Rondaij T; Institute of Physiology, University of Ljubljana,  Slovenia.
Jesih J; Dovc K; Battelino T; Potocnik N

Frontiers in Endocrinology. 17:1813865, 2026.

Introduction: Type 1 diabetes (T1D) is associated with an increased risk
of cardiovascular and autonomic complications. Although cardiopulmonary
exercise testing (CPET) is a valuable tool for assessing cardiorespiratory
function, data on physiological response to maximal exertion in
adolescents with T1D remain limited and inconsistent. This study aimed to
compare cardiovascular, respiratory, metabolic, and microvascular
responses to CPET in adolescents with T1D and healthy peers.

Methods: Sixteen participants aged 11-16 years (eight with T1D and eight
healthy controls), matched for anthropometric characteristics, underwent
CPET on a cycle ergometer. Respiratory gas exchange, heart rate, heart
rate variability, blood pressure, blood glucose, lactate concentration,
skin blood flow, skin temperature, and cutaneous vascular conductance were
measured at predefined time points during rest, exercise, and recovery.
Blood glucose, lactate concentration, and skin microvascular variables
were assessed at rest and during recovery.

Results: Adolescents with T1D demonstrated a significantly lower
VO2/power output slope and a higher ventilatory equivalent for oxygen at
maximal effort, suggesting altered oxygen uptake efficiency. Maximal power
output and maximal oxygen consumption did not differ between groups. Heart
rate responses and heart rate variability were similar throughout testing.
However, finger skin blood flow and cutaneous vascular conductance were
significantly lower in the T1D group at rest and during recovery.

Conclusion: Adolescents with T1D showed preserved cardiovascular function
and comparable overall exercise capacity to healthy peers, despite subtle
impairments in oxygen utilization and reduced skin microvascular function.
These findings indicate that even at a young age, T1D is associated with
altered metabolic, respiratory, and microvascular responses to maximal
exercise. The results suggest that peripheral, rather than central
mechanisms may underlie these differences, potentially involving glucose
levels or synthetic insulin effects on vascular endothelium.