Differences in the mass and quality of the quadriceps with age and sex and their relationships with knee extension strength

Abstract Background Although muscle quality evaluations are currently considered important for diagnosing sarcopenia, data from the general population are lacking. This study used mid‐thigh computed tomography measurements to evaluate age‐related and sex‐related differences in quadriceps femoris muscle quality and mass and their relationships with knee extension strength (KES). Methods Cross‐sectional data from 520 Japanese individuals (273 men and 247 women, mean age: 63.1 ± 10.6 years) were analysed. Mass and quality were assessed using quadriceps cross‐sectional areas (CSAs) and computed tomography values (CTVs), respectively. The four constituent muscles, intermuscular adipose tissue, and entire quadriceps area (total quadriceps muscles + intermuscular adipose tissue) were assessed, and the data were stratified by five age groups and sex. To evaluate age‐related decline, linear and quadratic equations were tested for fit according to the constituent muscles and sex. KES could be measured in 472 of the 520 participants (254 men and 218 women, mean age: 62.3 ± 10.3). Multiple linear regression analyses with age‐adjusted models were then used for evaluating the relationships between KES and quadriceps measurements. Results All muscle CSAs and CTVs showed downward trends with age (men: P