Researchers from the Sport Performance Research Institute in New Zealand wanted to find out which variation of the barbell squat—deep, parallel, or front—produced the greatest activation of the glutes, quads, and hamstrings.
Thirteen experienced resistance-trained female subjects performed a single set of 10 reps using their 10-rep max for each squat variation. Electromyography (EMG) electrodes were placed on the quads, hamstrings, and glutes. Maximum voluntary isometric contraction (MVIC) testing was performed and recorded for each muscle group. Foot placement was the same for all variations.
No differences in muscle activation were found for any of the squat variations. The authors speculate that because the 10RM load was adjusted to accommodate differences in strength, their results are different from some reports of greater EMG activity during deep squats. Hamstrings were not activated to any large extent during any variation.
Long-term studies favor deep squatting for the greatest muscle hypertrophy. Nevertheless, this data points out that front squats and parallel squats are effective alternatives to deep squatting when necessary.
Leave your ego at the door and find a weight that allows you to go as deep as possible while maintaining proper form. Over time, this will be the best for leg mass. Because squats do not effectively activate the hamstrings, be sure to include leg curls and stiff-leg deadlifts in your routine.