The widespread physical activity guidelines for adults recommends at least 150 minutes per week of moderate-intensity exercise or 75 minutes of vigorous intensity exercise. The benefits of completing this amount of weekly exercise are widely recognised. Despite this, the majority of adults fall short of the recommended physical activity guidelines with lack of time cited as the primary barrier to achieving weekly exercise goals. As a result, the use of high intensity interval training (HIIT) has been investigated as a more time-efficient strategy to improving health.
What is HIIT?
High intensity interval training uses short bursts of high intensity activity followed by a recovery period at a lower intensity. This ‘high intensity’ period may sound daunting for those newer to cardiovascular training. However, an individualised approach based on guidance from medical specialists and heart rate data ensures a safe and effective method of training. It must be assumed that any individual with a clinically relevant cardiovascular disease risk factor or diagnosed cardiovascular disease requires both a medical examination and a physician-supervised maximal exercise test prior to participation in HIIT (ACSM, 2010).
What are the benefits of HIIT?
The benefits of HIIT within the general population have been widely researched and accepted however, a growing body of evidence has investigated the safety, efficacy and enjoyment of a HIIT protocol within a cardiac population.
Moderate intensity continuous training (MICT) has traditionally been a foundation of aerobic-base exercise prescription resulting in short and long-term clinical benefits for individuals with cardiovascular disease. However, emerging research suggests using HITT alongside or as an alternative to MICT can result in similar or greater improvements in peak VO2 (the threshold of your body’s ability to transport and use oxygen during physical activity).
Similarly, a recent study by Keech et al (2020) found positive efficacy for reducing cardiovascular risk, high levels of patient enjoyment and no cardiovascular-related adverse events associated with the training. Specifically, researchers found significant reductions in both blood pressure and body fat. Importantly for cardiovascular risk, the fat loss appeared to disproportionately come from central areas and visceral fat stores within the trunk.
In addition, aerobic fitness also improved by an average of 12% or nearly 1 MET. As a reference, previous research has found improvements in cardiovascular fitness by 1 MET equates to a ∼8–17% reduction in all-cause and cardiovascular-related mortality.
Through the help of willing CP+R athletes and Exeter University, we have been able to conduct some of our own research investigating the cardiovascular benefits of high intensity interval training in a cardiac population. In line with previous research, our initial findings suggest that interval training is safe for individuals with moderate cardiovascular risk and as effective as steady state exercise in improving peak aerobic capacity. Moreover, we found an improvement in fatigue tolerance, running performance and blood glucose profile specific to the interval protocol.
How do we monitor HIIT?
The physiological and psychological demands of HIIT are greater compared to steady state training. Therefore, sufficient preparation and recovery is incredibly important to the safety and success of the individual. This not only includes a sufficient warm up and cool down but also adequate hydration and nutrition surrounding the HIIT sessions to ensure individuals are fuelling each session as best as possible to achieve optimal results and recovery.
Similarly, through the use of heart rate monitors, HIIT sessions can be monitored to ensure individuals are adhering to the target exercise intensity. This not only ensure optimal physiological adaptations but also the safety of the individual.
In summary, with sufficient medical screening and guidance, high intensity interval training offers individuals with cardiovascular disease an alternative method to improve cardiovascular fitness, increase physical activity and reduce cardiovascular risk. As a team, we pride ourselves of staying at the forefront of new research to adapt and grow to find the safest, effective and enjoyable approach to help our athletes live longer, better.