Force-velocity relationship of human muscle

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The research idea for this study came from Professor Anthony J Sargeant of Amsterdam and Professor David Jones (Birmingham University). It was the culmination of many years of Tony Sargeant encouraging members of his research group in Amsterdam to adapt a technique for studying rat muscle force velocity to small human hand muscles. The data was finally collected by Jo de Ruiter a post-doc in the Amsterdam research group.

The measurement of force/velocity relationships of fresh and fatigued human adductor pollicis muscle.

CJ De Ruiter, David A Jones, Anthony J Sargeant, Arnold de Haan.

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
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Post-Polio Syndrome

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The data collection and analysis of this research study was largely the work of Frans Nollet and Anita Beelen. Other senior authors provided input at various stages of planning and writing. Professor Anthony J Sargeant was the supervisor for the PhD thesis of which this work formed a part.

Disability and functional assessment in former polio patients with and without postpolio syndrome

Frans Nollet, Anita Beelen, Prins MH, Marianne de Visser, Anthony J Sargeant, Lankhorst GJ, de Jong BA 

Archives of Physical Medicine and Rehabilitation

Arch Phys Med Rehabil. 1999 Feb;80(2):136-143
Abstract
OBJECTIVES: To compare perceived health problems and disability in former polio subjects with postpolio syndrome (PPS) and those without postpolio syndrome (non-PPS), and to evaluate perceived health problems, disability, physical performance, and muscle strength.
DESIGN: Cross-sectional survey; partially blinded data collection.
SUBJECTS: One hundred three former polio subjects, aged 32 to 60yrs. This volunteer sample came from referrals and patient contacts. Criterion for PPS: new muscle weakness among symptoms.
MAIN OUTCOME MEASURES: Nottingham Health Profile (NHP), adapted D-code of the International Classification of Impairments, Disabilities and Handicaps, performance test, and muscle strength assessment.
RESULTS: PPS subjects (n = 76) showed higher scores (p < .001) than non-PPS subjects (n = 27) within the NHP categories of physical mobility, energy, and pain. On a 16-item Polio Problems List, 78% of PPS subjects selected fatigue as their major problem, followed by walking outdoors (46%) and climbing stairs (41%). The disabilities of PPS subjects were mainly seen in physical and social functioning. No differences in manually tested strength were found between patient groups. PPS subjects needed significantly more time for the performance test than non-PPS subjects and their perceived exertion was higher. Perceived health problems (NHP-PhysMobility) correlated significantly with physical disability (r = .66), performance-time (r = .54), and muscle strength (r = .38). With linear regression analysis, 54% of the NHP-PhysMobility score could be explained by the performance test (time and exertion), presence of PPS, and muscle strength, whereas strength itself explained only 14% of the NHP-PhysMobility score.
CONCLUSIONS: PPS subjects are more prone to fatigue and have more physical mobility problems than non-PPS subjects. In former polio patients, measurements of perceived health problems and performance tests are the most appropriate instruments for functional evaluation

Within a single muscle there can be large differences in fatiguability and other physiological properties

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This research carried out in Amsterdam under the direction of Professor Anthony J Sargeant demonstrated how within the same anatomical muscle there can be quiet different physiological properties in different areas of the same muscle. This work was part of the PhD research of Jo de Ruiter supervised by Professor Tony Sargeant and Arnold de Haan.

Repeated force production and metabolites in two medial gastrocnemius muscle compartments of the rats

De Ruiter CJArnold de HaanAnthony J Sargeant.

Journal of Applied Physiology
J Appl Physiol. 1995 Dec;79(6):1855-61
  • The most proximal and distal motor nerve branches in the rat medial gastrocnemius innervate discrete muscle compartments dominated by fast-twitch oxidative and fast-twitch glycolytic fibers, respectively. The functional consequences of the difference in oxidative capacity between these compartments were investigated. Wistar rats were anesthetized with pentobarbital sodium (90 mg/kg ip). Changes in force of both compartments during 21 isometric contractions (train duration 200 ms, stimulation frequency 120 Hz, 3 s between contractions) were studied in situ with and without blood flow. Without blood flow, force and phosphocreatine declined to a greater extent in the proximal than the distal compartment compared with the run with intact flow. After the protocol without blood flow, when flow was restored, the time constants for force recovery (which were closely associated to the recovery of phosphocreatine) were 37 +/- 7 (SD) (proximal compartment) and 148 +/- 20 s (distal compartment). It was concluded that the proximal compartment had a four times higher oxidative capacity and, therefore, a superior ability for repeated force production.

Human Muscle Power

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The ability of generating muscle power power is important whether you are an Olympic athlete, a ballet dancer, or an elderly person wanting to climb the stairs to go to bed. In this comprehensive review of his research Anthony Sargeant points out the importance of different types of muscle fibres that make up the human skeletal muscles that produce power in legs and arms. Tony also points out that in research seeking to measure human muscle power it is essential to measure or control the speed at which the power is generated (this is because power is the product of work and velocity).

Structural and functional determinants of human muscle power
by Anthony J Sargeant

Experimental Physiology
Exp Physiol. 2007 Mar;92(2):323-31

Measurements of human power need to be interpreted in relation to the movement frequency, since that will determine the velocity of contraction of the active muscle and hence the power available according to the power-velocity relationship. Techniques are described which enable movement frequency to be kept constant during human exercise under different conditions. Combined with microdissection and analysis of muscle fibre fragments from needle biopsies obtained pre- and postexercise we have been able ‘to take the muscle apart’, having measured the power output, including the effect of fatigue, under conditions of constant movement frequency. We have shown that fatigue may be the consequence of a metabolic challenge to a relatively small population of fast fatigue-sensitive fibres, as indicated by [ATP] depletion to approximately 30% of resting values in those fibres expressing myosin heavy chain isoform IIX after just 10 s of maximal dynamic exercise. Since these same fibres will have a high maximal velocity of contraction, they also make a disproportionate contribution to power output in relation to their number, especially at faster movement rates. The microdissection technique can also be used to measure phosphocreatine concentration ([PCr]), which is an exquisitely sensitive indicator of muscle fibre activity; thus, in just seven brief maximal contractions [PCr] is depleted to levels < 50% of rest in all muscle fibre types. The technique has been applied to study exercise at different intensities, and to compare recruitment in lengthening, shortening and isometric contractions, thus yielding new information on patterns of recruitment, energy turnover and efficiency.

Anthony J Sargeant

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.

Different regions within the same muscle can have very different properties

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This research was part of the PhD thesis of CJ (Jo) de Ruiter. It shows how within a single muscle there may be marked regional differences in physiological characteristics implying task dependent differences in recruitment patterns of motor units. The work was carried out under the direction of Anthony J Sargeant and Arnold de Haan.

Physiological characteristics of two extreme muscle compartments in gastrocnemius medialis of the anaesthetized rat

De Ruiter CJArnold de HaanAnthony J Sargeant
Acta Physiologica Scandavica
Acta Physiol Scand. 1995 Apr;153(4):313-24
Rat medial gastrocnemius (GM) muscle is a compartmentalized muscle. The functional properties and fibre type composition of the most proximal and most distal compartment were studied in in situ preparations. The proximal compartment contained predominantly fast twitch oxidative fibres. The distal compartment was mainly composed of fast twitch glycolytic fibres. With the use of two small electrodes placed around the primary nerve branches, both compartments could be separately stimulated within the same muscle. The length-force relationship was less broad and maximal twitch and tetanic forces were obtained at lower muscle lengths for the proximal compartment. The differences (mm) were 0.9 +/- 0.2 and 1.2 +/- 0.2 for maximal twitch and tetanic force (120 Hz) production, respectively (P < 0.001). The shortening velocity for maximal power production was lower (P < 0.001) for the proximal compartment (proximal: 57.1 +/- 2.7 mm s-1, distal: 73.1 +/- 3.0 mm s-1). During a standard fatigue test the fatiguability was significantly lower for the proximal compared with the distal fibres. Our findings suggest that the proximal compartment is likely to be activated in vivo during activities requiring relatively low power outputs for longer time periods. In contrast the distal compartment is probably recruited only during high power demanding short lasting activities. The presented model makes it possible to study fatigue related changes in power production of the ‘red’ and ‘white’ areas of the GM separately in a way that is probably meaningful with respect to in vivo function.