Cardiovascular responses to exercise of participants in a trial on the primary prevention of hypertension.

The Chicago study on the Primary Prevention of Hypertension (PPH) is a long-term, randomized controlled trial to test the ability of nutritional-hygienic non-pharmacological methods to prevent high blood pressure in hypertension-prone persons aged 30-44 years at entry. In order to assess the effects of this programme on cardiovascular responses to exercise, graded submaximal treadmill exercise tests were done serially at baseline and during the trial. Eighty-five participants (48 intervention, 37 control) successfully finished baseline and 2- or 3-year follow-up tests. The exercise maximal double product (DP) [systolic blood pressure (SBP) X heart rate/100] was significantly lower for both groups at 2-3 years compared with baseline, and this reduction was greater for the intervention than for the control group (-27.1 versus -15.5; P = 0.055). Similarly, improvement in maximal increase in DP (maximal DP minus standing DP) was greater for the intervention than the control group (-22.1 versus -9.9, respectively; P = 0.068). The lowest DP during the 6-min recovery period and the debt DP (lowest recovery DP minus standing DP) fell significantly at 2-3 years compared with baseline in the intervention but not in the control group (-12.7 versus -4.8; P = 0.017 for the first index, and -7.7 versus +0.9; P = 0.029 for the second). These interim data from this trial indicate that its intervention procedures favourably influenced cardiovascular responses to graded submaximal exercise.