HIIT [High Intensity Interval Training] for the Deconditioned Individual

HIIT for the Deconditioned Individual. An objection, or perhaps a concern, I frequently hear from health care professionals, as well as the general populous, is that HIIT or SIT might be applicable for an athletic population but that it has no place in the protocols for individuals that are deconditioned, obese or have cardiovascular disease. Interestingly, however, it is the general public who is often more accepting of this approach to exercise; of course, it is often easier to educate those with a blank slate than those with a partially completed scroll. While I can certainly appreciate why many people would think that HIIT might be dangerous for a deconditioned individual, it could not be farther from the truth.

First, Albert et al. reported, in the New England Journal of Medicine, that the absolute risk of sudden death from vigorous exercise is less than one in 1.5 million and, importantly, this very small risk is actually attenuated with habitual vigorous exercise27. Also, this finding did not take into account that some sudden deaths due to vigorous exercise were as a result of non controlled vigorous exercise – meaning, there would have been external pressures to engage in the activity. Again, a basic physiological principle is that the body adapts to stress. If you ask a very deconditioned individual to ride a bike or go for a run for 20 to 60 minutes, the intensity they will be able to maintain for that length of time will be about a nano‐calorie above sitting on the couch eating ice cream.

However, if they are told to exercise for just 20 to 60 seconds, even the most deconditioned individual can attain an intensity that will be both challenging and safe. I would argue that the thought process that high‐intensity exercise is unsafe for unfit individuals and that one should only prescribe LMICT to this population is, although perhaps counter intuitive, a dangerous one. This is because, at some point in time, life will require a burst of high‐ intensity exercise without much of a thought going into the decision of whether or not one is fit enough to do so.

If someone is trying to haul two heavy bags to catch their connecting flight or they are clearing snow to allow them to make it to an important meeting, the pressure of making that plane or meeting will typically override any concern for whether they have the necessary conditioning to safely accomplish that level of exertion. But when you ask that same deconditioned individual to give it all they have without the pressure of an external goal, they will stay within their comfort level.

In fact, it is more common that they will leave plenty in the tank when they are first beginning with HIIT and, so long as there is a modicum of exertion, this is just fine as they can progress over time. I am always telling people that they do not have to become an Olympic athlete overnight and taking it relatively easily in the first couple of weeks is a great approach.

But, as they start to see improvements in their level of cardiorespiratory conditioning, they need to go harder not longer. This is key, upon seeing improvements, too many people look to increase the length of the exercise interval. As soon as they do this, the most important ingredient for initiating a physiological change, the intensity of the exercise, will have been significantly diminished. Remember that it is about quality not quantity.

Well, apart from my own clinical experience, what other evidence do I have to argue that HIIT is an appropriate method of exercise for the deconditioned? Although it surprises many people, there is actually a significant body of research supporting HIIT for a deconditioned population. Because of the damage that a myocardial infarction (MI) has on heart muscle, a population of stable, post‐infarction heart failure patients is about as deconditioned as you are going to see. In this population, it is quite typical to see VO2 max values (expressed as ml A kg‐1 A min‐1) below 15, which is extremely low.

For comparison purposes, a typical college‐aged male would be about 45 and a typical college‐aged female would be about 35. While elite endurance athletes do have the highest values (Males ‐ 70 to 80+; Females ‐ 60 to 70+), there is no health benefit to having these extremely high numbers; rather, one simply needs to not reside in the gutter, so to speak, and aerobic capacities in the 50s, commonly seen in sprint and interval athletes (and primitive humans), are very healthy numbers.

The measurement of VO2 max has recently been found to be the single best predictor of both cardiac and all‐cause deaths among patients with established cardiovascular disease (CVD). So, improving it would obviously be prudent. We have so far clearly established that HIIT can improve VO2 max in normal subjects, the question is, can HIIT improve VO2 max in the severely deconditioned? A number of studies have indicated that high‐intensity exercise is key to aerobic and cardiovascular adaptations in patients with coronary artery disease (CAD),30 chronic heart failure (CHF), or left ventricular (LV) dysfunction; as well as, reducing the risk of coronary heart disease (CHD) in healthy subjects. Warburton et al. also showed that HIIT provided an effective tool to improve the cardiovascular fitness and health status of patients with CAD. Further, compared to a traditional exercise training model (LMICT), it was also shown that HIIT improved anaerobic tolerance to a greater extent without increasing the risk to the patient. So, much like normal subjects then. And, as we have seen before, with HIIT, less can be more based on the fact that it has been shown that a single weekly bout of exercise, so long as it is of a high intensity, can reduce the risk of cardiovascular death in both men and women. Interestingly, in this latter study, no additional benefit was found from increasing either the duration or frequency of the weekly exercise. Who cannot find the time for just one bout of HIIT per week?

In last year’s June issue of the American Heart Association journal, Circulation, Wisløff et al. showed some dramatic benefits of “aerobic” interval training, as compared to moderate continuous training, in heart failure patients. Aside from these dramatic benefits, a very important point to make about this study was the age of the subjects because chronic heart failure is a disease of the elderly; in fact 49% of patients with a first diagnosis are older than 80 years of age.

The majority of previous studies have excluded patients older than 70 years; yet, this study enrolled 27 patients, all with post‐infarction heart failure, with an average age of 75.5 years and 12 of the subjects were older than 80 years of age. The patients had an impaired LV ejection fraction of, on average, 29% and an average VO2 max of only 13 ml A kg A min‐1.

They were randomized to one of three exercise training protocols for 12 weeks, aerobic interval training (AIT), moderate continuous training (MCT), or to a control group that received standard advice, regarding physical activity, from their family doctor. The AIT and MCT groups met for supervised training twice weekly and performed one weekly session at home, which was designed to mimic the supervised training utilizing uphill walking.

Every three weeks, the control group also met for supervised treadmill walking at 70% of maximal heart rate (MHR), lasting 47 minutes. The AIT consisted of inclined treadmill walking at 95% of MHR for four, 4‐minute intervals with 3‐minute active recoveries at 50‐70% of maximal heart rate; total exercise time (including a 10 minute warm‐up and a three minute cool down) was 38 minutes. The MCT also consisted of inclined treadmill walking but at an intensity equivalent to 70‐75% of MHR for 47 minutes to make the training protocols isocaloric (i.e., of equal energy expenditure).

The difference in the increase in VO2 max, the single best predictor of deaths in patients with CVD, as a result of the two training protocols was striking, 14% for the MCT group and 46% for the AIT group. Anaerobic threshold, from an absolute perspective, also increased more in the AIT group compared to the MCT group. While MCT showed no change in work economy, AIT provided an improved work economy as demonstrated by a 15% reduced oxygen cost, an 8‐bpm lower heart rate, and a 59% lower blood lactate at a given submaximal walking speed.

An improved anaerobic threshold and work economy makes a huge difference in the day‐to‐day functional capacity of anyone, but particularly for individuals that are severely deconditioned. AIT also had dramatic improvements in heart morphology and performance, essential factors for individuals with heart failure. Of particular interest were increases in the LV ejection fraction (35%) and stroke volume (17%).

Interestingly, it was also shown that AIT, but not MCT, reduced the plasma levels of oxidized LDL by 9% and increased the patients’ antioxidant status by 15%. This latter increase correlated with the greater increase observed, by the AIT group, in flow mediated arterial dilation. Further, the patients’ quality of life, established via a questionnaire, increased more with AIT than MCT. It is also interesting to note that informal comments from the patients found the varied procedure of AIT motivating, whereas, MCT was described as “quite boring.”

So, at the end of the day, in patients with post‐infarction heart failure, AIT was superior to MCT in improving LV remodeling, aerobic and anaerobic capacity, arterial function, and quality of life. But I guarantee, a nationwide survey of health care professionals at this point in time, would yield the opposite prediction which, emphasizes again, the importance of research awareness.

Now, the alert reader will have recognized a difference in the interval training employed by the Wisløff research team compared to much of the research referenced in this manuscript, it was HIIT but not SIT. The 4‐minute work intervals employed by the Wisløff protocol are longer than the suggested 60‐second maximum I have promoted throughout this discussion.

As I described earlier, when one is exercising at an intensity that allows for a 4‐minute effort, it is not an “all‐out” effort; so one may think that a true “all‐out” effort, lasting from 20‐60 seconds, would create a much greater stress on the heart and, in turn, be less safe. However, by now, you will hopefully have grasped the fact that giving an “all‐out” burst of effort has a similar stress to the heart, and cardiovascular system, to a “maximal” aerobic effort; the remainder of the energy required to go “all‐out” comes from one’s anaerobic system.

The interval training utilized by the Wisløff group elicited a 95% peak heart rate; one does not get to their maximum heart rate in 20‐60 seconds. Consequently, it is my contention that HIIT, utilizing intervals of 20‐60 seconds, would produce results to an equal or even greater extent than found by Wisløff et al.

An interesting case‐study from a colleague, Robert Mottram, PT., who employed a 12‐minute per week SIT protocol with his clients, lends support to my contention; as well as, of course, all the research already discussed in individuals without heart failure.

A patient that had been cleared to exercise by his physician, following multiple bypass surgery, undertook the 12‐minute per week SIT protocol (using a portable stepping device called The X‐iser® Machine that will be discussed later in more detail) and returned to his cardiovascular specialist for a follow‐up after about eight weeks of training.

After numerous tests, he was given a clean bill of health and his physician was particularly pleased with the improvements he had made with respect to his cardiovascular condition. His physician’s first assumption was that the medication he had prescribed was having its desired effect. Upon learning that the prescription had not been fulfilled, the physician, next, assumed that the prescribed diet was the reason for his successful outcome.

Finally, after learning that his discipline to change his diet was nonexistent, the physician eventually realized that the only factor that could have caused the improvements in his patient’s cardiovascular condition was the 12‐minute per week SIT program. His recommendation upon obtaining this information . . . continue what you are doing!

Numerous other studies also support the benefit of HIIT for deconditioned individuals. HIIT has been shown as an effective protocol for improving respiratory muscle strength and endurance in patients with chronic obstructive pulmonary disease (COPD)39. Sturdy et al. assessed the feasibility of high‐intensity respiratory muscle training utilizing eight weeks of interval training that consisted of three 20‐minute training sessions per week.

Each 20‐minute session comprised seven 2‐minute bouts of breathing against a constant inspiratory threshold load with each bout separated by one minute of unloaded recovery. The inspiratory load was progressively incremented throughout the eight weeks of training. This protocol was used because it had been previously shown that improvement in respiratory muscle function from respiratory muscle training was dependent upon the magnitude of the training load and an interval training protocol would allow for higher training loads.

At the end of the study significant improvements were observed in respiratory muscle strength (32%) and endurance (56%) demonstrating that high‐intensity, interval‐based respiratory muscle training is feasible in patients with moderate‐ to‐severe COPD. Subsequent studies have also shown a benefit of HIIT to COPD patients40‐42 and it has also been demonstrated that HIIT is an effective protocol for, and can be well tolerated by patients with peripheral arterial disease. So, again, HIIT provides great benefit to the participant even in cases of severely compromised levels of conditioning.