Date of Award

2004

Document Type

Thesis

Publisher

Edith Cowan University

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Computing, Health and Science

First Supervisor

Dr Paul B. Laursen

Second Supervisor

Dr Angus Burnett

Abstract

Much of the previous research into understanding fatigue during prolonged cycling has found that endurance performance may be limited by numerous physiological, biomechanical, environmental, mechanical, and psychological factors. From the literature presently available, fatigue would appear to be task- and condition- specific. Studies demonstrating this, however, are limited. The purpose of this thesis, therefore, was to examine variables from multiple fatigue models concurrently to determine which variables were best related to fatigue during prolonged endurance exercise in hot versus cold conditions. Following a 100-km familiarization time trial (22°C) , nine endurance trained male cyclists ( VO2max = 62.1 ± 8.5 ml·kg-1min-1) completed two 100-km time trials, interspersed with five 1-km sprints, and four 4-km sprints, in hot (34°C) and cold (10°C) conditions. Rectal and skin temperatures, muscle activation of the lower limb via integrated electromyography (iEMG), expired gases, as well as blood measures of lactate, glucose, urea, bicarbonate hematocrit, and the electrolytes Na+, K+ and Cl- were measured. Rectal temperature increased significantly in both the hot and cold trials (P<0.001) and was significantly lower in the cold trial at nearly all measurements beyond 28-km (P<0.05; with exception of 62- and 88-km). Power output was significantly lower in the hot trial (22-km; P<0.05) prior to marked differences in rectal temperature (42-km; P0.05). iEMG of biceps femoris and soleus was also significantly lower in the hot trial (22-km and 15-km, respectively; P<0.05) prior to significant differences in rectal temperature. iEMG of vastus lateralis, however, was not significantly different between trials. Mean skin, mean body temperature and perceived thermal sensation were greater in the hot trial compared to the cold (all P<0.001). Blood sodium concentration was significantly lower in the hot trial compared to the cold (P<0.05). Perceived exertion, pain intensity in the quadriceps, heart rate, blood lactate, pH, and glucose concentration were not statistically different between trials. In the cold trial, power output declined during the 1-km and 4-km sprints (P<0.05), while iEMG of vastus latemlis and biceps femoris decreased significantly during 4-km sprints (P

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