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Titolo:
Effects of joint immobilization on firing rate modulation of human motor units
Autore:
Seki, K; Taniguchi, Y; Narusawa, M;
Indirizzi:
Int Budo Univ, Dept Exercise Physiol, Chiba 29952, Japan Int Budo Univ Chiba Japan 29952 ept Exercise Physiol, Chiba 29952, Japan
Titolo Testata:
JOURNAL OF PHYSIOLOGY-LONDON
fascicolo: 3, volume: 530, anno: 2001,
pagine: 507 - 519
SICI:
0022-3751(20010201)530:3<507:EOJIOF>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
MAXIMAL VOLUNTARY CONTRACTIONS; SKELETAL-MUSCLE; LIMB IMMOBILIZATION; DIFFERENT LENGTHS; TERM IMMOBILIZATION; FLEXOR MUSCLES; TRICEPS SURAE; DISUSE; FATIGABILITY; RECRUITMENT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
51
Recensione:
Indirizzi per estratti:
Indirizzo: Seki, K Univ Washington, Dept Physiol & Biophys, 357290, Seattle, WA 98195USA Univ Washington 357290 Seattle WA USA 98195 Seattle, WA 98195 USA
Citazione:
K. Seki et al., "Effects of joint immobilization on firing rate modulation of human motor units", J PHYSL LON, 530(3), 2001, pp. 507-519

Abstract

1. We investigated the effects of 6 weeks of immobilization on firing ratemodulation in motor units in the first dorsal interosseous (FDI) of human volunteers. The middle finger, index finger and thumb were immobilized for a period of 6 weeks in a fibre-glass cast, which kept FDI in a shortened position.2. During isometric contraction at 20, 40, 60 and 80 % of maximal voluntary contraction (MVC) (index finger abduction), motor unit action potentials were recorded from the FDI using a tungsten microelectrode, and the relationship between voluntary force and mean firing rate (MFR) was obtained by plotting the MFR of each motor unit action potential train as a function of voluntary force. Four recording sessions were held for each subject: before immobilization, after 3 and 6 weeks of immobilization, and after a 6 week recovery period.3. As a result of immobilization, FDI volume (as measured by computerized tomography (CT) scanning) decreased, with an accompanying reduction in aggregate EMG activity per day (P < 0.01). The force measured during MVC also decreased (P < 0.05).4. The slope of the relationship between voluntary force and MFR was significantly decreased after immobilization, as was the range of firing rate modulation (P < 0.01). Maximal MFR, estimated from the relationship between voluntary force and MFR, was decreased (P < 0.05).5. MFR was also plotted against voluntary force without being normalized with respect to MVC, and the slope of the regression line was decreased (P <0.05). Voluntary force when the MFR was 15 Hz was estimated from regression equations for the absolute force-MFR relationship, and it was increased after immobilization (P < 0.05).6. These results suggest that firing rate modulation shows two different adaptations to joint immobilization: a restriction of motoneurone firing to the lower rates and an enhancement of the voluntary force exerted when the MFR is relatively low.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 21/09/20 alle ore 01:47:11