Effect Of Passive-Heat Stress On Muscle Fatigue, Central Activation, And Cortical Excitability

Abstract

2) respectively. The measured variables found to be significantly highly correlated were Tc (r=0.649), Tsk (r=0.691), and HR (r=0.679). While there was no statistical difference in any variable analyzed for betweensessions, it was noted that a few subjects showed about 20-30% difference in PT between the two sessions.CONCLUSION: Physiological responses, as indexed by Tc, Tsk, and HR, in PE user performance testing were highly reproducible and variations in the measurements between the two repeated sessions were not statistically meaningful at the controlled experimental conditions. Factor(s) influencing the differences in PT observed in a few subjects was not clear, but elevation in body temperature did not seem to be responsible in the present study when considering Tc and Tsk. (No relationships reported)PURPOSE: Concurrent and construct validation of the OMNI Thermal Sensation Scale was examined using adult male (n =16) and female (n =5) subjects. METHODS:Subjects were 27.9 ± 4.6 years old, weighed 73.5 ± 15.5 kg, were 174.5 ± 9.4 cm tall and had a maximal oxygen uptake of 50.3 ± 8.3 ml[[Unsupported Character -Symbol Font &#159;]]kg -1 [[Unsupported Character -Symbol Font &#159;]]min -1 . Subjects ingested a thermistor capsule for the measurement of core temperature (Tc) approximately 8 hrs before the experimental trial. Weighted mean skin temperature (Tsk) was calculated using the following formula: Tsk = chest (0.25) + back (0.25) + thigh (0.30) + arm (0.20). Concurrent validity was established by correlating OMNI thermal sensation ratings (RTS) with Tc and Tsk temperatures obtained during treadmill walking while wearing fire fighter thermal protective clothing. Construct validity was established by correlating OMNI RTS with a construct specific 10 cm visual analogue scale (VAS). RESULTS: Tc ranged from 37.1 ± 0.1 o C to 38.9 ± 0.1 o C and Tsk ranged from 33.8 ± 0.1 o C to 38.7 ± 0.1 o C. OMNI RTS ranged from 1-5 and distributed as a positive linear function of Tc (r = 0.70, p <0.01) and Tsk (r = 0.72, p <0.01). OMNI RTS distributed as a positive linear function of the VAS responses which ranged from 0-10 cm (r = 0.92, p<0.01).CONCLUSIONS: Concurrent and construct validity were established for the OMNI Thermal Sensation Scale in healthy adults performing treadmill walking while wearing fire fighter thermal protective clothing. (No relationships reported)PURPOSE: Numerous investigations have reported that exercise-heat stress reduces human performance and exacerbates muscle fatigue; however, much less is known about the independent effects of heat stress in the absence of exercise (passive-heat stress). The purpose of this study was to evaluate the effect of passive-heat stress on the neuromuscular properties of the wrist flexor muscles. METHODS:We utilized a combination of techniques involving nerve stimulation and paired-pulse transcranial magnetic stimulation to assess changes in muscle strength, contractile properties and fatigue-resistance as well as central (voluntary) activation and intracortical excita...