Full range-of motion squats should be a principal exercise in any resistance training program because they produce superior results for the following reasons:
• You will maximally train all the muscles in the lower body with full-range squats. Research shows that deep squats will train the quads better than partial-range squats. Squatting low and using a heavy load is necessary to maximally train the posterior chain.
• You can increase speed and jump height more by using the full-range of motion squat as a fundamental training lift instead of a partial-range, heavier squat
• Occasionally including partial-range training in addition to full-range squats can help you overcome a plateau, but they should not be used at the exclusion of deep squats.
• You will perform more work doing full-range squats, and if you program your squats properly (more sets, fewer reps per set), squats can anchor a body composition/fat loss training program.
• Full-range squats require and support flexibility. Exclusive partial-range training can produce structural imbalances and reduce flexibility.
A recent study in the Journal of Strength and Conditioning Research provides further insight into the effect of range of motion (ROM) on performance in the squat. The study compared power, force, velocity, and work output during full- and partial-ROM squats with either 5 or 10 reps per set. The 5-set trials used a load of 83 percent of the 1RM, whereas the 10-set trials used a load of 67 percent of the 1RM. Partial-ROM was performed to 120⁰ of knee flexion and the full-ROM squat was performed to a depth in which the hip was parallel to the knee (not a deep squat in which the hamstring covers the calf, but interesting nonetheless).
Results showed that power and force were greatest when squatting in the partial-ROM with the heaviest load. This provides a classic example of how partials can be used for athletes who need to produce maximum force and power output. Peak velocity during the squat was highest in the full-ROM squats with the 67 percent load (10 reps). Researchers suggest athletes in high-speed sports that require running and jumping should use full-ROM squats.
In sports where force and power are the key determining factor, such as rugby or certain positions in football, partial-ROM squats could make up a larger component of training. Still, full-ROM squats ensure structural balance to prevent injury, and could train high force athletes for a quick first step in short sprints.
Take note that partial-ROM training with the lighter 67 percent load (10 reps) should be avoided because it produced the lowest values for all measurements. In addition, work output was greatest in the full-ROM conditions and the full-ROM heavy load (5 reps) trial resulted in 17 percent more work than the full-ROM light load (10 reps) trial. Researchers suggest using full-ROM heavy squats with appropriate reps for more sets if the goal is fat loss or hypertrophy. They call our attention to this approach since it goes against the typical bodybuilding method of using 8 to 12 reps per set.
Although this study focuses on “full-ROM” squats to parallel, healthy trainees should use full-ROM squats to a depth where the hamstring covers the knee. It is a misperception that deep squats are bad for the knee because they put too much shearing force on the knee. Research suggests that the greatest shear force on the knee is at the start of the squat when the lifter initiates the bend of the knee. In addition, an analysis performed on cadavers found that the pressure on the knee decreases as the knee flexion angle increases from parallel to a point where the hip is below the knee.
Then there’s the fact that just because there is shear force on the knee does not mean that the knee cannot handle that force. One of the best ways to supports the knee is to train the musculature that acts on the knee joint. Read more about squats in Six Reasons Everyone Should Do Squats.
Drinkwater, E., Moore, N., et al. Effects of Changing from Full Range of Motion to Partial Range of Motion on Squat Kinetics. Journal of Strength and Conditioning Research. 2012. 26(4), 890-896.