Multiparametric NMR-based assessment of skeletal muscle perfusion and metabolism during exercise in elderly persons: preliminary findings.
BACKGROUND
Aging is associated with a decline in exercise capacity that may be attributable to maladaptations in both skeletal muscle perfusion and metabolism; yet very little is known regarding the real-time, within-muscle interplay between these parameters during physical activity. Therefore, we utilized an unique nuclear magnetic resonance sequence to concomitantly examine changes in lower leg skeletal muscle perfusion and metabolism.


METHODS
In young (26+/-5 years, n=6) and older (70+/-5 years, n=6) healthy volunteers, arterial spin labeling measurements of muscle perfusion were combined with 31 Phosphorous (31P) nuclear magnetic resonance spectroscopy to monitor high-energy phosphate metabolites during and after 5 minutes of moderate-intensity (approximately 5W) plantar flexion exercise.


RESULTS
Compared with young, end-exercise perfusion was diminished in older participants (43+/-10 mL/100 g/minute, old; 60+/-7 mL/100 g.minute, young), accompanied by greater phosphocreatine (PCr) depletion (-28%+/-12%, old; -19%+/-7%, young) and elevated inorganic phosphate/PCr (0.41+/-0.2, old; 0.24+/-0.09, young); yet the time constant for PCr recovery (tau, an index of muscle oxidative capacity) was similar between groups (51+/-17 seconds, old; 48+/-7 seconds, young).


CONCLUSIONS
Together, these preliminary data provide evidence of an age-related decline in tissue perfusion and increased "metabolic stress" during exercise but demonstrate that overall oxidative capacity in the elderly does not appear negatively affected by this relatively hypoperfused state.
Department of Internal Medicine, University of California San Diego, La Jolla, CA, USA. walter.wray@hsc.utah.edu
D Walter
DW
Wray
Steven K
SK
Nishiyama
Aurélien
A
Monnet
Claire
C
Wary
Sandrine
S
Duteil
Pierre G
PG
Carlier
Russell S
RS
Richardson
D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D015444:Exercise; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*