This is an excerpt from Ageless Intensity by Pete McCall.
HIIT Could Help to Reduce the Risk of Developing Chronic Health Conditions
One risk of aging without regular exercise is developing chronic health conditions like heart disease, obesity, and type 2 diabetes; and yes, as with other forms of exercise, the evidence suggests that HIIT could be an important component for greatly reducing this risk. As mentioned previously, when you work at higher intensities, muscles will metabolize carbohydrate, specifically muscle glycogen, to produce ATP; one important benefit of exercise during the aging process is maintaining efficiency of carbohydrate metabolism in the muscle cells. As mentioned, specific enzymes like LPL are used to metabolize FFAs into ATP, and different enzymes are required for type II muscle fibers to convert glycogen to ATP. Research at Ball State University found that adults in their 70s who maintained a high level of fitness throughout their life span had enzyme levels similar to adults many years younger (Gries et al. 2018). This means that performing high-intensity exercise consistently through the aging process could help you to metabolize carbohydrate much more efficiently and reduce your risk of developing type 2 diabetes; because lower-intensity exercise relies on aerobic metabolism, it may not deliver the same benefit.
Hypertension is a common risk factor for developing further cardiovascular disease that could result in an early death. As arterial stiffness increases, it is more challenging for the heart to perform its function of pumping blood around the body. It’s widely accepted that low- to moderate-intensity cardiorespiratory exercise can help improve aerobic capacity and reduce risk factors, like hypertension, that could lead to heart disease. It’s important to note, however, that evidence is accumulating that HIIT could be an even more effective option than lower-intensity exercise for those at risk of heart disease. In a review of the literature comparing HIIT to continuous moderate-intensity exercise, Ciolac (2012) observed that the former is “superior” to the latter for improving cardiorespiratory fitness and improving numerous health markers that lower risks of developing hypertension and other forms of cardiorespiratory disease.
HIIT has been used successfully to help individuals reduce risk factors for heart disease, and in their review of the research on HIIT, Gibala and Shulgan (2017) found that studies have suggested that patients who have experienced heart attacks or heart surgery could benefit from HIIT as a component of rehabilitation. They also found that other studies showed that shorter, more intense workouts with HIIT could provide more favorable outcomes for heart patients than moderate-intensity, steady-state exercise. In one study, interval workouts were found to put less stress on the heart than steady-state aerobic exercise. In another study that lasted seven years, researchers tracked cardiac rehab patients who participated in both moderate-intensity and HIIT workouts and concluded that the risk of a cardiac event is low for both modes of exercise in a supervised setting. Another study noted, “The results of this randomized controlled study demonstrate that high-intensity aerobic exercise is superior compared to moderate-intensity exercise for increasing cardiorespiratory fitness in stable coronary artery disease patients” (Gibala and Shulgan 2017).
In a meta-analysis that reviewed the benefits of HIIT versus moderate-intensity continuous training (MCT) for individuals dealing with coronary artery disease, the study authors surveyed 12 studies on the topic and concluded that “HIIT is a safe and simple intervention that could potentially be beneficial for patients with coronary artery disease” (Gomes-Neto et al. 2017).
Salom Huffman and colleagues (2017) studied a group of recreationally active women between 40 and 64 to measure the effects of a concurrent exercise program that included resistance training with 40-second sprint intervals at 95 percent of age-predicted maximum heart rate (MHR). The purpose of the 12-week investigation was to determine how sprint interval training would affect the aerobic capacity of the women and whether those who were casual exercise participants could benefit from high-intensity exercise. Researchers observed that in addition to improving overall health, “exercise training programs of high intensity are well tolerated and convey significant aerobic capacity benefits in cohorts composed of older and low fitness individuals” (Salom Huffman et al. 2017).
Many of these benefits are similar to those derived from high-intensity strength and power training, and yes, they are important benefits, but the body cannot function at high intensity all of the time, which is why it is important to perform lower-intensity workouts as well. During lower-intensity exercise, you can help promote recovery from more challenging workouts while burning calories, but without placing as much stress on your body.