Effects of specific muscle training on VO₂ on-response and early blood lactate

The relationship between half time of the O₂ uptake on-response [t(1/2)VO₂on, seconds] and early blood lactate accumulation [ΔLa(b), mmol l^-1] at the onset of submaximal arm and/or leg exercise was the object of a cross-sectional study of sedentary subjects (S, n = 3), and kayakers (K, n = 8), and of a longitudinal study on 11 untrained subjects of specific arm vs. leg training. In supine arm cranking (W = 125 watts) S had an average t(1/2)VO₂on of 82 s and a ΔLa(b) of 9.2 mmol l^-1 compared to 47 ± 7 s and 4 ± 1.4 mmol l^-1, respectively, for K. In longitudinal trainees shorter t(1/2)VO₂on was accompanied by lower La(b) for the trained limbs. Specific limb conditioning in swimmers and runners resulted in shorter t(1/2)VO₂on. A linear relationship was observed between ΔLa(b) and t(1/2)VO₂on having an intercept on the time axis at 20 s and a slope proportional to muscle mass. Trained muscles were grouped closest to the intercept indicating local acceleration of the rate of O₂ transfer approaching the t(1/2)VO₂on for isolated perfused muscle at the onset of work. Since t(1/2) for local blood flow adjustment is shorter than t(1/2)VO₂on, it is concluded that factors distal to the capillary are specifically involved in the local training response.