<P> Primary endings of muscle spindles "respond to the size of a muscle length change and its speed" and "contribute both to the sense of limb position and movement". Secondary endings of muscle spindles detect changes in muscle length, and thus supply information regarding only the sense of position . Essentially, muscle spindles are stretch receptors . It has been accepted that cutaneous receptors also contribute directly to proprioception by providing "accurate perceptual information about joint position and movement", and this knowledge is combined with information from the muscle spindles . </P> <P> A major component of proprioception is joint position sense, which is determined by measuring the accuracy of joint--angle replication . Clinical aspects of joint position sense are measured in joint position matching tests that measure a subject's ability to detect an externally imposed passive movement, or the ability to reposition a joint to a predetermined position . These involve an individual's ability to perceive the position of a joint without the aid of vision . Often it is assumed that the ability of one of these aspects will be related to another; however, experimental evidence suggests there is no strong relation between these two aspects . This suggests that while these components may well be related in a cognitive manner, they may in fact be physiologically separate . </P> <P> More recent work into the mechanism of ankle sprains suggests that the role of reflexes may be more limited due to their long latencies (even at the spinal cord level), as ankle sprain events occur in perhaps 100 ms or less . In accordance, a model has been proposed to include a' feedforward' component of proprioception, whereby the subject will also have central information about the body's position before attaining it . </P> <P> Kinesthesia is a key component in muscle memory and hand - eye coordination, and training can improve this sense (see blind contour drawing). The ability to swing a golf club or to catch a ball requires a finely tuned sense of the position of the joints . This sense needs to become automatic through training to enable a person to concentrate on other aspects of performance, such as maintaining motivation or seeing where other people are . </P>

Where is skeletal muscle located relative to the skin