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Review
. 2025 Oct;26(10):e13949.
doi: 10.1111/obr.13949. Epub 2025 May 19.

Knee Extensor Structure and Function in Children, Adolescents, Adults, and Older Adults With Obesity: A Systematic Review and Meta-Analysis

Michael N Vakula  1 , Youngwook Kim  2 , Eadric Bressel  1
Affiliations
Review

Knee Extensor Structure and Function in Children, Adolescents, Adults, and Older Adults With Obesity: A Systematic Review and Meta-Analysis

Michael N Vakula et al. Obes Rev. 2025 Oct.

Abstract

Objective: This study aims to evaluate the association between obesity and both absolute and relative measures of knee extensor muscle structure and contractile function across different age groups, including children, adolescents, adults, and older adults.

Methods: A search for potential studies was performed in four electronic databases. Data were meta-analyzed using a random-effects model for our primary outcomes of knee extensor structure (muscle size and quality) and function (maximal force/torque, rapid torque, and fatigue) and compared between those with or without obesity in each age group.

Results: The findings indicate that obesity significantly increases absolute measures of knee extensor maximal contractile function and muscle size. However, obesity was associated with a decrease in relative measures of maximal and rapid contractile function and muscle quality. The association of obesity with these muscle characteristics varied by age group, with the effects on knee extensor structure and function diminishing with age.

Conclusions: This systematic review and meta-analysis demonstrate that while obesity enhances absolute knee extensor muscle size and maximal force/torque, it detrimentally affects relative muscle function and quality, particularly related to activities of daily living. These effects are less pronounced in older adults, suggesting that age modulates the impact of obesity on muscle structure and function. The findings underscore the importance of interventions targeting the improvement of relative muscle function and quality in individuals with obesity. Further research is necessary to better understand these relationships and to develop more effective intervention strategies for obesity.

Registration: This protocol was prospectively registered in the Open Science Framework (DOI: 10.17605/OSF.IO/ZGUK6).

Keywords: muscle; muscle function; muscle quality; muscle structure; obesity.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Search flow diagram of article inclusion process. NW: normal weight; OB: obesity.
FIGURE 2
FIGURE 2
Forest plot of absolute measures of maximal knee extensor contractile function.
FIGURE 3
FIGURE 3
Forest plot of absolute measures of rapid knee extensor contractile function.
FIGURE 4
FIGURE 4
Forest plot of measures of knee extensor size.
FIGURE 5
FIGURE 5
Forest plot of relative measures of maximal knee extensor contractile function.
FIGURE 6
FIGURE 6
Forest plot of relative measures of rapid knee extensor contractile function.
FIGURE 7
FIGURE 7
Forest plot of relative measures of knee extensor fatigue.
FIGURE 8
FIGURE 8
Forest plot of measures of knee extensor muscle quality.
See this image and copyright information in PMC

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