Abstract Swimming is a lifestyle intervention recommended by many clinicians in the prevention and treatment of hypertension. Yet, not all studies have agreed that swimming training can reduce blood pressure (BP). Inclusion of normotensive subjects could be a confounder for discrepancies among studies. In this one-year longitudinal study, long-term effects of swimming training on BP were investigated in 7 mild hypertensive patients (Systolic BP > 140 mmHg) and 16 normotensive controls. At baseline, these subjects (aged 21.5 0.1 years) did not participate in any form of sport training activity for the previous 3 months before enrollment into the training program. The training distance progressed from 0 (baseline) to 7 kilometers per week. BP and the homeostasis model assessment for insulin resistance (HOMA-IR) were determined under fasted condition at baseline and 48 h after the last swimming bout. The hypertensive patients displayed significantly greater HOMA-IR than age-matched normotensive controls. When data of all subjects were pooled, plasma glucose concentration was only slightly lowered after training, but weight, height, BMI, Systolic BP (SBP), diastolic BP (DBP) and HOMA-IR values were not significantly altered. However, when observation was restricted to the hypertensive patients, swimming training significantly lowered SBP by ~17 mmHg, concurrent with 41% reduction in HOMA-IR. Intriguingly, SBP in the normotensive subjects was elevated by ~ 6 mmHg after training. Conclusions: The present study found normalization rather than universal reduction effect of swimming training on BP. Furthermore, the BP-lowering effect of training in hypertensive patients appears to be associated with improvement in insulin sensitivity.
