Effects of Acute Caffeine Administration on Pituitary–Testicular Hormonal Responses and Muscle Damage Biomarkers following Muscular Endurance in Well Resistance–Trained Males

The purpose of this study was to investigate the effects of acute caffeine administration on pituitary-testicular hormonal (prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and total testosterone (TT)) responses and muscle damage biomarkers (creatine kinase (CK), creatine kinase-MB, myoglobin, and troponin) following muscular endurance test. In addition, total repetitions to failure were determined. Eleven well resistance-trained males (29.11±3.21 years) performed two consecutive trials (7 days apart). Using a double-blind, placebo-controlled, randomized crossover design, participants administered either 5 mg/kg of caffeine or a placebo 1 hour prior to the test. The test consisted of 3 sets × repetitions to failure at 70% of 1-RM, with 90 s recovery interval, in each bench press, biceps curl, shoulder press, leg press, back squat, and leg extension. Repetitions were counted in each set in each exercise. Blood samples were collected 1 h after the end of each trial from each participant to measure the aforementioned study parameters. Results indicated that caffeine had positively effect on FSH (p=.046) and TT (p=.049) but had negatively effect on CK (p=.012) compared to the placebo. However, no significant (p˃0.05) differences were found in PRL, LH, CK-MB, myoglobin, and troponin between trials. Total repetitions to failure were significantly (p=.013) greater in caffeine trial (334.38±9.70) than in the placebo (309.07±9.43). In conclusion: 5 mg/kg of caffeine administered 1 h prior to muscular endurance test performed by multiple resistance exercises had beneficial effect on FSH and TT probably due to affecting androgen receptors. However, the values of biomarkers of muscle damage were similar in both trials. Hence, male strength athletes may consider using this dose pre-training as an effective ergogenic aid during muscle endurance training.