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Visa fullständig version : Periodisk stretch och förlust av kraftutveckling


King Grub
2013-10-15, 08:38
INTRODUCTION:

The relative contributions of central versus peripheral factors to the force loss induced by acute continuous and intermittent plantarflexor stretches were studied.

METHODS:

Eighteen healthy young men with no apparent tissue stiffness limitations randomly performed 1) one 5-min stretch (continuous stretch; CS); 2) five 1-min stretches (intermittent stretch; IS); and 3) a control condition, on three separate days. The stretches were constant-torque ankle stretches performed on an isokinetic dynamometer. Gastrocnemius medialis oxygenation status was quantified during stretch using near infra-red spectroscopy. Measures of isometric plantarflexor peak torque (Tpeak), voluntary activation (%VA; interpolated twitch technique), EMG amplitude normalized by Mmax (EMG:M), V-wave amplitude and excitation-contraction (E-C) coupling efficiency (torque ratio between 20 and 80 Hz tetanic stimulations [20:80]) were taken before, immediately, and 15 and 30 minutes after each condition.

RESULTS:

IS caused substantial cyclic variations in tissue oxygenation, but CS resulted in a greater decrease in oxyhemoglobin concentration. Voluntary Tpeak decreased more after IS (-23.8%) than CS (-14.3%), and remained significantly depressed until 30 min after IS only (-5.6%). EMG:M (-27.7%) and %VA (-15.9%) were reduced only after IS. After CS and IS, the magnitude of decrease in Tpeak was correlated with decreases in EMG:M (r=0.81 and 0.89, respectively), %VA (r=0.78 and 0.93) and V-wave (r=0.51, only after IS). 20 Hz and 80 Hz tetanic torque were decreased after IS (-13.1% and -6.4%, respectively) and CS (-10.9% and -6.7%), but 20:80 was not different from the control group.

CONCLUSION:

These results suggest that IS reduced Tpeak more than CS, and these reductions were strongly associated with a depression in central drive.

Med Sci Sports Exerc. 2013 Oct 10. Intermittent Stretch Reduces Force and Central Drive more than Continuous Stretch.

knix
2013-10-15, 10:38
"greater decrease in oxyhemoglobin concentration"

d.v.s. lägre syrenivåer i musklerna?