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Downhill Running Acutely Elicits Mitophagy in Rat Soleus Muscle

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (7)

Purpose This study aimed to investigate the effects of downhill treadmill running on mitochondrial structure/function and expression levels of mitophagy-related proteins in rat skeletal muscle. Methods A total of 48 male adult Sprague-Dawley rats were randomly divided into a control group (C, n = 8) and an exercise group (E, n = 40). Rats in the E group were exercised on a treadmill down a 16 degrees decline at 16 m center dot min(-1) for 90 min and were further divided into 0 h (E0), 12 h (E12), 24 h (E24), 48 h (E48), and 72 h (E72) postexercise subgroups (n = 8 each). At each time point, the soleus muscle was collected under full anesthesia. Mitochondrial ultrastructural changes in skeletal muscle were observed by a transmission electron microscope. The content of quantitative enzyme citrate synthase and the activities of mitochondrial respiratory chain complex II and complex IV were measured by enzyme-linked immunosorbent assay. Protein expressions of skeletal muscle cytochrome c oxidase subunit 1 (COX1), PTEN-induced putative kinase 1 (PINK1), and mitochondrial Parkin microtubule-associated protein 1 light chain 3 (LC3) were determined by Western blot. Mitochondrial colocalizations with Parkin, ubiquitin (Ub), p62/sequestosome 1 (p62), and LC3 were measured by the immunofluorescence double labeling technique. Results After downhill treadmill running, the skeletal muscle mitochondrial structure changed dramatically, and a large amount of mitophagosomes were observed; the citrate synthase content and complex II activity were significantly lower (P < 0.05), whereas complex IV activity and COX1 protein level remained unchanged; the expression levels of PINK1, Parkin, Ub, p62, and LC3 were significantly higher than those in the C group (P < 0.05 or P < 0.01). Conclusion A session of downhill treadmill running activated the PINK1/Parkin pathway and facilitated mitochondrial colocalizations with Ub, p62, and LC3, causing mitophagy and mitochondrial damage within the skeletal muscle.

IF:4.48

Overactivation of the Reward System and Deficient Inhibition in Exercise Addiction

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (9)

Purpose: Behavior studies have found that exercise addiction is associated with high impulsivity. In other addictions, neural mechanisms of impulsivity reflect abnormalities in the reward and inhibition systems. In this study, we determined whether abnormalities existed in the reward and inhibition systems of exercise addicts. Methods: Three groups of male participants (15 exercise addicts, 18 regular exercisers, and 16 exercise avoiders) completed the Mini International Personality Item Pool (Mini-IPIP), the classic go/no-go task, and the exercise-related go/no-go task. Event-related potentials (ERP) were recorded during the go/no-go tasks, and correctly performed trials were analyzed. Results: Exercise addicts scored lower for extraversion and higher for neuroticism, reflecting a poor capacity for emotional regulation and impulse control, and had larger N2 and P3d amplitudes during the exercise-related go/no-go task. Exercise addicts and exercise avoiders demonstrated impaired accuracy in the exercise-related go/no-go task and had larger N2 amplitudes compared with regular exercisers during the letter-digit go/no-go task. Exercise addicts and regular exercisers showed larger Go-N1 and Go-P2 amplitudes compared with exercise avoiders during the exercise-related go/no-go task. Exercisers (exercise addicts and regular exercisers) demonstrated higher activation in response to exercise-related stimuli as reflected by larger N1 and P2, and addicts (exercise addicts) demonstrated poorer inhibition as reflected by larger N2 and P3d amplitudes. Go-N1 and Go-P2 were significantly correlated with no-go accuracy in exercise-related task. Conclusions: Exercise addicts scored higher for the neuroticism personality trait and exhibited overactivation of the reward system and underactivation of the inhibition system. Overactivation of the reward system may be related to long-term exposure to exercise. Underactivation of the inhibition system may be a crucial factor in exercise addiction.

IF:4.48

Transfer Learning Effects of Biofeedback Running Retraining in Untrained Conditions

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (9)

Purpose: Running gait retraining via peak tibial shock biofeedback has been previously shown to reduce impact loading and mitigate running-related symptoms. In previous research, peak tibial shock is typically measured and trained for one limb at a single constant training speed during all training sessions. The goal of this study was to determine how runners transfer learning in the trained limb to the untrained limb at different unconstrained speeds. Methods: Thirteen runners (3 females, age = 41.1 +/- 6.9 yr, running experience = 6.8 +/- 4.4 yr, weekly running distance = 30.7 +/- 22.2 km) underwent running gait biofeedback retraining via continuous tibial acceleration measured at the right distal tibia. Before and after the training, participants were asked to run at their self-selected constrained training speeds (2.8 +/- 0.2 m.s(-1)) and at 110% and 90% of the training speed. Pretraining and posttraining peak tibial shock values for each limb were compared. Results: Participants reduced peak tibial shock in the trained limb by 35% to 37% (P < 0.05, Cohen's d = 0.78-0.85), and in the untrained limb by 20% to 23% (P < 0.05, Cohen's d = 0.51-0.71) across the three testing speeds. The reduction was not significantly different between the trained and untrained limbs (P = 0.31-0.79, Cohen's d = 0.18-0.45). Similarly, there was no difference in peak tibial shock reduction among the three running speeds (P = 0.48-0.61, Cohen's d = 0.06-0.45). Conclusion: Participants demonstrated transfer learning effects evidenced by concomitant reduced peak tibial shock in the untrained limb, and the learning effects were retrained when running at a 10% variance of the training speed.

IF:4.48

Sodium Hyaluronate and Platelet-Rich Plasma for Partial-Thickness Rotator Cuff Tears

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (2)

Purpose The treatment of partial-thickness rotator cuff tears (PTRCT) remains controversial. Few studies have focused on the conservative and new measurements of small to medium PTRCT. The use of sodium hyaluronate (SH) or platelet-rich plasma (PRP) as a method for rotator cuff repair requires further investigation. The aim of this study was to evaluate the combined use of SH and PRP in the treatment of small to medium PTRCT. Study Design A double-blinded randomized trial was used in this study. Methods Individuals with PTRCT detected by clinical examination and magnetic resonance imaging (MRI) were included in this study. The patients were randomly assigned to receive subacromial injections of normal saline, SH, PRP, or SH + PRP once a week for 4 wk. The primary outcome measure was the Constant score, and the secondary outcomes included the American Shoulder and Elbow Surgeons (ASES) and the visual analog scale scores. All of the clinical outcomes were assessed at pretreatment and 1, 3, 6, and 12 months posttreatment. MRI was used to evaluate the evolution of the cuff defect after 1 yr. Results The PRP group and the SH + PRP group showed a significantly higher Constant score and ASES score after the treatments. There were significant differences between the SH + PRP group and the SH or PRP group at 12 months in the Constant, visual analog scale, and ASES scores. MRI results showed that the tear size significantly decreased in both the PRP and the SH + PRP groups, especially in the SH + PRP group. Conclusion Our study provided evidence of the efficacy of PRP injection in the healing of small to medium PTRCT. Moreover, the combined injection of SH and PRP yielded a better clinical outcome than SH or PRP alone.

IF:4.48

Associations of Resistance Exercise with Cardiovascular Disease Morbidity and Mortality

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (3)

Purpose Resistance exercise (RE) can improve many cardiovascular disease (CVD) risk factors, but specific data on the effects on CVD events and mortality are lacking. We investigated the associations of RE with CVD and all-cause mortality and further examined the mediation effect of body mass index (BMI) between RE and CVD outcomes. Methods We included 12,591 participants (mean age, 47 yr) who received at least two clinical examinations 1987-2006. RE was assessed by a self-reported medical history questionnaire. Results During a mean follow-up of 5.4 and 10.5 yr, 205 total CVD events (morbidity and mortality combined) and 276 all-cause deaths occurred, respectively. Compared with no RE, weekly RE frequencies of one, two, three times or total amount of 1-59 min were associated with approximately 40%-70% decreased risk of total CVD events, independent of aerobic exercise (AE) (all P values <0.05). However, there was no significant risk reduction for higher weekly RE of more than four times or 60 min. Similar results were observed for CVD morbidity and all-cause mortality. In the stratified analyses by AE, weekly RE of one time or 1-59 min was associated with lower risks of total CVD events and CVD morbidity regardless of meeting the AE guidelines. Our mediation analysis showed that RE was associated with the risk of total CVD events in two ways: RE had a direct U-shaped association with CVD risk (P value for quadratic trend <0.001) and RE indirectly lowered CVD risk by decreasing BMI. Conclusion Even one time or less than 1 hwk(-1) of RE, independent of AE, is associated with reduced risks of CVD and all-cause mortality. BMI mediates the association of RE with total CVD events.

IF:4.48

From Total Volume to Sequence Maps: Sophisticated Accelerometer Data Analysis

期刊: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, 2019; 51 (4)

Purpose: To date, epidemiological studies have focused on the potential health effects of total volume of physical activity (PA) or sedentary behavior (SB). However, two persons may have the same volume of PA or SB but accumulated in a completely different sequence. The pattern of accumulating PA and SB might be more important for health effects than the total volume. Therefore, the aim was to develop a sophisticated algorithm translating accelerometer data into detailed sequence maps considering how PA and SB are accumulated throughout the day. Methods: We developed a novel algorithm to convert accelerometer counts into a sequence map based on behavior states defined by a combination of intensity (SB, light, moderate, and vigorous intensity) and duration (sporadic accumulation or in bouts of different duration). In addition, hierarchical cluster analysis was applied to identify clusters of children with similar behavioral sequence maps. Results: Clustering resulted in seven clusters of children with similar PA and SB sequence maps: an average cluster (33% of children); a cluster with relatively more SB, light, and moderate PA in bouts (SB and PA bouters, 31%); a cluster characterized by more sporadic SB and light PA (light activity breakers, 26%); and four smaller clusters with 7% of the children or less. Conclusion: This novel algorithm is a next step in more sophisticated analyses of accelerometer data considering how PA and SB are accumulated throughout the day. The next step is identifying whether specific patterns of accumulating PA and SB are associated with improved health outcomes.

IF:4.48

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