You need stable legs to make an effective and powerful swing. "All good golfers push against the ground with their legs to get their hips and upper bodies turning powerfully through the shot," says Golf Digest fitness advisor Ben Shear. To build a stronger platform, start by doing body-weight-only exercises (see below). As a bonus, these moves greatly improve ankle mobility, which can protect your knees.
Do eight to 12 repetitions of each exercise, and then switch so the opposite leg that is supporting the movement. Once you become proficient, you can add external weight or resistance. Good posture and form is essential. Go as slow as necessary to maintain your balance.
1) LATERAL SQUAT
From a standing position--feet spread wide, toes forward, arms extended--squat laterally so one leg straightens and the other bends. It should feel like the right side of your rear end drops behind the heel of your right foot. Then drive off that foot to get back into the start position.
2) PRISONER SPLIT SQUATS
From a split stance, with your hands behind your head, elbows back and torso upright, drop the knee of the trail leg straight down. Pause and return to the start position.