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.
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Energetic and kinematic responses to morphology-normalised speeds of walking and running
- Authors: Williams, Martin Andrew
- Date: 1989
- Subjects: Running -- Physiological aspects , Walking -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5166 , http://hdl.handle.net/10962/d1016240
- Description: This study investigated the influence of human morphology upon selected physiological, biomechanical and psychological responses to horizontal locomotion. In so doing, it was possible to evaluate the effectiveness with which morphology-normalised speeds of walking and running reduced the between-subject variability that is inherent in human locomotor responses. Twenty caucasian males were divided into two groups on the basis of stature - ten subjects in each of a "short" category (<170cm) and a "tall" category (>185cm). All subjects were habituated to treadmill locomotion prior to exposure to three walking treatments (0.83, 1.39 and 1.94m.s⁻¹) and three running treatments (2.50, 3.06 and 3.61m.s⁻¹). During each of these five-minute locomotor conditions, energetic (V02), kinematic (cadence and stride length) and psychophysical (central and local RPE) data were captured. From these data, lines of best fit were calculated for each subject, allowing for a prediction of the abovementioned locomotor variables from known absolute rates of progression. Using suitable regression equations, subject responses to morphology-normalised speeds of walking and running were effectively extrapolated. When the rate of progression was expressed in absolute terms (m.s⁻¹), significant differences (P <0.05) were found between the stature-related groups with respect to both energetic and kinematic locomotor responses. Such differences were successfully eliminated when use was made of locomotor speeds relativised on the basis of morphology. This study concludes that the use of appropriately prescribed morphology-normalised rates of progression are effective in reducing the variability in locomotor responses between subjects differing significantly in stature.
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The effects of relative speed on selected physiological, kinematic and psychological responses at walk-to-run and run-to-walk interfaces.
- Authors: Candler, Paul David
- Date: 1987
- Subjects: Walking -- Physiological aspects , Running -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5164 , http://hdl.handle.net/10962/d1016081
- Description: [Conclusions] l) The two forms of human locomotion, walking and running, are distinctly different and in evaluating these gait patterns consideration must be given to this fact. 2) The impression created by the energy cost curves, that there is a single locomotor interface for both walking and running is a false one . There are two distinctly different locomotor interfaces, the walk-to-run interface and the run-to-walk interface. The former appears to correspond with the "metabolic intersection point" and therefore has some metabolic significance. The latter appears to be merely an "overshoot" of the walk-to-run interface and presently has no apparent metabolic significance. 3) Because the walk-to-run interface speed corresponds with the intersection point of the energy cost curves, physiological responses to walking and running at this speed do not differ significantly. However, cadence and stride length patterns for these two locomotor patterns are distinctly different at this point. 4) The identification of single physiological or kinematic factors during perceptions of exertion in any given situation is an extremely difficult if not impossible task. Perceived exertion should therefore be considered a multi-factorial concept and should be evaluated as such. 5) The use of relative speed as a technique for reducing inter-subject variability in physiological and kinematic factors is worthless unless diverse ranges in morphological linearity are a characteristic of one's subject pool
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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 .
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