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It has been clearly established that maximal force and power is lower in the morning compared to noon or afternoon hours. This morning neuromuscular deficit can be diminished by regularly training in the morning hours. However, there is limited and contradictory information upon hypertrophic adaptations to time-of-day-specific resistance training. Moreover, no cellular or molecular mechanisms related to muscle hypertrophy adaptation have been studied with this respect. Therefore, the present study examined effects of the time-of-day-specific resistance training on muscle hypertrophy, phosphorylation of selected proteins, hormonal concentrations and neuromuscular performance. Twenty five previously untrained males were randomly divided into a morning group (n = 11, age 23 ± 2 yrs), afternoon group (n = 7, 24 ± 4 yrs) and control group (n = 7, 24 ± 3 yrs). Both the morning and afternoon group underwent hypertrophy-type of resistance training with 22 training sessions over an 11-week period performed between 07:30-08:30 h and 16:00-17:00 h, respectively. Isometric MVC was tested before and immediately after an acute loading exclusively during their training times before and after the training period. Before acute loadings, resting blood samples were drawn and analysed for plasma testosterone and cortisol. At each testing occasion, muscle biopsies from m. vastus lateralis were obtained before and 60 min after the acute loading. Muscle specimens were analysed for muscle fibre cross-sectional areas (CSA) and for phosphorylated p70S6K, rpS6, p38MAPK, Erk1/2, and eEF2. In addition, the right quadriceps femoris was scanned with MRI before and after the training period. The control group underwent the same testing, except for MRI, between 11:00 h and 13:00 h but did not train. Voluntary muscle strength increased significantly in both the morning and afternoon training group by 16.9% and 15.2 %, respectively. Also muscle hypertrophy occurred by 8.8% and 11.9% (MRI, p < 0.001) and at muscle fibre CSA level by 21% and 18% (p < 0.01) in the morning and afternoon group, respectively. No significant changes were found in controls within these parameters. Both pre- and post-training acute loadings induced a significant (p < 0.001) reduction in muscle strength in all groups, not affected by time of day or training. The post-loading phosphorylation of p70S6Thr421/Ser424 increased independent of the time of day in the pre-training condition, whereas it was significantly increased in the morning group only after the training period (p < 0.05). Phosphorylation of rpS6 and p38MAPK increased acutely both before and after training in a time-of-day independent manner (p < 0.05 at all occasions). Phosphorylation of p70S6Thr389, eEF2 and Erk1/2 did not change at any time point. No statistically significant correlations were found between changes in muscle fibre CSA, MRI and cell signalling data. Resting testosterone was not statistically different among groups at any time point. Resting cortisol declined significantly from pre- to post-training in all three groups (p < 0.05). In conclusion, similar levels of muscle strength and hypertrophy could be achieved regardless of time of the day in previously untrained men. However, at the level of skeletal muscle signalling, the extent of adaptation in some parameters may be time of day dependent. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the changes in the resting level of serum cortisol, testosterone and T/C ratio in response to different training modalities and their variations. A secondary purpose was to identify if the various six weeks training programs are an effective way to improve physical fitness. 86 regularly active young males were assigned to one of six groups: Endurance constant running (ECR), Endurance interval running (EIR), Resistance training (RT), Explosive training (ET), Speed-endurance 50 m running (SER50) and Speed-endurance 150 m running (SER150) training. The resting levels of testosterone, cortisol and T/C ratio, as well as physical fitness, were measured. The ECR, EIR, and RT training program decreased COR level (P < 0.05). An increase of the T/C ratio was observed in the ECR and EIR group (P < 0.05). Except for SER50, each training program improved physical fitness. Our results suggest that endurance and resistance training modalities performed with a moderate to vigorous intensity may be a usable way to manage the resting cortisol level and enhance physical fitness in active young males., Competing Interests: The authors report no conflicts of interest in this work.