Human Muscle Fibre Types

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In this important series of studies a collaboration between the research group in Amsterdam led by Anthony Sargeant and that in London under the direction of Professor Geoffrey Goldspink used new techniques based on microdissection of fragments of human muscle fibre obtained by needle biopsy.
Characterization of human skeletal muscle fibres according to the myosin heavy chains they express

Steven EnnionJose A A Sant’ana PereiraAnthony J SargeantArchie YoungGeoffrey Goldspink.

Journal of Muscle Research and Cell Motility
J Muscle Res Cell Motil. 1995 Feb;16(1):35-43
Using a method of single muscle fibre analysis, we investigated the presence of RNA transcripts for various isoforms of the myosin heavy chain (MyoHC) gene in histochemically, immunohistochemically and electrophoretically characterized individual muscle fibres (n = 65) from adult human vastus lateralis muscle. A cDNA clone isolated in this study was shown to contain the 3′ end of a previously uncharacterized human MyoHC gene which is expressed specifically in human fast IIA muscle fibres and we conclude that this clone contains part of the human fast IIA MyoHC gene. In all the fibres histochemically, immunohistochemically and electrophoretically characterized as containing the previously classified IIB MyoHC (n = 23), it was shown that the human equivalent to the rat type IIX MyoHC gene is expressed. This observation was taken to suggest that the previously classified IIB muscles fibres in human muscle express a MyoHC isoform equivalent to the rat IIX, not the IIB, and would therefore be more accurately classified as IIX fibres.
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Organised exercise programmes are beneficial in the treatment of depression

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Dr David Veale (now Professor) was the psychiatrist working at the Royal Free Hospital, London responsible for this research. Professor Anthony Sargeant and Professor Anthony Mann were the consultants for these studies. The results indicate that many patients with depression benefited from organised programmes of exercise alongside normal treatment protocols.
Journal of The Royal Society of Medicine
J R Soc Med. 1992 Sep;85(9):541-4

Two clinical trials have been conducted in a sample of depressed patients to determine whether the addition of an aerobic exercise programme to their usual treatment improved outcome after 12 weeks. In the first trial, an aerobic exercise group had a superior outcome compared with a control group in terms of trait anxiety and a standard psychiatric interview. A second trial was then conducted to compare an aerobic exercise programme with low intensity exercise.

Both groups showed improvement but there were no significant differences between the groups. In neither trial was there any correlation between the extent of change in the subjects’ physical fitness due to aerobic exercise and the extent of the improvement of psychiatric scores.

Growth related changes in muscle properties

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The effect of growth on the dynamic performance of rat medial gastrocnemius muscle was studied. From approximately 1.5 to 5 months of age specific force increased by 18%.

Reductions were found in both optimal stimulation frequency (from 120 to 100 Hz) and optimal shortening velocity (by 16%) indicating that the fibres became slower. Specific power did not change during growth but was obtained at a lower shortening velocity. Possible mechanisms for the observed changes are discussed

Fatigue of human muscle

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As part of her PhD research the very talented and conscientious Anita Beelen collected this data under the direction of Professor Anthony J Sargeant. It was one of the first studies indicating how human muscle fatigue could be due to the selective fatigue of a relatively small population of muscle fibres.
Journal of Applied Physiology
J Appl Physiol. 1991 Dec;71(6):2332-7

The effect of fatigue as a result of a standard submaximal dynamic exercise on maximal short-term power output generated at different contraction velocities was studied in humans. Six subjects performed 25-s maximal efforts on an isokinetic cycle ergometer at five different pedaling rates (60, 75, 90, 105, and 120 rpm). Measurements of maximal power output were made under control conditions [after 6 min of cycling at 30% maximal O2 uptake (VO2max)] and after fatiguing exercise that consisted of 6 min of cycling at 90% VO2max with a pedaling rate of 90 rpm.

Compared with control values, maximal peak power measured after fatiguing exercise was significantly reduced by 23 +/- 19, 28 +/- 11, and 25 +/- 11% at pedaling rates of 90, 105, and 120 rpm, respectively. Reductions in maximum peak power of 11 +/- 8 and 14 +/- 8% at 60 and 75 rpm, respectively, were not significant. The rate of decline in peak power during the 25-s control measurement was least at 60 rpm (5.1 +/- 2.3 W/s) and greatest at 120 rpm (26.3 +/- 13.9 W/s). After fatiguing exercise, the rate of decline in peak power at pedaling rates of 105 and 120 rpm decreased significantly from 21.5 +/- 9.0 and 26.3 +/- 13.9 W/s to 10.0 +/- 7.3 and 13.3 +/- 6.9 W/s, respectively. These experiments indicate that fatigue induced by submaximal dynamic exercise results in a velocity-dependent effect on muscle power. It is suggested that the reduced maximal power at the higher velocities was due to a selective effect of fatigue on the faster fatigue-sensitive fibers of the active muscle mass.

Cold muscles results in higher lactate levels at the beginning of exercise in humans

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Research carried out by Anita Beelen as part of her programme of PhD programme under the direction of Professor Anthony Sargeant.It shows that compared to normal conditions when muscle is cold there is an initially higher level of lactate in the blood due to relative hypoxic muscle consequent upon cold induced vasoconstriction. Subsequently as the muscle warms the lactate level drops but its removal requires elevated oxygen uptake.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1991;63(5):387-92

The effect of low muscle temperature on the response to dynamic exercise was studied in six healthy men who performed 42 min of exercise on a cycle ergometer at an intensity of 70% of their maximal O2 uptake. Experiments were performed under control conditions, that is, from rest at room temperature, and following 45 min standing with legs immersed in a water bath at 12 degrees C. The water bath reduced quadriceps muscle temperature (at 3 cm depth) from 36.4 (SD 0.5) degrees C to 30.5 (SD 1.7) degrees C. Following cooling, exercise heart rate was initially lower, the mean difference ranged from 13 (SD 4) beats.min-1 after 6 min of exercise, to 4 (SD 2) beats.min-1 after 24 min of exercise. Steady-state oxygen uptake was consistently higher (0.2 l.min-1). However, no difference could be discerned in the kinetics of oxygen uptake at the onset of exercise. During exercise after cooling a significantly higher peak value was found for the blood lactate concentration compared to that under control conditions. The peak values were both reached after approximately 9 min of exercise. After 42 min of exercise the blood lactate concentrations did not differ significantly, indicating a faster rate of removal during exercise after cooling. We interpreted these observations as reflecting a relatively higher level of muscle hypoxia at the onset of exercise as a consequence of a cold-induced vasoconstriction. The elevated steady-state oxygen uptake may in part have been accounted for by the energetic costs of removal of the extra lactate released into the blood consequent upon initial tissue hypoxia

Effects of high frquency stimulation on muscle power

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Research carried out by Fabio Abbate as part of his PhD which was supervised by Anthony Sargeant and Arnold de Haan.
Journal of Applied Physiology
J Appl Physiol. 2000 Jan;88(1):35-40.

Abstract: The effects of high-frequency initial pulses (HFIP) and posttetanic potentiation on mechanical power output during concentric contractions were examined in the in situ medial gastrocnemius of the rat with an intact origin on the femur and blood supply. Stimulation of the muscle was performed via the severed sciatic nerve. In the experiments, HFIP or the potentiating tetanus was followed by a stimulation of 80, 120, or 200 Hz.

The results showed that both HFIP and the tetanus increased power output at high contraction velocities (>75 mm/s) when followed by a train of 80 or 120 Hz (200 Hz resulted in no effects). Mechanical power output was increased maximally by HFIP to 120 and 168% by the tetanus. Furthermore, when HFIP or the tetanus were followed by a train of 80 Hz, the peak power in the power-velocity curve tended to be shifted to a higher velocity.

Effect of temperature in paralysed muscles of people with spinal cord injury

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HL Gerrits collected this research data on spinal cord injured people as part of her PhD supervised by Professor Anthony Sargeant. One problem encountered in trying to assess any training induced changes in the contractile properties of the paralysed muscles using electrical stimulation is that the muscles can be colder than normal as a consequence of circulatory changes.
Clinical Science
Clin Sci (Lond). 2000 Jan;98(1):31-8

Low muscle temperature in paralysed muscles of individuals with spinal cord injury may affect the contractile properties of these muscles. The present study was therefore undertaken to assess the effects of increased muscle temperature on the isometric contractile properties of electrically stimulated paralysed quadriceps muscles. When muscle temperature at a depth of 3 cm was increased from approximately 32 degrees C to approximately 36 degrees C by ultra-short-wave application, the half-relaxation time shortened and low-frequency force responses became less fused, but the maximal rate of increase in force remained unchanged.

Heating had no effect upon either force decline or slowing of relaxation during fatiguing contractions. The force-frequency relationship of the paralysed quadriceps muscle was shifted to the right after the muscle was heated. Despite this shift, however, the relationship still resembled that in muscles of non-paralysed individuals, probably due to the unexplained high twitch forces. These results indicate that reduced muscle temperature in spinal-cord-injured individuals may lead to an underestimation of the changes in contractile properties in terms of relaxation rate or the degree of fusion with low-frequency stimulation. In addition, the force-frequency relationship of paralysed muscles does not accurately reflect the magnitude of these changes, even when the muscle is heated, and should therefore be treated with caution.