The effect of the dehydration levels on thermoregulatory responses and aerobic- and anaerobic capacity

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The maintenance of blood volume (BV) is an important factor for providing circulatory stability, thermoregulatory and maintaining performance during exercise. Hypovolemia from thermal dehydration or progressive pooling of blood in cutaneous blood vessels and the shifts in plasma volume (PV) reduces the central circulating blood volume. Under these condition cutaneous vasoconstriction leads to excessive heat storage in hot environment. The aim of the present study is to assess the effect of the dehydration level on thermoregulatory responses and aerobic- and anaerobic-work capacity and blood volume (BV)-aerobic work capacity relationship. The relationship of peak VO_2 with BV and PV indicated a significant positive correlation. The lactate threshold (LT), as a predictor of performance in aerobic exercise, was calculated from the exercise intensity at the point of plasma lactate concentration buildup to 4 mmol. The percentage of changes in PV during graded exercise decreased gradually from 10.7% to 20.7% in exhaustion. The shifts in PV at the point of LT level averaged 16.4% and the range of the PV shift in individual variations were from 12.5% to 19.6%. The relationship of the percentage of changes in PV at LT with total BV and PV in individual variations indicated a significant negative correlation. The strong positive relation between the shift in PV and total PV and results in a maintenance of the circulating BV.