The aim of the present study was to investigate the relationships between lactate exchange and removal abilities and the capacity to prolong exercise, as assessed by the time to exhaustion (Tlim) at a work rate corresponding to VO(2)max (Pa max ). The individual blood lactate recovery curves obtained for 13 untrained subjects after 5 min 90 % Pa max exercise were fitted to the biexponential time function: La(t) = La(0) + A(1) (1-e (-gamma(1) x t) + A(2) (1-e (-gamma(2) x t), where t is time into the recovery, La(0) is the arterialized lactate concentration measured at the end of the exercise, gamma(1) and gamma(2) are velocity constants denoting the lactate exchange and removal abilities, respectively. Tlim was positively related to gamma(1) and gamma(2) (r = 0.60, p < 0.05 and r = 0.56, p < 0.05, respectively) but was negatively related to La(0) (r = 0.75, p < 0.01). gamma()1 was positively related to the capillary density (r = 0.69, p < 0.01) and to the number of capillaries per type I fiber area (r = 0.62, p < 0.05). It was concluded that 1) high lactate exchange and removal abilities would allow continuing a high-intensity exercise for a longer duration, and 2) a high capillary density may explain the associated high lactate exchange ability.