Morphological, molecular and hormonal adaptations to early morning versus afternoon resistance training

Abstract

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-trai...

Effects of training, detraining, and retraining on strength, hypertrophy, and myonuclear number in human skeletal muscle

“…However, this was only partially successful. Whereas the increases in MT (~0.14% increase/day) and fiber CSA (~0.28% increase/ day) of the vastus lateralis muscle were similar to those observed in previous studies (5,18,43), the number of myonuclei remained unaffected by training. A possible explanation for this may be that the increase in fiber hypertrophy was too small (Ͻ20% in CSA and no significant increase in single fiber volume).…”

Clocking In, Working Out: Circadian Regulation of Exercise Physiology

“…A critical aspect of training adaptation (particularly for strength-based athletes) and the efficacy of exercise with age is the hypertrophic response within the muscle. While extensive research suggests that athletic performance peaks in the evening, it is unclear whether the muscle-intrinsic hypertrophic response is affected by the time of day at which resistance training occurs [102]. Hypertrophy is correlated with mTOR (mechanistic target of rapamycin) signaling [103], which exhibits circadian regulation in mouse liver [104].…”

Night time resistance exercise alters muscular IL-6-related protein signaling, but not muscle growth after 10 weeks of resistance training in male rats

“…The literature on this subject is limited and presents conflicting results. Earlier studies have shown that resistance training in the morning and afternoon periods produce similar gains in muscle strength, volume and cross-sectional area (CSA) after an 10-week (Sedliak et al 2009) or 11-week (Sedliak et al 2018) training period on untrained subjects. However, in another study, greater muscle CSA improvement was observed when RT was conducted in the morning compared to the evening (Küüsmaa et al 2016).…”