Is it Yet Time to Throw Away the Old Recipe Book and Consider High Intensity Intermittent Exercise in Clinical Populations?

Abstract

The first epidemiological exercise studies in the 1950's established a cause-effect relationship between levels of physical inactivity and cardiovascular disease. In the interim other longitudinal, cross-sectional, retrospective and prospective analyses have confirmed that physical activity is cardio-protective and also an inverse relationship exists between mortality rates and leisure time physical activity intensity. As such physical activity guidelines have emerged in the last 20 years, not only for sub-clinical, but also clinical populations. For example the American Heart Association (AHA) published 2009 exercise guidelines for people with type II diabetes [1]. The AHA publication is especially interesting as it was perhaps the first to make recommendations adjusting for both moderate- and vigorous-intensity exercise. Guidelines such as this have been primarily, but not exclusively, developed upon the relatively large volume of data from clinical exercise training trials of moderate intensity continuous exercise (MICE). There seem to be three pillars, or established reasons, why there exists a historical preference for MICE therapy in people considered to be medium to high risk for cardiovascular events. First, the stimulus from MICE is considered sufficient to stimulate health benefits. Second, the risk of serious medical events from MICE is considered acceptable, while intuitively high intensity exercise is considered by many to carry a higher risk of serious illness. Third, MICE is well tolerated by most people and is not likely to detract from exercise adherence. In the sections below emerging knowledge will 'test' these three concepts that have been pillars of invincibility for over 50 years.