Associations Between Exercise Blood Pressure And Left-Ventricular Mass Are Influenced By Cardiorespiratory Fitness In Adolescence

Objectives: Exaggerated blood pressure (BP) during submaximal exercise is associated with higher left-ventricular mass index (LVMI). Paradoxically, exercise BP and LVMI may be higher in those with greater cardiorespiratory fitness, but factors underlying this are poorly understood. This study aimed to determine relationships between exercise BP, fitness and LVMI in a population-based sample of adolescents. Methods: 4835 adolescents from the Avon Longitudinal Study of Parents and Children (age 15.4 ± 0.3 years, 49% male) completed a submaximal cycle test. Exercise BP was measured immediately on cessation of the test and fitness calculated as a ratio of maximal workload to heart rate achieved. Follow-up echocardiographic assessment of LVMI (n = 1638), cardiac output (CO, n = 1659) and total peripheral resistance (TPR, n = 1659) was completed 2.3 ± 0.3 years later. Results: Exercise systolic BP was associated with fitness (β = 22.25, 95% CI: 20.65–23.85) and increased step-wise across tertile of fitness (130 ± 15 vs. 137 ± 15 vs. 144 ± 15 mmHg). Exercise systolic BP was associated with LVMI after adjustment for age, sex and total fat-mass (β = 0.02, 0.004–0.040), but adjustment for fitness abolished this association (β = 0.0006, CI: −0.02–0.02). An association between exercise systolic BP and LVMI was only found among those in the lowest fitness tertile (β = 0.04, CI: 0.001, 0.077). CO increased step-wise (3.56 ± 0.86 vs. 3.76 ± 0.94 vs. 3.99 ± 0.98 L/min), but TPR reduced (23.76 ± 6.12 vs. 23.02 ± 5.93 vs. 22.26 ± 5.94) with fitness level. Conclusion: The association between exercise BP and LVMI in adolescence is influenced by fitness. Higher CO, but lower TPR with higher fitness suggests favourable physiological adaptation, rather than pathological reasons underlying elevations in exercise BP and LVMI.