Participants in a study on high-intensity interval training used a variety of methods, from rowing machines to sports like squash. Few of those who chose a HIIT program were still working out regularly after a year.

John Mahoney / Montreal Gazette files

With study after study proving that high-intensity interval training (HIIT) workouts are an express pass to improved fitness, it’s clear that short, high-energy bouts of exercise are just as effective as longer, less intense workouts.

But as tempting as it is to give up workouts of 30 minutes or more in favour of those that take less than half the time, there’s one feature of HIIT workouts that may cause the average Joe and Jill to think twice before jumping on the bandwagon.

They hurt.

For some, the promise of short-term pain for long-term gain is a motivating factor. But for most, the prospect of sweating through a tough workout, even a short one, is enough to make them avoid pulling on their gym shorts altogether. That makes one wonder about HIIT’s potential to change how the rest of us — the out of shape, overworked, overweight and over the hill — do our exercise.

It doesn’t help that most of the research surrounding HIIT has been performed in a lab setting and that most study subjects are university students, which can hardly be considered real-world conditions. So while there’s little debate about the potential of HIIT to get the same results as conventional exercise, it’s a moot point if the workouts are so unpalatable that only a few tough it out long enough to reap the benefits.

Understanding the potential for HIIT to change the way we do our workouts, but also the difficulties in sticking with it — especially for the long haul — a team of researchers from New Zealand gathered 250 overweight adults and asked them to choose either a three-times-a-week HIIT routine or more traditional moderate-intensity workout, and sustain it, unsupervised, for 12 months.

The researchers were interested not just in how many exercisers voluntarily chose HIIT over a moderate-intensity program, but also whether the HIIT exercisers were likely to still be exercising a year later and what kind of physiological changes occurred over the 12-month period.

Forty-two per cent of the 250 exercisers (104) chose HIIT and were offered a one-time training session where they performed three intervals of up to 30 seconds while keeping their intensity at 80 to 90 per cent of their maximum heart rate — a rating of eight or greater on a 10-point scale of perceived exertion. (Interestingly, 12 exercisers were unable to sustain the required level of intensity and 41 were able to work out at more than 90 per cent of their maximum heart rate.) The balance of the study subjects (146) chose the moderate-intensity workout.

Baseline fitness and health markers (height, weight, waist circumference, blood pressure, cholesterol) were obtained at the start of the study, with progress monitored at six and 12 months. Questionnaires were also administered to assess adherence and enjoyment. HIIT intensity was verified by way of heart rate monitors every three months to ensure participants were working out at the high end of their max heart rate.

At the end of 12 months, only 24 of the 104 HIIT exercisers were still working out regularly (at least twice a week). Another 17 were considered intermittent exercisers. The majority — 60 per cent — fell off the HIIT bandwagon completely.

Those who did adhere to the HIIT routine were more likely to be male and spent 21 to 24 minutes a week exercising at an intensity greater than 80 per cent of their max heart rate. They used a variety of methods, including hills, stairs, cardio equipment (stationary bikes, rowing machines, elliptical trainers), sports like squash, and home, gym or app-based circuit workouts.

Not surprisingly, those who stuck with the HIIT program had slimmer waists, less fat and healthier cholesterol levels than those who worked out less. But when it came to how much they enjoyed the workouts, the HIIT enthusiasts scored lower than those who didn’t exercise regularly.

As for how the three-times-a-week HIIT habit compared to 30 minutes of moderate-intensity exercise most if not all days of the week in terms of overall fitness and health, after 12 months there was no difference between them.

“Our findings demonstrate that the majority of participants proved able to perform HIIT at an adequate intensity … under supervision, but much smaller numbers met our participation targets of at least twice per week, particularly over the longer term,” said the study’s authors. “Thus it appears that HIIT can be effectively undertaken by most overweight and obese people with minimal training, but that long-term adherence remains a significant challenge.”

Given the results, it could be that HIIT workouts aren’t so much a way of life, but an option for days when time is tight and/or energy levels are high. But that’s not the only take-home message: it’s notable that most overweight study subjects who chose HIIT were capable of working out at near maximum effort for short bursts, proving that we’re often capable of more than we think.



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