Regulation of Circulatory Muscle-specific MicroRNA during 8 km Run.

Acute prolonged endurance running has been shown to alter muscle-specific circulating microRNA (miRNA) levels. Here, eighteen participants completed an 8 km run. We assessed the levels of hsa-miR-1-3p, -133a-3p, -133b, and -206 and their correlation with conventional biomarkers following exercise. Compared to before exercise (Pre), 8 km run significantly increased the lactate level immediately after exercise (0 h). Myoglobin (Mb) level increased at 0 h while creatine kinase (CK) level increased 24 h after exercise (24 h). The levels of creatine kinase MB isoenzyme (CK-MB) and cardiac troponin I (cTnI) were all elevated at 24 h and within the normal physiological range; The levels of hsa-miR-1-3p, -133a-3p, -133b significantly increased at 0 h but only hsa-miR-133a-3p still elevated at 24 h. Only hsa-miR-206 level decreased at 24 h; Additionally, the changes of hsa-miR-1-3p and hsa-miR-133a-3p were correlated with Mb at 24 h. These findings suggest that muscle-specific miRNA elevation in plasma is likely physiological and that these miRNA may be used as potential biomarkers for load monitoring in individuals.

Time-Course Responses of Muscle-Specific MicroRNAs Following Acute Uphill or Downhill Exercise in Sprague-Dawley Rats.

Objective: The physiological characteristics and acute responses underpinning uphill running differ from those of downhill running and remain less understood. This study aimed to evaluate time-course changes of muscle-specific microRNA (miRNA) responses in striated muscle or circulation in response to uphill and downhill running. Methods: Male Sprague-Dawley rats (n = 84) were randomly assigned to a sedentary group (n = 12) and an exercise group (n = 72). The exercise group performed 90 min of uphill or downhill running. The striated muscle (quadriceps, gastrocnemius, soleus, and cardiac muscle) or circulation (plasma, exosome, exosome-free) levels of six muscle-specific miRNAs (miR-1, miR-133a, miR-133b, miR-206, miR-208a, and miR-499) were assessed at rest, immediately following exercise, and during recovery (1 h and 48 h). Results: Our results show that miR-1 and miR-133a levels are both decreased in quadriceps following downhill running (p < 0.05) while there is no change after uphill running (p > 0.05). In gastrocnemius, both uphill and downhill running decreased miR-1 level immediately after exercise and returned to baseline during recovery (p < 0.05): interestingly, only miR-499 significantly increased following uphill running (p > 0.05). Of the cell-free miRNAs in circulation, only the miR-133b levels in plasma were not affected following uphill running (p > 0.05); the other miRNA levels significantly increased immediately after exercise (p < 0.05), decreased at 1 h and significantly increased at 48 h after exercise (p < 0.05). All selected miRNA levels in exosomes were not affected following uphill running (p > 0.05), while all selected miRNA levels significantly increased during early recovery after downhill running (p > 0.05). In addition, only the miR-133a level in the exosome-free condition showed significant changes following uphill running (p < 0.05), while miR-1, miR-133a, and miR-499 levels showed significant changes after downhill running (p < 0.05). Conclusion: The results indicate that miRNA undergoes dynamic changes in tissue may play an important role in regulating different stress/adaptation following uphill and downhill running. It is likely that changed miRNA levels in plasma may act as a new biomarker for monitoring whole muscular stress during recovery.

Incidence and Characteristics of Meniscal Injuries in Cadets at a Military School, 2013-2015.

CONTEXT: Meniscal injury is common among military service members. OBJECTIVE: To examine the incidence and characteristics of meniscal injuries in cadets at a single military institution between 2013 and 2015. DESIGN: Cohort study. SETTING: Meniscal-injury data were collected at the Center of Rehabilitation Training, the People's Liberation Army University of Science and Technology. PATIENTS OR OTHER PARTICIPANTS: A total of 2479 cadets participating in physical activities between 2013 and 2015. MAIN OUTCOME MEASURE(S): Injury rates, injury proportions by body mass index, risk ratios (RRs), and injury proportion ratios were reported with 95% confidence intervals (CIs). RESULTS: The overall incidence rate was 10.08 (95% CI = 6.84, 14.84) per 1000 person-years. A multiple-comparisons test revealed differences in the relative injury rate in overweight or obese cadets versus normal-weight cadets and underweight cadets (χ2 = 8.98, P = .01). No differences were found between injured normal-weight cadets and underweight cadets (P = .66, RR = 1.39, 95% CI = 0.32, 6.06) or between injured overweight or obese cadets and injured underweight cadets (P = .24, RR = 0.42, 95% CI = 0.09, 1.91). The absolute injury rate was higher for overweight and obese cadets compared with normal-weight cadets (P < .01, RR = 0.30, 95% CI = 0.13, 0.69). The overall proportional distribution for patterns of injury was 2:1 (medial to lateral) for meniscal injuries. Grade 2 injuries were the most common. CONCLUSIONS: The high frequency and level of severity of meniscal injuries may negatively affect the readiness and health of cadets. High body mass index was a risk factor for meniscal injury.