Fig. 5.

Paired-samples difference (Δ) in surplus P_i→ATP flux and substrate concentrations of the enzymes GAPDH and phosphoglycerate kinase (PGK) between steady-state exercise and resting conditions. Paired-samples (n = 9) mean difference ± SE (exercising-resting values) for surplus V_Pi-ATP and substrate concentrations of the enzymes GAPDH and PGK; P_i, ADP, and H⁺. Surplus V_Pi-ATP was calculated by subtracting the net rate of oxidative ATP synthesis, V_ATP (estimated as the immediate postexercise PCr resynthesis rate), from the rate of P_i→ATP flux during exercise (V_Pi-ATP) to provide an estimate of the component of the ST measurement not explained by suprabasal mitochondrial ATP synthesis. Data from volunteers in group B have been averaged to provide one value per person to avoid inappropriate weighting (hence n = 9). A paired-samples t-test was used to test for significant differences between resting and exercising conditions (P values shown).