Effects of age on muscle energy metabolism and oxygenation in the forearm muscles

Purpose: The effects of aging on muscle metabolism and oxygenation have not yet been elucidated. We evaluated the effects of aging on energy metabolis m and oxygenation in sedentary healthy subjects by simultaneously measuring P-31-magnetic resonance spectroscopy (MRS) and near-infrared spectroscopy (NIRS). Methods: Nine young (28.1 +/- 5.0 yr) and nine older (61.4 +/- 4.6 yr) healthy subjects were studied. The P-31-MR spectrum was obtained every 15 s during and after hand gripping exercise. Intracellular pH (pHi) and PC r(PCr+Pi) [PCr: phosphocreatine, Pi: inorganic phosphate] were calculated a s an index of energy metabolism. The time constant of the PCr/(PCr+Pi) reco very (tau PCr) was calculated. With NIRS, we evaluated the recovery rates o f oxygenated (RHbO(2)) and deoxygenated hemoglobin (RHb) during the initial 10 s of recovery. Results: The PCr/(PCr+Pi) and pHi at rest and at complet ion of the exercise and tau PCr did not differ between young and older subj ects. However, RHbO(2) and RHb were significantly slower in older subjects than in young subjects. Conclusions: The results suggest that muscle,energy metabolism in the forearm muscle was not affected by aging. The slower RHb O(2) and RHb in older subjects suggested impaired O-2 supply, which was pro bably due to impaired peripheral circulation caused by the process of aging .