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F19U FREE COMMUNICATION/POSTER SKELETAL MUSCLE II

MUSCLE ARCHITECTURAL FEATURES AND OXYGEN SUPPLY DURING ISOMETRIC CONTRACTION

Miura, H1; McCully, K2; Miyachi, M3; Chance, B4

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Medicine & Science in Sports & Exercise: May 2001 - Volume 33 - Issue 5 - p S263
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This study tested whether regional differences in oxygen supply could result from differences in muscle fiber architecture. Architectural properties, oxygen supply and consumption in medial head of gastrocnemius muscle (MG) were determined in vivo in six men using B-mode ultrasound and functional near infrared imaging (NIR) devices. Fascicle length, fascicle angle, total-Hb (sum of deoxygenated and oxygenated Hb) and deoxy/oxygenation (deoxygenated Hb or oxygenated Hb) were obtained in the distal and proximal portions in MG at rest and during contraction. The diameter of tibialis posterior artery was measured in two of subjects during contraction. Exercise protocol consisted of the 1-min isometric plantar flexion at 10.0kg load. Muscle contraction produced larger changes (delta: difference between rest and exercise values) in fascicle length (−15.7 vs. −8.5 mm) and fascicle angle (11.3 vs. 3.5 degrees) in the distal compared to proximal portion (p < 0.05 for all comparisons). It also produced larger changes (delta) in total-Hb (−0.22 vs. −0.15 optical density) and deoxygenation (0.11 vs. 0.07 optical density) in the distal compared to proximal portion (p < 0.05 for all comparisons). There were significant correlations between delta total-Hb and delta fascicle length (r = 0.92, p < 0.05), and between delta total-Hb and delta fascicle angle (r = −0.85, p < 0.05), between delta deoxygenation and delta fascicle length (r = −0.80, p < 0.05), between delta deoxygenation and delta fascicle angle (r = 0.89, p < 0.05). The reduced diameter of tibialis posterior artery was also found during contraction. Therefore, the larger changes in fascicle length and fascicle angle in the distal portion support the hypotheses that NIR measured differences in oxygen supply between distal and proximal portions are due to the architectural alterations in muscle and blood vessels.

©2001The American College of Sports Medicine