The absorption of work by a muscle stretched during a single twitch or a short tetanus

Abbott, B. C.; Aubert, X; Hill, A. V.

doi:10.1098/rspb.1951.0048

Cited by 80 publications

(25 citation statements)

References 7 publications

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“….J. WO7ODS different speeds depends on many factors, but forces up to 1-8 Po have been reported (Katz, 1939;Abbott, Aubert & Hill, 1951). Hill (1939) showed that maximum efficiency of muscle shortening occurs at 0-2 Vmax* We found subjects cycled with maximum efficiency at speeds of rev/mill, a conclusion which can also be drawn from the work of Asmussen (1952) and Banister & Jackson (1967) (Fig.…”

Section: Discussionsupporting

confidence: 74%

Integrated electromyogram and oxygen uptake during positive and negative work.

Bigland-Ritchie¹,

Woods²

1976

The Journal of Physiology

260

157

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SUMMARY1. Integrated electromyogram (e.m.g.) from the vastus lateralis muscles, and steady-state rates of oxygen uptake, were measured simultaneously during the performance of set rates of positive (concentric) and negative (eccentric) work at 50 rev/min on a motorized bicycle ergometer.2. Similar experiments were also carried out at other pedalling rates and using other leg muscles.3. The relationships between each of the variables (integrated e.m.g., oxygen consumption) and mean torque on pedals were found to be lineal (r > 0-98) with a remarkable degree of reproducibility in surface e.m.g. for each subject over several months.4. The ratio of the e.m.g. slopes at 50 rev/min (positive/negative) was 1-96 + 0-12 while the same ratio for the oxygen uptake slopes was 6-34 + 0-82. The discrepancy between the ratios suggests that not only is less muscle fibre activity required to maintain the same exerted force during negative work exercise, but there is also a substantial reduction in the oxygen uptake when the fibres are stretched. This was observed for all speeds of pedalling.

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Section: Discussionsupporting

confidence: 74%

Integrated electromyogram and oxygen uptake during positive and negative work.

Bigland-Ritchie¹,

Woods²

1976

The Journal of Physiology

260

157

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“…The extra stretch was about 0-1 um per sarcomere in the 1 s period after shortening and the mean tension was about 0-4 N. The work done in stretching the central part of the muscle by this amount would have been about 2-7 mJ/g. The effect of such a stretch on the heat production may be estimated from the results ofprevious experiments on externally applied stretches (Abbott, Aubert & Hill, 1951;Hill & Howarth, 1959). The effect depends on the velocity of stretch; when the rate of sarcomere stretch is about 0-1 /Zm/s, as in the present case, there is extra heat production associated with the stretch (Fig.…”

Section: Discussionmentioning

confidence: 96%

The variation in shortening heat with sarcomere length in frog muscle.

Homsher¹,

Irving²,

Lebacq³

1983

The Journal of Physiology

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SUMMARY1. Pairs of frog semitendinosus muscles were stimulated tetanically for 2 s at 0 0C and, after 0 75 s of isometric contraction, were released at constant velocity for 0-16 s. The distance shortened was 0 3 jsm per sarcomere. The extra heat (shortening heat) associated with the release was determined by comparison with isometric control tetani.2. The mean sarcomere length at the start of stimulation was varied between 2-25 and 3-75 jsm. At the greater initial lengths there was considerable resting tension and heat was absorbed during releases of unstimulated muscles. This thermoelastic effect was also present during stimulation, so shortening heat values were calculated from the difference between the heat production ofthe stimulated and unstimulated muscle for releases over the same length range and at the same velocity.3. Laser diffraction was used to measure mean sarcomere length in the part of the muscle from which heat was recorded. At the greater initial lengths these central sarcomeres slowly elongated by a small amount during nominally isometric tetani. When a release was given during a tetanus the central sarcomere shortening was slightly less than that in a release of the unstimulated muscle with the same change of muscle length. In the period of a tetanus after the release had ended the rate of central sarcomere elongation was greater than that in an isometric tetanus.4. Shortening heat production had a large early component, during and just after the release, then continued to increase slowly up to the end of the tetanus. It is likely that sarcomere length redistribution along the muscle is responsible for the apparent slow phase, but has little effect on the early component.5. Shortening heat (determined as the early component) decreased linearly with increasing muscle length in the range studied. The intercept on the length axis was 3'78 + 0-08 ,sm per sarcomere (mean + s.E. of mean, n = 7, based on sarcomere length before stimulation). The corresponding intercept for the isometric tension before the release was 3-78+0'03 sum per sarcomere. The isometric heat rate at this time also decreased with increasing muscle length, but at 3 75 j#m per sarcomere was still 50-0 + 2-0 % of its maximum value.6. The results suggest that shortening heat, like isometric tension, is produced by the interaction of thick and thin filaments in contracting muscle.

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“…I The drastic fall in energy liberation when a muscle is stretched during contraction has been repeatedly confirmed both by myothermal methods (Abbott, Aubert & Hill, 1951;Abbott & Aubert, 1951;Hill & Howarth, A. F. HUXLEY 8 MUSCULAR CONTRACTION 1959;Wilkie, 1968) and by measurement of phosphorylcreatine utilization (Wilkie, 1968) and appearance of inorganic phosphate (Curtin & Davies, 1973). It is not yet clear whether the net energy liberation in a complete twitch can drop to zero, as suggested by the results of Hill & Howarth (1959) or whether there is always a residual energy liberation at least equal to the 'activation heat'.…”

Section: The Mechanism Of Contractionmentioning

confidence: 99%