Abstract
Background Cardiorespiratory fitness (CRF) is a strong predictor of cardiovascular morbidity and mortality. This study aimed to describe age- and sex-specific reference values for CRF in healthy adults in Kazakhstan and to examine age-related changes in key physiological parameters, including peak heart rate and body mass index.Methods The research included 3271 nonsmoking adults aged 20 to 59 years, free of health issues, who performed symptom-limited incremental cardiopulmonary exercise testing on a cycle ergometer between 2018 and 2025. The highest 30-s average value from exercise testing defined peak oxygen uptake (VO2 peak).Results VO2 peak were lower in older age groups in both sexes. In men, VO2 peak values was 43.4 ± 7.41 mL/kg/min during ages 20–29 and 38.3 ± 6.32 mL/kg/min during ages 50–59. In women, corresponding VO2 peak values were 39.2 ± 6.49 and 30.8 ± 5.78 mL/kg/min. Peak heart rate also was lower in older ages (men: 174 ± 11 to 142 ± 8 bpm; women: 179 ± 10 to 143 ± 11 bpm). Simple linear regression results showed that age was a significant predictor of VO2 peak, BMI, and peak heart rate in both men and women (p < .001).Conclusion This study provides the first nationally relevant descriptive data on CRF reference values for Kazakh adults.