Figure S1.
Noninvasive investigation of mechanical performance and bioenergetics in gastrocnemius muscle using dynamic 31P-MR spectroscopy. (A) Force reduction at the end of the 6-min fatiguing bout of exercise and expressed as percent of the maximal force value reached during the exercise. (B and C) PCr/ATP (B) and pH (C) in resting muscle. (D and E) Extent of PCr consumption (D) and drop of intracellular pH (E) at the end of the 6-min exercise. (F) Time constant of PCr resynthesis (τPCr) during the post-exercise recovery period. Given that PCr synthesis during the post-exercise recovery period relies exclusively on oxidative ATP synthesis, τPCr is considered as an in vivo index of mitochondrial capacity. It is calculated by fitting the PCr resynthesis time-course to a monoexponential function with a least mean-squared algorithm: τPCr = −t/ln(PCrt/ΔPCr), where ΔPCr is the extent of PCr depletion measured at the start of the recovery period. Data are means ± SEM. Statistical analysis was performed using unpaired two-tailed Mann–Whitney tests. For each parameter, there is no difference between both groups whatever the age.