Large variability exists in muscle adaptive response to resistance exercise (RE) training between individuals. Recent studies have revealed a significant role for microRNAs (miRNAs) in skeletal muscle plasticity. In this study, we investigated how RE affects miRNA expression and whether the variability of muscle hypertrophy to RE training may be attributed to differential miRNA regulation in the skeletal muscle. To screen high and low responders to RE, we had 18 young men perform arm curl exercise training. After screening, all the men performed 12 wk of lower body RE training, but only the high or low responders participated in the acute RE test before training. Muscle biopsies were obtained from the vastus lateralis muscle at baseline, 3 h after acute RE, and after the training period. Total RNA was extracted from the skeletal muscle, and miRNA expression (800 miRNAs) was analyzed. RE training increased the cross-sectional area of the biceps brachii (−1.7–26.1%), quadriceps (2.2–16.8%), and hamstrings (1.6–18.4%). Eighty-five and 102 miRNAs were differentially expressed after acute and chronic RE, respectively (P < 0.05). Seventeen miRNAs, especially 23b-3p, 26a-5p, 32-5p, 148b-3p, and 376a-3p, were differentially expressed at baseline, and 23 miRNAs, especially let-7a-5p, 95, 148a-3p, and 376a-3p, and 26 miRNAs, especially 30d-5p and 376a-3p, were differentially regulated after acute and chronic RE, respectively, in the skeletal muscle between high and low responders, indicating that the expression patterns of several miRNAs are altered by acute or chronic RE, and that miRNAs are involved in skeletal muscle adaptation to RE training.

Background: Dehydroepiandrosterone (DHEA) is precursor of sex steroid hormone. We demonstrated that acute DHEA injection to type 1 diabetes model rats induced improvement of hyperglycemia. However, the effect of the combination of DHEA administration and exercise training on insulin resistance is still unclear. This study was undertaken to determine whether 6-weeks of DHEA administration and/or exercise training improve insulin resistance in obese male rats. Methods: After 14 weeks of a high-sucrose diet, obese male Wistar rats were assigned randomly to one of four groups: control, DHEA administration, exercise training, and a combination of DHEA administration and exercise training (n = 10 each group). Results: After 6-weeks of DHEA administration and/or exercise training, rats in the combination group weighed significantly less and had lower serum insulin levels than rats in the other groups. Moreover, the rats treated with DHEA alone or DHEA and exercise had significantly lower fasting glucose levels (combination, 84 ± 6.5 mg/dL; DHEA, 102 ± 9.5 mg/dL; control, 148 ± 10.5 mg/dL). In addition, insulin sensitivity check index showed significant improvements in the combination group (combination, 0.347 ± 0.11; exercise, 0.337 ± 0.16%; DHEA, 0.331 ± 0.14; control, 0.308 ± 0.12). Muscular DHEA and 5α-dihydrotestosterone (DHT) concentrations were significantly higher in the combination group, and closely correlated with the quantitative insulin-sensitivity check index (DHEA: r = 0.71, p < 0.01; DHT: r = 0.69, p < 0.01). Conclusion: These results showed that a combination of DHEA administration and exercise training effectively improved fasting blood glucose and insulin levels, and insulin sensitivity, which may reflect increased muscular DHEA and DHT concentrations.

Acute aerobic exercise (AE) is a major physiological stimulus for skeletal muscle glucose uptake through activation of 5′ AMP‐activated protein kinase (AMPK). However, the regulation of glucose uptake by acute resistance exercise (RE) remains unclear. To investigate the intracellular regulation of glucose uptake after acute RE versus acute AE, male Sprague–Dawley rats were divided into three groups: RE, AE, or nonexercise control. After fasting for 12 h overnight, the right gastrocnemius muscle in the RE group was exercised at maximum isometric contraction via percutaneous electrical stimulation (3 × 10 sec, 5 sets). The AE group ran on a treadmill (25 m/min, 60 min). Muscle samples were taken 0, 1, and 3 h after completion of the exercises. AMPK, Ca2+/calmodulin‐dependent protein kinase II, and TBC1D1 phosphorylation were increased immediately after both forms of exercise and returned to baseline levels by 3 h. Muscle IGF1 expression was increased by RE but not AE, and maintained until 3 h after RE. Additionally, Akt and AS160 phosphorylation were sustained for 3 h after RE, whereas they returned to baseline levels by 3 h after AE. Similarly, GLUT4 translocation remained elevated 3 h after RE, although it returned to the baseline level by 3 h after AE. Overall, this study showed that AMPK/TBC1D1 and IGF1/Akt/AS160 signaling were enhanced by acute RE, and that GLUT4 translocation after acute RE was more prolonged than after acute AE. These results suggest that acute RE‐induced increases in intramuscular IGF1 expression might be a distinct regulator of GLUT4 translocation.

This study investigated the effects of a high intensity interval training (HIIT) program on both physical fitness and executive functions in children. Fifty-six children aged 8–12 years participated in this study, and were divided into a HIIT group and a control group. The HIIT group performed three sessions of the 8- to 10-min HIIT program per week for 4 weeks. Before and after the intervention, 20-m shuttle runs, sit-ups, and standing long jumps were assessed as test of physical fitness. In addition, the executive function was assessed using the digit span forward (DSF) test, digit span backward (DSB) test, and Tower of Hanoi test. Only the HIIT group experienced significant improvement when completing the 20-m shuttle run (p = 0.042) and sit-ups (p < 0.001). Regarding executive function, the number of correct answers in DSB test significantly increased only in the HIIT group (p = 0.003). However, the standing long jump, DSF, and the Tower of Hanoi test performance did not change after intervention. The findings of the present study suggest that HIIT has positive effects on a core executive function such as working memory in addition to components of the physical fitness such as cardiorespiratory endurance and muscular endurance.