Exercising in Hot Conditions: How Does it Effect Blood Glucose in People With T1D (T1D-Heat)

The Effect of Acute Heat Exposure on Glucose Use During Moderate-intensity Exercise in People With Type 1 Diabetes

A randomised, crossover, counterbalanced repeated measures study will be conducted to examine the effect of acute heat exposure on rate of change in blood glucose concentration during 40 minutes of moderate-intensity exercise and for 30 minutes after exercise. Participants will complete two experimental conditions during two separate laboratory visits, with the order of conditions randomised. One condition will be a temperate condition of 20°C with 50% relative humidity (Temperate), the other will be 40°C with 50% relative humidity (Heat). Visits will be identical, including time of day, except for the condition. Visits will be separated by 24h. Testing will take place in the laboratories of the Research Institute for Sport and Exercise Sciences at Liverpool John Moores University.

Study Overview

• Status: Recruiting
• Conditions: Type 1 Diabetes (T1D)
• Intervention / Treatment: Behavioral: Exercise

• Study Type: Interventional
• Enrollment (Estimated): 38
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Matthew Cocks, PhD; Phone Number: 447540191292; Email: m.s.cocks@ljmu.ac.uk

Study Locations

• United Kingdom
  • Liverpool, United Kingdom, L33AF
    • Recruiting
    • Liverpool John Moores University
    • Contact: Matthew Cocks, PhD; Phone Number: 4407540191292; Email: m.s.cocks@ljmu.ac.uk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• T1D diagnosis more than 1 years ago (to ensure participants are out of the honeymoon period)

• Using insulin therapy with multiple daily injections (MDI), insulin pump (pump), or hybrid closed-loop (HCL)

  o If using a HCL system have experience of using a pre-programmed basal rate in manual mode during exercise

• Aged 18-65 years
• Regularly engaged in endurance exercise (training at least twice per week for ≥30 minutes per session)

Exclusion Criteria:

• Pregnancy
• <6 months postpartum or stopped breastfeeding <1 month before recruitment
• Existing cerebrovascular or cardiovascular disease
• Significant history of hyperglycaemia (HbA1c >85 mmol/mol)
• History of severe hypoglycaemia requiring third party assistance within the last 3 months
• Body weight <36.5kg
• Difficulty swallowing tablets
• Appointment for an MRI test that cannot be rescheduled
• Obstructive gastrointestinal disease
• History of gastrointestinal surgery
• Have an implanted medical device

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Temperate; 40 minutes of moderate intensity continuous exercise at 20°C with 50% relative humidity	Behavioral: Exercise; exercise in the heat or temperate conditions
Experimental: Heat; 40 minutes of moderate intensity continuous exercise at 40°C with 50% relative humidity	Behavioral: Exercise; exercise in the heat or temperate conditions

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
blood glucose	change in blood glucose concentration	Baseline pre exercise to end of exercise (40 minutes)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Core temperature	change in core temperature	Baseline pre exercise to end of exercise (40 minutes)
Skin temperature	change in skin temperature	Baseline pre exercise to end of exercise (40 minutes)
Free fatty acids	change free fatty acid concentration	Baseline pre exercise to end of exercise (40 minutes)
insulin	Change in insulin concentration	Baseline pre exercise to end of exercise (40 minutes)
glucagon	change in glucagon concentration	Baseline pre exercise to end of exercise (40 minutes)
epinephrine	change in epinephrine concentration	Baseline pre exercise to end of exercise (40 minutes)
norepinephrine	change in norepinephrine concentration	Baseline pre exercise to end of exercise (40 minutes)
cortisol	change in cortisol concentration	Baseline pre exercise to end of exercise (40 minutes)
Growth hormone	change in Growth hormone concentration	Baseline pre exercise to end of exercise (40 minutes)
lactate	change in lactate concentration	Baseline pre exercise to end of exercise (40 minutes)

Collaborators and Investigators

• Sponsor: Liverpool John Moores University

Study record dates

Study Major Dates

• Study Start (Actual): November 1, 2025
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): November 1, 2026

Study Registration Dates

• First Submitted: November 25, 2025
• First Submitted That Met QC Criteria: January 5, 2026
• First Posted (Actual): January 14, 2026

Study Record Updates

• Last Update Posted (Actual): January 14, 2026
• Last Update Submitted That Met QC Criteria: January 5, 2026
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Keywords: exercise; heat
• Additional Relevant MeSH Terms: Endocrine System Diseases; Metabolic Diseases; Autoimmune Diseases; Immune System Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Behavior; Nutritional and Metabolic Diseases; Diabetes Mellitus, Type 1; Motor Activity; Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena; Exercise
• Other Study ID Numbers: 25/SPS/065

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: On request to PI

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No