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Prado-Nóvoa O, Rodríguez J, Zorrilla-Revilla G, Vidal-Cordasco M, Mateos A. Evaluating the human capacity of carrying loads without costs: A scoping review of the Free-Ride phenomenon. Am J Hum Biol 2022; 34:e23794. [PMID: 36056617 DOI: 10.1002/ajhb.23794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/26/2022] [Accepted: 07/28/2022] [Indexed: 01/25/2023] Open
Abstract
OBJECTIVES Several researchers have obtained discordant results testing the human capability to transport loads without added locomotion costs. Carrying loads has an extended relevance to human ecology, thus a review of the Free-Ride phenomenon detection according to the existing literature is needed. METHOD A search was made in November 2021 in SCOPUS, Google Scholar, and Web of Science to identify studies comparing the energy expenditure of loaded and unloaded locomotion. Descriptive percentages were calculated with the data obtained from each study, and a Chi-squared (χ2 ) independency test and a contingency table were applied to observe the relationship between sample characteristics, experimental procedures, and the detection of the Free-Ride. RESULTS A total of 45 studies met the inclusion criteria. Eighty two percent do not detect the Free-Ride phenomenon. The general detection is independent of sex, experience, load position, load size, and speed (p value >.05) although the papers detecting the Free-Ride have some common characteristics. CONCLUSION The literature does not support a Free-Ride capacity, but future research testing this phenomenon should consider the load size, the load position, the level of expertise, or the speed. As the Free-Ride is not generalizable, it can be hypothesized that other mechanisms may have emerged during human evolution to buffer the energetic demands of load carrying.
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Affiliation(s)
- Olalla Prado-Nóvoa
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK
| | - Jesús Rodríguez
- National Research Center on Human Evolution (CENIEH), Burgos, Spain
| | | | - Marco Vidal-Cordasco
- EvoAdapta Research group, Department of Historical Sciences, University of Cantabria, Santander, Spain
| | - Ana Mateos
- National Research Center on Human Evolution (CENIEH), Burgos, Spain
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Hudson S, Vanwanseele B, Barwood M, Low C, Cooke C, Lloyd R. The energetic, kinematic and kinetic responses to load carried on the back, on the head and in a doublepack. ERGONOMICS 2021; 64:1191-1204. [PMID: 33830853 DOI: 10.1080/00140139.2021.1909754] [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: 09/21/2020] [Accepted: 03/22/2021] [Indexed: 06/12/2023]
Abstract
The determinants of energy saving phenomena reported for load carried on the head, back and in a doublepack remain unclear. This study compared the energetic, kinematic and kinetic responses to head (H), back (B) and doublepack (DP) loading. Fifteen volunteers walked on an instrumented treadmill at 3 km.h-1 with 0, 3, 12 and 20 kg in each loading method. Whole body motion, ground reaction forces (GRF) and metabolic cost were measured. H was less economical than B (p = 0.014) and DP (p = 0.010). H was also associated with increased step length (p = 0.045), decreased cadence (p = 0.001), greater trunk (p < 0.001) and hip (p < 0.001) extension and greater minimum vertical GRF (p = 0.001) than B and DP. In conclusion, no energy saving was found for head- or back-loading but economy may be improved with methods that cause smaller perturbations from unloaded walking. Practitioner summary: Energy saving phenomena have been reported for load carried on the head, back and in a doublepack, yet the determinants are unclear. This study shows that smaller perturbations from unloaded to loaded walking are associated with improved economy for certain load carriage conditions, such as the doublepack.
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Affiliation(s)
- Sean Hudson
- School of Human and Health Sciences, University of Huddersfield, Huddersfield, UK
| | | | - Martin Barwood
- School of Social and Health Sciences, Leeds Trinity University, Leeds, UK
| | - Chris Low
- Carnegie School of Sport, Leeds Beckett University, Leeds, UK
| | - Carlton Cooke
- Carnegie School of Sport, Leeds Beckett University, Leeds, UK
| | - Ray Lloyd
- School of Social and Health Sciences, Leeds Trinity University, Leeds, UK
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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; 185:e1168-e1174. [PMID: 32248224 DOI: 10.1093/milmed/usaa050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/17/2020] [Accepted: 03/05/2020] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION The ability to carry heavy loads is an important and necessary task during numerous outdoor activities and especially in military operations. The aim of this study was to investigate factors associated with load-carrying ability in men and women with and without extensive load-carrying experience. MATERIALS AND METHODS The energy expenditure during carrying no load, 20, 35, and 50 kg at 2 walking speeds, 3 and 5 km h-1, was studied in 36 healthy participants, 19 men (30 ± 6 years, 82.5 ± 7.0 kg) and 17 women (29 ± 6 years, 66.1 ± 8.9 kg), experienced (>5 years) in carrying heavy loads (n = 16, 8 women) or with minor or no such experience (n = 20, 9 women). A standard backpack filled with weights to according carry load was used during the walks. Anthropometric data, leg muscle strength, as well as trunk muscle endurance and muscle fiber distribution of the thigh, were also obtained. Extra Load Index (ELI)-the oxygen uptake (VO2) during total load over unloaded walking-was used as a proxy for load-carrying ability at 20, 35, and 50 kg (ELI20, ELI35, and ELI50, respectively). In addition to analyzing factors of importance for the ELI values, we also conducted mediator analyses using sex and long-term carrying experience as causal variables for ELI as the outcome value. The study was approved by the Regional Ethics Committee in Stockholm, Sweden. RESULTS For the lowest load (20 kg), ELI20, was correlated with body mass but no other factors. Walking with 35 and 50 kg load at 5 km h-1 body mass, body height, leg muscle strength, and absolute VO2max were correlated, while relative VO2max, trunk muscle endurance, and leg muscle fiber distribution were not correlated to ELI35 and ELI50.ELI50 at 5 km h-1 differed between the sexes. This difference was only mediated by the difference in body mass. Neither muscle fiber distribution, leg muscle strength, trunk muscle endurance, and body height nor did absolute or relative VO2max explain the difference.Participants with long-term experience of heavy load carrying had significant lower ELI20 and ELI50 values than those with minor or no experience, but none of the above studied factors could explain this difference. 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.
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Affiliation(s)
- Manne Godhe
- Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden
| | - Torbjörn Helge
- Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden
| | - C Mikael Mattsson
- Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden
| | - Örjan Ekblom
- Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden
| | - Björn Ekblom
- Åstrand Laboratory of Work Physiology, The Swedish School of Sport and Health Sciences, P.O. Box 5626, SE-114 86 Stockholm, Sweden
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Hudson S, Cooke C, Davies S, West S, Gamieldien R, Low C, Lloyd R. Inter-individual variability in load carriage economy and comparisons between different load conditions. APPLIED ERGONOMICS 2020; 82:102968. [PMID: 31600713 DOI: 10.1016/j.apergo.2019.102968] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 09/29/2019] [Accepted: 09/30/2019] [Indexed: 06/10/2023]
Abstract
Equivocal findings exist for the economy associated with load carried close to the body's centre of mass. Individual variation could explain some of the equivocal findings. This research aimed to examine the extent of individual variation in loaded walking economy. Eighteen females carried load on the back, head and split between the front and back. Individual variation in relative load carriage economy (ELI) was primarily assessed using standard deviation, coefficients of variation (CV) and intraclass correlation coefficients (ICC). There was large inter-individual variation in ELI values with highest mean CV's of 16%, 12% and 10% for head-, back- and combined front and back-loading. Mean ELI values were not significantly different between methods. The large amount of individual variation found here suggests future load carriage research should account for individual variation, particularly when considering sample size and when making inferences on the economy associated with different types of load carriage using group mean data.
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Affiliation(s)
- Sean Hudson
- University of Huddersfield, Huddersfield, Yorkshire, UK.
| | | | - Simeon Davies
- Cape Peninsula University of Technology, Cape Town, South Africa
| | - Sacha West
- Cape Peninsula University of Technology, Cape Town, South Africa
| | - Raeeq Gamieldien
- Cape Peninsula University of Technology, Cape Town, South Africa
| | - Chris Low
- Leeds Beckett University, Leeds, Yorkshire, UK
| | - Ray Lloyd
- Leeds Trinity University, Leeds, Yorkshire, UK
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Prado-Nóvoa O, Rodríguez J, Vidal-Cordasco M, Zorrilla-Revilla G, Mateos A. No sex differences in the economy of load-carriage. Am J Hum Biol 2019; 32:e23352. [PMID: 31675143 DOI: 10.1002/ajhb.23352] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 08/09/2019] [Accepted: 09/30/2019] [Indexed: 11/07/2022] Open
Abstract
OBJECTIVES Load transport activities are of vital importance to current foragers for daily subsistence tasks; thus, it has been suggested that these practices have transformed physical and behavioral characteristics through human evolution. Together with the procurement targets and strategies, the transportation of resources acquired while foraging is strongly influenced by the sex of the foragers. In hunter-gatherer societies, women, despite their smaller body size, usually carry heavier burdens than males. In this study, whether those behavioral differences can be explained by a different economy of load-carriage by sex, irrespective of the body mass of the individuals, is investigated. MATERIAL AND METHODS The energy expenditure of a sample of 48 volunteers (21 females, 27 males) during a set of locomotion and burden transport trials was monitored. Two indexes were computed to compare the increment in the cost of locomotion relative to the load carried by sex. RESULTS The results demonstrate that both males and females, carrying the same relative loads, experience the same increment over the cost of their unloaded locomotion. Therefore, apart from obvious differences in body mass, there is no evidence of a dissimilar economy favoring one sex over the other that would explain the differences in load-carriage activities observed among current foraging populations. CONCLUSIONS These outcomes provide new conclusions about the constraints of the behavioral ecology of burden transport activities, and highlight the necessity to reevaluate, from an evolutionary perspective, the ideas about the sexual division of subsistence labor in hunter-gatherer and agriculturalist populations.
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Affiliation(s)
| | - Jesús Rodríguez
- National Research Center on Human Evolution (CENIEH), Burgos, Spain
| | | | | | - Ana Mateos
- National Research Center on Human Evolution (CENIEH), Burgos, Spain
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Hudson S, Cooke C, Davies S, West S, Gamieldien R, Low C, Lloyd R. A comparison of economy and sagittal plane trunk movements among back-, back/front- and head-loading. ERGONOMICS 2018; 61:1216-1222. [PMID: 29757714 DOI: 10.1080/00140139.2018.1474267] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 05/02/2018] [Indexed: 06/08/2023]
Abstract
It has been suggested that freedom of movement in the trunk could influence load carriage economy. This study aimed to compare the economy and sagittal plane trunk movements associated with three load carriage methods that constrain posture differently. Eighteen females walked at 3 km.h-1 with loads of 0, 3, 6, 9, 12, 15 and 20 kg carried on the back, back/front and head. Load carriage economy was assessed using the Extra Load Index (ELI). Change in sagittal plane trunk forward lean and trunk angle excursion from unloaded to loaded walking were assessed. Results show no difference in economy between methods (p = .483), despite differences in the change in trunk forward lean (p = .001) and trunk angle excursion (p = .021) from unloaded to loaded walking. We conclude that economy is not different among the three methods of load carriage, despite significant differences in sagittal plane trunk movements. Practitioner summary: This article shows, based on mean data, that there is no difference in economy among back, back/front and head-loading, despite differences in trunk movement. It is possible a combination of factors align to influence individual economy, rather than a single set of factors, applicable to all individuals for each method.
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Affiliation(s)
- Sean Hudson
- a School of Social and Health Sciences , Leeds Trinity University , Leeds , UK
| | - Carlton Cooke
- a School of Social and Health Sciences , Leeds Trinity University , Leeds , UK
| | - Simeon Davies
- b Department of Sport Management, Cape Peninsula University of Technology , Cape Town , South Africa
| | - Sacha West
- b Department of Sport Management, Cape Peninsula University of Technology , Cape Town , South Africa
| | - Raeeq Gamieldien
- b Department of Sport Management, Cape Peninsula University of Technology , Cape Town , South Africa
| | - Chris Low
- c Carnegie School of Sport, Leeds Beckett University , Leeds , UK
| | - Ray Lloyd
- a School of Social and Health Sciences , Leeds Trinity University , Leeds , UK
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Hudson S, Cooke C, Lloyd R. The reliability of the Extra Load Index as a measure of relative load carriage economy. ERGONOMICS 2017; 60:1250-1254. [PMID: 28092227 DOI: 10.1080/00140139.2017.1282629] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/07/2017] [Indexed: 06/06/2023]
Abstract
The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h-1, 6 km·h-1 and a self-selected speed. Trial conditions were repeated 7 days later to assess test-retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy. Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.
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Affiliation(s)
- Sean Hudson
- a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK
| | - Carlton Cooke
- a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK
| | - Ray Lloyd
- a School of Social and Health Sciences, Leeds Trinity University , Leeds , UK
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Porter G, Hampshire K, Dunn C, Hall R, Levesley M, Burton K, Robson S, Abane A, Blell M, Panther J. Health impacts of pedestrian head-loading: A review of the evidence with particular reference to women and children in sub-Saharan Africa. Soc Sci Med 2013; 88:90-7. [DOI: 10.1016/j.socscimed.2013.04.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 04/05/2013] [Accepted: 04/08/2013] [Indexed: 11/29/2022]
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