Excessive Treadmill Training Produces different Cardiac-related MicroRNA Profiles in the Left and Right Ventricles in Mice.

High-volume training followed by inadequate recovery may cause overtraining. This process may undermine the protective effect of regular exercise on the cardiovascular system and may increase the risk of pathological cardiac remodelling. We evaluated whether chronic overtraining changes cardiac-related microRNA profiles in the left and right ventricles. C57BL/6 mice were divided into the control, normal training, and overtrained by running without inclination, uphill running or downhill running groups. After an 8-week treadmill training protocol, the incremental load test and training volume results showed that the model had been successfully established. The qRT-PCR results showed increased cardiac miR-1, miR-133a, miR-133b, miR-206, miR-208b and miR-499 levels in the left ventricle of the downhill running group compared with the left ventricle of the control group. Similarly, compared with the control group, the downhill running induced increased expression of miR-21, miR-17-3p, and miR-29b in the left ventricle. Unlike the changes in the left ventricle, no difference in the expression of the tested miRNAs was observed in the right ventricle. Briefly, our results indicated that overtraining generally affects key miRNAs in the left ventricle (rather than the right ventricle) and that changes in individual miRNAs may cause either adaptive or maladaptive remodelling with overtraining.

[The effects of sustained military occupational activities on inhibitory control ability in low temperature environment].

Objective: To evaluate the effects of sustained military occupational activities on inhibitory control ability in low temperature environment, which could provide a basis for accurate military physical training. Methods: Twenty healthy male young cadets (mean age: (23. 32±1. 62)y; height: (175. 34±4. 14)cm; body weight: (68. 19±3. 12)kg) were enrolled in this experiment. A number of military tasks last 36 hours were completed in the ordinary (16℃～23℃) and low(-3℃～-1℃) temperature environment, and the RR interval and core temperature were recorded. The stroop-word-color test and critical frequency test were performed before and after the activities. Results: Compared with rest, the heart rate, excess post-exercise oxygen consumption and training impulse were increased significantly (P＜0. 05) in military occupational activities, however there was no significant difference between the two activities (P＞0. 05). Compared with the rest, the average and maximum core temperature were increased significantly (P＜0. 05), however, compared with the ordinary temperature environment, the average core temperature in the low temperature environment was increased significantly (P＜0. 05), and there was no significant difference in the maximum core temperature (P＞0. 05). Compared with rest, the inhibitory control ability after the two activities was significantly lower (P＜0. 05), which was much worse in the low temperature environment than that in the ordinary temperature environment (P＜0. 05). In addition, compared with rest, both activities led to obvious mental fatigue (P＜0. 05), which was more serious in low temperature environment (P＜0. 05). Conclusion: The sustained military activities can impair the inhibitory control ability, and cause the mental fatigue, in addition, the stress of low temperature can aggravate the negative effects.

Excessive Treadmill Training Enhances Brain-Specific MicroRNA-34a in the Mouse Hippocampus.

Background: An imbalance between total training load and total recovery may cause overtraining (OT). The purpose of the present study was to verify the effects of OT on the expression of brain-derived neurotrophic factor (BDNF), its receptor tropomyosin receptor kinase B (TrkB) and p75 and the dynamic expression patterns of brain-specific miR-34a and miR-124 or inflammation-related miR-21 and miR-132 in the mouse hippocampus. Method: Eight weeks old C57BL/6J mice were randomly assigned to the control (CON), normal training (NT) and OT groups. An 8-week OT training protocol was applied to evaluate the phenotype of mice endurance (incremental load test, ILT) and cognitive capacity (Morris water maze test). We used qRT-PCR and immunoblotting to detect changes in the molecular level of hippocampal samples. Result: Compared with the CON, both NT and OT decreased bodyweight after 8-week training. After 8-week of training, NT increased the exhaustion velocity (EV) while the EV of OT was lower than NT. Mice in NT decreased the escape latency than CON. The percentage of time spent in the probe quadrant and the number of crossing platform times in NT were higher than CON and OT. The BDNF, p75 and TrkB mRNA levels were increased in NT than CON, only the p75 mRNA was increased in OT. The NT exhibited increased protein levels of BDNF and TrkB compared to CON. The protein expression of BDNF was decreased in OT than NT and CON. The protein level of p75 in the OT was higher than in NT and CON. In addition, the phosphorylation level of TrkB in OT was higher than CON and NT. Only the miR-34a level was increased in the OT. Moreover, the expression of miR-34a was found to be negatively correlated with the expression of BDNF, and the increase in miR-34a level was accompanied by a decrease in performance. Conclusion: In summary, the training-evoked increase in the BDNF level may help to improve performance, whereas this conditioning is lost after OT. Moreover, miR-34a potentially mediated changes in the expression of BDNF and may reflect the decrease in performance after OT.

[Effects of sustained military physical related activity on balance ability].

OBJECTIVE: To evaluate the effects of sustained military physical related activity on balance abilities and the role of visual system in it, so as to provide the basis for precise training. METHODS: Fifty-four healthy males (age: 20.28±3.72 y, height: 173.21±5.67 cm; weight: 64.29±5.12 kg) were recruited in this experiment. Multiple military subjects were completed within 36 hours, and the workload was recorded (randomly select 11 people). After military activity, the balance abilities with opened eyes (54 people) and closed eyes (randomly selected 27 people) were evaluated. RESULTS: In terms of internal load, the heart rates (HR), excess post-exercise oxygen consumption (EPOC) and training impulse (TRIMP) for all exercises were increased significantly in military activity compared with rest (P＜0.05). Regard to balance abilities, compared to the rest with eyes-opened, the sway path-total (SPT), sway path-A-P ( SPAP ), sway path-M-L (SPML), sway V-total (SVT), sway V-A-P (SVAP), and sway V-M-L (SVML)after sustained military activity with eyes-opened were increased significantly (P＜0.05), while sway maximal amplitude-A-P (SMAAP), sway maximal amplitude-M-L (SMAML), and area of 100% ellipse (AE) had no significant changes; Compared to the rest, all indicators after the military activity with eyes-closed were significantly increased (P＜0.05). So vision could control the amplitude and area after the military activity. CONCLUSION: Sustained military related activity can damage the balance ability. After sustained military activity, the degree of damage of the balance ability in the closed-eyes is greater than that of the open-eyes, the amplitude and range of the center of gravity are increased, indicates that the visual system plays major role in controlling attitude stability.

[Effect of lower-limb dominance and non-dominance shuttle runs under load carriage on the balance responses in young cadets].

OBJECTIVE: This test was designed to evaluate the effect of lower-limb dominance and non-dominance shuttle runs under load carriage during different exercise load at the same exercise intensity on the balance responses. METHODS: Ten healthy young males were joined in this experiment, they were (20.80±2.04) years old and (173.99±2.87) cm tall. In a randomized cross-over design, they performed four times shuttle runs under unilateral load carriage:20 m×5 at dominant side, 20 m×5 at non-dominant side, 20 m×10 at dominant side, 20 m×10 at non-dominant side respectively. Balance abilities were evaluated immediately and 20 minute post-exercise respectively, and R-R interval was recorded. RESULTS: The HR, EPOC and TRIMP for all exercise load were increased significantly after shuttle runs compared to rest (P<0.01), the EPOC and TRIMP for 20 m×10 shuttle runs were significantly higher than those for 20 m×5 shuttle runs at the dominant and non-dominant side (P<0.01). Compared to the rest, the instability indices (general, anteroposterior and mediolateral movement) for 20 m×5 and 20 m×10 shuttle runs immediately post-exercise at the dominant and non-dominant side were increased significantly (P<0.05), and the magnitude of the mediolateral movement for 20 m×10 shuttle runs was higher than that of 20 m×5 shuttle runs (P<0.05). While there were no obvious difference between the dominant and the non-dominant side (P>0.05), which showed symmetrical change. In addition, during 20 minute recovery, the balance ability for all exercise load was returned to the rest value (P>0.05). CONCLUSIONS: The shuttle runs could impair the trunk control ability immediately post-exercise, the magnitude of mediolateral movement was increased as the exercise load increased. The changes of balance responses were similar between the dominant and the non-dominant side, the dominant and the non-dominant side might show cross-effects.