This study assessed physiological and cardiac factors associated with 10-km running performance in a group of highly trained endurance runners age 21-63 years. Participants (N = 37) underwent a resting echocardiograph and incremental treadmill running test. They also provided information on their recent 10-km races. Data were analyzed using "best subsets" multiple regression. Declines with age were found for 10-km running speed (0.26 m · s-1 · decade-1), maximum heart rate (4 beats/decade), VO2peak (6 ml · kg-1 · min-1 · decade-1), velocity at lactate threshold (1 m · s-1 · decade-1), and VO2 at lactate threshold (4 ml · kg-1 · min-1 · decade-1). The percentage of VO2peak at which lactate threshold occurred increased with age by 1.5% per decade. The rate of change of displacement of the atrioventricular plane at the left free wall and septum both declined by 1 cm · s-1 · decade-1. The best single predictor of 10-km running speed was velocity at lactate threshold
