This exercise complex develops strength and balance in the posterior chain (glutes, low-back, hamstrings). Development and strengthening of the posterior chain, particularly the hamstrings, is very important for preventing ACL injuries, a common injury among freeskiers.
Step one: Straigh leg press-up. Start laying on a mat, with a Swiss ball beneath your feet. Raise your hips by contracting your core so that your body is one straight line from your shoulders to your feet. Relax and lower your butt to the ground. Repeat.