Influences of body composition upon the relative metabolic and cardiovascular demands of load-carriage (original) (raw)
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Effects of load carriage on physiological determinants in adventure racers
PLOS ONE
Adventure racing athletes need run carrying loads during the race. A better understanding of how different loads influence physiological determinants in adventure racers could provide useful insights to gauge training interventions to improve running performance. We compare the maximum oxygen uptake (VO2max), the cost of transport (C) and ventilatory thresholds of twelve adventure running athletes at three load conditions: unloaded, 7 and 15% of body mass. Twelve healthy men experienced athletes of Adventure Racing (age 31.3 ± 7.7 years, height 1.81 ± 0.05 m, body mass 75.5 ± 9.1 kg) carried out three maximal progressive (VO2max protocol) and three submaximal constant-load (running cost protocol) tests, defined in the following quasi-randomized conditions: unloaded, 7% and, 15% of body mass. The VO2max (unload: 59.7 ± 5.9; 7%: 61.7 ± 6.6 and 15%: 64.6 ± 5.4 ml kg-1 min-1) did not change among the conditions. While the 7% condition does neither modify the C nor the ventilatory thresholds, the 15% condition resulted in a higher C (5.2 ± 0.9 J kg-1 m-1 ; P = 0.001; d = 1.48) than the unloaded condition (4.0 ± 0.7 J kg-1 m-1). First ventilatory threshold was greater at 15% than control condition (+15.5%; P = 0.003; d = 1.44). Interestingly, the velocities on the severe-intensity domain (between second ventilatory threshold and VO2max) were reduced 1% equivalently to 1% increasing load (relative to body mass). The loading until 15% of body mass seems to affect partially the crucial metabolic and ventilatory parameters, specifically the C but not the VO2max. These findings are compatible with the concept that interventions that enhance running economy with loads may improve the running performance of adventure racing's athletes.
Cardio-Respiratory and Metabolic Changes during Continuous Uphill-Downhill Load Carriage Task
Department of Human Physiology with Community Health , Vidyasagar University , Midnapore , West Bengal, 2015
Indian Army soldiers are deployed in hilly and mountainous regions of eastern and western part of the Himalayas to guard the borders. In this context they are required to march uphill and downhill with moderate to heavy load continuously for long duration. The physiological cost of such activities has been of specific interest for maintenance of optimum soldier performance. Studies on physiological changes during continuous uphill and downhill climbing are rare. A study was therefore undertaken to find the effect of uphill and downhill walk with load on the physiological parameters in laboratory conditions. Twelve soldiers with mean (± SD) age-26.8 (± 3.9) yrs, height-170.6 (± 3.2) cm and weight 66.2 (± 6.8) kg participated in the study as volunteers to measure the energy cost and physiological changes of continuous uphill and downhill load carriage task. The soldiers were subjected to treadmill walking at a speed of 3 km/ h. They had to undergo continuous uphill walking at 0, 5, 10, 15 and 20% gradients and downhill walking in the opposite manner. Participants walked 6 mins in each gradient. Total duration of walk was 60 min. The volunteers carried 10.7 and 21.4 kg load beside without load. Oxygen consumption (VO 2), Heart rate (HR), and energy expenditure (EE), were measured breath by breath using Metamax 3B system throughout the test. Relative work load (RWL, %VO 2 max) was calculated as percentage of VO 2 max. Repeated measure ANOVAs were used to predict level of significance across the experimental conditions. The mean (± SD) VO 2 max of the participants was found to be 52.6 (± 3.8) ml/min/kg. All the physiological parameters increased significantly with the increase in uphill gradient irrespective of the loads. VO 2 , EE and %VO 2 max decreased till 5% downhill gradient, but slight increase was observed at the level walking. HR continued to decrease till the downhill walking reached 0% gradient with and without load. Relative work load reached above the recommended limit (35% of VO 2 max) at 10% and above uphill gradients in both the load conditions. This information will be helpful in making strategy for designing uphill and downhill load march in mountains for Army personnel and hitch hikers.
Physiological factors of importance for load carriage
2017
The energy expenditure during carrying no load, 20, 35 and 50 kg at two walking speeds, 3 and 5 km/h, was studied in 36 healthy participants, 19 men (30 ± 6 yrs, 82.5 ± 7.0 kg) and 17 women (29 ± 6 yrs, 66.1 ± 8.9 kg). Anthropometric data, leg muscle strength as well as trunk muscle endurance and muscle fibre distribution of the thigh were also obtained. To load the participant a standard backpack filled with extra weight according to the carrying weight tested was used. Extra Load Index (ELI), the oxygen uptake (VO2) during total load over no-load-exercise, was used as a proxy for load carrying ability. In addition to analyzing factors of importance for the ELI values, we also conducted mediator analyzes using sex and long term carrying experience as causal variables for ELI as the outcome value. For the lowest load (20 kg), ELI20, was correlated with body mass but no other factors. Walking at 5 km/h body mass, body height, leg muscle strength and absolute VO2max were correlated to...
Influence of body mass on maximal oxygen uptake: effect of sample size
European Journal of Applied Physiology, 2001
Basal metabolic rate is scaled to body mass to the power of 0.73, and we evaluated whether a similar scaling applies when the O 2 transport capacity of the body is challenged during maximal exercise (i.e. at maximal O 2 uptake, _ V O 2max ). The allometric relationship between _ V O 2max and body mass (y a á x b , where y is _ V O 2max and x is body mass) was developed for 967 athletes representing 25 dierent sports, with up to 157 participants in each sport. With an increasing number of observations, the exponent approached 0.73, while for ventilation the exponent was only 0.55. By using the 0.73 exponent for _ V O 2max , the highest value [mean (SD)] for the males was obtained for the runners and cyclists [234 (16) ml á kg )0.73 á min )1 ], and for the females the highest value was found for the runners [189 (14) ml á kg )0.73 á min )1 ]. For the females, aerobic power was about 80% of the value achieved by the males. Scaling may help both in understanding variation in aerobic power and in de®ning the physiological limitations of work capacity.
Military Medical Research
Background: The present study was undertaken to determine the effect of different uphill and downhill gradients on cardiorespiratory and metabolic responses of soldiers while carrying heavy military loads in two different modes. Methods: Eight physically fit male soldiers with a mean age 32.0 ± 2.0 years, a mean height of 169.5 ± 4.9 cm, and a mean weight of 63.8 ± 8.4 kg volunteered for this study. Each volunteer completed treadmill walking trials at a speed of 3.5 km/h while carrying no external load, 31.4 kg load in a distributed mode (existing load carriage ensembles) and compact mode (new back pack) over 5 different downhill and uphill gradients (− 5, − 10%, 0, 5, 10%) for 6 min at each gradient. During the walking trials, heart rate (HR), oxygen uptake (VO 2), respiratory frequency (RF) and energy expenditure (EE) were determined by the process of breath-by-breath gas analysis using a K4b 2 system. The average of the last 2 min data from each 6 min walking trial for each individual was subjected to statistical analysis. Results: All parameters (HR, VO 2 , RF, and EE) gradually increased with the change in gradient from downhill to level to uphill. The distributed mode showed higher values compared to compact mode for all gradients, e.g., for VO 2 , there was a 10.7, 7.4, 5.1, 28.2 and 18.7% increase in the distributed mode across the 5 different gradients. Conclusion: It can be concluded from the present study that the compact mode of load carriage is more beneficial than the distributed mode in terms of cardiorespiratory responses while walking on downhill and uphill surfaces with a 31.4 kg load.
Military medicine, 2005
This study assessed the metabolic responses of South African soldiers marching at different speeds and carrying varying loads. The main objective was to establish the physiological cost of a range of speed/load combinations to identify the energy requirements to meet a diversity of march objectives. Thirty male soldiers marched on a treadmill for 6 minutes with varying combinations of speed and load, established through numerous pilot studies and in consultation with military personnel. The four speeds were 3.5, 4.5, 5.5, and 6.5 km x (-1), combined with the four loads of 20, 35, 50, and 65 kg, totaling 16 combinations. Each participant completed eight of the 16 conditions, during which the participants wore standardized military gear and were attached to a portable ergospirometer (the Metamax, Cortex, Leipzig, Germany) for the duration of the march. Based on the responses, five discrete categories of speed/load combinations were identified. These combinations were categorized as no...
The studies aimed at determine the effect of body mass index (BMI) on aerobic power (VO2 max) and energy expenditure (EE) during manual operation in primary agro-processing. Selected physiological and anthropometry properties of voluntary group of thirteen subjects were measured with respect to manual lifting of loads through the vertical distance of 0.92m from ankle level to inlet opening of thresher during threshing operation. The measured properties showed that height and weight ranged from 1.65m to 1.83m and 53g to 78g respectively, the calculated BMI ranged from 18.38kg/m 2 to 28.65kg/m 2 . Heart rate at rest (HRrest) and maximum heart rate (HRmax)
Physiological Responses to Body Weight–Supported Treadmill Exercise in Healthy Adults
Archives of Physical Medicine and Rehabilitation, 2011
Objective: To determine whether the relationships of heart rate, rating of perceived exertion (RPE), and ground reaction forces (GRFs) with oxygen consumption rate (V O 2) during treadmill exercise are altered by partial body weight support (BWS) via lower-body positive pressure. Design: Repeated-measures design. Setting: Exercise physiology laboratory. Participants: Healthy, active adults (Nϭ12); mean age Ϯ SD, 45.1Ϯ12.6 years. Interventions: Not applicable. Main Outcome Measures: V O 2 , heart rate, RPE, and GRFs were measured during walking and running at 3 levels (0%, 25%, 50%) of BWS. Before exercise, standing heart rate and blood pressure were measured under each BWS condition. Results: Standing heart rates were 7 beats/min lower (PϽ.05) and systolic blood pressures were 10mmHg higher (PϽ.001) at 50% BWS compared with 0% BWS, but mean blood pressure while standing and the relationship of heart rate with V O 2 during walking and running were not altered by BWS. While walking, the RPE at a V O 2 of 10 mL • kg-1 • min-1 was statistically lower (PϽ.05) at 0% BWS compared with 25% and 50% BWS (mean values, 7 vs 8 points), but RPE was not different among conditions while running at a V O 2 of 25 mL • kg-1 • min-1. Peak normal GRFs at specified V O 2 levels and RPE values were reduced (PϽ.05) with increasing BWS for walking and running. Conclusions: Because partial BWS does not alter the relationship of heart rate with V O 2 during exercise and has minimal effect on the relationship of RPE with V O 2 , training heart rate and RPE values do not appear to require adjustment with partial BWS. Reduced GRFs at specified V O 2 levels from partial BWS suggest that there are important clinical applications of this technology.