The Influence of Age and Obesity-Altered Muscle Tissue Composition on Muscular Dimensional Changes: Impact on Strength and Function

• Published in: The journals of gerontology. Series A, Biological sciences and medical sciences Vol. 75; no. 12; p. 2286
• Main Authors: Giuliani, Hayden K, Shea, Nic W, Gerstner, Gena R, Mota, Jacob A, Blackburn, J Troy, Ryan, Eric D
• Format: Journal Article
• Language: English
• Published: United States 01.12.2020
• Subjects: Absorptiometry, Photon; Adult; Aged; Body Composition; Humans; Image Interpretation, Computer-Assisted; Isometric Contraction; Male; Middle Aged; Muscle Strength - physiology; Obesity - physiopathology; Quadriceps Muscle - diagnostic imaging; Quadriceps Muscle - physiopathology; Signal Processing, Computer-Assisted; Torque; Ultrasonography - methods; Walking Speed; Dynapenia; Echo intensity; Sarcopenia; Walking speed; Ultrasonography
• ISSN: 1758-535X
• DOI: 10.1093/gerona/glaa206

The purpose of this study was to determine if muscular dimensional changes with increases in torque production are influenced by age- and obesity-related increases in intramuscular fat, and its relationship to percent body fat (%BF), echo intensity (EI), strength, and maximum walking speed. Sixty-six healthy men were categorized into 3 groups based on age and body mass index status (young normal weight [YNW], older normal weight [ONW], and older obese [OB]). Participants underwent %BF assessments, resting ultrasonography to determine muscle size (cross-sectional area [CSA]) and EI of the superficial quadriceps, and a 10-m maximum walking speed assessment. Maximal and submaximal (rest-100% MVC in 10% increments) isometric leg extension strength was assessed while changes in rectus femoris (RF) CSA, width, and depth were obtained with ultrasonography. Echo intensity and %BF were different among all groups (p ≤ .007), with the YNW and OB groups exhibiting the lowest and highest %BF and EI values, respectively. The RF increased in depth and decreased in width with increases in torque intensity for all groups. The ONW group demonstrated no change (-0.08%) in RF CSA across torque intensities, whereas the YNW group (-11.5%) showed the greatest decrease in CSA, and the OB group showed a more subtle decrease (-4.6%). Among older men, a greater change in RF CSA was related to poorer EI (r = -0.355) and higher %BF (r = -0.346), while a greater decrease in RF width was associated with faster walking speeds (r = -0.431). Examining muscular dimensional changes during contraction is a unique model to investigate the influence of muscle composition on functional performance.