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00005768-200905001-0305800005768_2009_41_483_russ_ambulation_5miscellaneous< 16_0_1_0 >Medicine & Science in Sports & Exercise©2009The American College of Sports MedicineVolume 41(5) Supplement 1May 2009p 483Hindlimb Muscle Quality And Ambulation In Old Rats: 2859: Board #6 May 30 9:30 AM - 11:00 AM[G-12 Free Communication/Poster - Age, Sex and Race Influences on Muscle and Bone: MAY 30, 2009 7:30 AM - 11:00 AM ROOM: Hall 4F]Russ, David W.1; Horner, Angela1; Biknevicius, Audrone2; Ward, Christopher W.31Ohio University, Athens, OH. 2Ohio University College of Osteopathic Medicine, Athens, OH. 3University of Maryland School of Nursing, Baltimore, MD.(Sponsor: Randall Keyser, FACSM)Email: russd@ohio.edu(No relationships reported)PURPOSE: To assess age-related declines in muscle contractile function and locomotion in an animal model.METHODS: In situ force frequency data and in vitro sarcoplasmic reticulum (SR) Ca2+release and reuptake rates were collected from the plantarflexor muscles of 5 young (6-8 months) and 5 old (24-26 months) F344/BN rats. Videographic and ground reaction force measurements were used to assess gait biomechanics in a subset of these animals (n = 3/group).RESULTS: The plantarflexors of old rats produced significantly less force (∼20%) than those of the young rats (P=0.046), but age-related atrophy was minimal. Only the medial gastrocnemius showed a trend (P=0.10) for age-related loss of mass. When muscle force was expressed relative to muscle mass (muscle quality) the effect of age disappeared, but a significant age X frequency interaction (P=0.036) persisted, such that the muscle quality was reduced in old muscles only in response to higher frequencies (> 50 Hz). When contractile forces were expressed relative to body mass however, marked reductions (>50%) were observed for all frequencies (all P < 0.01). SR release was impaired in old vs. young muscles (∼20%, P = 0.036), but SR reuptake was surprisingly enhanced (∼25%, P = 0.42). Locomotor analyses revealed that old rats moved significantly more slowly than young rats (0.41 +/- 0.12 vs. 0.80+/-0.18 m/s). Qualitatively, old rats exhibited greater gait asymmetry and spinal flexion than young rats during all stride phases. Additionally, while the gaits of young rats tended to exhibit either spring-like or pendular center-of-mass mechanics, those of old rats were extremely variable, falling within the domain of "intermediate mechanics."CONCLUSIONS: Older animals exhibit a frequency-specific reduction in muscle quality, even in instances where muscle atrophy is minimal. This impairment may be releated to SR calcium release, but not reuptake. These losses in muscular performance are magnified when expressed relative to body mass, and may contribute to marked locomotor dysfunction with aging.Hindlimb Muscle Quality And Ambulation In Old Rats: 2859: Board #6 May 30 9:30 AM - 11:00 AMRuss, David W.; Horner, Angela; Biknevicius, Audrone; Ward, Christopher W.G-12 Free Communication/Poster - Age, Sex and Race Influences on Muscle and Bone: MAY 30, 2009 7:30 AM - 11:00 AM ROOM: Hall 4F541