A muscle development system comprising a clip (10) for attaching a resilient band to a fixed point; and a sleeve (16) for fitting round a body cylinder, for example arm or leg or torso. The sleeve (16) has at least one attachment device for allowing attachment of the resilient band (14) to the sleeve. The clip (10) has a body part (22) shaped to allow the resilient band (14) to be spirally or helically wound round it.