Based on previous studies on sports in hypertension, we expected the intervention to result in a decrease of systolic 24h-ambulatory BP (systolic ABP) of at least 6 mm Hg in the training group with no changes in the control group.16,17 This difference was considered to be clinically relevant. A sample size of 23 in each group has 80% power to detect a difference in means of 6 mmHg assuming that the common standard deviation is 7 mmHg, a baseline systolic ABP of 140 mmHg and a two-sided p\<0.05. We estimated the drop-out rate to be about 15% leading to a sample size of 27 patients per group.

Patients are recruited from our hypertension outpatient clinic. Inclusion criteria are current antihypertensive treatment, diastolic ABP ≤ 90 mmHg, age of ≥ 60 years. Prior to the exercise program, cardiac function is examined by ECG and echocardiogram. Exclusion criteria are regular engagement in physical exercise training in the past 12 weeks prior to inclusion in the study, symptomatic peripheral arterial occlusive disease, aortic insufficiency or stenosis \> stage I, hypertrophic obstructive cardiomyopathy (HOCM), congestive heart failure (\> NYHA II), uncontrolled cardiac arrhythmia with haemodynamic relevance, systolic office BP ≥ 180 mmHg, signs of acute ischemia in exercise ECG, change of antihypertensive medication in the past 6 weeks prior to inclusion in the study or during follow-up period. According to these criteria 54 patients are enrolled and randomized to exercise and control group.

Physical performance is assessed using a modified Bruce-protocol. Arterial elasticity is measured by pulse-wave analysis of the radial artery. Endothelium-dependent vasodilation is assessed sonographically by flow-mediated vasodilation. 24h-ABP monitoring is performed using Spacelabs 90207 monitors. The follow-up BP and vascular measurements of the training group are conducted within 2 days after the last training session.

The training program, consisting of walking on a treadmill according to an interval-training pattern, is carried out 3 times weekly for 12 weeks. If patients miss a training session, the program is prolonged until 36 workouts are carried out. The initial duration of training sessions is 30 minutes. During the first week, training consists of 5 workloads of 3 min; between workloads patients walk with half-speed for 3 min. Exercise duration is gradually increased to 4 x 5 min a day in the second week, 3 x 8 min in the third, 3 x 10 min in the fourth and 2 x 15 min in the fifth week. In the sixth and further weeks, exercise is progressively increased to 30, 32 and 36 min and is carried out without interruption. Training intensity corresponds to the speed necessary to reach a lactate concentration of 2.5 ± 0.5 mmol/l in capillary blood slightly above the aerobic threshold. Heart rate during training is controlled by a heart-rate monitor. As lactate concentration sinks below 2.0 mmol/l or exercise heart rate decreases by more than 5/min as a result of training adaptation, treadmill speed is increased by 0.5 km/h or elevation is increased by 3% to maintain training intensity. We have previously shown that this training protocol leads to a substantial increase of physical performance in short time. During training patients are continuously supervised by a physician.