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THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS

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The Journal of Sports Medicine and Physical Fitness 2012 December;52(6):665-73

lingua: Inglese

Muscle sympathetic nerve activity during intermittent handgrip exercise

Hachiya T. 1, Aizawa S. 2, Blaber A. P. 1, Saito M. 2

1 Laboratory of Applied Physiology, Toyota Technological Institute, Nagoya 468-0511, Japan;
2 Aerospace Physiology Laboratory, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada


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AIM: This study evaluated whether central command plays an important role in activating muscle sympathetic nerve activity (MSNA) during short-term maximal handgrip contractions.
METHODS: The increase in MSNA was examined while influence of minimizing for other factors such as mechanoreflex, metaboreflex and fatigue during repetitive exercise in seven 19- to 26-year-old participants. Maximal voluntary handgrips (15-s contraction with a 45-s relaxation) were performed 10 times with a 15-s pause between alternate hands. MSNA was recorded from the tibial nerve analyzed using the burst frequency (BF) and total sympathetic nerve activity.
RESULTS: The BF increased with the first unit, from 14.9±1.8 bursts·min-1 at baseline to 27.7±3.4 bursts·min-1 during contraction. The increase in the MSNA during contractions remained unchanged throughout the repetitions. The BF declined to baseline during the relaxation periods. The peak grip force decreased from 333±25 N for the first grip to 216±20 N for the last contraction. The MSAN increase remained constant despite a possible reduction in mechanoreflex during exercise as indicated from decreased maximal handgrip force.
CONCLUSION: We suggested that the MSNA response was induced mainly by central command during short-term maximal handgrip contraction without metaboreflex influence and attenuated mechanoreflex input.

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thachiya@hotmail.com