Strength (knee extensor peak torque) correlates inversely with measures of mature CD56dim natural killer (NK) cell responses to K562 leukemia cells in cohort D. CD56dim NK cell CD107a (A) is a measure of cytotoxic granule release and correlated inversely with peak torque for all subjects (ρ = −0.475, p = 0.001), but not for each sex considered individually. CD56dim NK cell MIP-1β chemokine production (B) correlated inversely with peak torque for all subjects (ρ = −0.384, p = 0.006), but not for each sex considered individually.