Effect of hiking training at high-altitude on V’O2 and Q’ kinetics in healthy sedentary women

Aim: Previous studies have shown faster pulmonary oxygen uptake (V’O2) kinetics after trekking performed in high-altitude [1]. We tested the hypothesis that 2 weeks of training performed in high-altitude (hypoxia) can induce a significant acceleration of the V'O2 and cardiac output (Q’) kinetics in adult sedentary women, as compared to a similar training performed at the sea level (normoxia). Methods: 7 moderately active young women (25±7 yy; 68±11 kg, 165±8 cm) were recruited by the Department of Basic and Applied Medical Sciences of the University ‘G.d’Annunzio’-Chieti-Pescara. A first sea level(SL)training program consisting in daily trekking for 2 wk was done in Italy(Chieti, Italy): the covered difference in height was changeable (160m- 800m) and performed in different time (3 to 6h). Five months later the same training program was repeated in high altitude (HA)(>5000m) (Ama Dablam, Nepal). Before and immediately after 14 days of trekking performed, , at SL and in HA, breath-by-breath oxygen uptake and beat-by-beat cardiac output were measured. These were evaluated during: i) an incremental ramp cycling test up to exhaustion to calculate V’O2max and ventilatory threshold; ii) three consecutive square wave tests (separated by 6 min of recovery) performed at approximately 50 % of V’O2max to calculate a primary phase (τ2) of V’O2 and Q’ kinetics. V’O2 and Q’ values of each bout were 1-s normalised, aligned and ensemble-averaged. Friedman’s test was applied. Results: Absolute and relative V’O2max(PRE-SL 32,90±6,27ml/kg/min; POST-SL 33,45±4,64ml/kg/min; PRE-HA 33,43±4,10ml/kg/min; POST-HA 35,26±4,53ml/kg/min)and Q’max (PRE-SL 13,1±2,2l; POST-SL 13,3±1,9l; PRE-HA 12,8±1,5l; POST-HA 13,3±1,8) values did not change as a result of any of the two training. τ2of V’O2 kinetics (PRE-SL 25,43±5,29s; POST-SL 17,76±4,58s; PRE-HA 17,78±3,60s; POST-HA 13,84±4,70s) were significantly smaller after each training (P < 0.05). τ2of Q’ kinetics (PRE-SL 23,97±6,47s; POST-SL 18,99±3,66s; PRE-HA 22,97±12,74s; POST-HA 18,82±7,67s) were not significantly smaller after both training. Conclusion: 2 wks of same hiking training, at SL or HA, do not change V’O2maxand Q’max: this confirm that this moderate and brief training, even in hypoxia, could not increase maximal cardiovascular response s [2]. However, the hypoxic stimulus summated at 2 wk of moderate training signifcantly improved a primary component of V’O2 kinetics [3].