Table 2. Muscle energetics during 3 min of intense dynamic kneeextension exercise.
| Time interval (s) | |||||||
|---|---|---|---|---|---|---|---|
| Energy source | 0–30 | 30–60 | 60–90 | 90–120 | 120–150 | 150–180 | 0–180 |
| (1) Oxygen consumption (J s−1) | 57.6 ± 7.5 | 132.8 ± 9.7 | 168.0 ± 16.9 | 176.8 ± 22.0 | 182.0 ± 22.6 | 196.7 ± 19.6 | 152.3 ± 15.3 |
| (2) Net PCr hydrolysis (J s−1)a | 27.0 | 15.0 | 6.3 | 1.7 | 0.8 | 0.3 | 8.6 |
| (3) Net ATP hydrolysis (J s−1)b | 0.4 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 |
| (4) Lactate accumulation (J s−1)a | 40.6 | 64.3 | 12.6 | 7.9 | 6.3 | 5.0 | 21.7 |
| (5) Lactate release (J s−1) | 4.1 ± 1.2 | 11.4 ± 2.1 | 17.1 ± 2.6 | 19.0 ± 2.9 | 18.2 ± 2.7 | 18.4 ± 2.4 | 14.7 ± 2.2 |
| Σ(1–5) Total metabolic input (J s−1) | 133.8 | 224.1 | 204.6 | 206.0 | 207.9 | 221.0 | 197.9 |
| Total energy turnover (J s−1)c | 181.9 ± 13.6 | 197.2 ± 16.3 | 211.0 ± 17.4 | 216.0 ± 21.0 | 220.8 ± 20.4 | 228.1 ± 23.2 | 209.2 ± 15.3 |
Data represent mean rates for 30 s time intervals and the overall mean for 180 s. Measured data are depicted as means ±s.e.m. for 5 subjects. aNet PCr hydrolysis and lactate accumulation estimations are based on the initial and final values observed in biopsy samples from vastus lateralis obtained in parallel studies with the same experimental protocol (J. Bangsbo, P. Krustrup, J. Gonz.alezález-Alonso & B. Saltin, unpublished; ΔPCr 16.3 mmol (kg wet wt)−1 and Δlactate 22.3 mmol (kg wet wt)−1; see also Bangsbo et al. 1990, for similar measurements) and the kinetics described by Gollnick & Hermansen (Fig. 3, p. 12; 1973) and Sinclair et al. (1999). Heat produced per mole of ATP used was assumed to be 35 kJ for ATP and PCr hydrolysis, 65 kJ for glycogenolysis and 72 kJ for oxidation (Curtin & Woledge, 1978; Woledge & Reilly, 1988). P:O ratio was assumed to be constant throughout exercise and equal to theoretical 3.0. Total metabolic input was calculated as the sum of the energy input from oxygen consumption, net ATP and net PCr hydrolysis and lactate production. bNet ATP hydrolysis estimation (ΔATP 1.1 mmol (kg wet wt)−1) is based on data from Hellsten et al. (1999). cTotal energy turnover was calculated by summing power output and rate of heat production.