Human performance and energy cost of lifting and lowering weight

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Research carried out by Michiel de Looze and submitted as part of his PhD thesis completed in Amsterdam under the direction of Anthony Sargeant

Relationships between energy expenditure and positive and negative mechanical work in repetitive lifting and lowering

De Looze MP

Toussaint HM

Commissaris DA

Jans MP

Anthony J Sargeant.

Journal of Applied Physiology
J Appl Physiol  1994
77(1):420-426
  • Determining the separate energy costs of the positive and negative mechanical work in repetitive lifting or lowering is quite complex, as a mixture of both work components will always be involved in the up- and downward motion of the lifter’s body mass. In the current study, a new method was tested in which coefficients specifically related to the positive and negative work were estimated by multiple regression on a data set of weight-lifting and weight-lowering tasks. The energy cost was obtained from oxygen uptake measurements. The slopes of the regression lines for energy cost and mechanical work were steeper for positive than for negative work. The cost related to the negative work was approximately 0.3-0.5 times the cost of the positive work. This finding is well in line with data obtained directly from other isolated activities of either positive or negative work (e.g., ladder climbing vs. descending). However, the intercept values of the regression lines were not significantly different from zero or were even negative. This was most likely due to the metabolic energy not related to processes that yield mechanical work (e.g., isometric muscle actions) that was not constant among trials.

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

Anthony Sargeant reviews the effect of fatigue and temperature on human muscle power

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In this review based on a Key Note Lecture to a Dutch Physiological Society Symposium Tony Sargeant explains how human muscle power is affected by changes in muscle temperature and by fatigue. Importantly that the magnitude of changes depends on the speed of the muscle contraction generating power and the muscle fibre types present in the muscles.
International Journal of Sports Medicine
Int J Sports Med. 1994 Apr;15(3):116-121

In human locomotion the ability to generate and sustain power output is of fundamental importance. This review examines the implications for power output of having variability in the metabolic and contractile properties within the population of muscle fibres which comprise the major locomotory muscles. Reference is made to studies using an isokinetic cycle ergometer by which the global power/velocity relationship for the leg extensor muscles can be determined.

The data from these studies are examined in the light of the force velocity characteristics of human type I and type II muscle fibres. The ‘plasticity’ of fibre properties is discussed with reference to the ‘acute’ changes elicited by exercise induced fatigue and changes in muscle temperature and ‘chronic’ changes occurring following intensive training and ageing

Method for measuring high energy phosphates in fragments of human muscle fibres

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This research publication describes a method developed in the Amsterdam Department of Anthony Sargeant. The data was collected by an outstanding Greek PhD student, Christina Karatzaferi, directed by Tony and his colleague Arnold de Haan.
Journal of Chromotography
J Chromatogr B Biomed Sci Appl. 1999 Jul 9;730(2):183-91

Abstract A sensitive and reproducible method for the determination of adenine nucleotides (ATP, IMP) and creatine compounds [creatine (Cr), phosphocreatine (PCr)] in freeze-dried single human muscle fibre fragments is presented. The method uses isocratic reversed-phase high-performance liquid chromatography of methanol extracts. Average retention times (min) of ATP, IMP and PCr, Cr from standard solutions were 10.6+/-0.42, 2.11+/-0.06 (n=6) and 10.5+/-0.31 and 1.19+/-0.02 (n=9), respectively. Detection limits in extracts from muscle fibre fragments were 2.0, 1.0, 3.0 and 2.0 mmol/kg dm, respectively. The assay was found successful for analysis of fibre-fragments weighing > or = 1 microg.

Research into RNA in skeletal muscle

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Petra Habets was a PhD student directed by Anthony Sargeant. This research publication  was part of her PhD thesis. It was a collaborative research project in Amsterdam that developed out of research first pursued by Jose Sant’ana Periera, a previous PhD student in Tony Sargeant’s department.
Journal of Histochemistry and Cytochemistry
J Histochem Cytochem. 1999 Aug;47(8):995-1004

Quantification of a specific muscle mRNA per total RNA (e.g., by Northern blot analysis) plays a crucial role in assessment of developmental, experimental, or pathological changes in gene expression.

However, total RNA content per gram of a particular fiber type may differ as well. We have tested this possibility in the distinct fiber types of adult rat skeletal muscle. Sections of single fibers were hybridized against 28S rRNA as a marker for RNA content. Quantification of the hybridization showed that the 28S rRNA content decreases in the order I>IIA>IIX>IIB, where Type I fibers show a five- to sixfold higher expression level compared to Type IIB fibers. Results were verified with an independent biochemical determination of total RNA content performed on pools of histochemically defined freeze-dried single fibers. In addition, the proportion of myosin heavy chain (MHC) mRNA per microgram of total RNA was similar in slow and fast fibers, as demonstrated by Northern blot analysis. Consequently, Type I fibers contain five- to sixfold more MHC mRNA per microgram of tissue than IIB fibers. These differences are not reflected in the total fiber protein content. This study implies that proper assessment of mRNA levels in skeletal muscle requires evaluation of total RNA levels according to fiber type composition

Maximum force of fresh and fatigued human muscle

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As head of department Anthony Sargeant had spent many years encouraging his junior colleagues to adapt a technique used to measure muscle force in a rat muscle preparation to measure electrically elicited force in human hand muscles. Finally collaborating with Professor David A Jones (a friend and colleague with a lot of experience in electrical stimulation of human muscle) Tony finally got colleagues to develop the technique reported in this research paper. David Jones and Anthony Sargeant both acted as subjects and provided critical input in the experiments for the development and application of these techniques.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1999 Sep;80(4):386-93

The purpose of the study was to obtain force/velocity relationships for electrically stimulated (80 Hz) human adductor pollicis muscle (n = 6) and to quantify the effects of fatigue. There are two major problems of studying human muscle in situ; the first is the contribution of the series elastic component, and the second is a loss of force consequent upon the extent of loaded shortening. These problems were tackled in two ways.

Records obtained from isokinetic releases from maximal isometric tetani showed a late linear phase of force decline, and this was extrapolated back to the time of release to obtain measures of instantaneous force. This method gave usable data up to velocities of shortening equivalent to approximately one-third of maximal velocity. An alternative procedure (short activation, SA) allowed the muscle to begin shortening when isometric force reached a value that could be sustained during shortening (essentially an isotonic protocol). At low velocities both protocols gave very similar data (r2 = 0.96), but for high velocities only the SA procedure could be used. Results obtained using the SA protocol in fresh muscle were compared to those for muscle that had been fatigued by 25 s of ischaemic isometric contractions, induced by electrical stimulation at the ulnar nerve. Fatigue resulted in a decrease of isometric force [to 69 (3)%], an increase in half-relaxation time [to 431 (10)%], and decreases in maximal shortening velocity [to 77 (8)%] and power [to 42 (5)%]. These are the first data for human skeletal muscle to show convincingly that during acute fatigue, power is reduced as a consequence of both the loss of force and slowing of the contractile speed.

Measuring the forces on pedals during cycling

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Anita Beelen was an outstanding PhD student supervised by Anthony Sargeant who presented this research paper as part of the methodology used for her PhD thesis at the Vrije University of Amsterdam. Frank Wijkhuizen was the technician who helped to design and build the equipment in the electrical and engineering workshop of the Academic Medical Centre in Amsterdam.
European Journal of Applied Physiology
Eur J Appl Physiol Occup Physiol. 1994;68(2):177-81

An isokinetic cycle ergometer has been developed to measure power output generated over a wide range of constant velocities. The ergometer system has two operating modes and it can be instantly switched from one to another. In its conventional mode the cycle ergometer is connected to a conventional electrically braked cycle ergometer so that the subjects can perform submaximal steady-state exercise.

For maximal power measurements the system can be instantly switched to an isokinetic control mechanism which allows a constant pedalling rate to be set in the range of 23-180 rev.min-1. In both operating modes the forces generated on the pedals are monitored by strain-gauges mounted inside the pedals. This enables information to be obtained regarding the direction of forces generated at the foot-pedal interface. The output from the strain-gauges was A-D converted and stored along with data giving pedal and crank position. Data was sampled 150 times in each revolution of the crank. Force data are usually analysed for maximal peak power (highest instantaneous power generated during each revolution), mean power (power generated over a complete revolution), extension and flexion power (power generated during leg extension and leg flexion respectively). This system allows characterisation of the relationship between maximal leg power and pedalling rate, both under control and exercise-induced potentiation and fatigue conditions. Thus it is possible for example to quantify instantly the magnitude of fatigue induced by preceding dynamic exercise of a given duration, intensity or contraction velocity.