Author(s): RATTALINO, L., VIEIRA, T.M., DELLO IACONO, A., Institution: POLYTECHNIC UNIVERSITY OF TURIN, Country: ITALY, Abstract-ID: 1068

INTRODUCTION:
The Autoregulation Rest Redistribution Training (ARRT) is a cluster-set resistance training method in which the resistance training structure is personalised according to an individual autoregulation target. Specifically, the number of clusters, repetitions per cluster and between-cluster rest intervals are dynamically adjusted to mitigate the within-session fatigue causing a decay of resistance training performance. While emerging evidence points to the superior performance effects of the ARRT method compared to traditional (TRA) resistance training methods, the underpinning neuromuscular fatigue mechanisms remain unexplored. Therefore, the aim of this study was to compare the effects of TRA and ARRT approaches on mechanical outputs and electromyographic responses during isokinetic contraction tasks.
METHODS:
Eighteen male subjects performed two experimental sessions in a randomized order. Both sessions consisted of 24 isokinetic single-leg extension repetitions, executed in concentric mode at a speed of 60 degrees ∙ s-1 and performed according to two training configurations; traditional (TRA): 3 sets of 8 repetitions with 120s interset rest, ARRT: a personalized combination of clusters, repetitions per cluster, and between-cluster rest regulated upon a 20% peak torque loss threshold from the first repetition. Work outputs were recorded repetition-by-repetition. Surface electromyograms (EMG) were recorded from the Vastus Medialis (VM), Rectus Femoris (RF) and Vastus Lateralis (VL) muscles, at both the proximal and distal portions. For each movement cycle, the mean frequency (MNF) of the EMG spectrum was computed according to the Choi-Williams time-frequency analysis. Then, changes in MNF across repetitions were considered to assess how prone the muscles were to fatigue: the myoelectric manifestation of muscle fatigue. The effects of TRA and ARRT on work outputs and EMG responses were investigated using linear mixed-effect and spline mixed-effects models, respectively.
RESULTS:
A significant interaction between protocol and repetition was found on work loss (0.41J × repetition, p<0.001) indicating that TRA induced greater work loss per repetition compared to ARRT. Overall, no significant effects of training protocol were found on changes in MNF (p=0.059). However, a main effect of muscle was found indicating greater MNF changes in the RF compared to both VM and VL (both p<0.001). Finally, similar MNF responses were observed between the proximal and distal portions of the muscles (p=0.956).
CONCLUSION:
The ARRT approach resulted in a similar myoelectric manifestation of fatigue as the TRA, indicating a comparable peripheral metabolic stress induced by TRA and ARRT. It is therefore possible the distinct mechanical outputs between the two training methods may have stemmed from neural and motivational factors.