The squat is a fundamental exercise that belongs in everyone’s program. This movement hits all the large muscles of the legs: quadriceps, hamstrings, calves and glutes.
The prevailing variation, with the bar across the shoulders, is depicted in this image.
Photo courtesy of Wikipedia
It’s a great exercise. However, I’ve moved away from programming this version for my clients. I outline my reasoning in my newest vlog. Incidentally, when I recorded this, I neglected to mention a safety aspect. Some people may not have the shoulder mobility to position the bar correctly.
Squatting with the bar across your shoulders places a load on your spine. Moreover, outside stress on the spine, spinal compression and spinal flexion can all contribute to back pain.
Conclusion: everyone benefits from including the squat in their strength program. But different variations will be appropriate for different people. My go-to is the goblet squat or some variation of the single leg squat. They pose less injury risk and get my clients the results they need.