Effects of growth and ageing on muscle properties

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Margriet Lodder completed this research as part of her PhD which was supervised by Anthony Sargeant and Arnold de Haan. The research examined age related changes in muscle properties using a rat model.
Journal of Muscle Research and Cell Motility
J Muscle Res Cell Motil. 1993 Feb;14(1):47-53

Morphological and functional changes as well as changes in fibre-type composition were investigated in the left extensor digitorum longus (EDL) muscles of male Wistar rats of approximately 40, 60, 120 and 700 days old. A number of morphological changes occurred in the EDL muscle during growth. While from 40 to 120 days muscle mass and cross-sectional area (CSA) increased by 247 and 192%, changes in muscle and fibre lengths were much smaller (44 and 17%, respectively).

Besides morphological changes tetanic force was also found to increase (approximately 307%) up to 120 days. Because this increase in force was greater than the increase in CSA, specific force increased by approximately 29% between 40 and 60 days. Thereafter, specific force stayed rather constant. From 40 until 60 days changes were also found in the force-frequency and force-velocity curve, which indicate a slowing of the muscles (until 60 days). Changes in fibre-type composition of the EDL muscle were found to occur later during growth between 60 and 120 days. In this period an increase in the relative total area of Type IIBd fibres and a decrease in the relative total area of Type IIBm fibres (corresponding to the Type 2X and IIB fibres, respectively), were found; this was apparently due to a conversion of many Type IIBm into Type IIBd fibres and not to a difference in cross-sectional growth between these fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Human Musculo-tendon properties: Methodological considerations

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Detailed measurements using ultra-sonography underpin this important contribution to research on musculo tendon function in the intact human.
Clinical Biomechanics
Clin Biomech (Bristol, Avon). 1999 Nov;14(9):661-6

OBJECTIVE: In the present study, we examined the hypothesis that the tibialis anterior tendon moment arm increases during maximum isometric dorsiflexion as compared with rest.

BACKGROUND: In musculoskeletal modelling applications, moment arms from passive muscles at rest are assumed representative of those measured during isometric muscle contraction. The validity of this assumption is questionable in musculotendon actuators enclosed by retinacular systems as in tibialis anterior.

 

DESIGN AND METHODS: Sagittal-plane magnetic resonance images of the right ankle were taken in six subjects at rest and during maximum isometric dorsiflexion at six ankle angles between dorsiflexion and plantarflexion having the body placed in the supine position and the knee flexed at 90 degrees. Instant centres of rotation in the tibio-talar joint, tibialis anterior tendon action lines and moment arms were identified in the sagittal plane at ankle angles of -15 degrees, 0 degrees,+15 degrees and +30 degrees at rest and during maximum isometric dorsiflexion.

RESULTS: At any given ankle angle, the tibialis anterior tendon moment arm during maximum isometric dorsiflexion increased by 0.9-1.5 cm (P<0.01) compared with rest. This was attributed to a displacement of both tibialis anterior tendon action line by 0.8-1.2 cm (P<0.01) and all instant centres of rotation by 0.3-0.4 cm (P<0. 01) distally in relation to their corresponding resting positions.

CONCLUSIONS AND IMPLICATIONS: The assumption that the tibialis anterior tendon moment arm does not change from rest to maximum isometric dorsiflexion is invalid. Erroneous tendon forces, muscle stresses and joint moments by as much as 30% would be calculated using resting tibialis anterior tendon moment arms in the moment equilibrium equation around the ankle joint during maximum isometric dorsiflexion.

RELEVANCE: A substantial increase in the tibialis anterior tendon moment arm occurs from rest to maximum isometric dorsiflexion. This needs to be taken into consideration when using planimetric musculoskeletal modelling for analysing maximal static ankle dorsiflexion loads

Functional electrical stimulation (FES) for people with spinal cord injury

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HL Gerrits carried out the data collection for this research study as part of her PhD programme supervised by Professor Anthony Sargeant. It shows how Functional Electrical Stimulation may mitigate the changes that occur when muscles are paralysed following spinal cord injury.
Spinal Cord
Spinal Cord. 2000 Apr;38(4):214-23

STUDY DESIGN: A longitudinal training study.

OBJECTIVES: To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training.

SETTINGS: The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands.

 

METHODS: Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE.

RESULTS: Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaffected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses.

CONCLUSION: FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which reflect an early response of long-term disused muscles.

Age effects on muscle fatigue and recovery

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Research into muscle fatigue in older compared to young rats. There seemed to be differences which may be related to the population of faster muscle fibres which seemed to take longer to recover from fatigue in the older rat muscles. The data for this publication was collected by Arnold de Haan who had been PhD student of Professor Anthony Sargeant.
Quarterley Journal of Experimental Physiology
Q J Exp Physiol. 1989 Sep;74(5):715-26

Force-velocity, power-velocity and unloaded shortening data were obtained from in situ medial gastrocnemius muscle-tendon complexes (stimulated at 60 Hz) with intact circulation of mature male rats (approximately 125 days old). Measurements were carried out at the end of a long (15 s) contraction (fatigued muscles) or with a short (1 s) contraction either in the fresh state (fresh muscles) or in muscles which had recovered for 15 min after a long contraction. Compared to the fresh state fatigue reduced isometric force by 57%, maximal shortening velocity by approximately 40% and maximal power output by 81%.

These reductions were similar to data previously obtained with younger rats (40 days old). However, the velocity data of the muscles which had recovered for 15 min after a long contraction showed a greater reduction in the mature rats. This difference between the two age groups together with a difference in the changes in the initial parts of the isometric force time curves suggest an age-dependent response of the fast-fatigable fibre population of these mixed muscles. In a separate series of experiments the underlying mechanism of the recovery from fatigue was studied in a group of young rats. Fatigue was induced with five long (15 s) contractions (each at 5 min intervals). The recovery of isometric force and power output was monitored with short contractions which indicated a plateau of recovery but the absolute values were still reduced after 60 min (85 and 71% of prefatigue values, respectively). Phosphocreatine concentration recovered rapidly, whereas the ATP concentration was still markedly reduced after 1 h of recovery. The time courses of recovery of inosine-5′-monophosphate (IMP) and lactate concentrations resembled those of force and power output. Thus it is possible that age-dependent differences in IMP and/or lactate production may play a role in fatigue and recovery from fatigue.

Research into the true efficiency of human movement at different muscle contraction frequencies

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This research was carried out in Copenhagen by Richard Ferguson as part of a collaboration initiated by Professor Anthony Sargeant and Jens Bangsbo. Richard Ferguson was at the time a PhD student working under the supervision of Tony Sargeant and Dr Derek Ball.
Journal of Applied Physiology
J Appl Physiol. 2000 Nov;89(5):1912-8

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

Research into muscle function of people with spinal cord injury

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This research into methods for assessing human muscle function was carried out by HL Gerrits as part of her PhD under the joint direction of Maria Hopman, Anthony Sargeant and Arnold de Haan.
Clinical Physiology
Clin Physiol. 2001 Jan;21(1):105-13

Abstract This study assessed the reproducibility of electrically evoked, isometric quadriceps contractile properties in eight people with spinal cord injury (SCI) and eight able-bodied (AB) individuals. Over all, the pooled coefficients of variation (CVps) in the SCI group were significantly lower (ranging from 0.03 to 0.15) than in the AB group (ranging from 0.08 to 0.21) (P<0.05). Furthermore, in all subjects, the variability of force production increased as stimulation frequency decreased (P<0.01). In subjects with SCI, variables of contractile speed are clearly less reproducible than tetanic tension or resistance to fatigue. Contractile properties of quadriceps muscles of SCI subjects were significantly different from that of AB subjects. Muscles of people with SCI were less fatigue resistant (P<0.05) and produced force-frequency relationships that were shifted to the left, compared with AB controls (P<.01). In addition, fusion of force responses resulting from 10 Hz stimulation was reduced (P<.05) and speed of contraction (but not relaxation) was increased (P<0.05), indicating an increased contractile speed in paralysed muscles compared with non-paralysed muscles. These results correspond with an expected predominance of fast glycolytic muscle fibres in paralysed muscles. It is concluded that quadriceps dynamometry is a useful technique to study muscle function in non-paralysed as well as in paralysed muscles. Furthermore, these techniques can be reliably used, for example, to assess therapeutic interventions on paralysed muscles provided that expected differences in relative tetanic tension and fatigue resistance are larger than approximately 5% and differences in contractile speed are larger than approximately 15%

Fundamental Research into Muscle – important insights for understanding muscle function in health and disease

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Meticulous research carried out by Arnold de Haan (later Professor) as part of his PhD completed under the supervision of Professor Anthony Sargeant. It might be noticed that although the experimental work in the laboratory was conducted entirely by Arnold de Haan there are eight authors on this paper. Research by committee is not always productive but it was very much the tradition in the Faculty which Tony joined in 1985. After a few years he managed to achieve a more realistic approach with only those who made a ‘significant’ contribution being listed as authors.
European Journal of applied Physiology
Eur J Appl Physiol Occup Physiol. 1988;57(1):64-9

The effect of muscle dimensions on economy (force-time integral divided by the amount of energy utilized) was investigated in male rats (body mass range 95-490 g), anaesthetized with pentobarbital. The medial gastrocnemius muscle in situ performed 6 maximal isometric contractions of 350 ms duration (1.s-1) at twitch optimum length at 35 degrees C.

The areas under the 6 time-force curves were added to obtain force-time integral of the experiment. Differences of concentrations of ATP, phosphocreatine and lactate between experimental and contralateral (resting) muscles were used to calculate high-energy phosphate consumption due to stimulation. Muscle mass and cross-sectional area increased (approximately +400% and +300%, respectively) over the rat body mass range studied. Muscle length and length of the most distal fibre bundle increased by approximately 17 mm and 4 mm, respectively. Force-time integral (N.s) increased proportional to cross-sectional area whereas high-energy phosphate consumption (mumoles) increased proportional to muscle mass. The relative fraction of the total energy consumption utilized for force-independent processes was independent of rat body mass. The economy of the actomyosin system was unaffected during growth, whereas economy of the whole muscle decreased during growth by approximately 30% (p less than 0.001). The effect of muscle dimensions on economy is discussed with respect to human endurance capacity measured by voluntary isometric contractions