Blood Glucose Responses during Cardiopulmonary Incremental Exercise Testing in Type 1 Diabetes: A Pooled Analysis

• Published in: Medicine and science in sports and exercise 2021-06, Vol.53 (6), p.1142-1150
• Main Authors: MCCARTHY, OLIVIA, PITT, JASON, WELLMAN, BEN, ECKSTEIN, MAX L., MOSER, OTHMAR, BAIN, STEPHEN C., BRACKEN, RICHARD M.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Anaerobic Threshold; Blood Glucose - metabolism; Diabetes Mellitus, Type 1 - blood; Exercise Test - methods; Female; Glycated Hemoglobin - metabolism; Heart Rate; Humans; Lactic Acid - blood; Male; Middle Aged; Retrospective Studies; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000002584

PURPOSETo determine the glycemic responses to cardiopulmonary exercise testing (CPET) in individuals with type 1 diabetes (T1D) and to explore the influence of starting blood glucose (BG) concentrations on subsequent CPET outcomes. METHODSThis study was a retrospective, secondary analysis of pooled data from three randomised cross-over trials using identical CPET protocols. During cycling, cardiopulmonary variables were measured continuously, with BG and lactate values obtained minutely via capillary earlobe sampling. Anaerobic threshold (AT) was determined using ventilatory parameters. Participants were split into (i) euglycemic ([Eu] >3.9 to ≤10.0 mmol.L, n=26) and (ii) hyperglycemic ([Hyper] >10.0 mmol.L, n=10) groups based on pre-exercise BG concentrations. Data were assessed via general linear modelling techniques and regression analyses. P values of ≤0.05 were accepted as significant. RESULTSData from thirty-six individuals with T1D (HbA1c; 7.3±1.1% [56.0±11.5 mmol.mol]) were included. BG remained equivalent to pre-exercise concentrations throughout CPET, with an overall change in BG of -0.32±1.43 mmol.L. Hyper had higher HR at peak (+10±2 bpm, p=0.04) and during recovery (+9±2 bpm, p=0.038) as well as lower O2 pulse during the cool down period (-1.6±0.04 mL.beat, p=0.021). BG responses were comparable between glycemic groups. Higher pre-exercise BG led to greater lactate formation during exercise. HbA1c was inversely related to time to exhaustion (r=-0.388, p=0.04) as well as peak power output (r=-0.355, p=0.006) and O2 pulse (r=-0.308, p=0.015). CONCLUSIONThis study demonstrated 1) stable BG responses to CPET in patients with T1D 2) though pre-exercise hyperglycemia did not influence subsequent glycemic dynamics, it did potentiate alterations in various cardiac and metabolic responses to CPET 3) HbA1c was a significant factor in the determination of peak performance outcomes during CPET.