(20) EFFECTS OF VELOCITY BASED FEEDBACK ON NEUROMUSCULAR ACTIVITY DURING SUBMAXIMAL BACK SQUATS

Purpose: Research has shown that verbal encouragement and direction, including velocity-based cues, has improved performance for athletes across a myriad of sports (McNair et al., 1996; Blazevich et al., 2002; Weakley et al., 2020). The purpose of this investigation was to quantify neuromuscular activity across 70% and 80% loads while cueing participants to squat with the intent to increase velocity during the concentric phase.

Methods: 15 males aged 18–30 years with a mean training age of 7 years completed this study. Inclusion criteria included at least one-year of resistance training experience and currently engaging in resistance training three times per week with one lower body focused training day per week. Participants were appropriately prepped for electromyography (EMG) and 3-D motion capture (10-camera system and two force platforms). EMG were placed on the right leg quadriceps, hamstrings, and gluteal muscles. Full-body motion capture data were collected for each trial.  

Participants were given a ten-minute self-selected warm-up period prior to completing a 1 repetition maximum (1RM) back squat. Following the 1RM participants performed two sets of 3 reps at 70% and 80% of their measured 1RM. The first set was completed at a self-selected pace and the second set verbal and visual instructions were given to squat as fast as possible. A velocity-based training system was enabled throughout the session to provide real-time feedback during lifts.

The first two repetitions, from parallel to fully upright, analyzed in Visual 3D. Linear envelopes of EMG data were normalized to a maximum voluntary contraction and integrated. Peak sagittal plane hip and knee moments were calculated using lower limb kinematic and force data. Dependent T-Tests were run for 70% and 80% conditions to compare quadriceps, hamstrings, and gluteal muscle activation along with peak hip and knee sagittal plane moments between velocity conditions. Holm-Bonferroni method was used to control for type-I error.

Results: Quadriceps (p = 0.035 & p= 0.012) and gluteal (p=0.003 & p=0.002) activations were significantly increased during both the 70% and 80% 1RM. Hip moments were increased with velocity for both 70% and 80% 1RM (p=0.024 & p< 0.01, respectively). The averages of these data are presented in table 1.

Conclusions: Muscle activity of the primary hip and knee extensors along with peak hip moments were significantly increased with the presence of velocity-based intent to stand up from the squat faster, lending evidence to the notion that squatting faster involves increased dominance of hip musculature.

PRACTICAL APPLICATIONS: Strength coaches should strongly consider implementing velocity-based cueing with the intent to increase muscular effort at submaximal percentages during back squatting. Implementing this will enable athletes to engage more hip muscle activity and subsequent hip moments which in turn can improve hip extension to translate to sport.

Acknowledgements: None