Cardiorespiratory Fitness Is Impaired in Type ۱ and Type ۲ Diabetes

Background: Cardiorespiratory fitness (CRF) is a key indicator of overall health and an important predictor of cardiovascular morbidity and mortality. Individuals with diabetes mellitus, including both type ۱ diabetes (T۱D) and type ۲ diabetes (T۲D), often exhibit reduced CRF compared with healthy individuals. Impairments in glucose metabolism, vascular function, and mitochondrial capacity may contribute to diminished aerobic performance in these populations. Understanding the extent and mechanisms of CRF impairment in individuals with diabetes is important for developing effective exercise and rehabilitation strategies. Methods: This study was conducted as a narrative review of clinical and experimental studies investigating cardiorespiratory fitness in individuals with type ۱ and type ۲ diabetes. Relevant literature published between ۲۰۰۵ and ۲۰۲۵ was identified through systematic searches of PubMed, Scopus, and Web of Science databases. Eligible studies included adults or adolescents with T۱D or T۲D in whom CRF was assessed using standardized measures such as maximal oxygen uptake (VO₂max), peak oxygen uptake (VO₂peak), or graded exercise testing. Comparisons with healthy control groups were considered when available. Results: Evidence from the reviewed studies consistently indicates that individuals with both T۱D and T۲D demonstrate lower CRF compared with non‑diabetic individuals. Reduced VO₂max or VO₂peak values have been reported across different age groups and levels of physical activity. Several physiological mechanisms have been proposed to explain these impairments, including reduced cardiac output, endothelial dysfunction, impaired skeletal muscle oxidative capacity, and altered autonomic regulation. In addition, factors such as glycemic control, disease duration, body composition, and physical inactivity may further influence CRF levels. Conclusion: Cardiorespiratory fitness is commonly impaired in individuals with both type ۱ and type ۲ diabetes. Reduced aerobic capacity may contribute to increased cardiovascular risk and decreased functional capacity in these populations. Exercise training programs aimed at improving aerobic fitness should be considered an essential component of diabetes management. Further research is needed to clarify the mechanisms underlying CRF impairment and to identify optimal exercise interventions for improving fitness in individuals with diabetes.

کلیدواژه ها:

Cardiorespiratory Fitness ، Type ۱ Diabetes ، Type ۲ Diabetes ، VO₂max ، Exercise Physiology