If the thought of pumping iron or holding a plank doesn’t put a spring in your step, maybe the latest exercise trend to dominate social media will: Japanese interval walking.
The idea is simple: alternate between three minutes of fast and three minutes of slow walking, ideally for 30 minutes at a time.
“The fast walking pace is typically fast [enough] that you are not able to speak in long sentences,” said Dr Kristian Karstoft, an associate professor at the University of Copenhagen, who has studied the method. “And then the slow intervals are so slow that you are able to recover.” He added that people could often find it challenging to walk slowly enough during these intervals.
Putting the approach to the test, I hit the area around King’s Cross in central London.
I began striding out, as though late for a train. Three minutes later my watch beeped and I slowed down, pottering along as if searching for a dropped earring. Another beep and I sped up once more, arms swinging.
I was slightly worried what passersby might think of my erratic pace – I suspect I looked as if I needed the loo but dared not risk a jog. Already I was regretting attempting this without my two flat-coated retrievers: if they were in tow I could at least have blamed my dawdling intervals on their lamp-post sniffing.
After 30 minutes I felt warm, but not exactly out of puff.
Karstoft said the approach was particularly suited to people prone to running injuries, as walking is less hard on the joints, or middle-aged or older adults who do not do much regular training. People who were already pretty fit, he said, would need to jog or run for intervals to experience similar benefits.
The regime is similar to high-intensity interval training. People who are less active should start with regular walking and then try interval walking. Photograph: David Levene/The Guardian
The regime is similar to high-intensity interval training (Hiit). Dr Shaun Phillips, a senior lecturer in sport and exercise physiology at the University of Edinburgh, said: “High-intensity exercise can give similar benefits to moderate-intensity exercise but in a shorter time frame [or] with a lower volume of exercise. The use of high-intensity places a bigger stimulus on the body to adapt.”
But not everyone can keep up a furious pace, even when walking. Phillips said people who were less active or fit should start with normal walking to get into the swing of it, and then try interval walking.
“A way to maximise your ability to do high-intensity training is to do it with the alternating intensities, meaning the interval-based training,” Karstoft said.
While high-intensity interval walking has recently become popular on TikTok, where enthusiasts share videos of themselves earnestly striding around town parks, the idea goes back more than 20 years when scientists in Japan began studying it in middle-aged and older adults.
According to one Japanese study, involving an analysis of data from 139 healthy participants with an average age of 63, people who did high-intensity interval walking on four or more days a week over a five-month period increased their peak aerobic capacity, indicating an improvement in physical fitness. What’s more, these improvements were greater than for participants who had undertaken a walking regime of continuous, moderate intensity or who did no walking training.
The study also suggested high-intensity interval walking may reduce blood pressure and increase the strength of the knee joint.
A small randomised control trial by Karstoft and his colleagues found the approach could also benefit people with type 2 diabetes, including by improving their glycaemic control.
Four months of high-intensity interval walking was associated with greater benefits than continuous walking, even though the overall energy expenditure and mean training intensity were the same.
“Typically with interval walking, we’ve seen a gain in fitness level of around 15% to 20% compared to trivial or no improvements in fitness levels when subjects are doing the continuous walking [or no walking],” Karstoft said. “We’ve seen improvements in body composition with an average weight loss during four to six months of training of around three to five kilograms, mainly due to fat mass.”
A review on the topic published by Karstoft and his colleagues last year concluded that Japanese interval walking was a feasible and effective training regimen for older, fragile people. “It significantly enhances fitness, muscle strength, and health markers,” they wrote.
But, Phillips acknowledged, while some people like the challenge of higher intensity periods of exercise, others hate it.
“We’re certainly never going to come to the ideal exercise protocol that everybody loves,” he said. “It’s about trying to give as many workable and beneficial options as possible that people can pick from.”