The effect of long-term immobilization on the motor unit population of the cat medial gastrocnemius muscle

Rf, Mayer; Burke, RE; Toop, James; Ja, Hodgson; Kanda, Kenro; Bw, Walmsley

doi:10.1016/0306-4522(81)90156-1

Cited by 58 publications

(39 citation statements)

References 48 publications

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“…5 which also shows that the decrease in A firing rate after immobilization is larger in motor units of low recruitment threshold and large frequency modulation as compared to motor units of higher threshold and lower frequency modulation. Decrease in maximal firing rate could be explained by changes in proprioceptive afferents on the motoneurons (Mayer, Burke, Toop, Hodgson, Kanda & Walmsley, 1981) and/or MOTOR UNIT BEHA VIOUR AFTER IMMOBILIZATION reduced ability to activate motor units (Fuglsang-Frederiksen & Scheel, 1978;Sale et al 1982). This last point was suggested by the finding after immobilization of a smaller reflex potentiation which is closely controlled by the central drive (Upton, McComas & Sica, 1971).…”

Section: Discussionmentioning

confidence: 99%

Effects of immobilization on contractile properties, recruitment and firing rates of human motor units.

Duchateau¹,

Hainaut²

1990

The Journal of Physiology

179

120

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SUMMARY1. The contractile properties, recruitment and firing rates of motor units from the human adductor pollicis and the first dorsal interosseous were studied during voluntary isometric contractions after 6-8 weeks' immobilization of the corresponding limbs.2. In both muscles, motor units of different force thresholds showed a proportionally identical twitch tension decrease and slowing of their time course after immobilization.3. When expressed as a percentage of the maximal voluntary contraction, more high-threshold motor units were recorded in disused muscles than in control muscles, but the order of recruitment was maintained.4. The motor unit firing rate at recruitment was identical in control and disused muscles, but the maximal firing rate decreased in all motor units after immobilization. This decrease of the maximal firing rate was greater in motor units of lower threshold than in those of higher threshold.5. The results further document motoneuronal plasticity in human muscles of different fibre type composition.

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Section: Discussionmentioning

confidence: 99%

Effects of immobilization on contractile properties, recruitment and firing rates of human motor units.

Duchateau¹,

Hainaut²

1990

The Journal of Physiology

179

120

View full text Add to dashboard Cite

show abstract

“…Other reports describe immobilized cat units that produce weak tetanic forces and EMG with no measurable twitch force. 11,15,21 In contrast, those triceps brachii muscles with a manual score of 3 or higher can have functional impact. If these muscles contain only a few excitable units, they must be driven almost maximally to generate forces that are useful in everyday tasks.…”

Section: Discussionmentioning

confidence: 88%

Motor unit forces and recruitment patterns after cervical spinal cord injury

1997

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“…Pierre and Gardiner, 1985). However, a few studies demonstrated equal (Sjostrom et al, 1979;Mayer et al, 1981;Lindboe and Platou, 1982;Spector et al, 1982) or greater effects of immobilization on Type I1 fibers (Karpati and Engel, 1968;Herbison et al, 1978). Early cast removal did not minimize the extent of muscle atrophy.…”

Section: Discussionmentioning

confidence: 95%

Muscle atrophy continues after early cast removal following tendon repair

1992

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We studied soleus (SOL), plantaris (PLN), and gastrocnemius (GST) muscles to determine whether early cast removal minimizes muscle atrophy or permits recovery from atrophy after tendon repair. After right tendocalcaneus (Achilles tendon) was transected and repaired, rabbit right hindlimbs were immobilized with the ankle plantar flexed and the knee flexed to 90 degrees. Rabbits were maintained in the cast and sacrificed at 5, 15, or 21 days postoperatively or the cast was removed on day 5 and the animals sacrificed at day 15 or 21. SOL, PLN, and GST muscles of both limbs were removed and weighed, and then histochemical analyses were performed on SOL and PLN muscles. Immobilization decreased SOL muscle wet weights, mean fiber cross-sectional area, and percentage of Type I fibers and increased the percentage of Type IIc fibers. Ten days after cast removal (i.e., postoperative day 15), SOL muscle atrophy and fiber composition did not differ significantly from continuously immobilized controls. However, 16 days after cast removal (i.e., postoperative day 21), SOL muscle fiber cross-sectional area and fiber composition were near normal, differing significantly from continuously casted controls. At each of the time intervals studied, PLN (containing many glycolytic fibers) did not atrophy as much as SOL (containing mainly oxidative fibers). Our results indicate that 1) early cast removal prevents atrophy of PLN glycolytic fibers, but not oxidative fibers in either PLN or SOL, and 2) early cast removal promotes recovery from atrophy of both oxidative and glycolytic fibers. In spite of the many differences between rabbits and humans, these findings suggest that, although early cast removal may not prevent oxidative muscle fiber atrophy after postoperative immobilization, it may facilitate recovery from atrophy.

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The effect of long-term immobilization on the motor unit population of the cat medial gastrocnemius muscle

Cited by 58 publications

References 48 publications

Effects of immobilization on contractile properties, recruitment and firing rates of human motor units.

Effects of immobilization on contractile properties, recruitment and firing rates of human motor units.

Motor unit forces and recruitment patterns after cervical spinal cord injury

Muscle atrophy continues after early cast removal following tendon repair

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