Determinants of VO2 peak responsiveness to aerobic exercise training in adults with Type 2 diabetes: the PROTECTION study

Abstract

Aims In individuals with Type 2 diabetes (T2D), aerobic exercise training improves cardiorespiratory fitness (VO 2 peak), a key determinant of cardiovascular risk and mortality. However, substantial interindividual variability exists in VO 2 peak responsiveness, and its determinants remain poorly characterized. Methods and results A total of 108 adults with T2D participated in a 26-week supervised, high-volume, moderate-intensity cycling programme (three sessions/week). VO 2 peak was assessed by cardiopulmonary exercise testing pre-and post-intervention. Based on the individual technical error of measurement (mean: 1.3 mL/kg/min) and the minimal clinically important difference (3.5 mL/kg/min), participants were divided into three groups: non-responder (n = 14), responders (n = 33), and high-responders (n = 41). Baseline demographic, clinical characteristics, as well as physical activity and sedentary behaviour were compared. Determinants of change in VO 2 peak were identified using univariate and multivariable LASSO regression analyses. Eighty-eight participants completed the exercise programme (59.8 ± 9.2 years, 64% male). VO 2 peak improved by +3.6 ± 2.5 mL/kg/min (+17%). Compared with non-responders, high-responders exhibited lower fat mass, lower insulin resistance, and lower baseline fitness. Changes in VO 2 peak were negatively associated with female sex, smoking status, anthropo-metric measures, insulin resistance, and beta-blocker or GLP-1 agonist use. In contrast, positive associations were found with lung function, muscle strength, and haemoglobin. In multivariable regression, fat mass (%) and insulin resistance emerged as key baseline predictors for VO 2 peak responsiveness. Conclusion A 26-week moderate-intensity cycling programme improved VO 2 peak in adults with T2D, although responses varied widely. Initiating exercise early after diagnosis of (pre)diabetes, along with interventions improving body composition, may enhance improvements in cardiorespiratory fitness.-Lay summary This study found that a 6-month, supervised cycling programme significantly improved cardiorespiratory fitness in adults with Type 2 diabetes, although individual responses to exercise varied widely. Maintaining a healthy body composition and initializing the exercise programme early after diagnosis may enhance the benefits of structured exercise.