We all agree that exercise is good for you: but how hard and how often should you push yourself to get the best results?

A large study looking at the link between habitual physical activity and fitness levels shows that "moderate-vigorous physical activity" is the most efficient way of boosting fitness.

Gleaned from cardiopulmonary exercise tests (CPETs) and data from fitness-tracking wearables worn by 2,070 participants, the finding still held even when factoring in variables like age, sex, obesity, and cardiovascular risk, scientists report.

In terms of achieving changes in fitness, each minute of extra moderate-to-vigorous exercise on average was equivalent to about 3 minutes of walking, and equivalent to about 14 minutes less sedentary time. What's more, extra time exercising and increasing step counts each day seem to be able to offset the negative effects on fitness of being sedentary.

"By establishing the relationship between different forms of habitual physical activity and detailed fitness measures, we hope that our study will provide important information that can ultimately be used to improve physical fitness and overall health across the life course," says cardiologist Matthew Nayor from Boston University.

CPETs measure peak oxygen uptake or VO2, an indication of how much oxygen the body can use during exercise. The more oxygen the body can take on and process as it works, the higher the level of aerobic fitness.

It turns out that moderate-vigorous physical activity (or MVPA) is best for boosting VO2, based on these CPET results. Anything that gets your heart beating faster and your breathing heavier counts as MVPA – so a brisk walk or a bike ride, for example.

It's worth noting that the study focused on levels of fitness, rather than any health-related outcomes – but fitness is closely linked to a reduced risk of numerous health issues, including diabetes, cancer, and cardiovascular disease.

"Therefore, improved understanding of methods to improve fitness would be expected to have broad implications for improved health," says Nayor.

While it's no surprise that MVPA is good for your fitness, few previous studies have analyzed both physical activity levels and aerobic fitness as precisely as this research does, across so many people and at the same time.

As the study participants were part of a long-term research project (the Framingham Heart Study), the team was able to compare two separate datasets from the same people, eight years apart, to see the long-term impact of regular exercise.

There are limitations to the study too, because exercise affects us all differently, and this research looks at a bunch of similar middle-aged people from the same party of the world. Even so, it's a clear indication of the fitness and health benefits of MVPA.

"These findings are consistent with the notion that different forms of physical activity (especially MVPA) are associated with cardiorespiratory fitness in the general public regardless of one's age, sex, BMI, or cardiovascular disease status," the researchers explain.

The research has been published in the European Heart Journal.