Effects of a single habituation session on neuromuscular isokinetic profile at different movement velocities

Abstract

Single training session (STS) may increase the power output (i.e., maximal torque) in different contraction types; however, little is known about the neuromuscular adaptations to reach this enhancement. In this way, the present study examined the differences between knee extensors EMG, kinematics, and dynamometry at 60 and 180A degrees A s(-1) before (PRE) and after (POST) a STS. Seventeen healthy males completed three different tasks: (1) 5-maximal isokinetic knee extensions, without previous habituation (PRE) at 60 and 180A degrees A s(-1); (2) in the same day and after a proper rest, two bouts of 5-maximal isokinetic contractions (STS) at 60 and 180A degrees A s(-1); and (3) in a new visit, POST consisted in new 5-maximal isokinetic contractions at 60 and 180A degrees A s(-1). The main parameters examined were: knee extensors peak torque (PT), total work (TW), EMG (prior to the movement onset, agonist and antagonist activation), rate of force (RFD), and velocity development (RVD). There was significant increase in PT [12% (60A degrees A s(-1)) and 8.7% (180A degrees A s(-1))] and TW [13.5% (60A degrees A s(-1)) and 10.7% (180A degrees A s(-1))] from PRE to POST sessions. Increases in RFD were found for both velocities (p < 0.05); however, RVD and vastus lateralis EMG prior to the movement onset were significantly higher for POST only at 60A degrees A s(-1). The RFD percentage of change (%change) was significantly correlated to %change for PT at 60A degrees A s(-1) (r (2) = 0.53) and 180A degrees A s(-1) (r (2) = 0.45). In conclusion, STS improves neural strategies to contract muscles stronger and faster at the slowest velocity, while higher velocities present different adaptations and might need more practice to further adaptations.