Your nerves and muscles are always working together to control your limbs' movements. Commonly referred to as neuromuscular control, this coordination includes your neural network's ability to protect your muscles from being injured by being stretched too far. This "stretch reflex," a topic of sports medicine, governs muscular protection. On the other hand, "hyperactive stretch reflex" is more often discussed in neurological medicine.
The Stretch Reflex
Sports training involves muscle stretching, and the stretch reflex results from muscle fibers being lengthened beyond their normal range, according to the Stretching Institute. Sensing this abnormality, muscle spindles send nerve impulses to the spinal cord, which in turn instructs the muscle to contract. This near-instantaneous messaging prevents muscle tearing, and happens without your even being aware of it. The brain is completely uninvolved, since the nerve signals shoot only to the spine and back. Thus, a normal stretch reflex is protective and beneficial.
When Nerves Do Unusual Things
Too much nerve activity can overwhelm the muscle's ability to correct itself. Hyperactive neural activity can therefore lead to muscle spasm and incorrect positioning. According to Dartmouth Medical School researchers Alexander G. Reeves, M.D. and Rand S. Swenson, M.D., Ph.D., when physicians test your reflexes by tapping your knee or scraping your foot's sole, they are seeking quantitative measurements, with "zero" meaning no reflex is present, and "4+" indicating hyperactive reflex. The hyperactive responses can include clonus, where the reflex test causes unusually lengthy and sustained muscle contractions, or disconnected contractions, where the test elicits a response from a muscle that was not originally targeted.
Spasticity
With neurological dysfunction such as spasticity, limb movements can be noticeably affected. Spasticity involves abnormal, involuntary movements that can be driven by hyperactive stretch reflexes and are sometimes rooted in hereditary or congenital disorders, multiple sclerosis, brain or spinal injury or cerebral palsy, according to neurosurgeon Vincent Thamburaj. Sometimes muscle contractions get "stuck" and result in muscle and limb rigidity. This hypertonis --- or excessive muscle tone --- can affect everything from balance to motor control to sleep patterns.
Neural Training
Hyperactive stretch reflexes are neuromuscular dysfunctions and typically require treatment by medical professionals. Neurologists and biomechanical specialists study the vast array of symptoms, diagnoses and treatments, so if you have any doubt, consult a trained physician for advice and care. However, for the athlete or fitness enthusiast who wishes to improve basic neuromuscular health and coordination, simple balance exercises, such as the single-leg squat described by Peak Performance Online can help.
