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CONTRIBUTION OF PROTEIN INTAKE AND CONCURRENT EXERCISE TO SKELETAL MUSCLE QUALITY WITH AGING

N.D. Dicks, C.J. Kotarsky, K.A. Trautman, A.M. Barry, J.F. Keith, S. Mitchell, W. Byun, S.N. Stastny, K.J. Hackney

Background: The use of magnetic resonance imaging (MRI) derived functional cross-sectional area (FCSA) and intramuscular adipose tissue (IMAT) to define skeletal muscle quality is of fundamental importance in order to understand aging and inactivity-related loss of muscle mass. Objectives: This study examined factors associated with lower-extremity skeletal muscle quality in healthy, younger, and middle-aged adults. Design: Cross-sectional study. Setting and Participants: Ninety-eight participants (53% female) were classified as younger (20-35 years, n=50) or middle-aged (50-65 years, n=48) as well as sedentary (≤1 day per week) or active (≥3 days per week) on self-reported concurrent exercise (aerobic and resistance). Measurements: All participants wore an accelerometer for seven days, recorded a three-day food diary, and participated in magnetic resonance imaging (MRI) of the lower limbs. Muscle cross-sectional area (CSA) was determined by tracing the knee extensors (KE) and plantar flexors, while muscle quality was established through the determination of FCSA and IMAT via color thresholding. Results: One-way analysis of variance and stepwise regression models were performed to predict FCSA and IMAT. KE-IMAT (cm2) was significantly higher among sedentary (3.74 ± 1.93) vs. active (1.85 ± 0.56) and middle-aged (3.14 ± 2.05) vs. younger (2.74 ± 1.25) (p < 0.05). Protein intake (g•kg•day-1) was significantly higher in active (1.63 ± 0.55) vs. sedentary (1.19 ± 0.40) (p < 0.05). Sex, age, concurrent exercise training status, and protein intake were significant predictors of KE FCSA (R2 = 0.71, p < 0.01), while concurrent exercise training status and light physical activity predicted 33% of the variance in KE IMAT (p < 0.01). Conclusion: Concurrent exercise training, dietary protein intake, and light physical activity are significant determinants of skeletal muscle health and require further investigation to mitigate aging and inactivity-related loss of muscle quality.

CITATION:
N.D. Dicks ; C.J. Kotarsky ; K.A. Trautman ; A.M. Barry ; J.F. Keith ; S. Mitchell ; W. Byun ; S.N. Stastny ; K.J. Hackney (2019): Contribution of Protein Intake and Concurrent Exercise to Skeletal Muscle Quality with Aging. The Journal of Frailty and Aging (JFA). http://dx.doi.org/10.14283/jfa.2019.40

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