Protocol

We performed a prospective, randomized, controlled study in a three-arm design comparing aerobic dynamic exercise with isometric handgrip training and ‘‘sham isometric handgrip training’’. The duration of the program was 12 weeks in each group. Patients randomized to aerobic exercise were encouraged to participate in endurance training for 30 min 3–5 times per week at moderate intensity according to levels 12–13 of the Borg scale of perceived exertion.¹² There was neither a structured exercise program nor a supervised program.

Isometric handgrip training was performed five times weekly. According to a standard protocol, each session contained two hand contractions of 2 min at 30% of maximal power with each arm. Sham-handgrip training was conducted based on the same protocol but with only 5% of maximal power. Based on previous trials, it was hypothesized that contractions with 5% of maximal power do not induce relevant cardiovascular effects. The Zona device was used in both groups (Zona Health Inc., Boise, USA). The standard commercial version aims at 30% of maximal power. The ‘‘sham devices’’ were developed by a software modification of the company. Participants were not informed whether they were randomized to handgrip or sham-handgrip training.

Blood sampling and BP measurements were performed at baseline and after 12 weeks. Antihypertensive medication was not allowed to be changed during the study period of 12 weeks.