Research roundup: the true power of intensity revealed

Can training twice as hard offer four times the benefit?

We know any movement is good movement, and you don’t need to exhaust yourself to gain health benefits from exercise. But new research suggests that when you increase intensity, the payoff can be far greater, especially for heart health.

A large-scale study analyzed wearable data from more than 73,000 adults and reviewed outcomes related to all-cause mortality and cardio metabolic health. The findings were striking. Each minute of vigorous-intensity activity delivered the same benefit as four to nine minutes of moderate exercise, or more than 50 minutes of light activity. In other words, vigorous exercise was at least four times more powerful than moderate exercise for protecting the heart.

This debunks the long-held belief that one minute of vigorous exercise equals two minutes of moderate activity. It also raises questions about current World HealthOrganization guidelines, which suggest 150–300 minutes of moderate activity delivers similar benefits to 75–150 minutes of vigorous activity. According to Bryce Hastings, Les Mills Head of Research, “What we now know is that training at a higher intensity is far more potent than we once thought.”

So … if you’re short on time, go big on intensity

This new research supports earlier findings that brief, intense workouts can drive outsized health gains. An earlier review highlighted how just 20 minutes of High-Intensity Interval Training (HIIT) can create health benefits that are on par with a whole week of workouts. Some studies suggest even smaller doses work wonders. Four minutes of HIIT, three times per week for 12 weeks, has been shown to deliver similar improvements to 45-minute moderate-intensity sessions performed three times a week.

The transformative power of HIIT is not limited to the physical arena. There is plenty of science spelling out the perks of hitting it hard – including improved mental resilience, sharper focus, and stronger stress management.
CHECK OUT THE HIIT LIST‍

10 minutes of intense exercise can stimulate an anti-cancer effect

A short burst of high‑intensity exercise won’t just help your cardiovascular fitness; science shows it can spark anti-cancer activity too. The new study reveals how just 10 minutes of hard physical activity can release a surge of beneficial molecules into the bloodstream.

When lab researchers exposed these exercise‑driven blood changes to bowel cancer cells, they noted widespread genetic changes. More than 1,300 genes shifted their activity, including those involved in repairing damaged DNA, regulating energy use, and limiting tumor development. Many of the molecules elevated by exercise are also known to reduce inflammation, support healthy blood vessels, and improve metabolic function.

The most striking thing is how quickly these benefits appear. A single 10-minute workout was enough to send powerful signals to the body and initiate these protective responses.

These findings add to the evidence that physical activity is an important part of cancer prevention.

‍

Yes, you can have too much of a good thing

While vigorous training delivers clear benefits, more is not always better. Research suggests that spending more than 30 to 40 minutes with your heart rate above 90 percent of its maximum can increase the risk of overreaching and fatigue. And now, a large 2026 cohort study reinforces the value of balance, tracking the exercise habits of 110,000 adults in the US over 30years. Those who spread their training across a variety of activities saw greater health and longevity benefits and were 19% less likely to die than those who focused on just one type of exercise. As Dr Jinger Gottschall explains, vigorous intensity is valuable, but moderate‑intensity cardio also plays a critical role. “Moderate-intensity has been tested in countless studies and provides multiple benefits in terms of cardiovascular health, cholesterol levels, triglycerides, and fasting glucose.” She adds that effective exercise doesn’t just come down to cardio training. “Research shows a combination of cardio, strength and flexibility training fosters long-term engagement and results. We also know that injury incidence is reduced when you balance cardioexercise with flexibility and strength training,” explains Gottschall.

What counts as vigorous exercise?

Vigorous exercise is any activity that makes you breathe hard, raises your heart rate significantly, and makes sustained conversation difficult. It is typically when your heart rate hits between 70 – 85% of its max.

Running is a classic example, and it was the activity tested in much of the 2025 meta analysis. But it is far from the only option. HIIT, which involves alternating between high intensity (where your heart rate reaches above 90% max) and rest periods, is one of the most effective and accessible ways to train at a vigorous intensity.

HIIT workouts like LES MILLS GRIT™ and LES MILLS SPRINT™ are designed to place you firmly in the high-intensity zone. Find a workout near you or work out at home with LES MILLS+.

‍