Enhanced chemosensitivity after intermittent hypoxic exposure does not affect exercise ventilation at sea level

Abstract

The purpose of the present study was to test the hypothesis that the ventilatory response to exercise at sea level may increase after intermittent hypoxic exposure for 1 week, accompanied by an increase in hypoxic or hypercapnic ventilatory chemosensitivity. One group of eight subjects (hypoxic group) were decompressed in a chamber to 432 torr (where 1 torr=1.0 mmHg, simulating an altitude of 4,500 m) over a period of 30 min and maintained at that pressure for 1 h daily for 7 days. Oxygen uptake and pulmonary ventilation (V(E)) were determined at 40%, 70%, and 100% of maximal oxygen uptake at sea level before (Pre) and after (Post) 1 week of daily exposures to hypoxia. The hypoxic ventilatory response (HVR) was determined using the isocapnic progressive hypoxic method as an index of ventilatory chemosensitivity to hypoxia, and the hypercapnic ventilatory response (HCVRSB) was measured by means of the single-breath carbon dioxide method as an index of peripheral ventilatory chemosensitivity to hypercapnia. The same parameters were measured in another group of six subjects (control group). In the hypoxic group, resting HVR increased significantly ( P<0.05) after intermittent hypoxia and HCVRSB increased at Post, but the change was not statistically significant ( P=0.07). In contrast, no changes in HVR and HCVRSB were found in the control group. There were no changes in either V(E) or the ventilatory equivalent for oxygen during maximal and submaximal exercise at sea level throughout the experimental period in either group. These results suggest that the changes in resting hypoxic and peripheral hypercapnic chemosensitivities following short-term intermittent hypoxia have little effect on exercise ventilation at sea level.

Fitness and therapeutic potential of intermittent hypoxia training: a matter of dose

“…These investigations also show that the break in training for one or two days do not significantly affect the outcome of the IHT course. These conclusions were also expressed by Katayama et al [56,57], Koehle et al [58] and others. Later on, Katayama et al [59] conducted a study using the hypoxic tent, which was supported by 12.3% O 2 , one and 3 hours during the week.…”

Hypoxic ventilatory response is correlated with increased submaximal exercise ventilation after live high, train low

“…The relationship between hypoxic chemosensitivity and exercise _ V E following 7 days of intermittent hypoxia (1 h day À1 , 4,500 m) was recently examined (Katayama et al 2002). The authors reported no increase in exercise _ V E despite an increase in HVR.…”

“…The HVR increased after intermittent hypoxia, but no change in submaximal exercise _ V E was found. The authors therefore concluded that changes in hypoxic chemosensitivity had little effect on exercise _ V E (Katayama et al 2002).…”

“…Since it has been suggested the peripheral chemoreceptors act as a 'fine tuning' mechanism regulating exercise hyperpnoea (Whipp 1994), it seems plausible that increased peripheral chemoreceptor gain may contribute to enhanced exercise _ V E . The hypothesis that enhanced peripheral chemosensitivity would be related to increased exercise hyperpnoea in normoxia following 7 days of intermittent hypoxia (1 hAEday À1 , 4,500 m) was tested recently (Katayama et al 2002). The HVR increased after intermittent hypoxia, but no change in submaximal exercise _ V E was found.…”

Effects of intermittent hypoxia on the cerebrovascular responses to submaximal exercise in humans

“…Accordingly, IH increases chemoreceptor gain and increases exercise _ V E : Indeed, _ V E during submaximal exercise is elevated following 11 nights of simulated altitude (3,000 m) (Gore et al 2001). In contrast, others have failed to show any effect of IH on exercise hyperpnoea (Katayama et al 2002;Foster et al 2006). In the current study, there was no effect of IH on the ventilatory response to submaximal exercise.…”