mathew B. Energy cost and knee extensor strength changes following multiple day military load carriage. APPLIED ERGONOMICS 2021; 97:103503. [PMID: 34237588 DOI: 10.1016/j.apergo.2021.103503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 06/10/2021] [Accepted: 06/11/2021] [Indexed: 06/13/2023]
Abstract
Military exercises and recruit training requires soldiers, including new recruits, to undergo multiple days of substantial physical stress. The aim of this study was to evaluate the physiological impact of multiple days of military load carriage by addressing the hypothesis: A second day of load carriage increases oxygen uptake and reduces knee extensor torque compared to a single day of load carriage. A load carriage group (n = 12) (carrying 32 kg) and unloaded group (n = 14) walked on a treadmill for 2 h on two consecutive days. Knee extensor and flexor torque were assessed by dynamometry at speeds of: 0°·s-1,60°·s-1 and 180°·s-1 before and after load carriage on day one and two, and 24 h following day 2. Oxygen uptake was assessed via respiratory gas assessment at the 6th and 119th minute of load carriage on day one and two. When assessed by mixed methods ANOVA (alpha: 0.05), an interaction effect was observed for oxygen uptake (p < 0.001), with post hoc assessment highlighting second day of load carriage significantly increased oxygen uptake compared to day one post in the loaded group (28.9(3.0) vs 25.8(3.4), p = 0.048). An interaction effect was observed for all knee extensor variables (all p < 0.05). All knee extensor peak torque variables were significantly associated to oxygen uptake at 0°s-1 (r = -0.576, p < 0.05), 60°s-1 (r = -0.552, p < 0.05), and 180°s-1 (r = -0.589, p < 0.05). Two days of load carriage significantly increases oxygen uptake and reduces knee extensor and flexor torque compared to a single day of load carriage. Subsequently, physical training programmes aimed at increasing knee extensor strength may protect against increases in oxygen uptake.
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Affiliation(s)
- Scales James
- Canterbury Christ Church University, North Holmes Road, Canterbury, Kent, CT1 1QU, UK.
| | - Coleman Damian
- Canterbury Christ Church University, North Holmes Road, Canterbury, Kent, CT1 1QU, UK
| | - Brown Mathew
- Canterbury Christ Church University, North Holmes Road, Canterbury, Kent, CT1 1QU, UK
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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. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18084010. [PMID: 33920426 PMCID: PMC8069713 DOI: 10.3390/ijerph18084010] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 04/04/2021] [Accepted: 04/07/2021] [Indexed: 11/16/2022]
Abstract
Soldiers are often required to carry heavy loads that can exceed 45 kg. The physiological costs and biomechanical responses to these loads, whilst varying with the contexts in which they are carried, have led to soldier injuries. These injuries can range from musculoskeletal injuries (e.g., joint/ligamentous injuries and stress fractures) to neurological injuries (e.g., paresthesias), and impact on both the soldier and the army in which they serve. Following treatment to facilitate initial recovery from injuries, soldiers must be progressively reconditioned for load carriage. 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.
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Affiliation(s)
- Robin Orr
- Tactical Research Unit, Bond University, Gold Coast 4213, Australia; (R.P.); (J.J.K.)
- Correspondence: ; Tel.: +61-5595-5530
| | - Rodney Pope
- Tactical Research Unit, Bond University, Gold Coast 4213, Australia; (R.P.); (J.J.K.)
- School of Community Health, Charles Sturt University, Albury 2640, Australia
| | - Thiago Jambo Alves Lopes
- Research Laboratory of Exercise Science, Centro de Educação Física Almirante Adalberto Nunes, Brazilian Navy, Rio de Janeiro 21941-901, Brazil;
- Post-Graduation Program in Operational Human Performance/PPGDHO, Brazilian Air Force, University of the Air Force, Rio de Janeiro 21941-901, Brazil
| | - Dieter Leyk
- Research Group Epidemiology of Performance, German Sport University Cologne, 50933 Cologne, Germany;
- Bundeswehr Institute for Preventive Medicine, 56626 Andernach, Germany
| | - Sam Blacker
- Occupational Performance Research Group, Institute of Sport, University of Chichester, West Sussex PO19 6PE, UK;
| | - Beatriz Sanz Bustillo-Aguirre
- Ministry of Defence, Paseo de la Castellana 109, 28046 Madrid, Spain;
- Universidad San Pablo-CEU, CEU Universities, Avenida Montepríncipe s/n, Bohadilla del Monte, 28668 Madrid, Spain
| | - Joseph J. Knapik
- Tactical Research Unit, Bond University, Gold Coast 4213, Australia; (R.P.); (J.J.K.)
- United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA
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10
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Orr RM, Robinson J, Hasanki K, Talaber KA, Schram B, Roberts A. The Relationship Between Strength Measures and Task Performance in Specialist Tactical Police. J Strength Cond Res 2020; 36:757-762. [DOI: 10.1519/jsc.0000000000003511] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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11
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Treweek AJ, Tipton MJ, Milligan GS. Development of a physical employment standard for a branch of the UK military. ERGONOMICS 2019; 62:1572-1584. [PMID: 31486718 DOI: 10.1080/00140139.2019.1663271] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 08/23/2019] [Indexed: 06/10/2023]
Abstract
A Physical Employment Standard (PES) was developed for the British Royal Air Force Regiment (RAF Regt). Twenty-nine RAF Regt personnel completed eight critical tasks wearing Combat Equipment Fighting Order (31.5 kg) while being monitored for physical and perceptual effort. A PES was developed using task simulations, measured on 61 incumbents. The resultant PES consists of: 1) a battlefield test involving task simulations: single lift and point-of-entry (psss/fail); timed elements (react to effective enemy fire and crawl) set at 95th performance percentile; casualty evacuation (CASEVAC) casualty drag and CASEVAC simulated stretcher carry completed without stopping. 2) a Multi Stage Fitness Test level 9.10 to assess aerobic fitness to complete a tactical advance to battle. The task-based PES should ensure RAF Regt personnel have a baseline level of fitness to perform and withstand the physical demands of critical tasks to at least a minimum acceptable standard. Practitioner summary: A Physical Employment Standard (PES) was developed for the British RAF Regiment by measuring the physiological demands of critical tasks on a representative cohort of incumbent personnel. A task-based PES should ensure that only those candidates, irrespective of gender, race or disability, with the necessary physical attributes to succeed in training and beyond, are selected.
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Affiliation(s)
- Anthony J Treweek
- SO2 Physical Training Research, Air Command, RAF High Wycombe , Buckinghamshire , UK
| | - Michael J Tipton
- Exercise and Health Department, Department of Sport and Exercise Science, Portsmouth University , Hampshire , UK
| | - Gemma S Milligan
- Exercise and Health Department, Department of Sport and Exercise Science, Portsmouth University , Hampshire , UK
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Thomas R, Schram B, Irving S, Robinson J, Orr R. Associations between Specialist Tactical Response Police Unit Selection Success and Urban Rush, along with 2.4 km and 10 km Loaded Carriage Events. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16193558. [PMID: 31547573 PMCID: PMC6801417 DOI: 10.3390/ijerph16193558] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 09/07/2019] [Accepted: 09/17/2019] [Indexed: 11/16/2022]
Abstract
Officers serving in specialist tactical response police teams are highly trained personnel who are required to carry heavy loads and perform explosive tasks. The aim of this study was to determine whether performance on a loaded explosive occupational task (urban rush) or distance-based load carriage tasks (2.4 km or 10 km) were indicative of officer success on a specialist selection course (SSC). Eighteen male police officers (mean age = 32.11 ± 5.04 years) participated in the SSC over five consecutive days. Data were categorized into Group 1 (successful applicants, n = 11) and Group 2 (unsuccessful applicants, n = 7). Independent sample t-tests were performed to determine differences between groups, along with point-biserial correlations to investigate associations between anthropometric and event performance data and course completion success. Alpha levels were set at p = 0.05 a priori. Height (p = 0.025), body weight (p = 0.007), and 2.4 km loaded performance (p = 0.013) were significantly different between groups, where being shorter (rpb(16) = −0.526, p < 0.05), lighter (rpb(16) = −0.615, p < 0.01), and faster (rpb(16) = −0.572, p < 0.05) were associated with course success. While a loaded 2.4 km event is associated with success, a ceiling effect for an explosive anaerobic task and a longer 10 km task may exist, whereby increases in performance are not associated with selection success.
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Affiliation(s)
- Rhiannon Thomas
- Physiotherapy Department, Faculty of Health Sciences and Medicine, Bond University, Gold Coast 4226, Australia.
| | - Ben Schram
- Physiotherapy Department, Faculty of Health Sciences and Medicine, Bond University, Gold Coast 4226, Australia.
- Tactical Research Unit, Bond University, Gold Coast 4226, Australia.
| | - Shane Irving
- Tactical Research Unit, Bond University, Gold Coast 4226, Australia.
| | | | - Robin Orr
- Physiotherapy Department, Faculty of Health Sciences and Medicine, Bond University, Gold Coast 4226, Australia.
- Tactical Research Unit, Bond University, Gold Coast 4226, Australia.
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Scales J, Coleman D, O’Driscoll J, Brown M. Characteristics of torque production of the lower limb are significantly altered after 2 hours of treadmill load carriage. TRANSLATIONAL SPORTS MEDICINE 2018. [DOI: 10.1002/tsm2.54] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
| | | | | | - Mathew Brown
- Canterbury Christ Church University; Canterbury UK
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Boffey D, Harat I, Gepner Y, Frosti CL, Funk S, Hoffman JR. The Physiology and Biomechanics of Load Carriage Performance. Mil Med 2018; 184:e83-e90. [DOI: 10.1093/milmed/usy218] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 08/09/2018] [Indexed: 11/12/2022] Open
Affiliation(s)
- David Boffey
- Sport and Exercise Science, University of Central Florida, Orlando, FL
| | - Idan Harat
- Sport and Exercise Science, University of Central Florida, Orlando, FL
| | - Yftach Gepner
- Sport and Exercise Science, University of Central Florida, Orlando, FL
| | - Cheyanne L Frosti
- Sport and Exercise Science, University of Central Florida, Orlando, FL
| | - Shany Funk
- Israel Defense Forces, Combat Fitness Branch, Netanya, Israel
| | - Jay R Hoffman
- Sport and Exercise Science, University of Central Florida, Orlando, FL
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL
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Sol JA, Ruby BC, Gaskill SE, Dumke CL, Domitrovich JW. Metabolic Demand of Hiking in Wildland Firefighting. Wilderness Environ Med 2018; 29:304-314. [DOI: 10.1016/j.wem.2018.03.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/13/2018] [Accepted: 03/16/2018] [Indexed: 01/28/2023]
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Chatterjee S, Chatterjee T, Bhattacharyya D, Sen S, Pal M. Effect of heavy load carriage on cardiorespiratory responses with varying gradients and modes of carriage. Mil Med Res 2018; 5:26. [PMID: 30045754 PMCID: PMC6060468 DOI: 10.1186/s40779-018-0171-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 07/06/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The present study was undertaken to determine the effect of different uphill and downhill gradients on cardiorespiratory and metabolic responses of soldiers while carrying heavy military loads in two different modes. METHODS Eight physically fit male soldiers with a mean age 32.0 ± 2.0 years, a mean height of 169.5 ± 4.9 cm, and a mean weight of 63.8 ± 8.4 kg volunteered for this study. Each volunteer completed treadmill walking trials at a speed of 3.5 km/h while carrying no external load, 31.4 kg load in a distributed mode (existing load carriage ensembles) and compact mode (new back pack) over 5 different downhill and uphill gradients (- 5, - 10%, 0, 5, 10%) for 6 min at each gradient. During the walking trials, heart rate (HR), oxygen uptake (VO2), respiratory frequency (RF) and energy expenditure (EE) were determined by the process of breath-by-breath gas analysis using a K4b2 system. The average of the last 2 min data from each 6 min walking trial for each individual was subjected to statistical analysis. RESULTS All parameters (HR, VO2, RF, and EE) gradually increased with the change in gradient from downhill to level to uphill. The distributed mode showed higher values compared to compact mode for all gradients, e.g., for VO2, there was a 10.7, 7.4, 5.1, 28.2 and 18.7% increase in the distributed mode across the 5 different gradients. CONCLUSION It can be concluded from the present study that the compact mode of load carriage is more beneficial than the distributed mode in terms of cardiorespiratory responses while walking on downhill and uphill surfaces with a 31.4 kg load.
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Affiliation(s)
- Subhojit Chatterjee
- Defence Institute of Physiology and Allied Sciences, Defence Research & Development Organisation, Ministry of Defence, Government of India, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Tirthankar Chatterjee
- Defence Institute of Physiology and Allied Sciences, Defence Research & Development Organisation, Ministry of Defence, Government of India, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Debojyoti Bhattacharyya
- Defence Institute of Physiology and Allied Sciences, Defence Research & Development Organisation, Ministry of Defence, Government of India, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Suranjana Sen
- Defence Institute of Physiology and Allied Sciences, Defence Research & Development Organisation, Ministry of Defence, Government of India, Lucknow Road, Timarpur, Delhi, 110054, India
| | - Madhusudan Pal
- Defence Institute of Physiology and Allied Sciences, Defence Research & Development Organisation, Ministry of Defence, Government of India, Lucknow Road, Timarpur, Delhi, 110054, India.
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Colosio AL, Pogliaghi S. Quantification of energy expenditure of military loaded runs: what is the performance of laboratory-based equations when applied to the field environment? J ROY ARMY MED CORPS 2018; 164:253-258. [DOI: 10.1136/jramc-2017-000887] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 02/15/2018] [Accepted: 02/16/2018] [Indexed: 11/04/2022]
Abstract
IntroductionPerformance during army loaded runs provides a synthetic indicator of a soldier’s capacity to move while carrying loads and thereby remain able to execute a mission. The aim of this study was to estimate and compare the energy expenditure (EE) of army loaded runs, conducted in a field environment using laboratory-based equations and HR index (HRindex).Methods45 Ranger recruits had HR monitored during three loaded runs (10, 15 and 20 km) in full military equipment in the field environment. EE was calculated using reference equations (EE-Eq) and estimates of oxygen consumption based on HRindex (EE-HRindex). Correspondence between EE-Eq and EE-HRindex estimates was evaluated using a two-way analysis of variance, correlation test and Bland-Altman analysis.ResultsEE-Eq relative to time and weight was significantly higher for the 10 km (0.175±0.016) compared with 15 and 20 km (0.163±0.016 and 0.160±0.013 kcal/kg/min, not different). The overall EE-Eq increased significantly with distance (1129±59, 1703±80 and 2250±115 kcal for 10, 15 and 20 km). EE-Eq was not different from and highly correlated with EE-HRindex, with a small and non-significant bias and good precision between methods.ConclusionsOur study provides the first comprehensive data on HR and EE during long-distance loaded army runs, in full combat equipment, in actual field conditions. Equation-based estimates of EE during these heavy-intensity activities were not significantly different from and highly correlated with HR-based estimates. This corroborates the general applicability of the predictive equations in the field environment. Furthermore, our study suggests that time-resolved HR-based estimates of EE during army runs can be used to evaluate for the effects of context specificity, individual variability and fatigue in movement economy.
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Physiological and Biomechanical Responses to Prolonged Heavy Load Carriage During Level Treadmill Walking in Females. J Appl Biomech 2017; 33:248-255. [DOI: 10.1123/jab.2016-0185] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Heavy load carriage has been identified as a main contributing factor to the high incidence of overuse injuries in soldiers. Peak vertical ground reaction force (VGRFMAX) and maximal vertical loading rates (VLRMAX) may increase during heavy prolonged load carriage with the development of muscular fatigue and reduced shock attenuation capabilities. The objectives of the current study were (1) to examine physiological and biomechanical changes that occur during a prolonged heavy load carriage task, and (2) to examine if this task induces neuromuscular fatigue and changes in muscle architecture. Eight inexperienced female participants walked on an instrumented treadmill carrying operational loads for 60 minutes at 5.4 km·h–1. Oxygen consumption (), heart rate, rating of perceived exertion (RPE), trunk lean angle, and ground reaction forces were recorded continuously during task. Maximal force and in-vivo muscle architecture were assessed pre- and posttask. Significant increases were observed for VGRFMAX, VLRMAX, trunk lean angle,, heart rate, and RPE during the task. Increased vastus lateralis fascicle length and decreased maximal force production were also observed posttask. Prolonged heavy load carriage, in an inexperienced population carrying operational loads, results in progressive increases in ground reaction force parameters that have been associated with overuse injury.
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Dames KD, Smith JD. Effects of load carriage and footwear on lower extremity kinetics and kinematics during overground walking. Gait Posture 2016; 50:207-211. [PMID: 27649512 DOI: 10.1016/j.gaitpost.2016.09.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 09/08/2016] [Accepted: 09/09/2016] [Indexed: 02/02/2023]
Abstract
Kinetic and kinematic responses during walking vary by footwear condition. Load carriage also influences gait patterns, but it is unclear how an external load influences barefoot walking. Twelve healthy adults (5 women, 7 men) with no known gait abnormalities participated in this study (age=23±3years, height=1.73±0.11m, and mass=70.90±12.67kg). Ground reaction forces and 3D motion were simultaneously collected during overground walking at 1.5ms-1 in four conditions: Barefoot Unloaded, Shod Unloaded, Barefoot Loaded, and Shod Loaded. Barefoot walking reduced knee and hip joint ranges of motion, as well as stride length, stance time, swing time, and double support time. Load carriage increased stance and double support times. The 15% body weight load increased GRFs ∼15%. Walking barefoot reduced peak anteroposterior GRFs but not peak vertical GRFs. Load carriage increased hip, knee, and ankle joint moments and powers, while walking barefoot increased knee and hip moments and powers. Thus, spatiotemporal and kinematic adjustments to walking barefoot decrease GRFs but increase knee and hip kinetic measures during overground walking. The ankle seems to be less affected by these footwear conditions. Regardless of footwear, loading requires larger GRFs, joint loads, and joint powers.
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Affiliation(s)
- Kevin D Dames
- Kinesiology Department, SUNY Cortland, 1164 Professional Studies Building, Cortland, NY, 13045, USA.
| | - Jeremy D Smith
- School of Sport and Exercise Science, University of Northern Colorado, Campus Box 39, Greeley, CO 80639, USA
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Drain J, Billing D, Neesham-Smith D, Aisbett B. Predicting physiological capacity of human load carriage - a review. APPLIED ERGONOMICS 2016; 52:85-94. [PMID: 26360198 DOI: 10.1016/j.apergo.2015.07.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 06/07/2015] [Accepted: 07/07/2015] [Indexed: 06/05/2023]
Abstract
This review article aims to evaluate a proposed maximum acceptable work duration model for load carriage tasks. It is contended that this concept has particular relevance to physically demanding occupations such as military and firefighting. Personnel in these occupations are often required to perform very physically demanding tasks, over varying time periods, often involving load carriage. Previous research has investigated concepts related to physiological workload limits in occupational settings (e.g. industrial). Evidence suggests however, that existing (unloaded) workload guidelines are not appropriate for load carriage tasks. The utility of this model warrants further work to enable prediction of load carriage durations across a range of functional workloads for physically demanding occupations. If the maximum duration for which personnel can physiologically sustain a load carriage task could be accurately predicted, commanders and supervisors could better plan for and manage tasks to ensure operational imperatives were met whilst minimising health risks for their workers.
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Affiliation(s)
- Jace Drain
- Land Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, 3207, Australia.
| | - Daniel Billing
- Land Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, 3207, Australia
| | - Daniel Neesham-Smith
- Centre for Exercise and Sports Science, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, 3125, Australia
| | - Brad Aisbett
- Centre for Exercise and Sports Science, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, 3125, Australia
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Nightingale TE, Walhin JP, Thompson D, Bilzon JLJ. Influence of accelerometer type and placement on physical activity energy expenditure prediction in manual wheelchair users. PLoS One 2015; 10:e0126086. [PMID: 25955304 PMCID: PMC4425541 DOI: 10.1371/journal.pone.0126086] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 03/30/2015] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To assess the validity of two accelerometer devices, at two different anatomical locations, for the prediction of physical activity energy expenditure (PAEE) in manual wheelchair users (MWUs). METHODS Seventeen MWUs (36 ± 10 yrs, 72 ± 11 kg) completed ten activities; resting, folding clothes, propulsion on a 1% gradient (3,4,5,6 and 7 km·hr-1) and propulsion at 4km·hr-1 (with an additional 8% body mass, 2% and 3% gradient) on a motorised wheelchair treadmill. GT3X+ and GENEActiv accelerometers were worn on the right wrist (W) and upper arm (UA). Linear regression analysis was conducted between outputs from each accelerometer and criterion PAEE, measured using indirect calorimetry. Subsequent error statistics were calculated for the derived regression equations for all four device/location combinations, using a leave-one-out cross-validation analysis. RESULTS Accelerometer outputs at each anatomical location were significantly (p < .01) associated with PAEE (GT3X+-UA; r = 0.68 and GT3X+-W; r = 0.82. GENEActiv-UA; r = 0.87 and GENEActiv-W; r = 0.88). Mean ± SD PAEE estimation errors for all activities combined were 15 ± 45%, 14 ± 50%, 3 ± 25% and 4 ± 26% for GT3X+-UA, GT3X+-W, GENEActiv-UA and GENEActiv-W, respectively. Absolute PAEE estimation errors for devices varied, 19 to 66% for GT3X+-UA, 17 to 122% for GT3X+-W, 15 to 26% for GENEActiv-UA and from 17.0 to 32% for the GENEActiv-W. CONCLUSION The results indicate that the GENEActiv device worn on either the upper arm or wrist provides the most valid prediction of PAEE in MWUs. Variation in error statistics between the two devices is a result of inherent differences in internal components, on-board filtering processes and outputs of each device.
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Affiliation(s)
- Tom Edward Nightingale
- Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom
| | - Jean-Philippe Walhin
- Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom
| | - Dylan Thompson
- Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom
| | - James Lee John Bilzon
- Centre for DisAbility Sport and Health (DASH), Department for Health, University of Bath, Bath, Somerset, United Kingdom
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22
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Faghy MA, Brown PI. Preloaded Time Trial to Assess Load Carriage Performance. J Strength Cond Res 2014; 28:3354-62. [DOI: 10.1519/jsc.0000000000000555] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Mullins AK, Annett LE, Drain JR, Kemp JG, Clark RA, Whyte DG. Lower limb kinematics and physiological responses to prolonged load carriage in untrained individuals. ERGONOMICS 2014; 58:770-780. [PMID: 25428772 DOI: 10.1080/00140139.2014.984775] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The aim of this study was to simultaneously assess the changes in physiology, and kinematic and spatiotemporal features of gait, during prolonged load carriage in individuals without load carriage experience. Eleven males, representative of new military recruits, walked for 120 min at 5.5 km h(- 1), 0% grade, on a motorised treadmill while carrying a 22 kg load. The load ( ≤ 30% body mass) was distributed over a weighted vest, combat webbing and replica model firearm, to reflect a patrol order load. Oxygen consumption and heart rate increased throughout the trial; however, apart from a minor increase in step length, there were no changes in the kinematic or spatiotemporal parameters, despite an increase in perceived exertion and discomfort. These data suggest that individuals with no experience in load carriage are able to maintain normal gait during 2 h of fixed speed walking, while carrying a patrol order load ≤ 30% body mass.
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Affiliation(s)
- Alexandra K Mullins
- a School of Exercise Science, Australian Catholic University , Melbourne, Fitzroy VIC 3065 , Australia
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Blacker SD, Williams NC, Fallowfield JL, Willems MET. The effect of a carbohydrate beverage on the physiological responses during prolonged load carriage. Eur J Appl Physiol 2011; 111:1901-8. [PMID: 21234592 DOI: 10.1007/s00421-010-1822-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 12/27/2010] [Indexed: 10/18/2022]
Abstract
Effects of a carbohydrate beverage on the physiological responses to load carriage were examined. Ten fit male participants (age: 28 ± 9 years, body mass: 81.5 ± 10.5 kg, VO(2max): 55.0 ± 5.5 mL kg(-1) min(-1)) completed two test conditions in random order, walking on a treadmill (6.5 km h(-1)) for 120 min, carrying a 25-kg backpack. At 0 and 60 min of exercise participants consumed 250 mL of a placebo (flavoured water) (PLA) or 6.4% carbohydrate (CHO) beverage. There were no differences in VO(2,) respiratory exchange ratio (RER), heart rate or EMG activity of m. rectus femoris, m. vastus lateralis, m. semitendinosus and m. biceps femoris between conditions at minute 5 of exercise. The increase in VO(2) between minutes 5 and 120 was less during CHO than PLA (8 ± 5 vs. 14 ± 6%, P = 0.036). RER decreased during PLA, from 0.96 ± 0.05 at minute 5 to 0.87 ± 0.04 at minute 120 (P < 0.001), but not during CHO (P = 0.056). Heart rate increased between minutes 5 and 120 during PLA (16 ± 10%, P < 0.001) and CHO (12 ± 6%, P < 0.001), with no difference between conditions (P = 0.251). EMG peak RMS did not change between minutes 7 and 107 during PLA or CHO for the leg muscles. However, individual responses in EMG were highly variable (i.e. both increases and decreases in RMS). It was concluded that carbohydrate intake during load carriage reduced the VO(2) drift, which could be partially attributed to higher carbohydrate oxidation rates. Despite muscle fatigue/damage previously being identified as a cause of VO(2) drift, it appears that carbohydrate had no effect on neuromuscular responses during load carriage.
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Affiliation(s)
- Sam D Blacker
- Department of Sport and Exercise Sciences, University of Chichester, College Lane, Chichester, West Sussex, PO19 6PE, UK.
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Blacker SD, Williams NC, Fallowfield JL, Bilzon JL, Willems ME. Carbohydrate vs protein supplementation for recovery of neuromuscular function following prolonged load carriage. J Int Soc Sports Nutr 2010; 7:2. [PMID: 20157419 PMCID: PMC2821364 DOI: 10.1186/1550-2783-7-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 01/12/2010] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND This study examined the effect of carbohydrate and whey protein supplements on recovery of neuromuscular function after prolonged load carriage. METHODS TEN MALE PARTICIPANTS (BODY MASS: 81.5 +/- 10.5 kg, age: 28 +/- 9 years, O(2)max: 55.0 +/- 5.5 ml.kg(-1).min(-1)) completed three treadmill walking tests (2 hr, 6.5 km.h(-1)), carrying a 25 kg backpack consuming 500 ml of either: (1) Placebo (flavoured water) [PLA], (2) 6.4% Carbohydrate Solution [CHO] or (3) 7.0% Whey Protein Solution [PRO]. For three days after load carriage, participants consumed two 500 ml supplement boluses. Muscle performance was measured before and at 0, 24, 48 and 72 h after load carriage, during voluntary and electrically stimulated contractions. RESULTS Isometric knee extension force decreased immediately after load carriage with no difference between conditions. During recovery, isometric force returned to pre-exercise values at 48 h for CHO and PRO but at 72 h for PLA. Voluntary activation decreased immediately after load carriage and returned to pre-exercise values at 24 h in all conditions (P = 0.086). During recovery, there were no differences between conditions for the change in isokinetic peak torque. Following reductions immediately after load carriage, knee extensor and flexor peak torque (60 degrees .s(-1)) recovered to pre-exercise values at 72 h. Trunk extensor and flexor peak torque (15 degrees .s(-1)) recovered to pre-exercise values at 24 h (P = 0.091) and 48 h (P = 0.177), respectively. CONCLUSION Recovery of neuromuscular function after prolonged load carriage is improved with either carbohydrate or whey protein supplementation for isometric contractions but not for isokinetic contractions.
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Affiliation(s)
- Sam D Blacker
- University of Chichester, Faculty of Sport, Education and Social Sciences, West Sussex, UK
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