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Background/Objectives: The aim of the present study was to investigate the effect of two long-term reduced concurrent training frequencies (incorporating power training for the upper and high-intensity interval aerobic training for the lower extremities), in which participants performed one training session every either 7 or 14 days, after 12 weeks of systematic concurrent training on upper extremities' muscle strength, power, and morphology in young females. Methods: After a 12-week concurrent resistance and aerobic training period, participants were assigned into three groups and performed either one training session every 7 days (G7), or once every 14 days (G14), or detraining (GD) for 12 weeks, followed by 12 additional weeks of detraining. Results: Performance and muscle mass increased after the initial 12-week training period. After the reduced training frequency period, bench press 1-RM and aerobic power remained unchanged in G7 and decreased significantly in G14 (-5.9 ± 4.9%; -1.4 ± 4.5%). Muscle power and muscle thickness of the triceps branchii long head decreased significantly in G7 (-9.8 ± 7.7%; -0.9 ± 0.6%; respectively, p < 0.05) and G14 (-10.9 ± 7.6%; -2.8 ± 2.7%, respectively, p < 0.05), without significant differences between groups ( p > 0.05). Conclusions: In conclusion, 12 weeks of systematic concurrent resistance (upper extremities) and aerobic training (lower extremities) induced significant improvements in upper extremities muscle power/strength and muscle architecture characteristics. Both reduced training frequencies led to significant reductions in power performance. Thus, performing one training session every 2 weeks for 3 months may preserve 90 to 95% of the muscle power/strength, aerobic power and 72% of muscle mass adaptations achieved with systematic concurrent training. However, greater preservations in the above parameters could be observed if the training frequency is one training session per week.

Ultrasonography has been extensively used to evaluate skeletal muscle morphology. The echo intensity, i.e., the mean pixel intensity of a specific region of interest in an ultrasound image, may vary among muscles and individuals with several intramuscular parameters presumed to influence it. The purpose of this study was to investigate the correlation between muscle echo intensity and muscle fiber type composition in humans. Thirteen female physical education students (age: 22.3 ± 5.4 years, height: 1.63 ± 0.06 m, body mass: 59.9 ± 7.4 kg) with no history of systematic athletic training participated in the study. Body composition with dual X-ray absorptiometry, leg-press maximum strength (1-RM), echo intensity, and the cross-sectional area (CSA) of the vastus lateralis (VL) muscle according to ultrasonography were measured. Muscle biopsies were harvested from the VL site where the echo intensity was measured. VL echo intensity was not significantly correlated with the percentage of type I muscle fibers or with the percentage area of type I muscle fibers. However, when VL echo intensity was corrected for the subcutaneous fat thickness at the site of the measurement, it was significantly correlated with the percentage of type I muscle fibers (r = 0.801, p < 0.01) and the percentage area of type I muscle fibers (r = 0.852, p < 0.01). These results suggest that the echo intensity of the vastus lateralis muscle corrected for the subcutaneous fat thickness at the measurement site may provide an estimate of the muscle fiber type composition, at least in young moderately trained females.

Dietary protein with adequate essential amino acids effectively stimulates protein synthesis and improves muscle mass. Musculoskeletal disorders in lower or upper limbs are not uncommon among patients with type II diabetes mellitus (T2DM). Therefore, this study primarily examines the effects of chronic dietary protein manipulation on amino acids' profile and position sense in the elderly suffering from T2DM. A total of 26 individuals suffering from non-insulin-dependent T2DM (age > 55 years old) participated in a 12 week nutritional intervention. The subjects were randomly assigned and the control group received 0.8-1.0 g protein/kg/day, while the intervention group received 1.2-1.5 g protein/kg/day. Lean body mass, muscle strength, and position sense were assessed at baseline, as well as at the 6th and 12th week of the intervention. Only in the intervention group, the essential amino acids intake met the current nutritional recommendations ( p < 0.05), while, by the 12th week, only the intervention group showed significant improvement in the muscle strength of knee ( p < 0.05) and shoulder ( p < 0.05) extension. On the contrary, in the control group, a significant decline in appendicular lean mass ( p < 0.05) was observed by the 12th week. Position sense at the knee joint revealed a tendency for improvement in the intervention group by the 12th week (main effect of time p = 0.072). In the present investigation, it was revealed that the higher protein intake in the intervention group seemed to have positive effects on muscle strength and nearly positive effects on position sense.