['The longitudinal relationship between aerobic exercise and left ventricular (LV) mass in hypertension is not well known. We did a prospective study to investigate the long-term effect of regular physical activity on development of LV hypertrophy (LVH) in a cohort of young subjects screened for Stage 1 hypertension.', 'We assessed 454 subjects whose physical activity status was consistent during the follow-up. Echocardiographic LV mass was measured at entry, every 5 years, and/or at the time of hypertension development before starting treatment. LVH was defined as an LV mass >/=50 g/m(2.7) in men and >/=47 g/m(2.7) in women. During a median follow-up of 8.3 years, 32 subjects developed LVH (sedentary, 10.3%; active, 1.7%, P = 0.000). In a logistic regression, physically active groups combined (n = 173) were less likely to develop LVH than sedentary group with a crude OR = 0.15 (CI, 0.05-0.52). After controlling for sex, age, family history for hypertension, hypertension duration, body mass, blood pressure, baseline LV mass, lifestyle factors, and follow-up length, the OR was 0.24 (CI, 0.07-0.85). Blood pressure declined over time in physically active subjects (-5.1 +/- 17.0/-0.5 +/- 10.2 mmHg) and slightly increased in their sedentary peers (0.0 +/- 15.3/0.9 +/- 9.7 mmHg, adjusted P vs. active = 0.04/0.06). Inclusion of changes in blood pressure over time into the logistic model slightly decreased the strength of the association between physical activity status and LVH development (OR = 0.25, CI, 0.07-0.87).'] Does regular physical activity prevent development of left ventricular hypertrophy in hypertension?