title: Changes in passive tension after stretch of unexercised and eccentrically exercised human plantarflexor muscles.
abstract: The study measured the effect of stretch on passive mechanical properties in unexercised and eccentrically exercised plantarflexor muscles, to obtain insight into how stretch might serve athletes as a warm-up strategy. Passive torque, voluntary contraction strength and muscle soreness were measured before and after a large amplitude stretch given before and after a period of eccentric exercise and at 0, 1, 2 and 24 h later. Stretch of the unexercised muscle led to a 20% fall in passive torque which recovered within an hour. About 40% of the fall could be recovered immediately with a voluntary contraction. After eccentric exercise there was a rise in passive torque by 20% at 2 h post-exercise. This rise was postulated to result from an injury contracture in muscle fibres damaged by the exercise. It was accompanied by a fall in maximum voluntary torque and the development of muscle soreness at 24 h. Stretch of the exercised muscle led to a fall in passive torque and rise in pain threshold. It is proposed that in response to a stretch there is a fall in passive tension in the muscle due to stable cross-bridges in sarcomeres which could be recovered with a voluntary contraction and an additional component attributable to the elastic filament, titin. The size of the fall was not significantly different between exercised and unexercised muscle. These observations provide a physiological basis for the effects of passive stretches on skeletal muscle and help to explain why they are used as a popular warm-up strategy.
authors.affiliation: Department of Physiology, Monash University, PO Box 13F, Melbourne, VIC 3800, Australia.
authors.forename: Simone
authors.initials: S
authors.lastname: Reisman
authors.forename: Trevor J
authors.initials: TJ
authors.lastname: Allen
authors.forename: Uwe
authors.initials: U
authors.lastname: Proske
mesh_terms: D000704:Analysis of Variance; D000842:Ankle; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D053580:Muscle Strength / Q000502:physiology; D052580:Muscle Stretching Exercises; D009129:Muscle Tonus; D018482:Muscle, Skeletal / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology; D019415:Torque; D055815:Young Adult