Cardiac perturbations after high-intensity exercise are attenuated in middle-aged compared with young endurance athletes: diminished stress or depleted stimuli?

Strenuous exercise elicits transient functional and biochemical cardiac imbalances. Yet, the extent to which these responses are altered owing to aging is unclear. Accordingly, echocardiograph-derived left ventricular (LV) and right ventricular (RV) global longitudinal strain (GLS) and high-sensitivity cardiac troponin I (hs-cTnI) were assessed before (pre) and after (post) a 60-min high-intensity cycling race intervention (CRIT) in 11 young (18-30 yr) and 11 middle-aged (40-65 yr) highly trained male cyclists, matched for cardiorespiratory fitness. LV and RV GLS were measured at rest and during a semirecumbent exercise challenge performed at the same intensity (young: 93 ± 10; middle-aged: 85 ± 11 W, = 0.60) pre- and post-CRIT. Augmentation (change from rest-to-exercise challenge) of LV GLS (pre: -2.97 ± 0.65; post: -0.82 ± 0.48%, = 0.02) and RV GLS (pre: -2.08 ± 1.28; post: 3.08 ± 2.02%, = 0.01) was attenuated and completely abolished, in the young following CRIT, while augmentation of LV GLS (pre: -3.21 ± 0.41; post: -3.99 ± 0.55%, = 0.22) and RV GLS (pre: -3.47 ± 1.44; post: -1.26 ± 1.00%, = 0.27) was preserved in middle-aged following CRIT. While serum hs-cTnI concentration increased followingCRIT in the young (pre: 7.3 ± 1.6; post: 17.7 ± 1.6 ng/L, < 0.01) and middle-aged (pre: 4.5 ± 0.6; post: 10.7 ± 2.0 ng/L, < 0.01), serum hs-cTnI concentration increased to a greater extent in the young than in the middle-aged following CRIT ( < 0.01). These findings suggest that functional and biochemical cardiac perturbations induced by high-intensity exercise are attenuated in middle-aged relative to young individuals. Further study is warranted to determine whether acute exercise-induced cardiac perturbations alter the adaptive myocardial remodeling response. High-intensity endurance exercise elicits acute cardiac imbalances that may be an important stimulus for adaptive cardiac remodeling. This study highlights that following a bout of high-intensity exercise that is typical of routine day-to-day cycling training, exercise-induced autonomic, biochemical, and functional cardiac imbalances are attenuated in middle-aged relative to young well-trained cyclists. These findings suggest that aging may alter exercise-induced stress stimulus response that initiates cardiac remodeling in athlete's heart.