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Titolo:
Stretch- and H-reflexes of the lower leg during whole body cooling and local warming
Autore:
Oksa, J; Rintamaki, H; Rissanen, S; Rytky, S; Tolonen, U; Komi, PV;
Indirizzi:
Oulu Reg Inst Occupat Hlth, Physiol Lab, FIN-90220 Oulu, Finland Oulu Reg Inst Occupat Hlth Oulu Finland FIN-90220 IN-90220 Oulu, Finland Cent Hosp, Dept Clin Neurophysiol, Oulu, Finland Cent Hosp Oulu FinlandCent Hosp, Dept Clin Neurophysiol, Oulu, Finland Univ Jyvaskyla, Dept Biol Phys Activ, Oulu, Finland Univ Jyvaskyla Oulu Finland askyla, Dept Biol Phys Activ, Oulu, Finland
Titolo Testata:
AVIATION SPACE AND ENVIRONMENTAL MEDICINE
fascicolo: 2, volume: 71, anno: 2000,
pagine: 156 - 161
SICI:
0095-6562(200002)71:2<156:SAHOTL>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
PERFORMANCE; EMG; TEMPERATURE;
Keywords:
motor control; cooling; stretch-shortening cycle; stretch reflex; H-reflex;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Life Sciences
Citazioni:
15
Recensione:
Indirizzi per estratti:
Indirizzo: Oksa, J Oulu Reg Inst Occupat Hlth, Physiol Lab, AAPISTE 7, FIN-90220 Oulu, Finland Oulu Reg Inst Occupat Hlth AAPISTE 7 Oulu Finland FIN-90220 nland
Citazione:
J. Oksa et al., "Stretch- and H-reflexes of the lower leg during whole body cooling and local warming", AVIAT SP EN, 71(2), 2000, pp. 156-161

Abstract

Background: This study was undertaken to evaluate if possible changes in stretch- and H-reflexes could be related to the changes in the EMG activity of the cooled lower leg muscles observed during a stretch-shortening cycle exercise. Methods: Eight subjects wearing shorts and jogging shoes were exposed once to 27 degrees C and twice to 10 degrees C for 60 min each. Duringthe second exposure to 10 degrees C, the subject's lower legs were kept warm (10 degrees Clw) with electrical pillows. After the exposures Achilles tendon reflex (stretch reflex) was induced and the EMG activity of the triceps surae was measured. Immediately after reflex measurements the EMC activity of the triceps surae and tibialis anterior during a drop-jump (stretch-shortening cycle) was measured. After similar thermal exposures electricallyinduced H-reflex from the calf was measured. Results: During the preactivity and stretch phases the EMG activity of the triceps surae increased afterthe exposure to 10 degrees C, whereas during the shortening phase it decreased. During the shortening phase cooling, on the contrary, increased the activity of tibialis surae anterior. These changes disappeared at 10 degreesClw. At 10 degrees C the maximum EMG-amplitude of triceps surae during stretch reflex decreased (p < 0.05), reflecting suppressed muscle spindle activity. Suppressed spindle activity causes the agonist to be unfacilitated and the antagonist muscle contraction to be uninhibited, which was seen in the present study as decreased agonist and increased antagonist EMC activity during the shortening phase at 10 degrees C. The Hmax/Mmax-ratio, H-reflex latency and amplitude increased at 10 degrees C (p < 0.05), reflecting increased motoneuron pool excitability. This in part may explain the increased EMC activity during the preactivity and stretch phases. Conclusion: Cooling-induced increase in the excitability of the motoneuron pool and suppression of muscle spindle activity seem to be responsible of the EMG activity changes during the stretch-shortening cycle, consequently decreasing muscular performance.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 12/07/20 alle ore 06:54:14