Feeding the debate: Do masticatory muscles resist age-related decline better than lower limb muscles?

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.