Age-related declines in muscle mass and strength result from intrinsic ageing and reduced mechanical loading. Masticatory muscles, being continuously used for feeding, may be less affected. We cross-sectionally compared ageing effects on locomotor and masticatory muscles in 30 women: young (26±1.8 y), middle-aged (44.1±3.4 y), and older (69.5±3.1 y). Cross-sectional area (CSA) of the quadriceps femoris and masseter was assessed by panoramic ultrasound, and knee extension torque (KE) and bite force (BF) were measured via isokinetic dynamometry and a bite force sensor. Both muscles showed progressive age-related reductions. Quadriceps CSA declined to ~75% in middle-aged and 56 ± 13% (older) of young values, while masseter CSA declined to ~94% and 79%, respectively. Strength also declined (KE: ~81% and 62%; BF: ~75% and ~68% of young values; all p<0.05), with no difference between middle-aged and older adults. Effect sizes for CSA were larger in the quadriceps (d = 1.56-2.95) than masseter (d = 0.29-1.09). For strength, effect sizes from young to middle-aged were similar for KE and BF (d = 1.20 vs. 1.33) but greater for KE from young to older adults (d = 2.28 vs. 1.16). Both muscles were smaller and weaker in older groups, but while quadriceps strength roughly mirrored CSA reductions, masseter strength declined disproportionately, suggesting neuromuscular contributions beyond muscle size.
Schaun et al. (Fri,) studied this question.