Physiological and perceptual responses of SANDF personnel to varying combinations of marching speed and backpack load
- Authors: Christie, Candice Jo-Anne
- Date: 2002
- Subjects: Marching -- Physiological aspects , Walking -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5128 , http://hdl.handle.net/10962/d1005207 , Marching -- Physiological aspects , Walking -- Physiological aspects
- Description: The objective of the present study was to establish effective combinations of marching speed and backpack load in order to meet specific military requirements. Thirty infantrymen from the South African National Defence Force (SANDF) comprised the sample and experimental procedures were conducted in a laboratory setting using a Cybex Trotter treadmill. Sixteen conditions were set up which included combinations of four speeds (3.5, 4.5, 5.5, and 6.5 km.h⁻¹) and four backpack loads (20, 35, 50, and 65kg). Each subject was required to complete 8 of the sixteen conditions, each consisting of a six-minute treadmill march. Physiological data (heart rate, ventilation and metabolic responses), kinematic gait responses (step-rate and stride length) and perceptions of exertion (“Central” and “Local” RPE) were collected during the third and sixth minutes of the treadmill march and areas of body discomfort were identified post-march. Responses revealed five distinct categories of exertional strain. Three marches constituted “nominal” (below 40% VO₂max) and three “excessive” strain (above 75% VO₂ max). These represent combinations of extreme military demands and are highly unlikely to be utilised by the military. Three “tolerable” levels of required effort were recommended and these 10 combinations were further divided into three sub-categories. The “moderate” stress marches were identified as “ideal” for prolonged marches and had statistically similar responses of working heart rates (range of 118 bt.min⁻¹ to 127 bt.min⁻¹), energy expenditure (26 kJ.min⁻¹ and 27 kJ.min⁻¹) and ratings of perceived exertion (“Central” ratings of 10 and 11). Thus, marching at 5.5 km.h⁻¹with 20kg, 4.5 km.h⁻¹ with 35kg or 3.5 km.h⁻¹ with 50kg all require a similar energy cost. Four “heavy” category marches were identified for possible use when the duration of the march is reduced. During these marches responses were statistically similar with heart rates ranging from 127 bt.min⁻¹ to 137 bt.min⁻¹, energy expenditure from 32 kJ.min⁻¹ to 37 kJ.min⁻¹ and “Central” ratings of perceived exertion were 12 and 13. When short, high intensity marches are necessary, then combinations from the “very heavy” category may be utilised but with caution. During these marches, soldiers were taxed between 65% and 75% of VO2 max. The results of this study clearly demonstrate that the interplay between speed and load needs to be adjusted when determining “ideal” combinations for specific military demands. Essentially, if speed is of the essence then load must be reduced, and if heavy loads need to be transported then speed must be reduced.
- Full Text:
Economy and efficiency of human locomotion
- Authors: Goslin, Brian Richard
- Date: 1985
- Subjects: Walking -- Physiological aspects , Running -- Physiological aspects , Human locomotion
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5142 , http://hdl.handle.net/10962/d1007177 , Walking -- Physiological aspects , Running -- Physiological aspects , Human locomotion
- Description: Human locomotor economy and efficiency are highly variable. This study investigated the role that stature plays in this variation, by evaluating metabolic and respiratory responses to walking and running at speeds set relative to one's stature. Four groups of subjects: male, high V0₂ max (n = 11); male, average V0₂ max (n = 10); female, high V0₂ max (n = 10); and female, average V0₂ max (n = 11) were habituated to treadmill locomotion prior to the measurement of maximal oxygen consumption (V0₂ max). The V0₂ max test entailed 1 km.h⁻¹ increases per min from 3 to 6 km.h⁻¹ walking, and 7 - 17 km.h⁻¹ running then 1% grade increments per min until exhaustion. On each of four other occasions, the subject walked or ran at 6 of a variety of relative speeds - walking at 0.5, 0.7, 0.9, 1.1, 1.3; running at 1.5, 1.7, 1.9 and for selected subjects 2.1, 2.3 and 2.5 statures.s⁻¹ ,and grades - 0%, +3%, -3%. Steady-state respiratory and metabolic responses, and treadmill speed were monitored by an on-line computer system developed for this study. Cadence and RPE were also monitored. All subjects demonstrated an exponential relationship between V0₂ and walking relative speed (st.s⁻¹) (RS) . V0₂ (ml.kg⁻¹.min⁻¹ ) = 4.747 * e(1.371*RS) During running this relationship was essentially linear . The variability of economy at relative speed (9.08%) and absolute speed (9. 01%) did not differ. Male and female subjects did not differ in response to absolute speed but females were more economical at relative speeds (p<0.05). Those with high and average aerobic capacity did not differ in locomotor economy at relative speed. Higher freely-chosen stride length was associated with a higher V0₂ response as velocity increased. The V0₂ of uphill walking was 1.4 times greater than that for downhill walking (running: 1.28 times) . Stride length decreased with increasing speed in uphill locomotion but the reverse was the case for downhill. The economy and efficiency of walking was greater than that of running. Walking economy was maximal between 0.7 and 0.9 st. s⁻¹. Running economy remained essentially unaffected by increased velocity. The setting of locomotor velocity relative to stature does not minimize inter-subject variability in metabolic and respiratory response .
- Full Text: