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Myotonia (grip and percussion)

Grip myotonia is produced by an isotonic contraction of the fingers and results in a delayed relaxation time. This symptom may be minimized through repeated muscle contractions. This improvement is known as the "warm-up phenomenon." Direct percussion of the thenar eminence and forearm extensor muscle may also produce an extended contraction of these muscle groups. (Contributed by Dr. Richard Moxley III.)