Signs Of Muscle Damage Research Articles

Safety And Feasibility Of Strength Training In Patients With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a rapidly progressive and currently incurable neuromuscular disease. Understanding the role of exercise is important for these patients as high-intensity or eccentric actions can be damaging in DMD yet a lack of loading may exacerbate muscle dysfunction. While a few studies show submaximal exercise may be safe and potentially delay the loss of muscle function in DMD, no study has systematically examined the potential of strengthening exercise to improve muscle function or attenuate disease progression. PURPOSE: To examine the safety and feasibility of a pilot, in-home strengthening intervention consisting of knee extensor (KE) and flexor (KF) exercise in DMD. METHODS: Eight ambulatory boys with DMD [9.3 (0.8) yrs, BMI 19.0 (4.6) kg/m2] on corticosteroid therapy were recruited to undergo 12 weeks of isometric exercise training of the bilateral KE and KF. Exercise prescription consisted of 4 sets x 6 reps, 3x/week at a target intensity of 50% maximal volitional contraction (MVC). At baseline (BL), MVC testing and training familiarization were done for one week on site. The exercise equipment (custom built chair, laptop, and load cell) was subsequently shipped allowing for in-home training and supervision via live video conferencing for each session. Safety outcome measures to assess muscle damage included magnetic resonance proton transverse relaxation time (T2) of KE and KF, pain assessment, and creatine kinase levels at BL, 1, 6, and 12wks. Peak strength (KE and KF MVC) and time to ascend/descend 4 steps were also assessed at BL and 12wks. RESULTS: The 7 boys who completed the strength training program had a compliance of 84.9 (9.0)% for the exercise sessions. The safety measures did not indicate signs of muscle damage [non-significant change in mean T2: KE=2.3 (3.6)% and KF= 0.4 (4.6)%]. Peak torque increased by 20.6% for KE (p<0.01) and 14.3% for KF (p<0.05), and the time to ascend (13.5%, p<0.05) and descend (22.7%, p<0.05) steps improved after exercise training. CONCLUSION: This in-home, 12-week supervised strength training program was safe, feasible, and improved strength and function in boys with DMD. Future research is required to optimize the strengthening protocol and further explore its potential efficacy and clinical application.

Movement Patterns and Muscle Damage During Simulated Rugby Sevens Matches in National Team Players.

Pereira, LA, Nakamura, FY, Moraes, JE, Kitamura, K, Ramos, SP, and Loturco, I. Movement patterns and muscle damage during simulated rugby sevens matches in national team players. J Strength Cond Res 32(12): 3465-3474, 2018-The aim of this study was to analyze the match performance (i.e., distance covered in different intensities), signs of muscle damage (assessed by means of creatine kinase [CK] activity and rate of force development [RFD]), and neuromuscular fatigue (using linear sprint and vertical jump performances) after 3 single-day simulated matches performed by rugby sevens players from the Brazilian National team. Ten male rugby sevens players (25.2 ± 3.6 years; 88.7 ± 7.1 kg; 182.2 ± 6.3 cm) participated in this study. On the day before the matches, the athletes performed a 40-m sprint, a vertical jump assessment, and a maximal isometric force test. In the morning of the match day, blood samples were collected to analyze the CK activity. Afterward, 3 simulated rugby sevens' matches were performed with 2-hour intermission periods. The match performance (encompassing total distance and distance covered in different velocity ranges and body loads [BLs]) was obtained from global positioning system units. The statistical analysis was performed using a mixed model approach and the effect sizes (ESs) of the differences. The statistical significance level was set at p ≤ 0.05. Players were capable of maintaining the match performance when comparing the first and last games. Large (ES > 0.8) and significant (p ≤ 0.05) reductions were demonstrated in the total distance and BL when comparing the second with the first halves. Decrements in the explosive force capacity (assessed by means of RFD) and the squat jump (SJ) were noticed (ES varying from 0.55 to 1.14; p ≤ 0.05). The CK activity increased after the matches (ES = 1.29; p ≤ 0.05). The rugby sevens players were able to maintain the physical performance across 3 successive matches simulating the first day of a tournament. The augmented CK activity and the decreases in the SJ and RFD suggest that increased levels of muscle damage were experienced on the day after the matches. Therefore, the technical staff are encouraged to implement recovery strategies and planned substitutions during multiday tournaments to reduce the impact of accumulated fatigue and muscle damage on subsequent match performance. In addition, specific training strategies aimed at better simulating the match demands need to be implemented in the players' training routines.

Diabetes and High-Fat Diet Induce Different Pathologies in Mouse Skeletal Muscle Extracellular Matrix

Whether obesity and diabetes (DM) similarly affect composition and function of skeletal muscle extracellular matrix (ECM) has not been resolved. This study examines the effects of long term high fat diet (HFD) and DM on rodent skeletal muscle ECM were addressed. Five week old C57BL/6 male mice were randomly allocated to standard chow (control; n=26) or HFD (45% kcal fat; n=25). After 15 weeks chow and HFD mice were rendered diabetic (by low dose STZ, 65mg/kgx3d, I.P.) (DM, n=14; HFD+DM, n=14); nondiabetic mice acted as controls. Mice were euthanased after 30 weeks and plasma and quadriceps muscle were collected for analysis. Body weight and plasma insulin expectedly decreased with DM induction and increased with HFD (all p&amp;lt;0.05). High glucose occurred only in DM mice (∼14 mM; p&amp;lt;0.05), whereas only HFD increased muscle triglyceride (p&amp;lt;0.05). Both conditions induced a decrease in quadriceps weight and in grip strength performance (p&amp;lt;0.05). Quadriceps of DM mice showed increased CTGF/CCN2 (1.5-fold; p&amp;lt;0.05), TIMP-1 (2-fold; p&amp;lt;0.05), collagen-I (3-fold; p&amp;lt;0.05), -IV (2-fold; p&amp;lt;0.05), and -VI (2-fold; p&amp;lt;0.05) protein. In contrast, HFD induced a downregulation of CTGF/CCN2 (0.6-fold; p&amp;lt;0.05), MMP-1 (0.6-fold; p&amp;lt;0.05), and TIMP-2 (0.4-fold; p&amp;lt;0.05). In DM mice quadriceps centralized nuclei (p&amp;lt;0.05) and caspase 3 (protein; 1.5-fold; p&amp;lt;0.05) were increased, whereas caspase 3 was decreased in HFD (0.5-fold; p&amp;lt;0.05). Moreover, HFD induced a downregulation of ubiquitin ligase atrogin-1 protein (0.5-fold; p&amp;lt;0.05) and mRNA levels of serine/threonine kinase p70S6k (0.75-fold; p&amp;lt;0.05). Notably, no greater dysregulation of the muscle changes observed with DM alone or with HFD alone, was seen in HFD+DM mice. These data suggest that DM and HFD differentially affect skeletal muscle ECM: DM promotes a pro-fibrotic profile with signs of muscle damage, and HFD impairs regulatory protein turnover pathways, each inducing muscle dysfunction. Disclosure S.F. Martinez-Huenchullan: None. L.A. Ban: None. A. Tao: None. S.S. Sutanto: None. C. Tam: None. S. McLennan: None. S.M. Twigg: Advisory Panel; Self; Abbott. Consultant; Self; Abbott. Advisory Panel; Self; Novo Nordisk Inc., Sanofi-Aventis, AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company. Speaker's Bureau; Self; AstraZeneca, Merck Sharp &amp; Dohme Corp.. Other Relationship; Self; Abbott.

Performance and physiological analysis of 500 km non-stop cycling: a case study

ABSTRACTUltra-endurance sports have gained popularity over the last years. In this case, a well-trained cyclist completed 503.5 km non-stop (33.3 km.h−1). Speed and power output were reduced during the trial, being the reduction of power attributable to changes in pedal velocity rather than pedal forces. Heart rate (HR) showed an initial cardiovascular drift and progressively decreased independently of power. A decreased HR variability, a marked inflammatory response, signs of muscle damage and alterations of the haematological profile were observed after the trial. These adverse physiological effects were still present 24–48 h after exercise. A reduction in handgrip maximal voluntary contraction was observed immediately after the trial and 24 h later despite these muscles being minimally active during exercise. These findings show the high levels of stress to which the organism is subjected during ultra-endurance exercise even in the case of a trained cyclist.

High-intensity interval training in facioscapulohumeral muscular dystrophy type 1: a randomized clinical trial.

Increasing evidence suggests that high-intensity training (HIT) is a time-efficient exercise strategy to improve fitness. HIT has never been explored in neuromuscular diseases, likely because it may seem counterintuitive. A single session of high-intensity exercise has been studied without signs of muscle damage in facioscapulohumeral muscular dystrophy type 1 (FSHD1). We aimed to determine whether HIT is safe and effective in FSHD1 in a randomized, controlled parallel study. Untrained adults with genetically verified FSHD1 (n=13) able to perform cycle-ergometer exercise were randomized to 8weeks of supervised HIT (n=6) (3×10-min cycle-ergometer-HIT/week) or 8weeks of usual care (n=7). Following this, all participants performed 8weeks of unsupervised HIT (3×10-min cycle-ergometer-HIT/week). Primary outcome was fitness, maximal oxygen uptake/min/kg body weight. Furthermore, workload, 6-min walk distance, 5-time sit-to-stand time, muscle strength, and daily activity levels were measured. Pain, fatigue, and plasma-CK were monitored. Twelve patients completed the randomized part of the study. Plasma-CK levels and pain scores were unaffected by HIT. Supervised HIT improved fitness (3.3mlO2/min/kg, CI 1.2-5.5, P<0.01, n=6, NNT=1.4). Unsupervised HIT also improved fitness (2.0mlO2/min/kg, CI 0.1-3.9, P=0.04, n=4). There was no training effect on other outcomes. Patients preferred HIT over strength and moderate-intensity aerobic training. It may seem counterintuitive to perform HIT in muscular dystrophies, but this RCT shows that regular HIT is safe, efficacious, and well liked by moderately affected patients with FSHD1, which suggests that HIT is a feasible method for rehabilitating patients with FSHD1.

Physical Exercise in Aging: Nine Weeks of Leg Press or Electrical Stimulation Training in 70 Years Old Sedentary Elderly People.

Sarcopenia is the age-related loss of muscle mass and function, reducing force generation and mobility in the elderlies. Contributing factors include a severe decrease in both myofiber size and number as well as a decrease in the number of motor neurons innervating muscle fibers (mainly of fast type) which is sometimes accompanied by reinnervation of surviving slow type motor neurons (motor unit remodeling). Reduced mobility and functional limitations characterizing aging can promote a more sedentary lifestyle for older individuals, leading to a vicious circle further worsening muscle performance and the patients’ quality of life, predisposing them to an increased risk of disability, and mortality. Several longitudinal studies have shown that regular exercise may extend life expectancy and reduce morbidity in aging people. Based on these findings, the Interreg IVa project aimed to recruit sedentary seniors with a normal life style and to train them for 9 weeks with either leg press (LP) exercise or electrical stimulation (ES). Before and at the end of both training periods, all the subjects were submitted to mobility functional tests and muscle biopsies from the Vastus Lateralis muscles of both legs. No signs of muscle damage and/or of inflammation were observed in muscle biopsies after the training. Functional tests showed that both LP and ES induced improvements of force and mobility of the trained subjects. Morphometrical and immunofluorescent analyses performed on muscle biopsies showed that ES significantly increased the size of fast type muscle fibers (p<0.001), together with a significant increase in the number of Pax7 and NCAM positive satellite cells (p<0.005). A significant decrease of slow type fiber diameter was observed in both ES and LP trained subjects (p<0.001). Altogether these results demonstrate the effectiveness of physical exercise either voluntary (LP) or passive (ES) to improve the functional performances of aging muscles. Here ES is demonstrated to be a safe home-based method to counteract fast type fiber atrophy, typically associated with aging skeletal muscle.

Does blood flow restricted exercise result in prolonged torque decrements and muscle damage?

We are writing in regard to the recent paper from Wernbom et al. (2011) titled ‘‘Contractile function and sarcolemmal permeability after acute low-load resistance exercise with blood flow restriction.’’ The authors sought to investigate neuromuscular fatigue and recovery, as well as fiber morphology, following an acute bout of low-load resistance exercise with blood flow restriction (BFR). The authors should be commended on investigating the effects of BFR at the muscle fiber level, as this is an area that is presently poorly considered in the current literature. The authors hypothesized that exercise with BFR would result in signs of muscle damage. However, we have some concerns with the interpretation of the data presented in this study. Several of the authors’ main findings, highlighted in the discussion, may not necessarily be attributed to muscle damage. The authors’ first main finding was that there were markedly larger acute reductions (1 and 2 min postexercise) in maximum voluntary contraction (MVC) in the BFR leg compared to the free-flow leg. It should be emphasized that these greater acute reductions observed in the BFR leg were obtained with a MVC completed under BFR. Following the release of the cuff, there were no longer differences between groups. Furthermore, we question the reasoning behind having subjects’ complete repetitions to muscular failure under BFR, followed by two MVC’s which were also completed under BFR. If the purpose was to investigate the effects of low-load BFR on muscle damage, it seems more appropriate to release the cuff following the completion of the exercise bout for at least one of the immediate post MVC’s. This marked decrease in MVC can be questioned, because previous research has shown that decreases observed in MVC with BFR are almost returned to baseline within a minute following the release of the cuff (Yasuda et al. 2009). The authors second main finding was that part of the decline in MVC was longer lasting (at least 48 h), especially in the BFR leg. Again, the MVC’s which were different between conditions, were only observed when the MVC was completed under BFR. The authors’ suggestion that the decline in MVC was longer lasting is not supported by the data presented in the paper, which showed that there were no differences between groups at 4, 24, or 48 h postexercise. The authors’ third main finding was that there was an increased occurrence of fibers with elevated tetranectin staining in the BFR leg. The authors suggest this elevated tetranectin staining is indicative of muscle damage, because unpublished data from their laboratory suggest that severe eccentric exercise caused marked increases with intracellular tetranectin staining. While this is interesting, it should be noted that the exercise completed in this study was submaximal and not severe eccentric exercise. Furthermore, elevations in tetranectin staining were also observed in the free-flow leg which was not taken to muscular failure (work matched with BFR leg), indicating that the elevation in tetranectin may not have been reflective of muscle damage. The authors did state that tetranectin elevations are not necessarily only associated with muscle damage, but may also contribute to mechanotransduction processes, which may be of mechanistic importance for the explanation of the muscle hypertrophy Communicated by Susan A. Ward.

Changes in muscle temperature induced by 434 MHz microwave hyperthermia

Objective: To investigate the changes in temperature of human muscle during microwave hyperthermia. Methods: Skin surface and muscle temperatures were measured in 11 healthy adult men (mean (SD) age 24.3...

Aerobic training improves exercise performance in facioscapulohumeral muscular dystrophy

Exercise programs have been shown to increase strength and endurance in patients with myopathic disorders. The authors investigated the effect of aerobic training in patients with facioscapulohumeral dystrophy (FSHD). Twelve weeks of low-intense aerobic exercise improved maximal oxygen uptake and workload with no signs of muscle damage. The authors conclude that aerobic training is a safe method to increase exercise performance in patients with FSHD.

Blood serum metabolites and meat quality in crossbred pigs experiencing different lairage time

Pigs of two crosses: A (♀ Duroc × ♂Swedish Landrace) × ♂Pietrain (n=24) and B (♀ Swedish Landrace × ♂Large White) × ♂Pietrain (n=26) were used to investigate the effects of different lairage time (2 and 24 hours) on levels of stress and meat quality traits. No direct effect of lairage time on cortisol, lactate, electrolytes and meat quality parameters was observed. However, after long lairage time, pigs showed lower level of glucose and higher CK, AST and ALT activity. Crossbred B pigs exposed to short lairage time, showed higher blood lactate, sodium, and potassium level, higher drip loss and lower pHi, whereas there were no significant differences between the crossbreeds in the long lairage group. The results indicate that long lairage time decreases blood glucose level and produces signs of muscle damage. In the short lairage period, the crossbreed B showed a higher response to pre-slaughter handling affecting the meat quality.