Author(s): AUDET, A., MELVIN, A., BROWN, M., HILL, L., LEPLEY, A., KOZLOFF, K., Institution: UNIVERSITY OF MICHIGAN, Country: UNITED STATES, Abstract-ID: 921

INTRODUCTION:
Long distance running is a popular recreational activity, and participation in marathon and half marathon races has increased over the past several decades. Running-related injuries (RRI) are common and have a multifactorial etiology based on location and type of injury. Asymmetries in lower extremity lean mass may contribute to unbalanced muscle strength and functional loading between limbs. The impact of asymmetries in lower extremity lean mass (LELM) on RRI incidence remains unclear, particularly in recreational endurance runners. The purpose of this study was to prospectively evaluate the impact of LELM asymmetry on incidence of RRIs in a cohort of runners training for a half or full marathon.
METHODS:
153 (77M/76F; Age: 35.8+/-11.7yrs) recreational runners performed a maximal graded treadmill exercise test 10-12 weeks before their event (baseline), and a second test 3-4 weeks pre-race (83.8+/-29.7 days apart). Total body Dual Energy X-ray Absorptiometry scans were performed at each visit to evaluate total LELM and LELM asymmetry. Participants were instructed to maintain their typical training habits over the course of the study and were classified as injured or healthy based on self-reported injury status between visits. Injuries were defined as any running-related musculoskeletal impairment causing a self-reported disruption in training. Independent t-tests were used to evaluate differences in LELM asymmetry and VO2max between healthy and injured groups.
RESULTS:
Baseline VO2max (M=51.6+/-7.6ml/kg/min, F=46.2+/-6.7ml/min/kg; p<.001), and total LELM (M=76.7+/-4.7%, F=67.0+/-5.9%; p<.001) were significantly different between genders, but LELM asymmetry did not differ by gender (p>.05). 18 participants (11.7%) sustained an injury between visits. No significant differences in LELM asymmetry were present between healthy and injured participants or when divided by gender (p>.05). Injuries were subdivided by type (muscle, tendon, bone, ligament, or unknown; n=6 ,4, 3, 2, 3 respectively), and by location (hip/pelvis, knee/thigh, shank, foot/ankle; n=4, 8, 2, 4 respectively). Despite some difference in LELM asymmetry across injury types (ligament injury asymmetry of 4.86+/-0.57% vs. muscle asymmetry of 2.86+/-1.49%) and site (shank injury asymmetry of 4.39+/-0.28% vs. healthy participants 3.36+/-2.35%), low injury incidence precluded a meaningful assessment of those numbers.
CONCLUSION:
LELM asymmetry was not associated with RRI in our sample of recreational endurance runners training for a half or full marathon. The magnitude of asymmetry related to incidence of RRI may be greater than what was observed in the present sample. Alternatively, asymmetries in muscle functional capacity, independent of lean mass, may play a larger role on incidence of RRI in recreational runners.
This study received funding from Apple Inc. The funding source had no role in the analysis and
interpretation of the data or in the submission of this abstract.