A Finnish study reveals that physically active adults with well-managed, uncomplicated type 1 diabetes exhibit exercise test responses similar to healthy controls, challenging previous assumptions about diabetes-related cardiovascular impairments.
A new study in Physiological Reports suggests that physically active adults with long-standing, uncomplicated type 1 diabetes can respond to maximal exercise much like matched healthy volunteers. In a tightly screened Finnish cohort, researchers found no meaningful differences in oxygen uptake, breathing patterns, heart rate, stroke volume or cardiac output during a graded cycling test. The result cuts against several earlier reports that linked type 1 diabetes with lower peak fitness and altered cardiovascular responses, especially in people whose blood sugar control, body composition or complication status differed from those in the new trial.
The University of Eastern Finland team designed the study to remove many of the factors that can cloud exercise testing in diabetes. Participants with neuropathy, kidney disease, retinopathy, hypertension, smoking history or cardiovascular medication were excluded, leaving 15 adults with uncomplicated type 1 diabetes and 33 matched controls. On the day of testing, volunteers completed an incremental cardiopulmonary exercise test, with breathing gases, heart rhythm and stroke volume tracked throughout. The researchers also compared the full response at rest, at two ventilatory thresholds and at peak exertion, rather than relying only on the final score.
That broader view matters because earlier research has often painted a less reassuring picture. Pooled analyses published in 2021 found lower peak oxygen uptake and altered heart-rate responses in adults with type 1 diabetes, while another pooled analysis reported that higher pre-exercise glucose levels were associated with higher peak heart rates and lower oxygen pulse during recovery. Other studies have shown that cardiovascular autonomic neuropathy is linked to poorer exercise tolerance, and that higher HbA1c levels or less favourable body composition can be associated with weaker performance on cardiopulmonary testing. The Finnish paper argues that those differences may reflect complications, fitness levels or metabolic control rather than type 1 diabetes alone.
In this study, the exercise traces for the diabetes group and the control group rose in parallel. Stroke volume increased early and then levelled off as heart rate carried the remaining rise in cardiac output, which is the expected pattern in healthy, active adults. Ventilation, tidal volume, oxygen uptake and other gas-exchange measures also followed the same trajectory in both groups, with no statistically meaningful group-by-stage differences. The authors caution that the sample was small and that the findings do not prove equivalence, but they say the work supports a more nuanced view: in adults with uncomplicated type 1 diabetes who stay active and avoid major complications, the heart and lungs may behave normally under maximal stress.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
