We tested the hypothesis that two weeks of training performed at moderate intensity can induce a significant acceleration of the V'O₂-on kinetics in adult sedentary women. To this aim, breath-by-breath oxygen uptake (V'O₂) was measured in 8 women (25 yy ± 7; 68 kg ± 11, 165 cm ± 8) during: i) an incremental ramp cycling test up to exhaustion and; ii) during three consecutive square wave tests performed at approximately 50 % of V'O_2max before and immediately after a training program of daily trekking (6-3 hour d^-1) performed at near sea level and on irregular and undulating terrain.

Absolute and relative V'O_2max values did not increase as a result of the hiking training. The time constant of the primary phase (t₂: PRE: 23.1 s ± 8; POST 16.4 ± 6) of V'O₂ kinetics were significantly smaller after training (P < 0.05). Percent decrease of t₂ was significantly and negatively correlated with absolute V'O_2max at baseline (r = 0.69, P < 0.05). It is concluded that two weeks of training performed at moderate intensity are able to induce a significant acceleration of the dynamic response of oxidative metabolism during exercise that is not paralleled by any increase of V'O_2max in healthy sedentary women. Moreover, the extent of the improvement is affected by the value of V'O_2max at the baseline.