Contribution of Protein Intake and Concurrent Exercise to Skeletal Muscle Quality with Aging

• Published in: The Journal of frailty & aging Vol. 9; no. 1; pp. 51 - 56
• Main Authors: Dicks, N D, Kotarsky, C J, Trautman, K A, Barry, A M, Keith, J F, Mitchell, S, Byun, W, Stastny, S N, Hackney, K J
• Format: Journal Article
• Language: English
• Published: France Springer Nature B.V 01.01.2020
• Subjects: Accelerometers; Adult; Aerobic exercise; Age groups; Aged; Aging; Aging - physiology; Body fat; Cross-Sectional Studies; Diaries; Dietary Proteins - administration & dosage; Exercise; Exercise - physiology; Female; Fitness training programs; Food; Functional magnetic resonance imaging; Healthy food; Humans; Limbs; Lower limbs; Magnetic resonance imaging; Male; Metabolism; Middle age; Middle Aged; Muscle, Skeletal - physiology; Musculoskeletal system; Physical activity; Physical fitness; Proteins; Sedentary; Variance analysis; Young Adult; United States > US; North Dakota; functional CSA; aging; IMAT; Protein; physical activity
• ISSN: 2260-1341; 2273-4309
• DOI: 10.14283/jfa.2019.40

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. This study examined factors associated with lower-extremity skeletal muscle quality in healthy, younger, and middle-aged adults. Cross-sectional study. 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). 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. 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). 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.