Metabolic and physiological responses to graded exercise testing in individuals with type 1 diabetes using insulin pump therapy.

McCarthy OM; Birch Kristensen K; Christensen MB; Schmidt S; Ranjan AG; Nicholas C; Bain SC; Nørgaard K;
Bracken R;

Diabetes, obesity & metabolism [Diabetes Obes Metab] 2022 Dec 08.
Date of Electronic Publication: 2022 Dec 08.

Aims: 1) To profile acute glycaemic dynamics during graded exercise testing (GXT) and 2) explore the influence of glycaemic indicators on the physiological responses to GXT in adults with T1D using insulin pump therapy.
Methods: This was a retrospective analysis of pooled data from four clinical trials with identical GXT protocols. Data was obtained from 45 adults with type 1 diabetes using insulin pumps ([30 females], HbA 1c : 59.5±0.5 mmol.mol -1 [7.6±1.0 %], age: 49.7±13.0 years, diabetes duration: 31.2±13.5 years, V̇O 2peak : 29.5±8.0 mL.min -1 .kg -1 ). Integrated cardiopulmonary variables were collected continuously via spiroergometry. Plasma glucose (PG) was obtained every three minutes during GXT as well as the point of volitional exhaustion. Data were assessed via general linear modelling techniques with age and gender adjustment. Significance was accepted at P ≤0.05.
Results: Despite increasing duration and intensity, PG concentrations remained similar to rest values (8.8±2.3 mmol.L -1 ) throughout exercise (p=0.419) with an overall change of +0.3±1.1 mmol.L -1 . Starting glycaemia bore no influence on subsequent GXT responses. Per 1% increment in HbA 1c there was an associated decrease in V̇O 2peak of 3.8 mL.min -1 .kg -1 (p<0.001) and power peak of 0.33 -1 (p<0.001) concomitant with attenuations in indices of peripheral oxygen extraction ([O 2 pulse] -1.2 mL.beat -1 , p=0.023).
Conclusion: In adults with long-standing type 1 diabetes using insulin pump therapy, circulating glucose remains stable during a graded incremental cycle test to volitional exhaustion. Glycaemic indicators are inversely associated with aerobic rate, oxygen economy and mechanical output across the exercise intensity spectrum. An appreciation of these nexuses may help guide appropriate decision making for optimal exercise management strategies.