Ventilatory chemosensitive adaptations to intermittent hypoxic exposure with endurance training and detraining

Abstract

The present study was performed to clarify the effects of intermittent exposure to an altitude of 4,500 m with endurance training and detraining on ventilatory chemosensitivity. Seven subjects (sea-level group) trained at sea level at 70% maximal oxygen uptake (VO2 max) for 30 min/day, 5 days/wk for 2 wk, whereas the other seven subjects (altitude group) trained at the same relative intensity (70% altitude VO2 max) in a hypobaric chamber. VO2 max, hypoxic ventilatory response (HVR), and hypercapnic ventilatory response, as an index of central hypercapnic chemosensitivity (HCVR) and as an index of peripheral chemosensitivity (HCVRSB), were measured. In both groups VO2 max increased significantly after training, and a significant loss of VO2 max occurred during 2 wk of detraining. HVR tended to increase in the altitude group but not significantly, whereas it decreased significantly in the sea-level group after training. HCVR and HCVRSB did not change in each group. After detraining, HVR returned to the pretraining level in both groups. These results suggest that ventilatory chemosensitivity to hypoxia is more variable by endurance training and detraining than that to hypercapnia.

The effect of intermittent training in hypobaric hypoxia on sea-level exercise: a cross-over study in humans

“…In several other studies (Terrados et al 1988;Emonson et al 1997;Engfred et al 1994;Friedman et al 1990;Katayama et al 1998Katayama et al , 1999, which have also used a control group, significant increases in _ V V O 2max as a result of training in a hypobaric chamber have been found. However, none of these studies observed a significant difference in increase of the _ V V O 2max between the two kinds of training regimes (Table 5).…”

“…Several authors studied the effect of altitude training on Hb concentration and Hct, and higher values of both blood variables were found after a sojourn at altitude. Only few studies (Beidleman et al Emonson et al (1997) 9/9 u 2,500 -5 weeks 3 45 9**/16** Engfred et al (1994) 7/14 u 2,500 2 days 5 weeks 5 45 15*/11-15* a Friedman et al (1990) 14/7 u 2,500 -5 weeks 5 45 14*/12* Katayama et al (1998) 6/7 t 4,500 1.7 days 6 days 6 30 2, -4/6*, 5* Katayama et al (1999) 7/7 t 4,500 1 day 2 weeks 5 30 5*/7* *Significant change (P<0.05) **Significant change (P<0.01) a Expressed in absolute values 1997; Levine and Stray-Gundersen 1997) have also investigated the effect of altitude training on _ V V O 2max . One study even found (Beidleman et al 1997) …”

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

“…As far as we know, very few studies have measured simultaneously ventilatory chemosensitivity and exercise ventilation at sea level before and after hypoxic exposure (Levine et al 1992;Katayama et al 1999). These studies demonstrated that the ventilatory response to maximal exercise at sea level did not change after combined intermittent hypoxia and endurance training, despite a significantly increased HVR.…”

“…The measurement of maximum oxygen uptake ( _ V V O 2max ) was conducted in the same way as in our previous study (Katayama et al 1999). In short, an incremental protocol on an electromechanically braked bicycle ergometer was used for evaluating _ V V O 2max (i.e., starting at 60 W, the load was increased by 30 W every 2 min).…”

“…Resting HVR was determined by using a progressive isocapnic hypoxic test, and a rebreathing system similar to that of our previous study (Katayama et al 1999) was used. Inspired minute ventilation ( _ V V I ), end-tidal partial pressure of carbon dioxide and oxygen (P ET CO 2 and P ET O 2 , respectively), and arterial oxygen saturation (S a O 2 ) were measured continuously during rebreathing.…”