A new study published in the Journal of Sport and Health Science provides evidence that cardiorespiratory fitness tends to be higher in countries with greater gender equality and higher levels of human development. The findings suggest that social conditions and national policies may shape people’s access to physical activity and their ability to maintain physical health.

There is strong scientific agreement that being physically active helps prevent disease and supports long-term health. Regular movement improves cardiorespiratory fitness, which refers to the ability of the heart and lungs to supply oxygen to the muscles during activity. Higher levels of cardiorespiratory fitness are linked with a lower risk of death from all causes, including heart disease and cancer.

However, researchers have long suspected that fitness levels are not solely determined by individual choices. Factors such as where people live, their income, access to safe outdoor spaces, social support, and even national policies may influence how active they can be. Gender may also play a role. In many societies, women face more barriers to physical activity than men, including caregiving responsibilities, fewer sports opportunities, or concerns about safety.

Despite these observations, the relationship between fitness levels and broader societal factors has not been studied in depth. Previous research has focused mostly on children or used indirect measures of fitness. The current study aimed to close this gap by examining how cardiorespiratory fitness in adults relates to two specific indicators: the Human Development Index, which includes education, income, and life expectancy, and the Gender Inequality Index, which measures disparities between men and women in areas such as health, political power, and the labor market.

The researchers reviewed thousands of studies and selected 95 that included direct measurements of peak oxygen uptake, a key marker of cardiorespiratory fitness, in healthy adults. This measurement, often referred to as VO2peak, is collected during a maximal exercise test in which participants exert themselves on a treadmill or bicycle while their breathing is analyzed. These tests are considered the gold standard for measuring fitness.

The final dataset included over 119,000 adults, with roughly 58 percent men and 42 percent women. The participants came from a diverse group of countries including the United States, Brazil, Germany, China, and Japan. Each study was matched with the relevant Human Development Index and Gender Inequality Index scores for the country and year in which data were collected.

The researchers found that fitness tends to decrease with age and that, on average, women had lower VO2peak values than men. However, when comparing countries, they noticed a pattern: adults in countries with higher levels of human development and lower levels of gender inequality had higher fitness levels.

The relationship between development and fitness was especially pronounced among women. Women living in countries with high human development scores had higher VO2peak levels across all age groups. For men, this trend was mainly observed in those under 40 years old. This suggests that women may benefit more from living in supportive and equitable societies when it comes to maintaining physical fitness.

A similar pattern emerged when looking at gender inequality. In countries with less gender inequality, both men and women had higher cardiorespiratory fitness, but the effect was again stronger for women. The difference was most notable among women under 40. Young women living in countries with low gender inequality had fitness levels that were on average 6.5 mL/kg/min higher than those in countries with high gender inequality. This difference is large enough to matter for health, as even small increases in VO2peak are linked with reduced risks of chronic disease and early death.

These results suggest that policies and social structures that promote equality and development may indirectly support better health by enabling more people, especially women, to engage in regular and vigorous physical activity.

Although this study includes one of the largest datasets of directly measured VO2peak values ever compiled, it is not without its limitations. The researchers were only able to include studies that used standardized testing methods and reported data by age and sex. This meant that many large population studies that estimated fitness indirectly had to be excluded. While this choice improved the reliability of the results, it also limited the diversity of countries included.

Most of the data came from countries with medium to high development levels. There was a lack of data from countries with low development scores, which makes it difficult to understand the full range of global fitness patterns. Additionally, many of the studies did not provide information on participants’ race, ethnicity, or socioeconomic background. These gaps are important because they could affect how fitness relates to social inequality in different contexts.

The authors suggest that future research should aim to collect more data from underrepresented populations and countries. They also recommend investigating how specific social policies, such as workplace fitness programs or community sports initiatives, might improve cardiorespiratory fitness, especially for women and vulnerable groups.

The study, “Human development and gender inequality are associated with cardiorespiratory fitness: A global systematic review of VO2peak,” was authored by Nicolas J. Pillon, Joaquin Ortiz de Zevallos, Juleen R. Zierath, and Barbara E. Ainsworth.