Robach, Paul, Daniel Biou, Jean-Pierre Herry, Denis Deberne, Murielle Letournel, Jenny Vaysse, and Jean-Paul Richalet. Recovery processes after repeated supramaximal exercise at the altitude of 4,350 m. J. Appl. Physiol. 82(6): 1897-1904, 1997.We tested the hypothesis that prolonged exposure to high altitude would impair the restoration of muscle power during repeated sprints. Seven subjects performed two 20-s Wingate tests (WT1 and WT2) separated by 5 min of recovery, at sea level (N) and after 5-6 days at 4,350 m (H). Mean power output (MPO) and O₂ deficit were measured during WT. O₂ uptake (O₂) and ventilation (E) were measured continuously. Blood velocity in the femoral artery (FBV) was recorded by Doppler ultrasound during recovery. Arterialized blood pH and concentrations of bicarbonate ([HCO₃]), venous plasma lactate ([La]), norepinephrine ([NE]), and epinephrine ([Epi]) were measured before and after WT1 and WT2. MPO decreased between WT1 and WT2 by 6.9% in N (P < 0.05) and by 10.7% in H (P < 0.01). H did not further decrease MPO. O₂ deficit decreased between WT1 and WT2 in H only (P < 0.01). Peak O₂ after WT was reduced by 30-40% in H (P < 0.01), but excess postexercise O₂ consumption was not significantly lowered in H. During recovery in H compared with N, E, exercise-induced acidosis, and [NE] were higher, [Epi] tended to be higher, [La] was not altered, and [HCO₃] and FBV were lower. The similar [La] accumulation was associated with a higher exercise-induced acidosis and a larger increase in [NE] in H. We concluded from this study that prolonged exposure to high altitude did not significantly impair the restoration of muscle power during repeated sprints, despite a limitation of aerobic processes during early recovery.