Optimum pedalling rates in cycling

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The data for this research publication was collected in Amsterdam by Jerzy Zoladz and Arno Rademaker working under the supervision of Professor Anthony J Sargeant. The concept of optimum movement frequencies in human locomotion had been a long standing interest of Tony Sargeant’s and the results from this study build on earlier studies. It is concluded that choosing a high pedalling rate (around 100 revs/min) when performing high intensity cycling exercise may be beneficial since it provides greater reserve in power generating capability and this may be advantageous to the muscle in terms of resisting fatigue.

Human muscle power generating capability during cycling at different pedalling rates

Jerzy A Zoladz, Arno C H J Rademaker, and Anthony J Sargeant

Experimental Physiology

Exp Physiol. 2000 Jan;85(1):117-24

Abstract
The effect of different pedalling rates (40, 60, 80, 100 and 120 rev min-1) on power generating capability, oxygen uptake (O2) and blood lactate concentration [La]b during incremental tests was studied in seven subjects. No significant differences in O2,max were found (mean +/- S.D., 5.31 +/- 0.13 l min-1). The final external power output delivered to the ergometer during incremental tests (PI,max) was not significantly different when cycling at 60, 80 or 100 rev min-1 (366 +/- 5 W). A significant decrease in PI,max of 60 W was observed at 40 and 120 rev min-1 compared with 60 and 100 rev min-1, respectively (P < 0.01). At 120 rev min-1 there was also a pronounced upward shift of the O2-power output (O2-P) relationship. At 50 W O2 between 80 and 100 rev min-1 amounted to +0.43 l min-1 but to +0.87 l min-1 between 100 and 120 rev min-1. The power output corresponding to 2 and 4 mmol l-1 blood lactate concentration (P[La]2 and P[La]4 ) was also significantly lower (> 50 W) at 120 rev min-1 (P < 0.01) while pedalling at 40, 60, 80 and 100 rev min-1 showed no significant difference. The maximal peak power output (PM, max) during 10 s sprints increased with pedalling rate up to 100 rev min-1. Our study indicates that with increasing pedalling rate the reserves in power generating capability increase, as illustrated by the PI,max/PM,max ratio (54.8, 44.8, 38.1, 34.6, 29.2%), the P[La]4/PM,max ratio (50.4, 38.9, 31.0, 27.7, 22.9%) and the P[La]2/PM,max ratio (42.8, 33.5, 25.6, 23.1, 15.6%) increases.
Taking into consideration the O2,max, the PI,max and the reserve in power generating capability we concluded that choosing a high pedalling rate when performing high intensity cycling exercise may be beneficial since it provides greater reserve in power generating capability and this may be advantageous to the muscle in terms of resisting fatigue. However, beyond 100 rev min-1 there is a decrease in external power that can be delivered for an given O2 with an associated earlier onset of metabolic acidosis and clearly this will be disadvantageous for sustained high intensity exercise.
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Review of research into muscle power and fatigue

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Anthony Sargeant and David A Jones wrote this invited review for an important book on muscle fatigue edited by Simon Gandevia and others

The significance of motor unit variability in sustaining mechanical output of muscle

Anthony J Sargeant and David A Jones

Advances in Experimental Medicine and Biology
Adv Exp Med Biol. 1995;384:323-38
Neuromuscular function and fatigue have been studied using a wide variety of preparations. These range from sections of single fibers from which the cell membrane has been removed to whole muscles or groups of muscles acting about a joint in the intact animal. Each type of preparation has its merits and limitations. There is no ideal preparation; rather the question to be answered will determine the most appropriate model in each case and sometimes a combination of approaches will be needed. In particular, it is important to understand how the mechanical output of whole muscle can be sustained to meet the demands of a task and to take into account the organized variability of the constituent motor units.

Age Related Changes in Muscle Power

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Margriet Lodder completed this work in Amsterdam as part of her PhD research under the direction of Professor Anthony Sargeant
Effect of growth on efficiency and fatigue in extensor digitorum longus muscle of the rat
Margriet A Lodder

Arnold de Haan

Anthony J Sargeant.

European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1994;69(5):429-434
The effect of growth on work output, energy consumption and efficiency during repetitive dynamic contractions was determined using extensor digitorum longus muscles of 40-, 60-, 120- and 700-day-old male Wistar rats. When work output of each contraction was normalized to the work output of the first contraction it was found that work output initially increased over the first 10-20 contractions by approximately 8% in each age group. Thereafter a faster decrease in work output was found in the youngest group (approximately 2% each contraction) compared to the older groups (approximately 0.7% each contraction). After 40 contractions the reduction in work output was significantly different only between the youngest group and the two oldest groups (-30% vs -5%). These differences in fatigue were not associated with differences in adenosine 5′-triphosphate and phosphocreatine concentrations or in lactate production. Total work output and high-energy phosphate consumption increased by approximately 555% and 380% from age 40 to 120 days, respectively. Consequently, efficiency was significantly higher (approximately 32%) in the older groups compared to 40-day-old animals. Normalized for muscle mass, mean rate of high-energy phosphate consumption was similar in all groups whereas mean power output was significantly lower in the youngest group (approximately 46%). Thus, the difference in efficiency between the young and the other groups may be attributed to a lower external power production in the youngest group rather than changes in energy turnover

Fatigue during cycling is related to pedalling rate

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Research carried out by Anita Beelen under the direction of Anthony Sargeant extended his interest in short-term muscle power output (sometimes referred to as anaerobic power). In cycling it can be seen that the degree of fatigue from prior exercise is greater when measured at higher pedalling rates. This is consistent with fatigue inducing prior exercise reducing the power generation of the faster of the most fatigue sensitive muscle fibres in the mixed human leg muscles.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1993;66(2):102-107

The effect of prior submaximal exercise performed at two different pedalling frequencies, 60 and 120 rev.min-1, on maximal short-term power output (STPO) was investigated in seven male subjects during cycling exercise on an isokinetic cycle ergometer. Exercise of 6-min duration at a power output equivalent to 92 (SD 5)% maximal oxygen uptake (VO2max), whether performed at a pedalling frequency of 60 or 120 rev.min-1, reduced maximal STPO generated at 120 rev.min-1 to a much greater extent than maximal STPO at 60 rev.min-1. After 6-min submaximal exercise at 60 rev.min-1 mean reductions in maximal STPO measured at 120 and 60 rev.min-1 were 27 (SD 11)% and 15 (SD 9)% respectively, and were not significantly different from the reductions after exercise at 120 rev.min-1, 20 (SD 13)% and 5 (SD 9)%, respectively. In addition, we measured the effect of prior exercise performed at the same absolute external mechanical power output [236 (SD 30)W] with pedalling frequencies of 60 and 120 rev.min-1. Although the external power output was the same, the leg forces required (absolute as well as expressed as a proportion of the maximal leg force available at the same velocity) were much higher in prior exercise performed at 60 rev.min-1. Nevertheless, maximal STPO generated at 120 rev.min-1 was reduced after exercise at 120 rev.min-1 [20 (SD 13)%, P < 0.05] whereas no significant reduction in maximal STPO was found after prior exercise at 60 rev.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimum wheelchair propulsion techniques

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One of another in the series of practical human physiology studies that Anthony Sargeant supervised as Professor in the Academic Medical Centre of Amsterdam. In this case the data was collected by Luc van der Wooude (now Professor), a dedicated PhD student, under his supervision.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1989;58(6):625-32

To study the effect of different cycle frequencies on cardio-respiratory responses and propulsion technique in hand-rim wheelchair propulsion, experienced wheelchair sportsmen (WS group; n = 6) and non-wheelchair users (NW group; n = 6) performed wheelchair exercise tests on a motor-driven treadmill. The WS group wheeled at velocities of 0.55, 0.83, 1.11 and 1.39 m.s-1 and a slope of 2 degrees. The NW group wheeled at 0.83, 1.11 and 1.39 m.s-1 and a 1 degree slope. In each test, a 3-min period at a freely chosen cycle frequency (FCF: 100%) was followed by four 3-min blocks of paced cycle frequencies at 60%, 80%, 120% and 140% FCF. Effects of both cycle frequency and velocity on physiological and propulsion technique parameters were studied. Analysis of variance showed a significant effect (p less than 0.05) of cycle frequency on oxygen cost and gross mechanical efficiency in both the WS and NW group. This indicated the existence of an optimum cycle frequency which is close to the FCF at any given velocity. The optimum cycle frequency increased with velocity from 0.67 to 1.03 cps over the range studied (p less than 0.05). Oxygen cost was approximately 10% less at 100% FCF than at 60% or 140% FCF. Gross mechanical efficiency for the WS group at 100% FCF was 8.5%, 9.7%, 10.4% and 10.1%, respectively, at the four velocities.(ABSTRACT TRUNCATED AT 250 WORDS)

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%

Human Power Output in Short-term (anaerobic) exercise

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Professor Anthony J Sargeant carried out this seminal research while working for the Medical Research Council during 1975-76 although the data was not fully analysed, written up and finally published in the prestigious Journal of Applied Physiology until 1981. The subject of the research was human power output in short-term exercise lasting seconds rather than minutes. It was curious that while there had been an wealth of publications in the literature documenting Maximum Aerobic Power (VO2 max) in every conceivable situation and population there was scant systematic research on the power that humans could generate in exercise lasting a few seconds although AV Hill had carried out some early experiments as had Rodolfo Margaria. More recently Griffiths Pugh in the UK had initiated some attempts at measuring sprint performance on cycle ergometers although this had not been published. Pursuing Pugh’s approach Tony Sargeant used the cycle ergometer that he had developed to measure the forces generated on the cranks during sustained exercise but this time during brief sprint efforts lasting for seconds rather than minutes. It soon became clear that one of the problems with quantifying maximum short term power was simply that muscle force and muscle power were velocity dependent – as indeed AV Hill and others had shown in experiments many years previously. The consequence and paradoxical confounding effect of this inter-relationship was that in an all-out sprint lasting 20 seconds the subject would within a few revolutions reach maximum power when a load was applied to the ergometer and then as fatigue set in power would decrease in each revolution and the pedalling rate would start to slow. Paradoxically because the leg muscles were contracting at a slower rate muscle force actually increased during the maximum fatiguing sprint exercise because of the shift back down the force velocity relationship of muscle. At the same time it was obvious that the measurement of maximum power during each revolution was also dependent on the speed of muscle contraction as determined by the power velocity relationship such that loss of power was a product of both fatigue and the shift back down the power velocity relationship of human muscle.
To eliminate the confounding effect of velocity Tony Sargeant added a powerful electric motor which drove the cranks at a range of constant speeds despite the maximum efforts of subjects who were asked to attempt to speed up the rate of crank rotation. In this way it was possible for the first time in the scientific literature to measure the power velocity and force velocity relationship of the whole leg musculature of humans during brief exercise.
This approach allowed a whole series of studies to be undertaken in later years which looked at energy turnover in human muscle. The study was designed and all of the data collected by Tony Sargeant working alone. In pre-digital and pre desk-top computer days the forces generated and measured with the strain gauges were measured using high speed ultra-violet paper recorders. These paper recordings were then laboriously transcribed by hand by Tony before the computer programme designed by the MRC statistician, Elizabeth Hoinville, generated power and force data. In part of the study Professor Archie Young contributed his expertise by obtaining muscle biopsies from the subjects to determine the effect of muscle fibre type on the power output.
Journal of Applied Physiology
J Appl Physiol Respir Environ Exerc Physiol. 1981 Nov;51(5):1175-82

Force exerted and power generated were measured during short-term exercise performed on a bicycle ergometer that had been modified by the addition of an electric motor driving the cranks at a chosen constant velocity. Five subjects made a series of 20-s maximum efforts at different crank velocities (range 23–171 rev/min). The forces exerted were continuously monitored with strain gauges bonded to the cranks.

Peak force was exerted at approximately 90 degrees past top dead center in each revolution. During the 20-s effort peak force declined from the maximum level (PFmax) attained near the start of exercise, the rate of decline being velocity dependent. PFmax was found to be inversely and linearly related to crank velocity and when standardized for upper leg muscle (plus bone) volume (ULV) was given by PFmax (kgf/l ULV) = 27.51–0.125 crank velocity (rev/min). Integration of the force records with pedal velocity enabled power output to be calculated. Maximum power output was a parabolic function of crank velocity, the apex of the relationship indicating that the velocity for greatest power output was 110 rev/min. At this velocity our subjects achieved a maximum mean power output, averaged over a complete revolution, of 840 +/- 153 W (85 +/- 5 W/l ULV). This was compared with the calculated value for maximum mechanical power output from aerobic sources, which was 272 +/- 49 W (30 +/- 1 W/l ULV)