Single limb squats (SLS) challenge the core, hips, and feet. This difficult exercise is commonly prescribed to our sports teams, as generating single limb strength may improve muscular imbalances and provide strength in many ground-based movements.
Unfortunately, every time I see a group doing SLS, they are often doing them hazardously, increasing their chance of injury. Not long ago, I was doing a workshop in Texas and had the group perform single limb squats. This athletic group had numerous biomechanical flaws, most notably poor foot position! Many will think foot position, who cares! However, what occurs at the foot will translate motion to the knee and hip. If you are not setting up your foot correctly and engaging the correct foot musculature, your amount of hip and knee stress increases.
The most common foot abnormality during a single limb squat is compensated forefoot varus. This sounds complicated, but simply means the front half of the foot wants to rotate the bottom of the feet towards the sky, but the leg corrects this position by flattening the foot on the ground. Unfortunately, when this compensation occurs, the Achilles tendon and medial aspect of the knee (meniscus, MCL, etc.) have increased stress and injury risk!
During a single limb squat, those with compensated forefoot varus has been shown to have higher hip internal rotation (Silva 2014). This suggests having a compromised position in the front half of the foot alters position at the hip and knee.

Best Foot Position During Single Limb Squat

Instead of having forefoot varus during a SLS, having the foot flat on the ground, with the ankle, knee, and hip in a straight line is key for reducing stress and increasing performance of the SLS.

4 Techniques for Improving Foot Position During Single Limb Squat

1. Hip Strength: The glutes help control hip internal rotation. This contribution makes them extremely important for controlling the hip and foot. Ensure you have proper glute strength for your single limb squats.

 
2. Postural Stability: Many people with forefoot varus have poor balance, particularly moving forward and backward. Ensure adequate balance and train this system for improved SLS.
3. Remove Muscles Inhibiting Strength: From my experience, improving the soft tissue at the hip also improves glute strength and foot control. Try out these techniques.

 
4. Improve Intrinsic Foot Strength: The muscles in the feet control foot motion (duh!). Try these techniques out!

Conclusion

Remember, movement at the foot and trunk influence each other. Having a stable core and foot create stable bases for movement in many on-land tasks. Improve your foot position today for an improved SLS!
Reference
  1. Scattone Silva R, Maciel CD, Serrão FV. The effects of forefoot varus on hip and knee kinematics during single-leg squat. Man Ther. 2014 Jul 12. pii: S1356-689X(14)00127-1. doi: 10.1016/j.math.2014.07.001. [Epub ahead of print]
Written by John Mullen, DPT, CSCS