The effect of temperature, gradient, and load carriage on oxygen consumption, posture, and gait characteristics

Katrina Hinde,Carlton Cooke,Chris Low,Ray Lloyd

doi:10.1007/s00421-016-3531-7

Katrina Hinde, Carlton Cooke + Show 2 more

Open Access

https://doi.org/10.1007/s00421-016-3531-7

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Abstract

PurposeThe purpose of this experiment was to evaluate the effect of load carriage in a range of temperatures to establish the interaction between cold exposure, the magnitude of change from unloaded to loaded walking and gradient.MethodsEleven participants (19–27 years) provided written informed consent before performing six randomly ordered walking trials in six temperatures (20, 10, 5, 0, −5, and −10 °C). Trials involved two unloaded walking bouts before and after loaded walking (18.2 kg) at 4 km · h−1, on 0 and 10% gradients in 4 min bouts.ResultsThe change in absolute oxygen consumption (V̇O2) from the first unloaded bout to loaded walking was similar across all six temperatures. When repeating the second unloaded bout, V̇O2 at both −5 and −10 °C was greater compared to the first. At −10 °C, V̇O2 was increased from 1.60 ± 0.30 to 1.89 ± 0.51 L · min−1. Regardless of temperature, gradient had a greater effect on V̇O2 and heart rate (HR) than backpack load. HR was unaffected by temperature. Stride length (SL) decreased with decreasing temperature, but trunk forward lean was greater during cold exposure.ConclusionDecreased ambient temperature did not influence the magnitude of change in V̇O2 from unloaded to loaded walking. However, in cold temperatures, V̇O2 was significantly higher than in warm conditions. The increased V̇O2 in colder temperatures at the same exercise intensity is predicted to ultimately lead to earlier onset of fatigue and cessation of exercise. These results highlight the need to consider both appropriate clothing and fitness during cold exposure.

Highlights

Recreational trekking and mountaineering is becoming increasingly popular and affordable and activities, such as these, alongside numerous occupational tasks, usually require external loads to be carried
Results from the present study did differ to the previous findings as Oksa et al (2004) reported that heart rate results mirrored those of VO2 at both intensities, whereas our findings showed that heart rate did not change in proportion to changes in VO2 with temperature
The evidence leads to a rejection of the first hypothesis as the results of this investigation show that ambient temperature had no significant effect on the increase in oxygen consumption associated with load carriage

Summary

Introduction

Recreational trekking and mountaineering is becoming increasingly popular and affordable and activities, such as these, alongside numerous occupational tasks, usually require external loads to be carried. Loads can be carried in various ways, but in mountaineering, trekking and military operations, the backpack is recommended as the most versatile, appropriate, and economical method of manual load carriage (Knapik et al 1996). The general consensus regarding energy expenditure when carrying loads on the back is that as load increases, oxygen consumption and. New evidence suggests that during very heavy load carriage (up to 45 kg), the increases in oxygen consumption (VO2) are not proportional to the load mass (Phillips et al 2016a). The energy cost of carrying such loads depends on the weight of the load, and varies depending on the age, ethnicity, body mass of the participant, speed, terrain, and biomechanical factors (Givoni and Goldman 1971; Hainsman 1988; Phillips et al 2016b)

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