Increases In Knee Extension Muscle Activation But Not Peak Torque Following High Intensity Training

Autoregulatory progressive resistance exercise (APRE) modulates training intensity in response to individual performance to optimize increases in muscular strength. Muscular activation patterns during maximal torque production can provide additional insight to increased strength following an APRE training intervention. PURPOSE: The purpose of this study was to examine the effects of a 4-week APRE training program on peak torque and muscle activation in the vastus lateralis (VL) during maximal voluntary isokinetic knee extension. METHODS: Eight resistance trained males (age: 21.5 ± 2.3 yrs; height: 176.5 ± 6.8 cm; weight: 70.3 ± 17.8 kg) participated in upper- and lower-body APRE 4-times per week for 4-weeks. Participants performed 2 isokinetic maximal knee extensions at 60°/s before (PRE) and after (POST) 4-weeks of APRE training. Muscular activation of the VL was recorded using surface electromyography (EMG) and the mean root mean square (RMS) values were analyzed during the concentric phase of the muscle action. Paired samples t-test were used to compare the PRE and POST measurements for torque and average EMG RMS value (mV). RESULTS: There was no significant difference in peak torque from PRE to POST (p = 0.91; 206.49 ± 65.68 N to 207.25 ± 58.59 N; mean ± SE). Although, there was a significant increase between pre (61.58 ± 22.28 mV; mean ± SE) and post (76.49 ± 27.50 mV; mean ± SE) EMG amplitudes (p = 0.02). CONCLUSIONS: The lack of significant changes in peak torque, combined with the increase of EMG amplitude, suggests that APRE may enhance neuromuscular activation efficiency without directly influencing knee extension torque. These findings support the notion that improvements in muscle activation do not always correlate with functional strength gains.