Air250 Seated Leg Curl The 250 Leg Curl offers easy entry and exit in a seated position machine. Many people find a seated leg curl less intimidating. The seated position also protects the lower back by preventing the hamstrings from pulling the pelvis and straining the lower back. The leg cushions and seat back are easily adjusted to comfortably fit almost any user. An adjustable cushion holds the thighs in a comfortable and stable position for maximum results. Thumb buttons, which control resistance, are conveniently located on the thigh support.