PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Isometric Contraction”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed1987

The temperature dependence of isometric contractions of single, intact fibres dissected from a mouse foot muscle.

1. Isometric tension responses to electrical stimulation have been studied at 7.5 37.5 degrees C in single, intact fibres of the flexor digitorum brevis muscle of the mouse. A large number of reproducible tetani could be obtained at temperatures less than or equal to 35 degrees C. 2. The tetanic force per cross-sectional area generated at 25.0 degrees C was 375 +/- 56 kPa (mean +/- S.D., n = 16). 3. The curve relating maximum tetanic tension to temperature exhibited a transition between a level of almost unaltered force (25.0-32.5 degrees C) and a marked force decline (less than or equal to 20.0 degrees C). At temperatures higher than 35.0 degrees C force production was markedly depressed and this reduction was in some cases irreversible. 4. Twitch tension showed less regular dependence on temperature; it was reduced less than tetanic tension at low temperatures. Thus, the twitch/tetanus tension ratio was higher at low temperatures. 5. The times for twitch contraction and for twitch half-relaxation (i) ranged from 7 to 14 ms and from 6 to 15 ms at 35.0 degrees C and (ii) exhibited Q10 values of 3.2 +/- 0.4 and 4.0 +/- 0.6, respectively. 6. It is concluded that it is possible to use intact, single fibres dissected from mammalian skeletal muscle in physiological studies. Our results are close to previous results obtained from mammalian muscles except that the tetanic tension per cross-sectional area was found to be higher than commonly reported.

Animals↗
PubMed1984

Cumulative electromyography of the human masseter muscle during fatiguing isometric contractions.

Six adult males performed maximum voluntary tooth clenching (MVC) for 10, 20, 30, 40 s and, after 15 min, for 40, 30, 20, 10 s. During the isometric exercises the electrical currents of the masseter muscle were sampled by integrated and cumulative surface electromyography. Subjective masseter fatigue was present after 30 and 40 s of MVC clenching, accompanied by changes in myoelectrical activity. Strength testing of the masseter muscle, before and after endurance testing, showed that the strength increased by a significant 16% following two endurance tests. This observation was explained by a post-tetanic potentiation and/or a differentiated use of motor units in the fatigued muscle. It is concluded that brief MVC isometric activity, or strength testing, is not a reliable measure of fatigue in the masseter muscle when cumulative electromyography is used. Prolonged MVC isometric activity, or progressive endurance testing, monitors reliably the onset and progression of masseter fatigue.

Adult↗