Acute and delayed responses of steroidal hormones, blood lactate and biomarkers of muscle damage after a resistance training session: time-of-day effects.

BACKGROUND

The present study aimed to investigate the effect of time-of-days (TOD) on some biochemical and hormonal responses after resistance training sessions.

METHODS

Ten trained subjects (22±2 years) performed, in randomized order, three resistance-training-sessions at 7 a.m., 1 p.m. and 5 p.m. Each training-session included six upper and lower body resistance exercises with 3×10 repetitions. Blood lactate (Lac), creatine kinase (CK), lactate dehydrogenase (LDH), cortisol (C) and testosterone (T) were collected at rest, 3 min and 48 h after each-session.

RESULTS

At rest, steroidal hormones were higher in the morning compared to the evening (P<0.01), whereas, no significant TOD effect on Lac, CK or LDH was observed. 3min after training, whatever the TOD, Lac, CK and T increased significantly (P<0.001). However, a significant decrease in C and a significant increase of T/C ratio were registered only after morning training. 3 min and even 48 h after training, the diurnal variations (i.e., morning to evening) of CK and C have been altered with higher early evening values of CK and lower one of C; whereas, T, Lac and LDH conserved their resting diurnal variation. Additionally, 48 h after the morning session, CK and T/C ratio remained elevated compared to the baseline levels.

CONCLUSIONS

In conclusion, resistance exercises soliciting both lower and upper limbs seems to alter the diurnal variation of CK and C, to enhance the morning anabolism/catabolism status and to produce more favorable environment for muscular adaptation up to 48 h post-training.