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Changes in real-time muscle performance due to stretch-shortening cycle range of motion.

Authors
Cutlip-RG; Geronilla-KB; Baker-BA; Kashon-M
Source
Med Sci Sports Exerc 2003 May; 35(5)(Suppl 1):S387
NIOSHTIC No.
20044070
Abstract
PURPOSE: To investigate the effect of range of motion (ROM) on stretch-shortening (S-S) cycle-induced muscle injury in real-time using force and work parameters. METHODS: Testing was performed on dorsiflexor muscles of Sprague-Dawley rats in vivo. Animals were randomly assigned to a long ROM group (L-Inj) or short ROM group (S-Inj). The S-Inj group received 7 sets of 10 S-S cycles at 500/s between 70-120 ankle angle, whereas the L-Inj group received the same protocol between 90-140. Dorsiflexor muscles were electrically stimulated for 2.8 s each set and sets were administered every minute. Force and angular position were recorded continuously for each set. The force data collected during the S-S cycles were used to calculate peak, minimum, mean, and cyclic forces for each S-S cycle. Peak force was the maximum force during S-S cycles. Minimum force was the isometric force prior to each S-S cycle. Mean force was the average eccentric force during each S-S cycle. Cyclic force was the magnitude of eccentric force enhancement. The force and angular position data were used to calculate negative, positive, and net work for each S-S cycle. Negative work was the work absorbed in the eccentric phase of each S-S cycle. Positive work was the work performed in the concentric phase of each S-S cycle. Net work is the difference between negative and positive work. RESULTS: The different ROMs led to different force profiles for the two injury groups. ROM did not significantly affect peak force and mean force from Set 1 to Set 7 of the S-S cycles (p = 0.813 and 0.265, respectively). However, ROM did affect cyclic force and min force (p <0.0001 for both parameters). Real-time changes in negative work, positive work, and net work did not differ with ROM (p = 0.878, 0.879, and 0.652 respectively) but did change significantly from Set 1 to Set 7 (p = 0.001, 0.04, and 0.001, respectively). CONCLUSIONS: Longer ROM during S-S cycles resulted in a larger deficit in real-time muscle performance measures (cyclic force and minimum force). Real-time muscle performance measures also were sensitive to S-S cycle induced muscle injury.
Keywords
Injuries; Musculoskeletal-system; Musculoskeletal-system-disorders; Animals; Laboratory-animals; Muscle-tension; Muscle-stress; Mechanical-properties; Muscles; Muscle-tissue; Muscle-function; Injuries; Muscle-contraction; Force; Work-capability
CODEN
MSPEDA
Publication Date
20030501
Document Type
Abstract
Fiscal Year
2003
NTIS Accession No.
NTIS Price
Issue of Publication
5
ISSN
0195-9131
NIOSH Division
HELD
Source Name
Medicine and Science in Sports and Exercise
State
WV
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