I was told by a physical therapist that when performing leg extensions, the range of motion should only be the last 30 degrees of extension. Is this valid information?
Your question "Is this valid information?" is a great one. My answer will sound a bit strange (but hopefully thought provoking). Answer: I don’t know. What is the goal of the exercise? Why are they doing this exercise in the first place? To strengthen the quads? Strengthen for what: the machine or walking (life movements)? If it’s for life movements, then the entire exercise is WRONG (regardless of the range) seeing as the quads function as reactors to gravity and ground reaction forces, not by selectively contracting against an artificial machine. The leg extension exercise places a pad perpendicular across the tibia (usually both) while following a GUIDED path of motion. Just think through the position of your client on the machine (hip flexed) with a pad placed across both legs (sometimes one) while they knee extend against resistance – than ask, when do we ever do this in life? Is this necessary? If the quads get stronger on the machine, does this mean they know how to contract against the forces of life (gravity, ground reaction, mass and momentum)? My suggestion is, don’t do the exercise. Instead, teach your client how to decelerate the lower extremity against the natural forces of life, and they will thank you forever.