Squats for Firm Glutes and Calves
Unfortunately, altering foot stance when squatting won’t allow you to recruit different quadriceps muscles. The vastus lateralis (the quad muscle on the outer aspect of your thigh) works in concert with the vastus medialis (the “teardrop” muscle residing on the medial portion of the thigh, just above the knee) to maintain muscular balance at the knee joint during dynamic movement. EMG studies have not shown any significant difference in individual quadriceps muscle activity from squatting with varying stances. Bottom line: regardless of whether you squat wide or narrow, quadriceps recruitment remains constant.
That said, changing your squat stance would have an effect on the recruitment of other lower-body muscles. Wide-stance squats have been shown to significantly increase the involvement of the gluteus maximus and the adductors (the inner thigh muscles), with the greatest muscle activity noted at 140 percent of shoulder width. Increasing foot width beyond 140 percent has no additional benefit on muscle recruitment and will limit your range of motion, so don’t go any wider than this. Conversely, narrow-stance squats will increase activity of the gastrocnemius (one of the calf muscles) while reducing glute and adductor involvement. The optimal stance for narrow squats is approximately shoulder-width – any narrower and you’ll compromise balance, reducing your ability to generate maximal force in your lifts.
It is important to understand that changes in muscular activity are the result of stance width, not foot position. Studies repeatedly have shown that altering foot position alone (achieved by rotating the tibia bone of the lower leg) from 30 degrees of inward rotation to 80 degrees of outward rotation does not change muscle recruitment in any of the lower-body muscles. And given that extreme internal and external rotation of the tibia can impede the normal tracking of the patella, you should avoid this practice. Instead, keep your toes pointed in a way that allows your knee to move directly over your toes as you descend in the squat.
If you are looking to target the quads, consider performing front squats. The placement of the bar in front of the body tends to increase quad activity while reducing involvement of the glutes. It also has shown to be less stressful on the knees. However, as with the back squat, there is no front squat variation that will allow you to target individual quadriceps muscles.