Barbell
With the bar in front, the torso stays more upright and the knees travel further forward, shifting more of the work onto the quadriceps than a back squat. The upper back and abdominals work hard to keep the bar in place.
| Muscle | Role | Action |
|---|---|---|
| Quadriceps | Primary | Extends the knee; the rectus femoris also flexes the hip |
| Gluteus maximus | Secondary | Extends and laterally rotates the hip |
| Hip adductors | Secondary | Adduct the hip; the adductor magnus also extends it |
| Erector spinae | Secondary | Extends and laterally flexes the spine |
| Rectus abdominis | Secondary | Flexes the trunk and braces the abdomen |
| Soleus | Secondary | Plantarflexes the ankle |
Primary muscles are the prime movers; secondary muscles assist or stabilise. The balance shifts with grip, stance, range of motion and technique.