title: Acute effects of passive stretching of the plantarflexor muscles on neuromuscular function: the influence of age.
abstract: The acute effects of stretching on peak force (Fpeak), percent voluntary activation (%VA), electromyographic (EMG) amplitude, maximum range of motion (MROM), peak passive torque, the passive resistance to stretch, and the percentage of ROM at EMG onset (%EMGonset) were examined in 18 young and 19 old men. Participants performed a MROM assessment and a maximal voluntary contraction of the plantarflexors before and immediately after 20 min of passive stretching. Fpeak (-11 %), %VA (-6 %), and MG EMG amplitude (-9 %) decreased after stretching in the young, but not the old (P > 0.05). Changes in Fpeak were related to reductions in all muscle activation variables (r = 0.56-0.75), but unrelated to changes in the passive resistance to stretch (P ≥ 0.24). Both groups experienced increases in MROM and peak passive torque and decreases in the passive resistance to stretch. However, the old men experienced greater changes in MROM (P < 0.001) and passive resistance (P = 0.02-0.06). Changes in MROM were correlated to increases in peak passive torque (r = 0.717), and the old men also experienced a nonsignificant greater (P = 0.08) increase in peak passive torque. %EMGonset did not change from pre- to post-stretching for both groups (P = 0.213), but occurred earlier in the old (P = 0.06). The stretching-induced impairments in strength and activation in the young but not the old men may suggest that the neural impairments following stretching are gamma-loop-mediated. In addition, the augmented changes in MROM and passive torque and the lack of change in %EMGonset for the old men may be a result of age-related changes in muscle-tendon behavior.
authors: Neuromuscular Research Laboratory, Department of Exercise and Sport Science, University of North Carolina-Chapel Hill, 209 Fetzer Hall, CB #8700, Chapel Hill, NC, 27599-8700, USA, edryan@email.unc.edu.
authors: Eric D
authors: ED
authors: Ryan
authors: Trent J
authors: TJ
authors: Herda
authors: Pablo B
authors: PB
authors: Costa
authors: Ashley A
authors: AA
authors: Herda
authors: Joel T
authors: JT
authors: Cramer
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D052580:Muscle Stretching Exercises / Q000379:methods*; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult