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Jan. 8, 2025
Recent research has highlighted the benefits of intense exercise, and while it might be tough to love, your body certainly does. A growing body of evidence shows that pushing your body to its limits in short bursts can yield tremendous health benefits. Even if you’re not a fan of high-intensity exercise, the science is compelling: it can reduce your risk of death, boost brainpower, and help stave off chronic diseases.
A study published in September 2024 found that high-effort physical activity reduced the risk of death from any cause, while a 2024 August study revealed that high-intensity interval training (HIIT) helped stroke survivors improve their cardiovascular fitness rapidly. Other studies have found that intense exercise can curb hunger and reduce the risk of the most aggressive types of cancer.
According to Martin Gibala, PhD, professor of kinesiology at McMaster University in Ontario, even a few minutes of intense exercise can make a difference. His 2022 study found that accumulating just 4.4 minutes of vigorous physical activity per day significantly reduced the risk of death from cancer, cardiovascular disease, and other causes by up to 34%.
But what exactly makes intense exercise so beneficial? It starts with a biochemical response that triggers a cascade of changes in your body, remodeling your metabolism and physiology to improve cardiovascular fitness—one of the most important indicators of long-term health.
Defining “High Intensity”
The Centers for Disease Control and Prevention (CDC) defines vigorous exercise based on intensity. Absolute intensity measures the metabolic equivalents of task (METs) with a value of 6.0 or higher considered vigorous. Skipping rope, for example, has a MET value of 11. You can also gauge intensity through heart rate, where vigorous intensity kicks in at about 80% of your maximum heart rate.
Relative intensity is measured by how hard the exercise feels. If you rate your effort at 7 or 8 on a 10-point scale, or struggle to string more than a few words together, you’re likely in the vigorous zone.
The Science Behind Intensity
Intense exercise rapidly depletes your muscles’ stores of adenosine triphosphate (ATP), which is their primary energy source. This depletion activates a protein called AMPK, which triggers the production of another protein, PGC-1a. PGC-1a encourages the creation of more mitochondria, the powerhouses of cells that produce ATP. The more mitochondria you have, the more energy your muscles can generate.
In addition to increasing energy production, intense exercise stimulates faster muscle repair, expands capillary networks, and strengthens the heart, allowing it to pump more blood with each beat. While moderate-intensity exercise can lead to similar adaptations, these benefits manifest more quickly with high-intensity efforts.
Intensity and Muscle Growth
For those interested in strength training, intensity is also key. Whether you’re lifting heavy weights or lighter ones to failure, intensity dictates how much your muscles grow and strengthen. According to Brad Schoenfeld, PhD, professor of exercise science at Lehman College, lifting with higher intensity leads to better gains in muscle size, especially for more experienced lifters.
Even for those who aren’t focused on muscle growth, intensity matters. Engaging in short bursts of high-intensity exercise can deliver the same cardiovascular and metabolic benefits as longer, moderate-intensity workouts, without the extended time commitment. It’s especially useful for people who prefer quick, efficient workouts.
Time-Efficient High-Intensity Exercise
One of the biggest advantages of high-intensity exercise is that it doesn’t require much time. Studies show that even 11 minutes of vigorous bodyweight exercises done three times a week can improve cardiovascular fitness. Another study found that “weekend warriors” who fit a week’s worth of exercise into one or two intense sessions still saw significant reductions in mortality risk.
For those looking to incorporate high-intensity exercise into their daily routine, “exercise snacking” is another option—short, intense bursts of activity done at random times throughout the day.
The Key to Success: Consistency
Ultimately, the most important factor for reaping the benefits of high-intensity exercise is consistency. Gibala advises that the key is getting outside your comfort zone, but not so far that you risk injury. If you can consistently challenge yourself—even for just a few minutes a day—your body will thank you in the long run.
