The cross-sectional relationships among hyperthermia-induced hyperventilation, peak oxygen consumption, and the cutaneous vasodilatory response during exercise

Abstract

To test the hypothesis that the hyperthermia-induced ventilatory response relates to aerobic power and/or the cutaneous vasodilatory response during exercise, we asked 18 subjects to perform 3 kinds of exercise: an incremental exercise to determine peak oxygen consumption (V(O)(2peak)), a steady state exercise at 50% of V(O)(2peak) to determine the ventilatory response to increasing body temperature, and a steady state exercise at 60% of V(O)(2peak) to determine the cutaneous vasodilatory response to increasing body temperature. The ventilatory and cutaneous vasodilatory responses were evaluated by plotting the increase in minute ventilation or in forearm vascular conductance against the increase in oesophageal temperature. Regression analysis revealed that: (1) there was a negative relationship between the hyperthermic ventilatory response and cutaneous vasodilatory response, (2) there was a negative relationship between the hyperthermic ventilatory response and V(O)(2peak), and (3) there was a positive relationship between the cutaneous vasodilatory response and V(O)(2peak). These results support our hypothesis and suggest that exercise training suppresses the hyperthermic ventilatory response and improves the thermoregulatory response.

Ventilatory response to increasing body temperature: Characteristics and effect on central fatigue

“…When we examined relationships among the ventilatory sensitivity to increasing body temperature, V ・ O2peak and the cutaneous vasodilatory response, we found that ventilatory sensitivity to increasing body temperature has a significant negative relationship with V ・ O2peak and the sensitivity of cutaneous vasodilatory response (Fig. 3) 13) , which is consistent with the compensation hypothesis. On the other hand, Fujii et al 31) recently examined the effect of voluntary hypocapnic hyperventilation on heat-dissipating responses and reported that hypocapnia increases the Tes threshold for cutaneous vasodilation and reduces the sensitivity of the cutaneous vasodilatory response.…”

Short-term exercise-heat acclimation enhances skin vasodilation but not hyperthermic hyperpnea in humans exercising in a hot environment

“…We therefore suggest that hyperthermia-induced hyperventilation is augmented when thermoregulatory responses are impaired during passive heating at rest (hyperthermia-induced hyperventilation is linked to thermoregulatory responses). Consistent with this idea, Hayashi et al (2009) recently showed that during submaximal, moderate intensity exercise in a hot environment, the extent of hyperthermia-induced hyperventilation is inversely related to the thermoregulatory response (cutaneous vasodilation)-i.e., individuals who have a stronger cutaneous vasodilatory response show less hyperthermia-induced hyperventilation. Although this result was from a crosssectional analysis, it suggests that when thermoregulatory responses are enhanced by heat acclimation, hyperthermiainduced hyperventilation during submaximal, moderateintensity exercise may be attenuated.…”

“…Our results suggest that EHA reduces ventilation during exercise in a hot environment ( _ V E was reduced by 2.2-3.7 l min -1 ). It is known that hyperthermia stimulates ventilation in resting (Cabanac and White 1995;Fujii et al 2008b) and exercising humans (Beaudin et al 2009;Fujii et al 2008a, b;Hayashi et al 2006Hayashi et al , 2009Nybo and Nielsen 2001). Because exercising T es was significantly reduced by EHA, the reduction in exercise T es can be related to the lower exercise _ V E without changing the slope relating _ V E to T es (see below for detailed ''Discussion'').…”

“…In humans, hyperthermia reportedly stimulates ventilation in both resting (Cabanac and White 1995;Fujii et al 2008b) and exercising subjects (Beaudin et al 2009;Fujii et al 2008a, b;Hayashi et al 2006Hayashi et al , 2009White 2006;White and Cabanac 1996); this is the so-called ''hyperthermiainduced hyperventilation.'' Previous studies showed that individuals whose sweating response is impaired due to quadriplegia, ectodermal dysplasia, or spinal-cord injury show greater increases in ventilation than able-bodied subjects during passive heating at rest (Totel 1974;Wilsmore et al 2006).…”

Effect of hyperthermia-induced hyperventilation on central fatigue during exercise in heat

“…Nonetheless, it is possible that hyperthermia-induced hyperventilation has some connection to heat-dissipating responses. It has been reported, for example, that ventilatory sensitivity to increasing body temperature (slope of the regression line relating V ・ E to Tes) has a negative linear relationship with the sensitivity of cutaneous vasodilation in heated exercising humans 23) . It has also been reported that subjects with congenital anhidrotic ectodermal dysplasia and those with spinal-cord injuries, leading to reduced sweating responses, show greater increases in ventilation during hyperthermia at rest than healthy subjects 24,25) .…”