Intracellular Oxygenation During Ischemic Muscle Contractions

Abstract

Listen

Translate article

Proton magnetic resonance spectroscopy was used to investigate the effect of ischemic contractions on human skeletal muscle oxygenation. PURPOSE: To determine if ischemia+contraction produces greater muscle deoxygenation than ischemia alone. METHODS: 5 men performed the following protocols in a 4 tesla magnet: P1) 10 min of ischemic rest, then 4 min of intermittent maximal isometric voluntary contractions (MVCs), and P2) 1 min of ischemic rest, then 3.4 min of intermittent MVCs and 5.6 min of ischemic recovery. Deoxymyoglobin (dMb) was normalized to the peak obtained during 10 min of ischemic rest. RESULTS: In P1, dMb reached a plateau during 10 min of ischemic rest and was not affected by contractions (102 ± 4.1%). In P2, dMb increased rapidly, followed by a plateau that tended to be lower than that obtained during ischemic rest (86.7 ± 2.32%, p = 0.063). During ischemic recovery, dMb gradually increased to the same level observed during resting ischemia (102 ± 4.2%). CONCLUSIONS: The addition of contractions after 10 min of ischemia does not result in further desaturation, suggesting that the muscle is already fully desaturated. Overall, these results validate the use of 10 min of resting ischemia to calibrate the dMb by MRS, and suggest that the observed plateaus in the dMb signal reflect inadequate oxygenation rather than mitochondrial inhibition by metabolite accumulation. Support NIH AG21094, K02 AG023582