Because of this, there is a limited range of motion in which exercises can be performed — usually an extend - and - return movement (that is, forward and back) such as straightening the arms or legs to lift the weight and bending them again to release. (goldsgym.com)
When you bend and then straighten an arm at the elbow or a leg at the knee, your arm or leg moves through one plane of motion. (lasting-weight-loss.com)
Return to the starting position by straightening your arms, but not locking your elbows. (womenshealthandfitness.com.au)