Effects of age on muscle energy metabolism and oxygenation in the forearm muscles.
OBJECTIVE
The effects of aging on muscle metabolism and oxygenation have not yet been elucidated. We evaluated the effects of aging on energy metabolism and oxygenation in sedentary healthy subjects by simultaneously measuring 31P-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 31P-MR spectrum was obtained every 15 s during and after hand gripping exercise. Intracellular pH (pHi) and PCr/(PCr+Pi) [PCr: phosphocreatine, Pi: inorganic phosphate] were calculated as an index of energy metabolism. The time constant of the PCr/(PCr+Pi) recovery (tau PCr) was calculated. With NIRS, we evaluated the recovery rates of oxygenated (RHbO2) and deoxygenated hemoglobin (RHb) during the initial 10 s of recovery.


RESULTS
The PCr/(PCr+Pi) and pHi at rest and at completion of the exercise and tau PCr did not differ between young and older subjects. However, RHbO2 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 RHbO2 and RHb in older subjects suggested impaired O2 supply, which was probably due to impaired peripheral circulation caused by the process of aging.
Kutsuzawa
T
T
School of Health Sciences, Tokai University, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan. tkutsu@is.icc.u-tokai.ac.jp
Shioya
S
S
Kurita
D
D
Haida
M
M
Yamabayashi
H
H
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000502:physiology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010759:Phosphorus Isotopes; D019265:Spectroscopy, Near-Infrared
D010759:Phosphorus Isotopes; D010100:Oxygen