Rapid Strength in Adults Over 90 Years Declines More Than Maximal Strength and Skeletal Muscle Mass

Living beyond 90 years is rare worldwide. Although aging impairs neuromuscular function and body composition, little is known about changes in individuals over 90 years old. This cross-sectional study examined associations between age and neuromuscular-related parameters in adults over 90 years old.

A total of 42 individuals above 90 years old (94.9 ± 3.1 years, range: 90-102 years) attended laboratory testing. Participants underwent assessments of body composition (via dual-energy X-ray absorptiometry); quadriceps muscle thickness and quality (via ultrasonography); and knee extension maximum strength, rapid strength (i.e., rate of torque development [RTD]), and muscular endurance via isometric dynamometry.

Linear regression analyses revealed no significant associations between age and muscle mass (βs = -0.103, p = .506), quality (βs = 0.198, p = .222), and endurance (βs = -0.021, p = .916). However, age was negatively correlated with RTD during the later phases (150-350 ms) of isometric knee extension, with the most pronounced decline observed in the 100-200 ms interval (βs = -0.456, p = .014), corresponding to a mean reduction of ∼9% per year. Early-phase RTD (0-100 ms) showed marginal significance (p = .069), suggesting potential age-related neural impairments.

In individuals over 90 years old, neuromuscular decline appears more related to rapid strength (RTD) than to maximal strength or muscle quantity/quality. Significance/Implications: RTD loss may compromise abilities essential for independence, such as balance recovery and fall prevention. Targeting explosive strength rather than hypertrophy or maximal strength could be key for preserving mobility in extreme old age.