https://www.commed.vcu.edu/Chronic_Disease/2012/cochranrvwrschbias.pdf

The Cochrane Collaboration's tool for assessing risk of bias in randomised trials

Charge, Sophie B. P., and Michael A. Rudnicki. Cellular and Molecular Regulation of Muscle Regeneration. Physiol Rev 84: 209–238, 2004; 10.1152/physrev.00019.2003.—Under normal circumstances, mamma...

Cellular and Molecular Regulation of Muscle Regeneration

Mammalian skeletal muscle comprises different fiber types, whose identity is first established during embryonic development by intrinsic myogenic control mechanisms and is later modulated by neural and hormonal factors. The relative proportion of the different fiber types varies strikingly between species, and in humans shows significant variability between individuals. Myosin heavy chain isoforms, whose complete inventory and expression pattern are now available, provide a useful marker for fiber types, both for the four major forms present in trunk and limb muscles and the minor forms present in head and neck muscles. However, muscle fiber diversity involves all functional muscle cell compartments, including membrane excitation, excitation-contraction coupling, contractile machinery, cytoskeleton scaffold, and energy supply systems. Variations within each compartment are limited by the need of matching fiber type properties between different compartments. Nerve activity is a major control mechanism of the fiber type profile, and multiple signaling pathways are implicated in activity-dependent changes of muscle fibers. The characterization of these pathways is raising increasing interest in clinical medicine, given the potentially beneficial effects of muscle fiber type switching in the prevention and treatment of metabolic diseases.

Fiber types in mammalian skeletal muscles.

This review aims to summarize the latest developments with regard to physical fitness and several health outcomes in young people. The literature reviewed suggests that (1) cardiorespiratory fitness levels are associated with total and abdominal adiposity; (2) both cardiorespiratory and muscular fitness are shown to be associated with established and emerging cardiovascular disease risk factors; (3) improvements in muscular fitness and speed/agility, rather than cardiorespiratory fitness, seem to have a positive effect on skeletal health; (4) both cardiorespiratory and muscular fitness enhancements are recommended in pediatric cancer patients/survivors in order to attenuate fatigue and improve their quality of life; and (5) improvements in cardiorespiratory fitness have positive effects on depression, anxiety, mood status and self-esteem, and seem also to be associated with a higher academic performance. In conclusion, health promotion policies and physical activity programs should be designed to improve cardiorespiratory fitness, but also two other physical fitness components such us muscular fitness and speed/agility. Schools may play an important role by identifying children with low physical fitness and by promoting positive health behaviors such as encouraging children to be active, with special emphasis on the intensity of the activity.

Physical fitness in childhood and adolescence: a powerful marker of health

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Biomechanics And Motor Control Of Human Movement

The purpose of this study was to determine whether certain chemokines, which are highly expressed in injured skeletal muscle, are involved in the repair and functional recovery of the muscle after ...

Role of CC chemokines in skeletal muscle functional restoration after injury.

The primary objective of this study was to compare the magnitude of injury in mouse extensor digitorum longus (EDL) and soleus muscles induced by high-force eccentric contractions. A second objecti...

Eccentric contraction-induced injury in normal and hindlimb-suspended mouse soleus and EDL muscles

A new development in the testing of physical fitness of youth is the use of criterion-referenced standards (CRS). Although three national youth health-related physical fitness (HRPF) tests currently have CRS, a detailed description of the procedures used in their development has not been published nor have the standards been validated. Consequently, the scientific basis of these standards has been questioned. The purposes of this tutorial are (a) to discuss briefly issues related to the development of CRS for HRPF tests, (b) to provide a detailed description of procedures used in development of mile run/walk test CRS as an example, and (c) to illustrate how these standards can be validated. The objective is to stimulate discussion and critical evaluation of CRS for youth HRPF tests.

Criterion-referenced standards for youth health-related fitness tests: a tutorial.

The objective of this study was to determine whether altered intracellular Ca(2+) handling contributes to the specific force loss in the soleus muscle after unloading and/or subsequent reloading of mouse hindlimbs. Three groups of female ICR mice were studied: 1) unloaded mice (n = 11) that were hindlimb suspended for 14 days, 2) reloaded mice (n = 10) that were returned to their cages for 1 day after 14 days of hindlimb suspension, and 3) control mice (n = 10) that had normal cage activity. Maximum isometric tetanic force (P(o)) was determined in the soleus muscle from the left hindlimb, and resting free cytosolic Ca(2+) concentration ([Ca(2+)](i)), tetanic [Ca(2+)](i), and 4-chloro-m-cresol-induced [Ca(2+)](i) were measured in the contralateral soleus muscle by confocal laser scanning microscopy. Unloading and reloading increased resting [Ca(2+)](i) above control by 36% and 24%, respectively. Although unloading reduced P(o) and specific force by 58% and 24%, respectively, compared with control mice, there was no difference in tetanic [Ca(2+)](i). P(o), specific force, and tetanic [Ca(2+)](i) were reduced by 58%, 23%, and 23%, respectively, in the reloaded animals compared with control mice; however, tetanic [Ca(2+)](i) was not different between unloaded and reloaded mice. These data indicate that although hindlimb suspension results in disturbed intracellular Ca(2+) homeostasis, changes in tetanic [Ca(2+)](i) do not contribute to force deficits. Compared with unloading, 24 h of physiological reloading in the mouse do not result in further changes in maximal strength or tetanic [Ca(2+)](i).

https://www.physiology.org/doi/pdf/10.1152/jappl.1999.87.1.386

Intracellular Ca2+ transients in mouse soleus muscle after hindlimb unloading and reloading

WARREN, G. L., K. M. HERMANN, C. P. INGALLS, M. R. MASSELLI, and R. B. ARMSTRONG. Decreased EMG median frequency during a second bout of eccentric contractions. Med. Sci. Sports Exerc.,Vol. 32, No. 4, pp. 820 ‐ 829, 2000. Purpose: Others have reported preferential recruitment of fast motor units in muscles during performance of eccentric contractions and there is evidence that fast muscle fibers are more susceptible to eccentric contraction-induced injury. We tested the hypothesis that during a second bout of maximal eccentric contractions 1 wk after the first, there would be a reduction in the electromyographic (EMG) median frequency (MF) with minimal change in the EMG root-mean-square (RMS), indicating greater reliance on slower motor units. This could provide an explanation for the enhanced resistance to eccentric contraction-induced injury after a single bout of eccentric exercise. Methods: Human subjects performed 50 maximal voluntary eccentric (N 5 10) or concentric (N 5 10) contractions of the anterior crural muscles on two occasions separated by 1 wk. To determine whether MF changes during the second bout could be a consequence of injury to fibers in fast motor units, the anterior crural muscles of mice were electrically stimulated to perform 50 maximal eccentric ( N 5 10) or concentric (N 5 9) contractions on two occasions separated by 1 wk. In both the humans and mice, torque production and tibialis anterior muscle RMS and MF were measured during the two exercise bouts. Results: In human tibialis anterior muscle, MF was 30% lower (P , 0.01) during the second eccentric bout although RMS was the same. In the mice, RMS and MF were unchanged at any time after the first eccentric bout despite torque deficits similar to those observed in the humans. Conclusions: The data indicate that with repetition of maximal voluntary eccentric contractions, there is an increased activation of slow motor units and a concomitant

Gordon L. Warren

Papers

Role of CC chemokines in skeletal muscle functional restoration after injury.

Eccentric contraction-induced injury in normal and hindlimb-suspended mouse soleus and EDL muscles

Criterion-referenced standards for youth health-related fitness tests: a tutorial.

Intracellular Ca2+ transients in mouse soleus muscle after hindlimb unloading and reloading

Decreased EMG median frequency during a second bout of eccentric contractions.