Buffer capacity and lactate accumulation in skeletal muscle of trained and untrained men

Buffer capacity (beta) of skeletal muscle has been determined in trained (n = 7) and in sedentary subjects (n = 8). The trained subjects were active in ball games where a high degree of anaerobic energy utilization is required. Percentage fibre type occurrence in the thigh muscle was not significantly different in the two groups. However, there was a tendency towards a higher proportion of type I (slow-twitch) fibres (61.5 +/- 11.6% vs. 50.2 +/- 12.5%) and a lower proportion of type IIB fibres (2.1 +/- 3.5% vs 14.1 +/- 16.3%) in the trained subjects. The proportion of the cross-sectional area of the muscle biopsies that was made up of type I or type II fibres was not different in the two groups. All subjects performed an isometric contraction of the knee extensors to fatigue at 61% of their maximal voluntary contraction force. Muscle biopsies were taken from the quadriceps femoris muscle at rest and immediately after contraction. The buffer capacity of muscle was calculated from: beta = (Muscle lactate (work)-Muscle lactate (rest)/(Muscle pH (rest)-Muscle pH (work)). A higher buffer capacity (p less than 0.05) was observed in the trained subjects (beta = 194 +/- 30 mmol X pH-1 X kg-1 dry wt.) compared to the sedentary group (beta = 164 +/- 20) (mean +/- SD). An unexpected finding was that muscle lactate after contraction to fatigue was lower (30%, p less than 0.01) and muscle pH was higher (6.80 +/- 0.06 vs. 6.61 +/- 0.12, p less than 0.01) in the trained subjects than in the sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)