Exercise Machines to Avoid: Seated Leg Press

To understand why the leg press is not an ideal exercise to include in your workout routine, we must acknowledge ankle and hip mobility issues seen with the back squat and compare them to the leg press’s movement pattern.

Ankle Mobility

Ankle mobility is required to facilitate balance and control in both the ascent and descent of the squat. When flexibility at the ankle joint is limited, lifters have a tendency to allow their heels rise off the floor or collapse their ankles inward as they lower, which can result in an increased risk of injury because of compensatory movements up the kinetic chain at the knees, hips, and lumbar spine (i.e. valgus knee). If the lifter's heels rise off the floor or collapse during the lowering phase, efforts should be made to improve mobility around the talocrural and subtalar joints because they facilitate ankle dorsiflexion and aid with postural stability when squatting (Schoenfield, 2015). Hemmerich and others found that a dorsiflexion angle of 38.5° ± 5.9° was necessary to keep the heels down during a full squat. Unlike the squat however, the leg press machine does not allow the lifter to increase stability at the talocrual and subtalar joints because of the elevated position of the feet, whereas a traditional back squat places both feet on the ground.

Hip Mobility

During a squat, the mean hip range of motion (ROM) has been reported to be 95.4° ± 26.6° of flexion to reach a maximal squat (Hemmerich et al., 2006). When lifters lack adequate mobility at the hip they are likely to incorporate trunk flexion to achieve their desired squat depth, especially during deep squats or leg press movements; a compensatory movement pattern stemming from a possible lack of hip mobility. A study that measured the relationship between lower-extremity ROM and squat depth did not recommend trunk flexion under squat loading because of the increased stress placed on the lumbar spine when under load (Si-Hyun et al.,2015). As demonstrated by the photo above, the seated leg press places the pelvis in a fixed posterior tilt, which is similar to excessive lumbar flexion at the bottom of a bad squat pattern. More importantly, the seated position of the leg press does not allow the lifter to create a hinge motion at the hip joint, which is a necessary motion of shifting the hips backwards to initiate the lowering phase. A hip-hinge is used for eccentrically loading the gluteus maximus and allowing the hamstring complex to isometrically contract; this technique helps relieve some of the shear forces placed upon the Anterior Cruciate Ligament (Comana, 2014).

The seated leg press is a commonly prescribed exercise because of the multi-joint movement that incorporates large muscle groups. However, the movement pattern does not replicate many movements used in sports or daily living. Any individual that uses the leg press machine can potentially increase their chance of lower back and knee injuries if they are not fully aware of their body’s position when performing this exercise.

References

1. Comana, Fabio. "Diving Deeper into the Squat: Common Misconceptions." National Academy of Sports Medicine. 23 Oct. 2014.

2. Hemmerich A, Brown H, Smith S, Marthandam SS, Wyss UP. “Hip, Knee, and Ankle Kinematics of High Range of Motion Activities of Daily Living.” Journal of Orthopaedic Research. (2006): 24:770–781.

3. Kim, Si-Hyun et al. “Lower Extremity Strength and the Range of Motion in Relation to Squat Depth.” Journal of Human Kinetics 45 (2015): 59–69. PMC.

4. Schoenfeld BJ. “Squatting Kinematics and Kinetics and Their Application to Exercise Performance.” Journal of Strength and Conditioning Research (2010): 24:3497–3506.