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:
- Date Issued: 2002
Physiological and psychophysical responses of male soldiers to changes in marching gradient, speed and load
- Authors: Todd, Andrew Ivan
- Date: 2002
- Subjects: Soldiers -- South Africa -- Physiology , South Africa Army -- Physical training , Marching -- Physiological aspects , Psychophysiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5129 , http://hdl.handle.net/10962/d1005208 , Soldiers -- South Africa -- Physiology , South Africa Army -- Physical training , Marching -- Physiological aspects , Psychophysiology
- Description: The present study sought to investigate the effects of changes in gradient, under apparently optimal combinations of speed and load, on selected physiological, psychophysical and biophysical responses of military personnel. Subjects (n = 32) were required to march under level (0%), downhill (-10%) and uphill (+10%) conditions. Under each gradient, subjects marched with the following speed-load combinations: 4 km.h-1 carrying 50 kg, 5 km.h-1 carrying 35 kg and 6 km.h-1 carrying 20 kg, a total of nine experimental conditions. Subjects were required to march for six minutes under each condition. Physiological responses (HR, VO2, R, Br, VE, VT, EE) indicated that subjects were not overly taxed by the three speed-load combinations during level marching, which elicited submaximal demands. Furthermore, the results revealed that downhill marching with heavy loads results in similar responses to level marching, while lighter loads may result in significant reductions in physical demands compared to level marching. The physiological responses to uphill marching revealed that subjects were severely physically taxed under these conditions, regardless of speed-load combination. It is unlikely that soldiers would be able to maintain these intensities for an extended period without undue fatigue. It is evident from the psychophysical responses (Rating of Perceived Exertion and Body Discomfort) that subjects perceived the heavy load conditions, regardless of gradient, to be the most stressful on the cardiovascular and muscular systems. The positive gradient conditions also elicited elevated RPE and Body Discomfort responses, while lighter load downhill conditions were perceived to result in the least strain.
- Full Text:
- Date Issued: 2002