(6) NO DIFFERENCES IN NEUROMUSCULAR FUNCTION BETWEEN TRADITIONAL AND REST-REDISTRIBUTION SETS IN RESISTANCE TRAINED FEMALES

PURPOSE: The purpose of this study was to examine the time-course of changes in peak force and neuromuscular function of the quadriceps across rest-redistribution (RR) and traditional set (TS) during an isometric back squat exercise in females. METHODS: Fourteen healthy resistance-trained females with no recent history of lower extremity injury completed a total of two experimental visits where they performed the isometric back squat (SQ) on a force plate. Participants were randomized to perform either the RR (10 sets of 2 repetitions) or TS (4 sets of 5 repetitions) condition on visit one, and then completed the opposite condition on visit two. Visits were separated by ≥48 hours, but no more than seven days and completed at the same time of day (±1 h). Prior to both visits participants were asked to abstain from caffeine intake and exercise for 8 and 24 hours, respectively. For each repetition of the RR or TS protocol, participants pushed into a fixed barbell and were instructed to get to their max “as fast as possible,” hold it for approximately 5 s., and rest for approximately 5 s., between reps. Thirty-six seconds of rest (RR) or two minutes of rest (TS) between sets to equate the time and number of repetitions between protocols. EMG amplitude (AMP) and mean power frequency (MPF) of the vastus lateralis (VL) and rectus femoris (RF), as well as peak force (PF), were collected for all repetitions. Separate repetition (1^st/MID/LAST) × muscle (VL/RF) × condition (RR/TS) ANOVAs were run for EMG_AMP and EMG_MPF, while a repetition (1^st/MID/LAST) × condition (RR/TS) ANOVA was run for PF.

Results: There were no significant interaction effects for any dependent variables nor any main effects for PF (p >0.05 for all). For EMG_AMP, there was a significant main effect for muscle (p = 0.047), in which post-hoc analyses indicated that when collapsed across condition and repetition, VL_AMP (0.104 ± 0.046 mV) was significantly greater than RF_AMP (0.084 ± 0.040 mV; p =0.047). For EMG_MPF, there was a significant main effect for repetition, in which post-hoc analyses indicated that when collapsed across condition and muscle, EMG_MPF was significantly greater at rep 1 (82.1 ± 14.6 Hz) when compared to MID (74.9 ± 10.8 Hz, p=0.011) and LAST (73.9 ± 12.3 Hz, p=0.004). There was no significant difference between MID and LAST (p=0.999).

Conclusions: The primary finding of this investigation was a similar time-course of neuromuscular function across RR and TS isometric squat protocols in resistance-trained females. Surprisingly, there was no significant change in PF across time in either RR or TS. Participants displayed greater muscle excitation of the VL than the RF regardless of condition and repetition number, however, only EMG_MPF significantly decreased across exercise, while EMG_AMP did not change. PRACTICAL APPLCATIONS: Our results suggest that resistance-trained females were able to maintain consistent levels of force output and quadriceps muscle excitation across both the RR and TS protocols. Thus, our data suggest that practitioners can expect similar neuromuscular responses when implementing TS and RR isometric squat protocols with resistance-trained female clients based on the preference of their client. Future research can examine participant perceptions of TS and RR protocols by using session rating of perceived exertion, as different ways of allocating volume may provide more enjoyment and lead to greater exercise performance.

Acknowledgements: None