Summary
In an experimental study of load carrying the effects of mass (0, 5.4, 10.4 kg) and the type of support (on the shoulder or on waist) on parameters of physiological strain were quantified to determine the factor(s) which limit carrying time. Four categories of strain were investigated: metabolic (in terms of oxygen uptake), cardiovascular (in terms of heart rate), muscular (in terms of EMG activity) and skin pressure under the shoulder straps. Four young male subjects were tested on a treadmill using different combinations of load and speed. While standing, oxygen uptake was not influenced by the type or mass of the backpack, and averaged 10% maximal oxygen uptake. The heart rate increased significantly by 9 beats per min while standing wearing a backpack, independent of type of support or mass of backpack. While walking both the heart rate and the oxygen uptake were significantly influenced by the mass carried, but both types of strain remained below the tolerance limits for prolonged wear. Standing supporting a load did not significantly increase the root mean square value of the EMG signal of the trapezius pars descendens muscle. While walking, load carrying significantly increased the root mean square value, and, converted to force, the largest increase amounted to 2.7% of the maximal force for a load of 10.4 kg suspended from the shoulders. This was below levels of force producing fatigue, which was also indicated by an absence of changes in the median power frequency of the EMG signal. The pressure on the skin under the shoulder straps during load carrying on the shoulders was more than a factor of three times higher than the threshold value for skin and tissue irritation. Load transfer to the waist with a flexible frame reduced the pressures on the skin of the shoulder to far below the threshold value. On basis of these results it was concluded that even with relatively low loads the limiting factor was the pressure on the skin, if a waist belt did not relieve such pressure on the shoulders.
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References
Andersson GBJ, Ortengren R, Herberts PH (1977) Quantitative electromyographic studies of back muscle activity related to posture and loading. Orthop Clin North Am 8:85–95
Åstrand PO, Rodahl K (1986) Textbook of work physiology. Physiological bases of exercise. McGraw-Hill, New York
Björkstén M, Jonsson B (1977) Endurance limit of force in long term intermittent static contractions. Scand J Work Environ Health 3:23–27
Bloon D, Woodhull-McNeal P (1987) Postural adjustments while standing with two types of loaded backpack. Ergonomics 30:1425–1430
Bobet J, Norman RW (1982) Use of the average electromyogram in design evaluation. Investigation of a whole body task. Ergonomics 25:115–1163
Borghols EAM, Dresen MHW, Hollander AP (1978) Influence of heavy weight carrying on the respiratory system during exercise. Eur J Appl Physiol 38:161–169
Cook TM, Neumann DA (1987) The effects of load placement on the EMG activity of the low back muscles during load carrying by men and women. Ergonomics 30:1413–1423
Datta SR, Ramanathan NL (1971) Ergonomic comparison of seven modes of carrying load on the horizontal plane. Ergonomics 14:269–278
Datta SR, Chatterjee BB, Roy BN (1973) The relationship between energy expenditure, pulse rate with body weight, load carrying on the level. Ergonomics 16:507–513
Davies CTM (1968) Limitations to the prediction of maximal oxygen intake from cardiac frequency measurements. J Appl Physiol 24:700–706
Epstein Y, Rosenblum J, Burstein R, Sawka MN (1988) External load can alter energy cost of prolonged exercise. Eur J Appl Physiol 57:243–247
Evans WJ, Winsmann FR, Pandolf KB, Goldmann RF (1980) Self-paced hard work comparing men and women. Ergonomics 23:613–621
Evans OM, Zerbib Y, Farior MH, Monod H (1983) Physiological responses of load holding and load carriage. Ergonomics 26:161–217
Funaski A (1978) Depressant effect of rucksack-induced brachial plexus cord squeeze on endurance of isometric strength and simple reaction time. J Sci Labour 54:373–378
Goldman RF, Iampietro PF (1962) Energy cost of load carriage. J Appl Physiol 17:675–676
Grandjean E (1967) Fitting the task to the man. Taylor Francis, London
Hagberg M (1981) Workload, fatigue in repetitive arm elevations. Ergonomics 24:543–555
Holewijn M (1986) Load carriage a review. Report IZF 1986-28 TNO Institute for Perception, Soesterberg
Holewijn M, Lotens WA (1987) The influence of weight distribution carrying mode on the physical performance. Report IZF 1987-20 TNO Institute for Perception, Soesterberg
Husain T (1953) An experimental study of some pressure effects on tissues with reference to the bedsore problem. J Pathol Bacteriol 66:347–359
Jonsson B (1978) Kinesiology. In: Cobb WA, van Duijn H (eds) Contemporary clinical neurophysiology (EEG Supplement no. 34). Elsevier, Amsterdam
Jørgensen K (1985) Permissible loads based on energy expenditure measurements. Ergonomics 28:365–369
Kadefors R, Kaiser E, Petersen I (1968) Dynamic spectrum analysis of myo-potentials with special reference to muscle fatigue. Electromyography 8:39–74
Kilbom A (1976) Circulatory adaptation during static muscular contractions. A review. Scand J Work Environ Health 2:1–13
Kosiak M, Kubicek WG, Olson M, Danz JN, Kottke FJ (1958) Evaluation of pressure as a factor in the production of ischial ulcers. Arch Phys Med Rehabil 89:623–629
Legg SJ, Mahanty A (1986) Energy cost of backpacking in heavy boots. Ergonomics 29:433–438
Martin PE, Nelson RC (1986) The effects of carried loads on the walking patterns of men and women. Ergonomics 29:119–11202
Michael ED, Hutton KE, Howath SM (1961) Cardio-respiratory responses during prolonged exercise. J Appl Physiol 16:997–1002
Moritani T, Muro M, Kyiama A, Gaffney FA, Parsons D (1986) Electromechanical changes during electrically induced maximal voluntary contractions: surface, intramuscular EMG responses during sustained maximal voluntary contraction. Exp Neurol 88:484–499
Myles WS, Saunders PL (1979) The physiological cost of carrying light, heavy loads. Eur J Appl Physiol 42:125–131
Nag PK, Sen RN (1979) Cardio-respiratory performance of porters carrying loads on a treadmill. Ergonomics 22:897–907
Nag PK, Sebastian NC, Mavlankar MG (1980) Occupational work loads of Indian agricultural workers. Ergonomics 23:91–102
Pandolf KB, Haisman MF, Goldman RF (1976) Metabolic energy expenditure, terrain coefficients for walking on snow. Ergonomics 19:683–690
Pandolf KB, Givonni B, Goldman RF (1977) Predicting energy expenditure with loads while standing or walking very slowly. J Appl Physiol 43:577–581
Pierrynowski MR, Winter DA, Norman RW (1981) Metabolic measures to ascertain the optimal load to be carried by man. Ergonomics 24:393–399
Pimental NA, Pandolf KB (1979) Energy expenditure while standing or walking slowly uphill, downhill with loads. Ergonomics 22:963–970
Pimental NA, Shapiro Y, Pandolf KB (1982) Comparison of uphill, downhill walking, concentric, eccentric cycling. Ergonomics 25:373–380
Rohmert W (1966) Ermittlung von Erholungspausen für statische Arbeit des Menschen. Int Z Angew Physiol Einschl Arbeitsphysiol 18:123–164
Rothner AD, Wilbourn A, Mercer RD (1975) Ruck-sack packing. Pediatrics 56:822–824
Rutenfranz J (1985) Energy expenditure constrained by sex and age. Ergonomics 28:115–118
Sangeorzan BJ, Harrington RM, Wyss CR, Czerniecki JM, Matsen FA (1989) Circulatory and mechanical response of skin to loading. J Orthop Res 7:425–431
Scribano F, Burns M, Barron ER (1970) Design development and fabrication of a personnel armor load profile analyzer. Natick Technical Report AD 711876
Shoenfield J, Shapiro Y, Portugeeze D, Modan M, Sohar E (1977) Maximal backpack load for long distance hiking. J Sports Med 17:147–151
Sjøgaard G, Kiens B, Jørgensen K, Saltin B (1986) Intramuscular pressure EMG and blood flow during low-level prolonged static contraction in man. Acta Physiol Scand 128:475–484
Soule RG, Pandolf KB, Goldman RF (1978) Energy expenditure of heavy load carriage. Ergonomics 21:373–381
Stobbe TJ (1975) The tolerance of subjective discomfort induced by pressure applied to the forearm. Proceedings 19th Annual Meeting Human Factors Society 1975, pp 310–314
Stokes VP, Andersson C, Forssberg H (1989) Rotational and translational movement features of the pelvis and thorax during adult human locomotion. J Biomech 22:43–50
Zipp P, Gessner H, Faber S (1977) Elektrische und Biologische Eigenschaften von Elektrodenpasten. Biomed Tech (Berlin) 22:395–396
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Holewijn, M. Physiological strain due to load carrying. Eur J Appl Physiol 61, 237–245 (1990). https://doi.org/10.1007/BF00357606
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DOI: https://doi.org/10.1007/BF00357606