Active Voice: Evening Vs. Morning Aerobic Training – Which Is Better for Hypertension Treatment?
By John R. Halliwill, Ph.D., FACSM; Leando C. Brito, Ph.D.; Cláudia L. M. Forjaz, Ph.D.

High or elevated blood pressure (hypertension) affects one billion people worldwide and is one of the most important risk factors for development of cardiovascular disease. Current clinical guidelines highlight the use of aerobic training as a useful intervention, either alone or in combination with antihypertensive medication and other lifestyle changes to treat hypertension. However, benefits of exercise training, such as its ability to reduce blood pressure, appear to vary across studies and across individuals. Thus, an important research focus is to discover ways to potentiate exercise’s hypotensive effect.

Prior research has established an association between the reduction of blood pressure after a single exercise session and the long-term training effect on blood pressure. In previous work, we have shown that the effect of a single exercise session on blood pressure is greater when a person exercises in the evening than in the morning. Thus, we asked the question, is the long-term benefit of evening aerobic training on blood pressure greater than what is generated by morning exercise?

To answer this, as reported in the April 2019 issue of Medicine & Science in Sports & Exercise® (MSSE), we divided a cohort of 50 hypertensive men into three groups and randomly assigned them to exercise over the next 10 weeks either in the morning (7-9 a.m.) or evening (6-8 p.m.). The third group only stretched, instead of doing aerobic exercise. What was interesting to us is the fact that the only group showing a strong reduction in their blood pressure was the one that exercised in the evening. Other beneficial changes were observed in both exercise groups that were not seen with just stretching. From a clinical perspective, the blood pressure reduction (3 mmHg) observed with the evening exercise training is enough to predict an 8% reduction in the risk for stroke and a 5% reduction for coronary heart disease mortality.

The fact that blood pressure did not appear to improve with morning training surprised us. It might be due to the timing of when these individuals took their daily antihypertensive drugs. In other words, taking the medication in the morning might have hidden the benefits of morning exercise on blood pressure.

Does this mean hypertensives shouldn’t exercise in the morning? We wouldn’t go that far. It is important to remember that exercise generates numerous health benefits, and its ability to reduce blood pressure in those individuals with hypertension is just one. We think it is better to exercise, regardless of time of day, than to avoid physical activity. And it may be that morning training just takes longer than 10 weeks to reduce blood pressure.

We think our work, showing that time of day matters to exercise training responses, might stimulate more research on how to potentiate the health benefits of daily exercise. Based on the results to date, it looks like treating hypertensive individuals with aerobic training in the evening decreases blood pressure more effectively than training in the morning, but that aerobic training at either time of day still produces benefits to cardiovascular health.

About the authors:
John R. Halliwill, Ph.D., FACSM, is a professor of human physiology at the University of Oregon in Eugene, Oregon. His research focuses on identifying the hormonal, neural or metabolic factors that modulate cardiovascular system function during exposure to environmental and physical stresses. He is a leading researcher on mechanisms of blood pressure regulation after exercise (post-exercise hypotension).

Leandro C. Brito, Ph.D., is a post-doctoral researcher at the University of São Paulo, Brazil. His research focuses on exercise physiology, hemodynamic and circadian rhythms. His research interests also include interactions between sleep, exercise and cardiovascular autonomic control.

Cláudia L.M. Forjaz, Ph.D., is an associate professor at the University of São Paulo, Brazil. She has investigated the effects of exercise on blood pressure since 1998 and has published more than 100 papers about this subject. Due to her expertise on this topic, she has been invited to serve as vice president of the Brazilian Society of Hypertension and to participate in the conference on the Brazilian Hypertension Guidelines.