Electromyogram spectrum changes during sustained contraction related to proton and diprotonated inorganic phosphate accumulation: a 31P nuclear magnetic resonance study on human calf muscles
Summary The calf muscles of five clinically healthy men were submitted to isometric exercise and examined by 31 P nuclear magnetic resonance (NMR) spectroscopy and electromyography (EMG) to evaluate the influence of proton (H + ) and diprotonated forms of inorganic phosphate (H 2 PO 4 − ) accumulation on EMG spectrum changes. The experiments were performed in a supraconducting magnet (2.35 Tesla, 35-cm effective diameter) using a surface coil (7-cm diameter) positioned against the calf muscles. The EMG surface electrodes were applied on the gastrocnemius medialis muscle and acquisition of both NMR and EMG signals was synchronized. The exercise consisted of a sustained isometric contraction at 70% of the maximal voluntary contraction until exhaustion. A continuous decrease in phosphocreatine content and a large concomitant increase in H 2 PO 4 − was observed in the calf muscles of each subject. A significant increase in H + concentration was also found when considering the whole population but intracellular acidosis was low for two subjects. Moreover, a quasilinear decrease in mean power frequency (MPF) was found during the test. Changes in MPF were correlated with variations in H + and H 2 PO 4 − concentration but a more significant relationship was found when MPF changes were correlated with H 2 PO 4 − concentration. An interpretation of EMG spectrum changes in terms of an accumulation of by-products of anaerobic metabolism and an increase in the relative number of activated slow fibres is proposed.
- NDSL :
유료 다운로드의 경우 해당 사이트의 정책에 따라 신규 회원가입, 로그인, 유료 구매 등이 필요할 수 있습니다. 해당 사이트에서 발생하는 귀하의 모든 정보활동은 NDSL의 서비스 정책과 무관합니다.
원문복사신청을 하시면, 일부 해외 인쇄학술지의 경우 외국학술지지원센터(FRIC)에서
무료 원문복사 서비스를 제공합니다.
NDSL에서는 해당 원문을 복사서비스하고 있습니다. 위의 원문복사신청 또는 장바구니 담기를 통하여 원문복사서비스 이용이 가능합니다.
- 이 논문과 함께 출판된 논문 + 더보기