The Effect of Three Different Maximal Concentric Velocity Squat Protocols on MAPK Phosphorylation and Endocrine Responses.

The purpose of this study was to determine the effect of three different back squat protocols on intra-cellular signaling, endocrine responses, and power fatigue. Nine recreationally trained males (X±SD; age: 21.4±0.6yrs; height: 177.8±5.1cm; weight: 78.7±9.7kg), completed three maximal concentric velocity squat protocols in a randomized order. Testing protocols consisted of 5 sets of 10 repetitions at 30% of 1RM; 5 sets of 5 repetitions at 70% of 1RM; and 5 sets of 3 repetitions at 90% of 1RM. Average system power for each set was obtained with a tethered external dynamometer. Pre- and post-exercise blood draws were analyzed for lactate, testosterone, hGH, and cortisol. Muscle biopsies assessed pre- and post-exercise extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 phosphorylation via western blotting. Cortisol, hGH, and lactate increased post-exercise (p<0.05), but did not differ between protocols (p>0.05). Testosterone was unaltered (p>0.05). Average power was lower for the 90% protocol than for the 30% protocol across all sets (p<0.01). Average power was lower after the fourth and fifth set compared to the first and second set in the 90% protocol only (p<0.05). The ratio of phosphorylated-to-total ERK1/2 was higher post-exercise after 90% protocol only (p<0.05). The ratio of phosphorylated-to-total p38 was unaltered post-exercise (p>0.05). Resistance load appears to affect power fatigue across the five sets of resistance exercise. This study found modest changes in ERK1/2 and no changes in p38 phosphorylation following maximal concentric velocity squats. Exercise volume, modality, and training status of subjects may account for these findings.