Low volume, high intensity: Time-efficient exercise for the treatment of hypertension

High blood pressure is one of the leading global risks for mortality and is responsible for 13% of deaths globally.1 Global trends during the last 40 years show an increase in raised blood pressure worldwide, mainly in low-income and middle-income countries due to population growth and ageing,1 while the prevalence of raised blood pressure in high-income countries has decreased.2 However, with the new 2017 ACC/AHA Guidelines changing the definition of high blood pressure (blood pressure >130/80 mmHg instead of >140/90 mmHg), the proportion of adults in the United States labelled as having hypertension has suddenly increased from 32% to 46%.3 Nonpharmacological interventions of hypertension are therefore more important than ever and should be offered to all individuals. According to the guidelines DASH (Dietary Approaches to Stop Hypertension) diet can reduce systolic blood pressure by 11 mmHg, reduced intake of dietary sodium can reduce systolic blood pressure by 5–6 mmHg and aerobic exercise (90–150 min/week) can reduce systolic blood pressure by 5–8 mmHg.3 The guidelines recommend exercise for the prevention, treatment and control of hypertension. The blood pressure reduction by exercise matches the magnitude of that obtained with first-line antihypertensive medications.4 In a recent issue of EJPC, Gorostegi-Anduaga and colleagues evaluate the effectiveness on blood pressure of 16-week intervention in 175 overweight/obese, sedentary participants with hypertension (EXERDIET-HTA study).5 The participants were randomized to attention control (DASH diet + physical activity recommendations) or one of three groups with supervised aerobic exercise programs twice per week and DASH diet: high volume of moderate-intensity continuous training (HV-MICT, 45 min), high volume of high-intensity interval training (HV-HIIT, 45 min) and low volume of high-intensity interval training (LV-HIIT, 20 min). Contrary to their hypothesis, there was no between-group differences after intervention and all groups including the attention control reduced systolic blood pressure by 7–9 mmHg. At baseline, 87% of the participants were using antihypertensive drugs, and the medication could be withdrawn in 8% and reduced in 38% of the participants. The dropout rate was only 7%, which is impressive since the intervention was in overweight/obese and sedentary individuals. Physical activity is believed to be important especially in the early stage of hypertension, since the increase in blood pressure is mainly mediated through increased cardiac output and more manifest vascular changes with increased peripheral resistance have not yet developed.6 Unfortunately, there was no available information of how long the participants had been on antihypertensive medication. In the ENCORE Study the participants were not on antihypertensive medication and the reduction in blood pressure after intervention was greater compared with EXERDIET-HTA study.7 DASH diet only (DASH-A) group achieved significant blood pressure reductions and adding an exercise and weight loss program (DASH-WM) led to an even greater decrease in blood pressure. At 16 weeks, systolic blood pressure was reduced by 16 mmHg in the DASH-WM group, 11 mmHg in the DASH-A group and 3 mmHg in the usual care group.7 In contrast with the EXERDIET-HTA study other studies with higher-intensity aerobic exercise (90–95% of maximum heart rate) have reported a more pronounced reduction in systolic blood pressure compared with moderate-intensity continuous training (12 versus 4.5 mmHg).8 However, in this particular study there was no diet intervention and all participants using antihypertensive drug performed a wash-out before inclusion. The EXERDIET-HTA study nicely illustrates an increase in more than 1 metabolic equivalent of task (MET) after the 16-week intervention period for the three supervised exercise groups.5 The high-intensity interval training groups had significantly greater improvement in cardiorespiratory fitness than moderate-intensity continuous training, but there were no significant differences between the high-intensity interval training groups. Physical work capacity in MET has been shown to be a strong predictor of death and each 1-MET (3.5 ml/kg/min) increase in exercise capacity has been associated with a 12% decrease in risk of death.9 A meta-analysis found high-intensity interval training to increase cardiorespiratory fitness by almost double compared with moderate-intensity continuous training in patients with lifestyle-induced cardiometabolic disease.10 Cardiorespiratory fitness is a strong determinant of morbidity and mortality.11 One-year follow-up of the ENCORE study showed that sustained changes in dietary habits, weight and blood pressure persisted for 8 months after completion of the 16-week intervention compared with baseline. However, only 21% reported still exercising regularly 8 months after completing the intervention.12 Adherence to lifestyle changes is challenging and should be combined with behaviour counselling for long-term adherence. There are inequalities in who receives lifestyle counselling. In a population-based sample of hypertensive adults (N = 28,457), exercise advice was reported most frequently (75%), followed by advice to reduce salt intake (69%) and change of eating habits (62%). Individuals over 60 years with hypertension were less likely than younger people to receive guidance from the clinicians on lifestyle changes.13 Clinicians are well trained in which drug to prescribe to their patients, but do they have equal skills in giving lifestyle advice? To give adequate exercise counselling, the clinicians need to know that moderately intense activity enables the individuals to be able to speak, while during vigorous-intensity activity, individuals can say no more than a few words without pausing for a breath. The guidelines recommend moderate-intensity exercise 30 minutes per day 5–7 days per week.14 A higher-intensity regime could have additional cardiometabolic benefits for suitable individuals. The antihypertensive effects of exercise are not only dependent on the FITT (frequency, intensity, time, type) principle since the individual training response is also due to inheritance. There are several genes involved in determining response to exercise and it has been suggested that 17% of the reduction in resting systolic blood pressure after exercise is due to inheritance.15 The EXERDIET-HTA study is highly relevant and emphasizes the importance of lifestyle intervention as a first choice of intervention for blood pressure reduction.5 Even though the EXERDIET-HTA study did not provide us with a final answer with respect to optimal frequency, intensity or time, the type of exercise prescription with low volume and high intensity might be attractive for the individual to maintain exercise over time. The long-term follow-up of the results will be interesting. Studies such as the EXERDIET-HTA study will have to guide us on lifestyle intervention at a group level until we can design an exercise and diet program tailored for each individual’s genetics for maximum blood pressure reduction. The European Guidelines on cardiovascular disease prevention emphasize the importance of regular physical activity for patients with hypertension,16 but should consider the inclusion of more specific advice on low-volume and high-intensity exercise for suitable patients. CBI is the sole author of the manuscript and contributed to the conception and design of the work. CBI contributed to the acquisition, analysis, or interpretation of data for the work. CBI drafted and critically revised the manuscript. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.