Central and peripheral fatigue during passive and exercise-induced XXXX .

@entity308 @entity64 @entity73 @entity26 @entity2556 @entity116 @entity221 @entity65
PURPOSE: @entity221 was induced during prolonged exercise (ExH) and passive heating ( @entity2556 ) to isolate the influence of exercise on neuromuscular function during a maximal voluntary isometric contraction (MVC) of the quadriceps under heat stress. The influence of @entity65 in limiting endurance performance in the heat was also examined. METHODS: On separate days, eight males cycled to exhaustion at 60% maximal @entity26 uptake or were immersed in a water bath (   41  C) until rectal temperature (Tre) increased to 39.5  C. The ExH and @entity2556 interventions were performed in ambient conditions of 38  C and 60% relative humidity with Tre reaching 39.8  C during exercise. Before (control) and after each intervention, voluntary activation and force production capacity were evaluated by superimposing an electrically stimulated @entity116 during a 45-s MVC. RESULTS: Force production decreased immediately after @entity2556 and ExH compared with control, with the magnitude of decline being more pronounced after ExH (P < 0.01). Mean voluntary activation was also significantly @entity308 after both interventions (P < 0.01 vs control). However, the extent of decline in voluntary activation was maintained at    90% during both @entity2556 and ExH MVC. This decline accounted for 41.5% ( @entity2556 ) and 33.1% (ExH) of the decrease in force production. In addition, exhaustion coincided with a marked increase in HR (   96% of maximum) and a decline in @entity64 volume (25%) and mean arterial pressure (10%) (P < 0.05). CONCLUSIONS: The loss of force production capacity during @entity221 originated from central and peripheral fatigue factors, with the combination of heat stress and previous contractile activity exacerbating the rate of decline. Thus, the observed significant rise in thermal strain in ExH and @entity2556 @entity73 and was associated with an exercise performance limiting increase in @entity65 .
