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Dempsey AM, Yegian AK, Sibson BE, Lieberman DE. The effect of vertical load placement on metabolic rate during loaded walking in humans. ERGONOMICS 2023; 66:849-858. [PMID: 36193633 DOI: 10.1080/00140139.2022.2129096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 09/20/2022] [Indexed: 05/24/2023]
Abstract
We examined the effects of vertical load placement on the metabolic cost of walking. Twelve healthy participants walked on a treadmill with 13.8 and 23.4 kg loads in both high and low vertical positions. Metabolic rate was measured using respirometry. While load position had no effect on the net metabolic rate for the 13.8 kg load, the net metabolic rate with the 23.4 kg load was significantly reduced by 4.3% in the high vertical load position compared to the low vertical load position. Loads carried higher on the trunk were also associated with increased forward trunk lean that reduced the load gravitational moment arm in the sagittal plane suggesting that reduction of fore-aft upper body torques is an energy-saving mechanism during loaded walking. Practitioner Summary: Load placement within a backpack affects the biomechanics of load carriage. We experimentally tested the metabolic cost of high and low load placement during walking and found the high position to be less costly with large loads. Loading high may be the optimal technique for carrying heavy backpacks.
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Affiliation(s)
- Andre M Dempsey
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Andrew K Yegian
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Benjamin E Sibson
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Daniel E Lieberman
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
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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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Sibson BE, Tobolsky VA, Kistner TM, Holowka NB, Jemutai J, Sigei TK, Ojiambo R, Okutoyi P, Lieberman DE. Trunk muscle endurance, strength and flexibility in rural subsistence farmers and urban industrialized adults in western Kenya. Am J Hum Biol 2021; 34:e23611. [PMID: 33988283 DOI: 10.1002/ajhb.23611] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 04/21/2021] [Indexed: 12/25/2022] Open
Abstract
OBJECTIVES High trunk muscle endurance, strength, and moderate flexibility reportedly help maintain musculoskeletal health, but there is evidence for tradeoffs among these variables as well as sex differences in trunk muscle endurance and strength. To test if these observations extend similarly to both men and women in nonindustrial and industrial environments, we investigated intra-individual associations and group and sex differences in trunk muscle endurance, strength, and flexibility among 74 (35 F, 39 M; age range: 18-61 years) adults from the same Kalenjin-speaking population in western Kenya. We specifically compared men and women from an urban community with professions that do not involve manual labor with rural subsistence farmers, including women who frequently carry heavy loads. METHODS Trunk muscle endurance, strength, and flexibility were measured with exercise tests and electromyography (EMG). RESULTS We found a positive correlation between trunk extensor strength and endurance (R = .271, p ≤ .05) and no associations between strength or endurance and flexibility. Rural women had higher trunk extensor and flexor endurance, EMG-determined longissimus lumborum endurance, and trunk extensor strength than urban women (all p ≤ .05). Rural women had higher trunk extensor and flexor endurance than rural men (both p ≤ .05). Urban women had lower trunk flexor and extensor endurance than urban men (both p ≤ .01). CONCLUSIONS High levels of physical activity among nonindustrial subsistence farmers, particularly head carrying among women, appear to be associated with high trunk muscle endurance and strength, which may have important benefits for helping maintain musculoskeletal health.
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Affiliation(s)
- Benjamin E Sibson
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Victoria A Tobolsky
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Timothy M Kistner
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Nicholas B Holowka
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA.,Department of Anthropology, University at Buffalo, Buffalo, New York, USA
| | | | - Timothy K Sigei
- Department of Mathematics, Physics, and Computing, Moi University, Eldoret, Kenya
| | - Robert Ojiambo
- Division of Biomedical Sciences, University of Global Health Equity, Butaro, Rwanda
| | - Paul Okutoyi
- Department of Orthopaedics, Moi University Medical School, Eldoret, Kenya
| | - Daniel E Lieberman
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
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Looney DP, Santee WR, Blanchard LA, Karis AJ, Carter AJ, Potter AW. Cardiorespiratory responses to heavy military load carriage over complex terrain. APPLIED ERGONOMICS 2018; 73:194-198. [PMID: 30098635 DOI: 10.1016/j.apergo.2018.07.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 06/06/2018] [Accepted: 07/17/2018] [Indexed: 06/08/2023]
Abstract
This study examined complex terrain march performance and cardiorespiratory responses when carrying different Soldier loads. Nine active duty military personnel (age, 21 ± 3 yr; height, 1.72 ± 0.07 m; body mass (BM), 83.4 ± 12.9 kg) attended two test visits during which they completed consecutive laps around a 2.5-km mixed terrain course with either a fighting load (30% BM) or an approach load (45% BM). Respiratory rate and heart rate data were collected using physiological status monitors. Training impulse (TRIMP) scores were calculated using Banister's formula to provide an integrated measure of both time and cardiorespiratory demands. Completion times were not significantly different between the fighting and approach loads for either Lap 1 (p = 0.38) or Lap 2 (p = 0.09). Respiration rate was not significantly higher with the approach load than the fighting load during Lap 1 (p = 0.17) but was significantly higher for Lap 2 (p = 0.04). However, heart rate was significantly higher with the approach load versus the fighting load during both Lap 1 (p = 0.03) and Lap 2 (p = 0.04). Furthermore, TRIMP was significantly greater with the approach load versus the fighting load during both Lap 1 (p = 0.02) and Lap 2 (p = 0.02). Trained military personnel can maintain similar pacing while carrying either fighting or approach loads during short mixed terrain marches. However, cardiorespiratory demands are greatly elevated with the approach load and will likely continue to rise during longer distance marches.
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Affiliation(s)
- David P Looney
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA.
| | - William R Santee
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA; Oak Ridge Institute for Science and Education (ORISE), 1299 Bethel Valley Rd, Oak Ridge, TN, 37830, USA
| | - Laurie A Blanchard
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA
| | - Anthony J Karis
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA
| | - Alyssa J Carter
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA
| | - Adam W Potter
- US Army Research Institute of Environmental Medicine (USARIEM), 10 General Green Ave, Natick, MA, 01760, USA
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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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Gómez L, Díaz CA, Orozco GA, García JJ. Dynamic analysis of forces in the lumbar spine during bag carrying. INTERNATIONAL JOURNAL OF OCCUPATIONAL SAFETY AND ERGONOMICS 2017; 24:605-613. [PMID: 28753120 DOI: 10.1080/10803548.2017.1352224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
OBJECTIVE The intervertebral disc supports axial and shear forces generated during tasks such as lifting and carrying weights. The objective of this study was to determine the forces in the lumbar spine of workers carrying a bag on the head, on the shoulder and on the anterior part of the trunk. METHODS Kinematic measurements were recorded for 10 subjects carrying bags of 10, 20 and 25 kg on each of the three aforementioned positions. A simple dynamic model implemented in a custom program was then developed to determine the lumbar forces using the accelerations and positions obtained from the kinematic analysis. RESULTS The analyses yielded a maximum compressive force of 2338.4 ± 422 N when a 25-kg bag was carried on the anterior part of the trunk. CONCLUSION Carrying bags on the anterior part of the trunk generated higher lumbar forces compared to those developed by carrying the bag on the head or on the shoulder. Force levels suggest that this activity represents a moderate risk for the subjects. However, future biomechanical models should be developed to analyze the cumulative effect in the discs when longer periods of time are spent in this activity.
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Affiliation(s)
- Lessby Gómez
- a Escuela de Rehabilitación Humana , Universidad del Valle , Colombia.,b Facultad de Ciencias de la Salud , Universidad Libre-Cali , Colombia
| | - Carlos A Díaz
- c Escuela de Ingeniería Mecánica , Universidad del Valle , Colombia
| | - Gustavo A Orozco
- b Facultad de Ciencias de la Salud , Universidad Libre-Cali , Colombia
| | - José J García
- d Escuela de Ingeniería Civil y Geomática , Universidad del Valle , Colombia
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Muslim K, Nussbaum MA. The effects of a simple intervention on exposures to low back pain risk factors during traditional posterior load carriage. APPLIED ERGONOMICS 2017; 59:313-319. [PMID: 27890142 DOI: 10.1016/j.apergo.2016.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 08/22/2016] [Accepted: 09/08/2016] [Indexed: 06/06/2023]
Abstract
Traditional posterior load carriage (PLC), typically performed without the use of an assistive device, is associated with a high prevalence of low back pain (LBP). However, there are few studies that have evaluated potential interventions to reduce exposures to LBP risk factors. This work examined the effects of a simple, potentially low-cost intervention using an assistive device (i.e., carrying aid) on exposures to factors related to LBP risk during PLC. Torso kinematics and kinetics, slip risk, and ratings of perceived discomfort (RPD) were obtained during simulated PLC on a walkway. Consistent with earlier results, increasing load mass substantially increased torso flexion and lumbosacral flexion moment, as well as RPDs in all anatomical regions evaluated. Using the carrying aid with a higher load placement resulted in substantially lower mean lumbosacral moments when carrying the heaviest load. In contrast, using the carrying aid with a lower load placement resulted in substantially higher torso flexion angles, higher mean lumbosacral moments when carrying heavier loads, and higher peak lumbosacral moments across all load masses. With use of the carrying aid, both higher and lower load placement resulted in significantly lower RPDs in the elbows and hands compared to the control condition. In summary, use of a carrying aid with higher load placement may be beneficial in reducing the risk of LBP during PLC. Future studies are needed, though, to improve the device design and to enhance external validity.
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Affiliation(s)
- Khoirul Muslim
- Industrial Engineering, Institute of Technology Bandung, Bandung, West Java, 40134, Indonesia
| | - Maury A Nussbaum
- Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA, 24061, USA.
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Muslim K, Nussbaum MA. Traditional posterior load carriage: effects of load mass and size on torso kinematics, kinetics, muscle activity and movement stability. ERGONOMICS 2015; 59:99-111. [PMID: 25994335 DOI: 10.1080/00140139.2015.1053538] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 05/14/2015] [Indexed: 06/04/2023]
Abstract
UNLABELLED Traditional posterior load carriage (PLC), done without the use of an assistive device (e.g., backpack), has been associated with low back pain (LBP) development. This study evaluated the effects of important task demands, related to load mass and size, on potential mechanisms linking traditional PLC with LBP. Nine healthy participants completed PLC tasks with three load masses (20%, 35% and 50% of individual body mass) and three load sizes (small, medium and large). Torso kinematics, kinetics, muscle activity and slip risk were evaluated during PLC on a walkway, and torso movement stability was quantified during PLC on a treadmill. Increasing load mass caused increased torso flexion, L5/S1 flexion moment, abdominal muscle activity and torso movement stability in the frontal plane. Increasing load size also caused higher torso flexion, peak torso angular velocity and acceleration, and abdominal muscle activity. Complex interactive effects of load mass and size were found on paraspinal muscle activity and slip risk. Specific task demands, related to load mass and size, may thus influence the risk of LBP during PLC. PRACTITIONER SUMMARY This study examined the effects of load mass and size on low back pain (LBP) risk using intermediary measures derived from torso kinematics, kinetics and muscle activity. Our current findings, along with earlier work, suggest that load mass and size can influence LBP risk, and that use of smaller and light loads may be beneficial during PLC.
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Affiliation(s)
- Khoirul Muslim
- a Industrial Engineering , Institute of Technology Bandung , Bandung , Indonesia
| | - Maury A Nussbaum
- b Department of Industrial and Systems Engineering , Virginia Tech , Blacksburg , USA
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Castillo ER, Lieberman GM, McCarty LS, Lieberman DE. Effects of pole compliance and step frequency on the biomechanics and economy of pole carrying during human walking. J Appl Physiol (1985) 2014; 117:507-17. [DOI: 10.1152/japplphysiol.00119.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study investigates whether a flexible pole can be used as an energy-saving method for humans carrying loads. We model the carrier and pole system as a driven damped harmonic oscillator and predict that the energy expended by the carrier is affected by the compliance of the pole and the ratio between the pole's natural frequency and the carrier's step frequency. We tested the model by measuring oxygen consumption in 16 previously untrained male participants walking on a treadmill at four step frequencies using two loaded poles: one made of bamboo and one of steel. We found that when the bamboo pole was carried at a step frequency 20% greater than its natural frequency, the motions of the centers of mass of the load and carrier were approximately equal in amplitude and opposite in phase, which we predicted would save energy for the carrier. Carrying the steel pole, however, resulted in the carrier and loads oscillating in phase and with roughly equal amplitude. Although participants were less economical using poles than predicted costs using conventional fixed-load techniques (such as backpacks), the bamboo pole was on average 5.0% less costly than the steel pole. When allowed to select their cadence, participants also preferred to carry the bamboo pole at step frequencies of ∼2.0 Hz. This frequency, which is significantly higher than the preferred unloaded step frequency, is most economical. These experiments suggest that pole carriers can intuitively adjust their gaits, or choose poles with appropriate compliance, to increase energetic savings.
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Affiliation(s)
- Eric R. Castillo
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts
| | | | - Logan S. McCarty
- Department of Physics and Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts
| | - Daniel E. Lieberman
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts
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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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Head load carriage and pregnancy in West Africa. Clin Biomech (Bristol, Avon) 2011; 26:889-94. [PMID: 21703740 DOI: 10.1016/j.clinbiomech.2011.05.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 05/19/2011] [Accepted: 05/22/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND The postures of the trunk and of the head relative to the trunk adopted during the specific task of head load carriage were measured for a group of pregnant women and a control group of non-pregnant women because this activity was identified as a risk factor for back pain during pregnancy. METHODS The postural data of the trunk and of the head relative to the trunk were collected using two inclinometer devices and an electrogoniometer, respectively. FINDINGS During walking, the load on the head caused significantly larger upper trunk extension and smaller flexion of the head relative to the trunk. The amplitude of motion of the upper trunk and of the head relative to the trunk, as measured by the standard deviation of walking angles, was found to decrease as a result of carrying a load on the head and compensated by increased motion at the sacrum. Pregnant women showed larger upper trunk movements than their counterpart in the frontal and sagittal planes during the unloaded walking trials. INTERPRETATION These posture modifications were believed to be adopted by the subjects to provide better stability for the load during walking. These prolonged postural strains caused by the trunk being displaced from its normal position can lead to muscle fatigue and ultimately to musculoskeletal injuries. The larger movements of the upper trunk for the pregnant women were hypothesized to be due to the enlarged abdomen of pregnant women as it creates a larger moment about L5/S1 and increases instability.
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Lloyd R, Parr B, Davies S, Cooke C. A kinetic comparison of back-loading and head-loading in Xhosa women. ERGONOMICS 2011; 54:380-391. [PMID: 21491280 DOI: 10.1080/00140139.2011.558636] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The purpose of this study was to compare the kinetic responses associated with ground reaction force measurements to both head-loading and back-loading in a group of Xhosa women. Altogether, 16 women were divided into two groups based on their experience of head-loading. They walked over a force plate in three conditions: unloaded or carrying 20 kg in either a backpack or on their head. The most striking finding was that there was no difference in kinetic response to head-loading as a consequence of previous experience. Considering the differences between the load carriage methods, most changes were consistent with increasing load. Head-loading was, however, associated with a shorter contact time, smaller thrust maximum and greater vertical force minimum than back-loading. Both loading conditions differed from unloaded walking for a number of temporal variables associated with the ground contact phase, e.g. vertical impact peak was delayed whilst vertical thrust maximum occurred earlier. STATEMENT OF RELEVANCE: Consideration of the kinetics of head and back load carriage in African women is important from a health and safety perspective, providing an understanding of the mechanical adaptations associated with both forms of load carriage for a group of people for whom such load carriage is a daily necessity.
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Affiliation(s)
- R Lloyd
- Division of Sport and Exercise Sciences, University of Abertay Dundee, UK.
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Biomechanical Differences Associated with Two Different Load Carriage Systems and their Relationship to Economy. HUMAN MOVEMENT 2011. [DOI: 10.2478/v10038-011-0006-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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