Effects of repetitive tetanic stimulation at long intervals on excitation‐contraction coupling in frog skeletal muscle.

Bruton, Joseph D.; Lännergren, Jan; Westerblad, Håkan

doi:10.1113/jphysiol.1996.sp021570

Cited by 20 publications

(25 citation statements)

References 22 publications

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“…A series of subsequent studies further highlighted the acute β 2 ‐agonist‐induced augmentation in peak twitch or tetanic [Ca 2+ ] i on skeletal muscles for doses ranging from 1 to 50 μ m (Bruton et al . ; Ha et al . ; Prakash et al .…”

Section: Discussionmentioning

confidence: 99%

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

Ramonatxo

Sirvent

et al. 2015

The Journal of Physiology

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Key pointsr Clenbuterol is an adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a shift towards faster muscle fibres, when administered chronically at high doses.r However, when normalized to the muscle surface area, the increase in muscle force is no longer increased and even depressed.r We show that muscle contraction and relaxation force kinetics were significantly reduced particularly in fast contracting muscles.r We show that action potential-elicited Ca 2+ transients were depressed in the fast contracting muscle.r Our data show that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca 2+ release during contraction could partially explain these deleterious effects.Abstract Clenbuterol is a β 2 -adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a slow-to-fast phenotypic shift. The aim of the present study was to test the effects of chronic clenbuterol treatment on contractile efficiency and explore the underlying mechanisms, i.e. the muscle contractile machinery and calcium-handling ability. Forty-three 6-week-old male Wistar rats were randomly allocated to one of six groups that were treated with either subcutaneous equimolar doses of clenbuterol (4 mg kg −1 day −1 ) or saline solution for 9, 14 or 21 days. In addition to the muscle hypertrophy, although an 89% increase in absolute maximal tetanic force (P o ) was noted, specific maximal tetanic force (sPo) was unchanged or even depressed in the slow twitch muscle of the clenbuterol-treated rats (P < 0.05). The fit of muscle contraction and relaxation force kinetics indicated that clenbuterol treatment significantly reduced the rate constant of force development and the slow and fast rate constants of relaxation in extensor digitorum longus muscle (P < 0.05), and only the fast rate constant of relaxation in soleus muscle (P < 0.05). Myofibrillar ATPase activity increased in both relaxed and activated conditions in soleus (P < 0.001), suggesting that the depressed specific tension was not due to the myosin head alteration itself. Moreover, action potential-elicited Ca 2+ transients in flexor digitorum brevis fibres (fast twitch fibres) from clenbuterol-treated animals demonstrated decreased amplitude G. Py and C. Ramonatxo contributed equally to the study. after 14 days (−19%, P < 0.01) and 21 days (−25%, P < 0.01). In conclusion, we showed that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca 2+ release during contraction could partially explain these deleterious effects.

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Section: Discussionmentioning

confidence: 99%

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

Ramonatxo

Sirvent

et al. 2015

The Journal of Physiology

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“…It is possible that FLD may result from changes in the physiology of the muscle tissue, and could be a precursor of muscle-fiber damage during repetitive work. Evidence has been presented that the muscle fiber is more sensitive to mechanical perturbations (Bruton et al 1996) and is at an increased risk of structural damage (Duncan 1987) with the increased intracellular Ca 2+ ion concentrations associated with FLD. To date, the development of muscle fatigue during simulated repetitive work has not been investigated over the course of a full workday.…”

Section: Introductionmentioning

confidence: 99%

Electromyographic activity of the human extensor carpi ulnaris muscle changes with exposure to repetitive ulnar deviation

Bennie¹,

Ciriello

Johnson

et al. 2002

European Journal of Applied Physiology

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With little known about the changes in muscle physiology due to repetitive work during an 8 h workday, our objective was to quantify the changes in muscle activity due to this type of work. Using a repeated measurements design, 13 healthy women participated in three conditions, each lasting 2 days: a control condition where they remained inactive, and two repetitive work conditions involving repeated ulnar deviation of the wrist at 20 and 25 repetitions a minute at workloads which they themselves had deemed acceptable for 8 h through a psychophysical protocol. Electromyographic (EMG) activity of the extensor carpi ulnaris muscle was recorded during voluntary isometric contractions (20% and 60% maximal voluntary contraction) eight times throughout the work and control days at 0, 2, 4.25, 6.75, 8, 9, 10, and 11 h. The amplitude of the EMG signal was lower on workdays compared to the control days. Although power was significantly reduced in all spectrum bands of the EMG power spectra, the reductions were not uniform across the entire frequency range, giving rise to different shapes of the EMG power spectra. Initial median frequency of the EMG signal showed no change between the control and workdays (P = 0.51); however, the decline of the median frequency with respect to time over the course of each isometric contraction was steeper during workdays compared to control days (P = 0.003). These changes suggest that the muscles are in an early stage of fatigue when working for an 8 h day.

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“…It is unclear how long this effect persists after exercise, as this was only examined in one study to date, and the results were somewhat equivocal at the one recovery time examined (3.5 h) (210 ] i also greatly prolongs PCD in Xenopus fast-twitch fibers (69,70,269). On the other hand, in a recent study fatigue was induced by repeated tetani in isolated mouse fibers exposed to N-benzyl-p-toluene sulfonamide (BTS), which inhibits cross-bridge force production (66).…”

Section: Prolonged Reduction In Ca 2؉ Releasementioning

confidence: 99%

Skeletal Muscle Fatigue: Cellular Mechanisms

Allen¹,

Lamb²,

Westerblad³

2008

Physiological Reviews

1,867

1,876

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Repeated, intense use of muscles leads to a decline in performance known as muscle fatigue. Many muscle properties change during fatigue including the action potential, extracellular and intracellular ions, and many intracellular metabolites. A range of mechanisms have been identified that contribute to the decline of performance. The traditional explanation, accumulation of intracellular lactate and hydrogen ions causing impaired function of the contractile proteins, is probably of limited importance in mammals. Alternative explanations that will be considered are the effects of ionic changes on the action potential, failure of SR Ca2+ release by various mechanisms, and the effects of reactive oxygen species. Many different activities lead to fatigue, and an important challenge is to identify the various mechanisms that contribute under different circumstances. Most of the mechanistic studies of fatigue are on isolated animal tissues, and another major challenge is to use the knowledge generated in these studies to identify the mechanisms of fatigue in intact animals and particularly in human diseases.

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Effects of repetitive tetanic stimulation at long intervals on excitation‐contraction coupling in frog skeletal muscle.

Cited by 20 publications

References 22 publications

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

Electromyographic activity of the human extensor carpi ulnaris muscle changes with exposure to repetitive ulnar deviation

Skeletal Muscle Fatigue: Cellular Mechanisms

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