Muscle Fibre can co-express different isoforms of Myosin Heavy Chain

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Anthony Sargeant directed this work on skeletal muscle as Head of the Amsterdam research group. The meticulous work was carried out by Jose Sant’Ana Pereira who was one of Tony Sargeant’s PhD students.

The mATPase histochemical profile of rat type IIX fibres: correlation with myosin heavy chain immunolabelling

Jose A A Sant’Ana PereiraArnold de HaanWessels AAnton F MoormanAnthony J Sargeant.

Journal of Histochemistry
Histochem J. 1995 Sep;27(9):715-22
In the present study we report a novel histochemical method which, by sequential pre-incubations in alkaline and acidic media, selectively differentiates muscle fibres expressing myosin heavy chain IIX, on the basis of a specific profile for myofibrillar actomyosin ATPase (mATPase) activity. The enzyme reactions were tested for specificity by means of anti-myosin heavy chain monoclonal antibodies, which were characterized on Western blots of muscle homogenates. Enzyme histochemical reactions with the traditional pH buffers were compared to those of the new method and, in conjunction with the immunoreactions, used to confirm the relationship between MyHC expression and the distinct profiles for mATPase. Immunohistochemical reactions demonstrated that the new method only differentiates those fibres expressing myosin heavy chain IIX. The method revealed a continuum in which the intermediate staining intensities corresponded to hybrid fibres expressing myosin heavy chain IIX in combination with either the IIA or IIB forms. Quantitative histochemistry and immunohistochemistry (by image analysis), used to examine the relationship between staining intensities for mATPase and amounts of myosin heavy chain IIX expression, revealed that the new method discriminates well between hybrid fibres expressing variable amounts of the IIX isoform (r2 = 0.93)

The mechanics of cycling – calculating air and rolling resistance

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Cycling performance depends upon overcoming air and rolling resistance in this research the results of ‘coasting down’ experiments were used by the authors to calculate these components. The experiments were performed in the massive indoor Flower Hall near Amsterdam on a Sunday morning. Anthony Sargeant was the head of the research department which carried out this work.

Air friction and rolling resistance during cycling

Gert de GrootAnthony J SargeantJos Geysel

Medicine and Science in Sports and Exercise
Med Sci Sports Exerc. 1995 Jul;27(7):1090-5
  • To calculate the power output during actual cycling, the air friction force Fa and rolling resistance Fr have to be known. Instead of wind tunnel experiments or towing experiments at steady speed, in this study these friction forces were measured by coasting down experiments. Towing experiments at constant acceleration (increasing velocity) were also done for comparison. From the equation of motion, the velocity-time curve v(t) was obtained. Curve-fitting procedures on experimental data of the velocity v yielded values of the rolling resistance force Fr and of the air friction coefficient k = Fa/v2. For the coasting down experiments, the group mean values per body mass m (N = 7) were km = k/m = (2.15 +/- 0.32) x 10(-3)m-1 and ar = Fr/m = (3.76 +/- 0.18) x 10(-2)ms-2, close to other values from the literature. The curves in the phase plane (velocity vs acceleration) and the small residual sum of squares indicated the validity of the theory. The towing experiments were not congruent with the coasting down experiments. Higher values of the air friction were found, probably due to turbulence of the air.

Human muscle fatigue

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Anita Beelen presented this research as part of her PhD thesis supervised by Professor Anthony Sargeant. Uniquely the study used electrical stimulation superimposed upon on maximal voluntary activation in dynamic exercise.

Fatigue and recovery of voluntary and electrically elicited dynamic force in humans

Anita BeelenAnthony J SargeantDavid A JonesC. J. de Ruiter

Journal of Physiology
J Physiol. 1995 Apr 1;484 ( Pt 1):227-235
1. Percutaneous electrical stimulation of the human quadriceps muscle has been used to assess the loss of central activation immediately after a bout of fatiguing exercise and during the recovery period.
2. Fatigue was induced in eight healthy males by a maximal effort lasting 25 s performed on an isokinetic cycle ergometer at a constant pedal frequency of 60 revolutions per minute. The cranks of the ergometer were driven by an electric motor. Before and after the sprint, subjects allowed their legs to be passively taken round by the motor. During the passive movement the knee extensors were stimulated (4 pulses; 100 Hz). Peak voluntary force (PVF) during the sprint and peak stimulated forces (PSF) before and in recovery were recorded via strain gauges in the pedals. Recovery of voluntary force was assessed in a series of separate experiments in which subjects performed a second maximal effort after recovery periods of different durations.
3. Peak stimulated forces were reduced to 69f8 + 9 3 % immediately after the maximal effort, (P< 0 05), but had returned to pre-exercise values after 3 min. The maximum rate of force development (MRFD) was also reduced following fatigue to 68f8 + 11 0% (P < 0’05) of control and was fully recovered after 2 min. PVF was reduced to 72-0 + 9 4% (P< 0 05) of the control value following the maximal effort. After 3 min voluntary force had fully recovered.
4. The effect of changing the duration of the fatiguing exercise (10, 25 and 45 s maximal effort) resulted in an increased degree of voluntary force loss as the duration of the maximal effort increased. This was associated with an increased reduction in PSF measured immediately after the exercise.
5. The close association between the changes in stimulated force and voluntary force suggests that the fatigue in this type of dynamic exercise may be due to changes in the muscle itself and not to failure of central drive.