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

  • Nathan D. DicksEmail author
  • C. J. Kotarsky
  • K. A. Trautman
  • A. M. Barry
  • J. F. Keith
  • S. Mitchell
  • W. Byun
  • S. N. Stastny
  • K. J. Hackney
Original Research



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.

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).


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.

Key words

Protein functional CSA IMAT physical activity aging 



The authors gratefully acknowledge the contributions of Rachel Iverson and Dan Streeter.

Source of Funding: We acknowledge research funding support from Sanford Health/NDSU Collaborative Research Seed Grant Program.

Conflicts of Interest: There are no conflicts of interest.

Ethics declaration: The host university’s Institutional Review Board for the protection of human participants approved all procedures.


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Copyright information

© Serdi and Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Nathan D. Dicks
    • 1
    • 2
    Email author
  • C. J. Kotarsky
    • 1
  • K. A. Trautman
    • 1
  • A. M. Barry
    • 1
    • 3
  • J. F. Keith
    • 1
    • 4
  • S. Mitchell
    • 1
    • 5
  • W. Byun
    • 1
    • 6
  • S. N. Stastny
    • 1
  • K. J. Hackney
    • 1
  1. 1.Department of Health, Nutrition, & Exercise SciencesNorth Dakota State UniversityFargoUSA
  2. 2.Concordia College, Department of Nutrition, Dietetics and Exercise ScienceMoorheadUSA
  3. 3.Department of Health, Human Performance, and RecreationPittsburg State UniversityPittsburgUSA
  4. 4.Department of Family and Consumer SciencesUniversity of WyomingLaramieUSA
  5. 5.Sanford HealthFargoUSA
  6. 6.Department of Health, Kinesiology, and RecreationUniversity of UtahSalt Lake CityUSA

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