Effect of muscle warming on sprint power of humans

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This research by demonstrated for the first time that the magnitude of the effect of warming up human muscle on sprint power depended on the speed of movement. Thus, the faster the speed of movement the greater was the benefit of warm-up.

The study was made possible by the development of the isokinetic cycle ergometer which allowed the pedalling rate to be held constant during an all-out sprint effort. [see Anthony J Sargeant, Elizabeth Hoinville, Archie Young (1981)]

European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1987;56(6):693-8

The effect of changing muscle temperature on performance of short term dynamic exercise in man was studied.

Four subjects performed 20 s maximal sprint efforts at a constant pedalling rate of 95 crank rev.min-1 on an isokinetic cycle ergometer under four temperature conditions: from rest at room temperature; and following 45 min of leg immersion in water baths at 44; 18; and 12 degrees C.

 

Muscle temperature (Tm) at 3 cm depth was respectively 36.6, 39.3, 31.9 and 29.0 degrees C. After warming the legs in a 44 degrees C water bath there was an increase of approximately 11% in maximal peak force and power (PPmax) compared with normal rest while cooling the legs in 18 and 12 degrees C water baths resulted in reductions of approximately 12% and 21% respectively. Associated with an increased maximal peak power at higher Tm was an increased rate of fatigue.

Two subjects performed isokinetic cycling at three different pedalling rates (54, 95 and 140 rev.min-1) demonstrating that the magnitude of the temperature effect was velocity dependent: At the slowest pedalling rate the effect of warming the muscle was to increase PPmax by approximately 2% per degree C but at the highest speed this increased to approximately 10% per degree C.

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Improving circulation of the paralysed legs of people with spinal cord injury

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This publication was one of a series of research papers resulting from a collaboration between the the Amsterdam research group of Professor Tony Sargeant and Professor Maria Hopman in the University of Nijmegen. In this paper it was shown that circulation to the paralysed legs could be significantly improved by training using functional electrical stimulation.
Archives of Physical Medicine and Rehabilitation
Arch Phys Med Rehabil. 2001 Jun;82(6):832-9

Abstract

OBJECTIVE: To test whether a short period of training leads to adaptations in the cross-sectional area of large conduit arteries and improved blood flow to the paralyzed legs of individuals with spinal cord injury (SCI).

DESIGN: Before-after trial.

SETTING: Rehabilitation center, academic medical center.

 

PARTICIPANTS: Nine men with spinal cord lesions.

INTERVENTION: Six weeks of cycling using a functional electrically stimulated leg cycle ergometer (FES-LCE).

MAIN OUTCOME MEASURES: Longitudinal images and simultaneous velocity spectra were measured in the common carotid (CA) and femoral (FA) arteries using quantitative duplex Doppler ultrasound examination. Arterial diameters, peak systolic inflow volumes (PSIVs), mean inflow volumes (MIVs), and a velocity index (VI), representing the peripheral resistance, were obtained at rest. PSIVs and VI were obtained during 3 minutes of hyperemia following 20 minutes of FA occlusion.

RESULTS: Training resulted in significant increases in diameter (p < .01), PSIVs (p < .01), and MIVs (p < .05), and reduced VI (p < .01) of the FA, whereas values in the CA remained unchanged. Postocclusive hyperemic responses were augmented, indicated by significantly higher PSIVs (p <.01) and a trend toward lower VI.

CONCLUSION: Six weeks of FES-LCE training increased the cross-sectional area of large conduit arteries and improved blood flow to the paralyzed legs of individuals with SCI

Walking downhill causes damage to human muscle

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Walking downhill on a motor driven treadmill requires the leg extensor muscles to act as brakes by performing eccentric contractions, that is the muscle are activated but actually stretched so that they slow down and control the rate of descent of the body centre on mass. Eccentric contractions have been used previously to generate experimental muscle damage as evidenced by the appearance of creatine kinase in the plasma and visual disruption of the muscle fibres within biopsies. In this research Professor Sargeant reports on the progessive increase in energy cost of exercise walking downhill to the point of collapse and the consequent long term loss of normal muscle function.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1987;56(6):704-11

4 subjects performed repeated eccentric contractions with leg extensors during prolonged downhill walking (-25% gradient) at 6.44 km.h-1 until collapse due to muscle weakness (range of exercise duration 29 to 40 min).

During the exercise oxygen uptake rose progressively from approximately 45% of the previously determined VO2max at 10 min to approximately 65% at the end of the exercise. Following the exercise there was an immediate, significant, and sustained reduction in maximal voluntary isometric contraction, and short term (anaerobic) power output measured concentrically on an isokinetic ergometer. These reductions in muscle function persisted for 96 hours post exercise, and were reflected by significant reductions in the tension generated at low frequency (20 Hz) relative to higher frequency (50 Hz) percutaneous stimulation of the quadriceps. All four subjects showed an increase in plasma levels of creatine kinase post eccentric exercise. Performing concentric contractions by walking uphill for one hour at a significantly greater metabolic cost failed to induce comparable reductions in muscle function. These results provide evidence for the consequences of prolonged eccentric work upon dynamic function which complements earlier reports of structural, enzymatic, and static function changes

Carnitine supplementation had little effect on human exercise performance

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In this research study Carolyn A Greig, the talented PhD student of Professor Anthony J Sargeant, carried out a study at the  Rayne Research Institute of University College Hospital which failed to demonstrate any significant effect of carnitine on exercise performance.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1987;56(4):457-60

Two trials were conducted to investigate the effects of L-carnitine supplementation upon maximum and submaximum exercise capacity. Two groups of healthy, untrained subjects were studied in double-blind cross-over trails. Oral supplementation of 2 g per day L-carnitine was used for 2 weeks in the first trial and the same dose but for 4 weeks in the second trial.

Maximum and submaximum exercise capacity were assessed during a continuous progressive cycle ergometer exercise test performed at 70 rpm. In trial 1, plasma concentrations of lactate and beta-hydroxybutyrate were measured pre- and post-exercise. In trial 2, pre- and post-exercise plasma lactate were measured. The results of treatment with L-carnitine demonstrated no significant changes in maximum oxygen uptake (VO2max) or in maximum heart rate. In trial 1, there was a small improvement in submaximal performance as evidenced by a decrease in the heart-rate response to a work-load requiring 50% of VO2max. The more extensive trial 2 did not reproduce the significant result obtained in trial 1, that is, there was no significant decrease in heart rate at any given submaximal exercise intensity, under carnitine-supplemented conditions. Plasma metabolic concentrations were unchanged following L-carnitine, in both trials. It is concluded, that in contrast to other reports, carnitine supplementation may be of little benefit to exercise performance since the observed effects were small and inconsistent

Efficiency of Human Muscle at different contraction frequencies

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This research was a collaboration between Manchester and Copenhagen. Richard Ferguson was the talented young PhD student of Professor Anthony J Sargeant who collected data in Copenhagen for this publication under the supervision of Jens Bangsbo.
Journal of Applied Physiology
J Appl Physiol. 2000 Nov;89(5):1912-8

Abstract A novel approach has been developed for the quantification of total mechanical power output produced by an isolated, well-defined muscle group during dynamic exercise in humans at different contraction frequencies. The calculation of total power output comprises the external power delivered to the ergometer (i.e., the external power output setting of the ergometer) and the “internal” power generated to overcome inertial and gravitational forces related to movement of the lower limb. Total power output was determined at contraction frequencies of 60 and 100 rpm. At 60 rpm, the internal power was 18+/- 1 W (range: 16-19 W) at external power outputs that ranged between 0 and 50 W. This was less (P<0.05) than the internal power of 33+/-2 W (27-38 W) at 100 rpm at 0-50 W. Moreover, at 100 rpm, internal power was lower (P<0.05) at the higher external power outputs. Pulmonary oxygen uptake was observed to be greater (P<0.05) at 100 than at 60 rpm at comparable total power outputs, suggesting that mechanical efficiency is lower at 100 rpm. Thus a method was developed that allowed accurate determination of the total power output during exercise generated by an isolated muscle group at different contraction frequencies

Strength training for athletes and in rehabilitation is very specific

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Professors Anthony J Sargeant and David A Jones were the PhD supervisors respectively for Carolyn A Greig and Olga M Rutherford who both held PhD studentships awarded by the UK Sports Council.
Journal of Sports Sciences
J Sports Sci. 1986 Autumn;4(2):101-7
Olga M Rutherford, Carolyn A Greig, Anthony J Sargeant, David A Jones.

 

The effects of strength training of the quadriceps on peak power output during isokinetic cycling has been investigated in group of 17 young healthy volunteers. Subjects trained by lifting near-maximal loads on a leg extension machine for 12 weeks. Measurements of maximal voluntary isometric force were made at 2-3 week intervals and a continual record was kept of the weights lifted in training.

Peak power output was measured at 110 rev min-1 and at either 70 or 80 rev min-1 before and after the 12 week training period. Measurements of maximum oxygen uptake (VO2max) were made on 12 subjects before and after training. The greatest change was in the weights lifted in training which increased by 160-200%. This was accompanied by a much smaller increase in maximum isometric force (3-20%). There was no significant change in peak power output at either speed. The VO2max remained unchanged with training. The role of task specificity in training is discussed in relation to training regimes for power athletes and for rehabilitation of patients with muscle weakness.

Human Muscle Power in Cycling

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After a year of hard work as an MRC Fellow attached to McMaster University Medical Centre in Hamilton, Ontario, Canada,Professor Anthony Sargeant introduced and eventually succeeded in building an isokinetic cycle ergometer to measure human muscle power. This publication by the PhD student McCarteney was the result – reproducing though perhaps less elegantly the previous publication of Professor Sargeant – [viz: Anthony J Sargeant, Elizabeth Hoinville, Archie Young.Maximum leg force and power output during short-term dynamic exerciseJ Appl Physiol Respir Environ Exerc Physiol. 1981 Nov;51(5):1175-82 ]

Journal of Applied Physiology
J Appl Physiol Respir Environ Exerc Physiol. 1983 Jul;55(1 Pt 1):212-7

A cycle ergometer has been designed to measure the force exerted on the pedal cranks during maximum effort at a variety of constant velocities. Preset crank velocities of 13-166 rpm are established by a controlled 3-hp motor and cannot be overcome by the subject. Torque is measured by strain gauges bonded to the crank shafts; peak torque, peak power, work, and average power are derived for each pedal cycle.

Studies in 30 healthy male subjects established reproducibility and normal standards. During exercise for 45 s at a constant velocity of 60 rpm, there was a wide intersubject variation in both maximal torque (118-226 N . m) and the percentage decline in torque (27.2-52.0%). The decline in torque was inversely related to maximal O2 intake (r = 0.84). During short (10-s) periods of exercise at six crank velocities between 60-160 rpm, a linear inverse relationship between maximal peak torque and pedal crank velocity was observed. The peak torque-velocity relationship and the percentage decline in peak torque during 30s exercise at 60, 100, and 140 rpm were reproducible within a given subject, the coefficient of variation was less than 10%