M.S. Hunt, K.R. Delaney, G.E. Garza, L.E. Bourgeois, R.S. McCulloch

Gonzaga University, Spokane, WA

Weighted squats are a common training and rehabilitation exercise. Stability during the exercise is critical to prevent injury and two major muscles groups working throughout the dynamic movement of the squat include the hip abductors and quadriceps. Weakness in these muscles reduces stability of the entire lower extremity kinetic chain and may result in excess knee loading. PURPOSE: This study aimed to increase glute activation during a squat, therefore increasing knee stability to aid injury prevention relating to weightlifting. METHODS: Thirty (18-23 yr) students that participated in weightlifting activities at least three days a week were recruited. Surface electromyography (EMG) of the gluteus maximus, gluteus medius, and vastus lateralis (normalized to Maximum Voluntary Isometric Contractions (MVIC)) and 2-dimensional motion capture data were collected. A six-minute jogging warm- up was followed by five barbell squats (with 15% of their body weight). After a five-minute rest, ten repetitions of four glute-activation exercises were performed on each leg, followed by five more barbell squats. Mean muscle activity (as % MVIC) of the middle three squats were compared between trials and changes in changes in the peak medial, peak lateral, range, and standard deviation were compared between trials. Paired t-tests were used with a=.05. RESULTS: There was a decrease in gluteus maximus activation (trial 1: 26.18 ± 14.12 %, trial 2: 23.59 ± 12.14 %). There was a significant decreases in gluteus medius recruitment (trial 1: 30.69 ± 15.88 %, trial 2: 29.59 ± 16.17 %, p=0.05) and vastus lateralis muscle activation ( trial 1: 128.41 ± 81.75 %, trial 2: %, p=0.036) following the glute targeting warmup. No significant differences were seen in knee kinematics for medial or lateral movement, or standard deviation of knee movement. CONCLUSION: Our kinematic results show that the squat form was unchanged, while muscle recruitment decreased following a glute targeting warmup. This suggests that the warmup caused the measured muscles to output similar forces with decreased activation, or possibly shifted activation to other muscles. The findings imply that glute targeting activities are a beneficial squat warmup for knee stability, force production and performance improvements.

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