You may lift, run, bike, take the occasional class, and otherwise work hard to keep fit. But that doesn't mean that all of your muscles are getting the attention they need. Your hips may be tight (which makes your glutes weak). Or your core could be soft (which means your back is likely tight). Fortunately, such problems are easy to diagnose by doing a simple overhead squat. This compound movement requires every major muscle group to work in concert and instantly pinpoints if an area is tight and needs to be stretched or is weak and needs to be strengthened, says Alain Aguilar, lecturer in exercise and sport science at the University of North Carolina at Chapel Hill. Test yourself using the guide below, then incorporate any needed fixes into your workouts. Correcting the imbalances you can't see will help you gain better results from training and prevent future injuries.