This study evaluates a digital decision-support tool designed to help individuals with type 1 diabetes prepare for exercise. This netIOB \& Exercise Tool (NEXT) uses glucose data and insulin delivery history to recommend individualized strategies such as carbohydrate intake, insulin adjustments, or delays in exercise start time. Participants will complete three structured aerobic or mixed-exercise sessions using different guidance approaches: (A) published consensus-based standard-of-care guidelines (B) usual personal care routines (C) the NEXT tool The study compares glucose outcomes, safety, and carbohydrate use across these conditions to inform better exercise preparation and support tools for people with diabetes.
People with type 1 diabetes often experience unpredictable changes in blood glucose levels before, during, and after physical activity. While consensus guidelines exist to help mitigate these risks, many individuals continue to encounter hypoglycemia or rely on excessive carbohydrate intake around exercise. This study evaluates a software-based tool, netIOB \& Exercise Toolkit (NEXT), that provides real-time, individualized guidance for exercise preparation. The tool uses data from continuous glucose monitors (CGMs), insulin delivery history, and exercise timing to suggest adjustments such as carbohydrate intake, temporary targets, or delayed start times. Its goal is to reduce hypoglycemia and carbohydrate burden while preserving exercise safety and feasibility. The trial uses a randomized, crossover design in which participants complete three supervised moderate-intensity exercise sessions, each under a different preparation strategy. The guidance methods include consensus standard-of-care, usual personal care, and the investigational NEXT tool. Each session is followed for 48 hours to assess glycemic and behavioral outcomes. Exploratory analyses will stratify glycemic and treatment outcomes based on pre-exercise net insulin-on-board (netIOB) levels, categorized into predefined strata (e.g., 0.0-1.0u, 1.0-2.0u, 2.0-3.0u, 3.0u+), to assess potential effect modification across intervention arms. The NEXT tool is investigational and classified as IDE-exempt. Findings from this study may inform the design of future clinical trials and support the development of open-source methods for exercise preparation in diabetes.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
SUPPORTIVE_CARE
Masking
NONE
Enrollment
10
Study staff provide insulin and carbohydrate adjustment advice based on consensus exercise management guidelines (Moer et al., 2024), tailored to the planned activity.
Participants independently manage their insulin and carbohydrate decisions around exercise, using their routine practices without study-provided guidance.
An investigational software tool generates individualized insulin and carbohydrate adjustment recommendations before and after exercise using CGM data and recent insulin delivery. Study physicians review and relay these recommendations to participants.
Stanford University
Palo Alto, California, United States
Composite Score of Glycemic Safety and Carbohydrate Burden
This composite outcome integrates glycemic safety and carbohydrate burden during and after exercise. The Glycemic Safety subscore is calculated from percent time spent \<70 mg/dl and \<54 mg/dl, number of treated hypoglycemic events, and nadir glucose, with heavier penalties for Level 2 hypoglycemia. The Carbohydrate Burden Subscore is based on total grams og carbohydrates consumed and the number of treatment episodes. A glycemic safety and carbohydrate burden composite metric score of zero is equal to no risk of hypoglycemia without carbohydrate consumption.
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
Percent-Based Continuous Glucose Monitor Metrics
Assess standard continuous glucose monitoring (CGM) metrics during defined time windows relative to exercise (0-90 minutes, 0-6 hours, 6-24 hours, and 24-48 hours post-exercise). These include: * Percent Time in Range (TIR): 70-180 mg/dL * Percent Time Below Range (TBR): \<70 mg/dL and \<54 mg/dL * Percent Time Above Range (TAR): \>180 mg/dL and \>250 mg/dL
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
Glucose Concentration and Variability Metrics from Continuous Glucose Monitor
Mean glucose level, glucose standard deviation (SD), and coefficient of variation (CV) will be calculated using CGM data collected over defined time periods relative to exercise. These metrics describe overall glycemic variability and will be used to assess the stability of glucose control following each intervention. Units of Measure: Mean glucose: mg/dL SD: mg/dL CV: %
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
Frequency of Hypoglycemic Events
Number of hypoglycemic episodes per participant at thresholds of \<70 mg/dL and \<54 mg/dL, stratified by treatment arm. Events will be classified as treated or untreated.
Time frame: Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise); total of 7.5 hours per visit (3 visits).
Glucose Nadir Value
Lowest glucose value (nadir mg/dl) recorded per participant during exercise period and 0-6 hours post-exercise, as measured by CGM.
Time frame: Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise); total of 7.5 hours per visit (3 visits).
Time to First Hypoglycemic Event
Time (in minutes) from exercise start to the first hypoglycemic episode (\<70 mg/dL) for each participant.
Time frame: Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise); total of 7.5 hours per visit (3 visits).
Carbohydrate Consumption for Hypoglycemia Prevention/Treatment
Quantify carbohydrate use related to exercise using: * Total grams of carbohydrate consumed * Number of carbohydrate treatment episodes * Categorization as prophylactic or reactive
Time frame: Exercise (0 to 90 minutes); total of 1.5 hours per visit (3 visits).
Total and Programmed Insulin Delivery
Compare the total insulin delivered (actual) to the amount that would have been delivered based on the participant's pre-programmed basal rates. This includes both basal and bolus insulin.
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
Frequency of User-Initiated Pump Adjustments
Number of times participants manually modified insulin delivery during the exercise period, including suspensions, temporary targets, exercise mode, or basal rate changes.
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
Duration of User-Initiated Pump Adjustments
Cumulative duration of user-initiated pump modifications, including time spent in temporary targets, pump suspensions, and exercise modes.
Time frame: Baseline (1 hour pre-exercise), Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise), Mid Post-Exercise (6 to 24 hours after exercise), Late Post-Exercise (24 to 48 hours after exercise); total of 50.5 hours per visit (3 visits).
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