Andrew C. Fry¹, Justin X. Nicoll², Dimitrije Cabarkapa^1,, Paige N. Stephens¹

This study examined acute hormonal responses to multi-joint free weight exercise and single joint machine exercise. Six weight-trained males performed 3 sets of 10 repetitions at 70% of 1RM with one minute rest between each set on either the barbell squat (FW) or three single joint machine weight exercises (MW; i.e., leg curl, leg extension, back extension) using similar primary movers in a randomly-ordered crossover design. Testosterone (T), cortisol (C), growth hormone (GH), and lactate (HLa) were determined from blood samples 15 minutes before (PRE) and 5 minutes after (POST) each exercise session performed at the same time of day. The MW group completed significantly more estimated external work than the FW group (J; MW = 30776±2152, FW = 19728±2399), but the FW protocol resulted in a greater HLa response (mmol^.L^-1; MW, PRE = 1.2±0.1, POST = 6.7±0.7; FW, PRE = 1.5±0.1, POST = 10.5±1.6). Both exercise modalities exhibited similar increases in T (nmol^.L^-1; MW, PRE = 13.4±2.7, POST = 17.6±2.9; FW, PRE = 15.5±2.8, POST = 17.6±3.5) and GH (g^.L^-1; MW, PRE = 1.4±0.3, POST = 6.8±3.3; FW, PRE = 1.1±0.1, POST = 4.3±2.0), despite the lower work performed by the FW protocol. Although C increased for both protocols, the FW session induced a greater C response (nmol^.L^-1; MW, PRE = 463.2±147.8, POST = 448.1±144.1; FW, PRE = 444.4±174.0, POST = 696.9±220.4). While using similar muscle mass, these results suggest that the acute hormonal response is partially dependent on exercise modality. Despite completing less estimated external work, FW exercise protocol yielded similar or greater endocrine responses when compared to MW resistance training modality.

endocrine, training, testosterone, growth hormone, lactate, cortisol