Meeting Abstract

98.2  Wednesday, Jan. 7  Effects of aging on locomotor dynamics and hindlimb muscle force production in the rat HORNER, AM*; RUSS, DW; BIKNEVICIUS, AR; Ohio Univ., Athens, OH; Ohio Univ. School of Physical Therapy, Athens, OH; Ohio Univ. College of Osteopathic Medicine, Athens, OH ah312505@ohio.edu

Attenuation of locomotor function is common in many species of animals as they age. Examples of age-related locomotor impairments include increased joint stiffness, decreased ability to repair muscle tissue, and decreasing fine motor control capabilities. These factors may contribute to gait abnormalities and substantially limit an animals maximum speed. Consequently, the effect of aging on locomotion has important implications for survivorship in numerous animal taxa. In this study we examined age-related changes in locomotion and muscle mechanics in young (~6 months) and old (~24 months) rats (Rattus norvegicus, Fischer Brown-Norway 344 crosses). Analyses of gaits and kinematics revealed that older rats moved significantly slower, had longer support durations at comparable Froude numbers, performed fewer symmetric gaits, and moved with greater spinal flexion at all phases within a stride. Additionally, aged rats did not tend to move exclusively with either pendular mechanics or spring-mass mechanics as was found in the young rats; rather, the external mechanical energy profiles of the older animals were extremely variable and mostly within the domain of intermediate mechanics. In situ analyses of the plantarflexor muscles (soleus, plantaris, medial and lateral gastrocnemius) demonstrated similar reduced maximum force generation in old vs. young muscles, despite comparable muscle masses and force-frequency characteristics. These force deficits were shown to be more extreme when normalized to body weight.