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JFSF Vol 7, No 3, September 2022, p.123-132

doi: 10.22540/JFSF-07-123


Original Article

Moderate to vigorous physical activity, leucine, and protein intake contributions to muscle health in middle age

Kara A. Stone1, Allison M. Barry2, Christopher J. Kotarsky3, Nathan D. Dicks4, Sherri N. Stastny5, Wonwoo Byun6, Steven Mitchell5,7, Ryan McGrath5, Kyle J. Hackney5

  1. Department of Kinesiology and Health Studies, University of Central Oklahoma, Edmond, OK, USA
  2. Health, Human Performance, and Recreation Department, Pittsburg State University, Pittsburg, KS, USA
  3. Department of Health and Human Physiological Sciences, Skidmore College, Saratoga Springs, NY, USA
  4. Nutrition, Dietetics, and Exercise Science Department, Concordia College, Moorhead, MN, USA
  5. Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND, USA
  6. Department of Health, Kinesiology, and Recreation, The University of Utah, Salt Lake City, UT, USA
  7. Department of Radiology, Sanford Health, Fargo, ND, USA

Keywords: Aging muscle, Leucine, Middle-age, Physical activity, Protein


Objective: Identify contributors to differences in the muscle size and strength of sedentary and active young and middle-aged adults. Methods: This cross-sectional study included 98 participants aged 20-65 years. Participants were categorized based on age and self-reported physical activity (PA) habits. Participants completed a strength assessment of knee extensors (KEPT), knee flexors (KFPT), plantar flexors (PFPT), and dorsiflexors (DFPT), a 3-day dietary intake log, 7-day accelerometry, and a magnetic resonance imaging (MRI) scan for muscle cross-sectional area analysis of the right quadriceps (CSAq). Results: There were significant age and activity-related group effects for relative protein intake (p<0.001), relative energy intake (p=0.04), KEPT (p=0.01), CSAq (p=0.002), PFPT (p=0.004) and DFPT (p=0.003). Moderate, moderate-to-vigorous, and vigorous PA were positively associated with CSAq (R2=0.69- 0.71; p<0.05), KEPT (R2=0.61-0.63; p<0.05), and PFPT (R2=0.31-0.36; p<0.05). Relative protein intake and daily leucine intake were significantly and positively associated with CSAq (R2=0.70 and 0.67 respectively; p<0.05), KEPT (R2=0.62 and 0.65 respectively; p<0.05), and PFPT (R2=0.29 and 0.28 respectively; p<0.05). Conclusion: Muscle size and strength were lower in middle age relative to younger age, but increased PA, protein intake, and leucine intake was associated with the preservation of muscle size and strength in larger muscle groups of the lower body.
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