Current study demonstrated the impact of heat therapy on skeletal muscle function in a model of Duchenne muscular dystrophy (DMD). The aim of this study was to: (1) examine the impact of treatment temperature on the skeletal muscle adaptation in DBA/2J mice; and (2) determine the impact of repeated HT for 3 consecutive weeks on body composition and skeletal muscle function in D2.mdx, a model of DMD. From study 1, we revealed that HT at 39℃ for 3 weeks significantly promoted relative muscle mass of both EDL and soleus muscle in DBA/2J mice. However, from study 2, HT at 39℃ for 3 weeks does not improve muscle function or increase muscle mass in a mouse model of DMD.

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Yes / Force–length relationships derived from isometric activations may not directly apply to muscle force production during dynamic contractions. As such, different muscle starting lengths between isometric and dynamic conditions could be required to achieve maximal force and power. Therefore, this study examined the effects of starting length [±5–10% of length corresponding to maximal twitch force (L0)] on work loop (WL) power output (PO), across a range of cycle frequencies, of the soleus (SOL) and extensor digitorum longus muscle (EDL; N=8–10) isolated from ∼8 week old C57 mice. Furthermore, passive work was examined at a fixed cycle frequency to determine the association of passive work and active net work. Starting length affected maximal WL PO of the SOL and EDL across evaluated cycle frequencies (P0.494). For the SOL, PO produced at −5% L0 was greater than that at most starting lengths (P0.6), except −10% L0 (P=0.135, d1.08), except versus −5% L0 (P=0.124, d0.163, d<1.04). For the SOL, higher passive work was associated with reduced PO (Spearman's r=0.709, P<0.001), but no relationship was observed between passive work and PO of the EDL (Pearson's r=0.191, r2=0.04, P=0.184). This study suggests that starting length should be optimised for both static and dynamic contractions and confirms that the force–length curve during dynamic contractions is muscle specific. / The full-text of this article will be released for public view at the end of the publisher embargo on 30 Apr 2025.

Yes / Evidence suggests vitamin D3 (VD) supplementation can reduce accumulation of adipose tissue and inflammation and promote myogenesis in obese individuals, and thus could mitigate obesity-induced reductions in skeletal muscle (SkM) contractility. However, this is yet to be directly investigated. This study, using the work-loop technique, examined effects of VD (cholecalciferol) supplementation on isolated SkM contractility. Female mice (n = 37) consumed standard low-fat diet (SLD) or high-fat diet (HFD), with or without VD (20,000 IU/kg-1 ) for 12 weeks. Soleus and EDL (n = 8-10 per muscle per group) were isolated and absolute and normalized (to muscle size and body mass) isometric force and power output (PO) were measured, and fatigue resistance determined. Absolute and normalized isometric force and PO of soleus were unaffected by diet (P > 0.087). However, PO normalized to body mass was reduced in HFD groups (P  0.588). HFD reduced EDL isometric stress (P = 0.048) and absolute and normalized PO (P  0.493). Cumulative work during fatiguing contractions was lower in HFD groups (P  0.060). This study uniquely demonstrated that high-dose VD had limited effects on SkM contractility and did not offset demonstrated adverse effects of HFD. However, small and moderate effect sizes suggest improvement in EDL muscle performance and animal morphology in HFD VD groups. Given effect sizes observed, coupled with proposed inverted U-shaped dose-effect curve, future investigations are needed to determine dose/duration specific responses to VD, which may culminate in improved function of HFD SkM. NEW FINDINGS: What is the central question of this study? Can vitamin D supplementation alleviate detrimental effects of high-fat diet (HFD) consumption on contractile performance of isolated skeletal muscles? What is the main finding and its importance? The present study is the first to examine the synergistic effects of HFD consumption and vitamin D supplementation on the contractile performance of isolated skeletal muscle. These findings suggest high dose vitamin D has limited effects on force, power or fatigue resistance of isolated mouse soleus and extensor digitorum longus.

Background: Vitamin D is crucial for skeletal muscle function. 25-hidroxyvitamin D (25(OH)D) has been correlated with skeletal muscle mass and intramyocellular lipid (IMCL) content. The purpose of this study was to understand how calcitriol, the active vitamin D metabolite, directly affects myocellular size and lipid partitioning. Methods: C2C12 myotubes were treated with calcitriol (100nM) or vehicle control for 24 or 96 h. Myotube diameter and protein synthesis rate were measured to determine effects of calcitriol on myocellular size. Intramyocellular triacylglycerol (IMTG), diacylglycerol (DAG), and ceramide content were measured by LC/MS. Expression of genes involved in lipid packaging and lipolysis were measured by RT-PCR. Insulin-stimulated phosphorylated Akt (Thr 308) was determined by western blot. Results: Calcitriol did not affect myocellular size or protein synthesis rate. Calcitriol increased total DAG and ceramides in a sub-species specific manner. Calcitriol increased IMTG area, but did not affect total IMTG content. Calcitriol reduced mRNA content of diglyceride acyltransferase and increased mRNA content of lipid packaging genes. Calcitriol did not negatively affect insulin-stimulated pAkt. Conclusions: These results suggest calcitriol directly alters lipid content and packaging in skeletal muscle cells. Altering the expression of lipid packaging genes and increasing IMCL subspecies content may be mechanisms by which vitamin D improves skeletal muscle function in vivo.

Purpose: The aims of these studies were to examine the effects of wearing different grades of graduated compression stockings (GCS) on performance, physiological, and perceptual measures before, during, and after exercise in well-trained runners. Method: Two separate running studies were conducted where participants wore different grades of GCS compared with a placebo control stocking in random, counter-balanced order: (1) a field study focussed on a series of 10-km running performances on a 400m track; (2) a laboratory study that examined the effects of 40-min treadmill running on physiological, perceptual, and muscle function responses. Changes in muscle function and damage were determined pre- and post-run by measuring creatine kinase (CK) and myoglobin (Mb) concentrations, counter-movement jump (CMJ) height, muscle soreness, and pressure sensitivity. Physiological measurements of heart rate (HR), oxygen uptake (V&O2), blood lactate concentration [La], and ratings of perceived exertion (RPE) were measured during running. Pre- and post-run perceptual scales assessed comfort, tightness and pain associated with wearing GCS. Results: There were no significant differences in 10-km run time, mean HR, V&O2, [La], and RPE for participants wearing different GCS in (1) and (2) (P<0.05). Con and Low were rated most comfortable (P<0.05) and Hi were tightest (P<0.05) and induced more pain (P<0.05) when GCS were compared in both studies. CMJ was better in participants wearing Low and Med GCS post-run compared with Con in (1) and for Con and all GCS at 0 h post-exercise in (2). CK and Mb levels were higher (P<0.05) and pressure sensitivity was more pronounced (P<0.05) at 0 h post-run for Con and all GCS (2). Few participants (4/10) reported muscle soreness at any one location in (2). Conclusions: Well-trained runners did not experience improved performance, physiological, or perceptual responses when wearing different grades of GCS during 10- km track or 40 min treadmill running compared with a control garment. 40 min treadmill running at 80% V&O2 max may not be strenuous enough to elicit a loss of muscle function in well-trained runners. Runners felt more comfortable wearing GCS that had less compression.

Limitations are found when verifying tests for stability of the shoulder and pelvic girdle, which compromises the ability to evaluate this variable for professional practice and scientific research. Proper core stability capability is important by preventing low back pain and improving performance in sports. The aim of this master thesis was to evaluate the reproducibility of the Upper Body Test and to apply it to evaluate the stabilization capacity of the shoulder and pelvic girdle after a training program with functional characteristics, performed with two methodologies of movement organization. For this, a study was carried out to evaluate the reproducibility of the test in young adults, during three days of evaluations, through the intraclass correlation coefficient, coefficient of variation and graphical analysis of Bland-Altman, as well as identification of the minimum detectable change of the instrument. A controlled clinical trial was then conducted with three groups: grouped training group, alternate training group, and control group. The groups performed a training period with functional characteristics, with the same training load, differentiated by the methodological organization of the training way. One group trained in a grouped manner, one alternately according to functional movement patterns, and the control group did not perform any type of training. The groups were evaluated before and after 10 weeks of training through the Upper Body Test. Statistical difference was observed between the first and second test sessions, with standardization of the evaluations for the third session. Thus, the very high reproducibility (r = 0.87 to 0.94) was found between the second and third evaluations, with a low variation (3.31% to 5.91%) and agreement between the measurements obtained with the Upper Body Test. The minimal detectable difference between the patterns shows greater sensitivity to the body hemispheres (3.3 to 3.8). From the reproducibility obtained for the test and 10 weeks of training, it was verified that the group that trained in a grouped way obtained statistical improvement between the initial and final moments of the training, with a small effect size for the measurements in relation to the hemispheres Body. The group of grouped training had statistical difference in relation to the control group. Thus, it is concluded that Upper Body Test presents reliability for assessing the capacity of stabilizing the shoulder and pelvic girdle in young adults, and that the way of grouped functional training promotes an improvement in this capacity of stabilization. / A adequada capacidade de estabilidade do core é importante por prevenir dor lombar e melhorar o rendimento em esportes. Testes para verificar a estabilidade do core ganham notoriedade nos últimos anos, entretanto limitações são encontradas para os testes propostos para verificar a capacidade de estabilização das cinturas escapular e lombo-pélvica, estas consideradas parte integrante do core. O objetivo desta dissertação foi avaliar a reprodutibilidade do Upper Body Test e aplicá-lo para avaliação da estabilidade das cinturas escapular e lombo-pélvica após um programa de treinamento funcional, realizado com duas formas de organização de movimentos. Para isto, foi realizado um estudo para avaliar a reprodutibilidade do teste em 31 adultos jovens, através do coeficiente de correlação intraclasse, coeficiente de variação e análise gráfica de Bland-Altman, bem como, identificação da diferença mínima detectável do instrumento. Em seguida, foi realizado um ensaio clínico controlado com três grupos: grupo de treinamento agrupado, grupo de treinamento alternado e grupo controle. Os grupos realizaram um período de treinamento funcional, com a mesma carga e diferenciados pelo agrupamento ou alternância de ações funcionais, e o grupo controle não realizou nenhum tipo de treinamento. Os grupos foram avaliados antes e após 10 semanas de treinamento por meio do Upper Body Test. Foi observado, diferença estatística para o alcance relativo, entre a primeira e a segunda sessão de testes, com padronização dos testes para a terceira sessão. Desse modo, encontrou-se alta a muito alta reprodutibilidade (r = 0,87 a 0,94) entre a segunda e terceira avaliação, com baixa variação (3,31% a 5,91%) e concordância entre as medidas obtidas com o Upper Body Test. A diferença mínima detectável para o teste, apresenta maior sensibilidade para os hemisférios corporais (3,3 a 3,8). Obtida a reprodutibilidade do teste, e aplicadas 10 semanas de treinamento, foi constatado que o grupo de treinamento agrupado obteve melhora estatística, para a estabilidade das cinturas escapular e lombo-pélvica entre os momentos inicial e final da intervenção, com um tamanho do efeito pequeno para as medidas em relação aos hemisférios corporais. O grupo de treinamento agrupado obteve diferença em relação ao grupo controle. Assim conclui-se que Upper Body Test apresenta fiabilidade para avaliação da capacidade de estabilização da cintura escapular e lombo-pélvica em adultos jovens, e que a maneira de treinamento funcional agrupada promove melhora nessa capacidade de estabilização. / São Cristóvão, SE

Polypterus is an extant fish that is used as a model to understand the fin-to-limb evolutionary transition. Polypterus exhibits muscle phenotypes relevant to this transition. In particular, plastic changes in bone and muscle in Polypterus have been shown in response to spending time in a terrestrial environment. Muscle fiber changes are usually associated with changes in the performance demand placed on those muscles. We hypothesize that muscle fibers are recruited differently between aquatic and terrestrial environments to explain the change in fiber type. How pectoral fin muscle activity changes between swimming and walking is mostly unknown. Hence, this study utilizes electromyography (EMG) and high-speed videography to understand how the muscle activity pattern and function of all four pectoral fin muscle groups change during swimming and walking in aquatically raised fish. In this experiment, aquatically raised fish were placed in water and on land to observe changes in fin muscle function between behaviours. This study aims to understand how the instantaneous changes in the behaviour of the fish, particularly in the pectoral fin, could explain the muscle plasticity found in previous research. This study showed that fish adduct their pectoral fins much faster with increased muscle effort during walking compared to swimming. The adductor muscle also had the biggest change in function, activating for the majority of the fin-stroke cycle and therefore undergoing eccentric contraction. The increase in muscle effort seen in this study is consistent with the muscle fiber transition seen in fish that spend long periods on land, and the dramatic change of EMG magnitudes found in the adductor muscle may explain muscle damage previously found following acute walking.

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