Using a Personalized Decision Support Tool to Help People With Type 1 Diabetes Manage Exercise (NEXT)

Net-IOB & Exercise Toolkit Pilot Trial: Randomized, Crossover Evaluation of a Behavioral Decision Support Advisor to Improve Glycemic Safety During and After Exercise in Adults With Type 1 Diabetes (NEXT)

This study evaluates a clinician-facing decision-support toolkit designed to assist adults with type 1 diabetes in preparing for moderate-intensity exercise. The netIOB & Exercise Toolkit (NEXT) integrates recent glucose data and insulin delivery history to provide individualized suggestions regarding exercise timing, insulin adjustments, and carbohydrate intake.

Adults with type 1 diabetes will complete three supervised exercise sessions under different pre-exercise guidance approaches:

(A) published consensus-based standard-of-care guidance, (B) usual personal care routines, and (C) guidance informed by the NEXT Toolkit.

A healthy adult control group will complete a single supervised exercise session to provide comparative physiologic data.

Study Overview

• Status: Not yet recruiting
• Conditions: Type 1 Diabetes (T1D); Type 1 Diabetes Mellitus (T1DM); Exercise Physiology; Type 1 Diabetes Mellitis
• Intervention / Treatment: Behavioral: Standard-of-Care Guidance (SoC); Behavioral: Usual Care (UC); Device: netIOB & Exercise Toolkit (NEXT); Device: Continuous Glucose Monitoring; Device: Continuous Ketone Monitoring

Detailed Description

People with type 1 diabetes frequently experience variable glucose responses before, during, and after physical activity, including exercise-associated hypoglycemia and the need for unplanned carbohydrate intake. Although consensus-based recommendations exist to guide exercise preparation, many individuals continue to rely on trial-and-error strategies that can be burdensome or difficult to generalize across activities.

This study evaluates the netIOB & Exercise Toolkit (NEXT), a software-based, clinician-facing decision-support system intended to contextualize exercise preparation using recent continuous glucose monitoring (CGM) data and insulin delivery history. The Toolkit estimates net insulin-on-board relative to an individual's programmed basal insulin profile and presents structured, non-automated suggestions related to exercise timing, insulin target adjustments, and carbohydrate intake. All decisions remain under clinician and participant control.

The primary study population consists of adults with type 1 diabetes who complete three supervised, moderate-intensity exercise sessions in a randomized, three-period crossover design. Each session is conducted under a different pre-exercise strategy: consensus standard-of-care guidance, usual personal care routines, or guidance informed by the NEXT Toolkit. Sessions are separated by washout periods to minimize physiologic carryover, and glycemic, insulin delivery, and behavioral outcomes are assessed during exercise and for up to 48 hours post-exercise.

In addition, a healthy adult control group completes a single supervised exercise session without pre-exercise glucose or insulin management interventions. This group is included to provide comparative physiologic context for exploratory analyses.

Exploratory analyses will examine relationships between pre-exercise net insulin-on-board (netIOB) strata and glycemic, insulin, and treatment outcomes across exercise sessions. These analyses are intended to characterize patterns of response rather than to test formal efficacy hypotheses.

Participants in both the type 1 diabetes and healthy control groups will wear a commercially available continuous ketone monitoring (CKM) sensor (SiBio KS1) for exploratory data collection during exercise and defined post-exercise monitoring periods. CKM data are collected solely for research purposes, are not used to guide clinical or study-related decisions, and are not intended to evaluate device performance.

The NEXT Toolkit is classified as a non-significant risk, IDE-exempt investigational tool. Results from this pilot study are intended to inform future research design and the development of transparent, open-access methods for studying exercise physiology and glucose management in diabetes.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Ryan Kingman, BS; Phone Number: 650-736-4417; Email: rkingman@stanford.edu
• Study Contact Backup: Name: Dessi Zaharieva, PhD; Phone Number: 628-238-9420; Email: dessi@stanford.edu

Study Locations

• United States
  • California
    • Palo Alto, California, United States, 94304
      • Stanford University
      • Principal Investigator: Rayhan Lal, MD
      • Contact: Ryan Kingman, BS; Phone Number: 650-736-4417; Email: rkingman@stanford.edu
      • Contact: Dessi Zaharieva, PhD; Phone Number: 628-238-9420; Email: dessi@stanford.edu
      • Sub-Investigator: Dessi Zaharieva, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria Inclusion Criteria: All Participants (Type 1 Diabetes and Healthy Control Groups)

• Adults between the age of 18-60 years
• Able to perform moderate intensity walking for 60 minutes (target 40-60% age-predicted maximal heart rate).
• Willing and able to comply with study procedures, including supervised exercise visits and device wear
• Able to provide written informed consent

Inclusion Criteria: Type 1 Diabetes Group Only

• Clinical diagnosis of type 1 diabetes for >1 year, based on the investigator's clinical judgement
• Current use of continuous subcutaneous insulin infusion with Tandem Control-IQ and a compatible continuous glucose monitor (CGM) for >1 month prior to enrollment
• Stable insulin delivery regimen, with no planned changes to insulin pump settings or insulin dosing strategy during the study period
• Consistent CGM use during the month prior to enrollment (>80% data availability)

Inclusion Criteria: Health Control Group Only

• No diagnosis of diabetes or other disorders of glucose metabolism
• Not using insulin or glucose-lowering medications

Exclusion Criteria Exclusion Criteria: All Participants

• Intercurrent illness or medical condition that precludes safe participation in moderate-intensity exercise (e.g., unstable cardiopulmonary disease, uncontrolled arrhythmia, or uncontrolled hypertension), as previously assessed by the participant's primary care physician
• Known coronary artery disease with symptoms limiting moderate physical activity, or history of myocardial infarction, percutaneous coronary intervention, or coronary artery bypass grafting within the past 12 months
• Pregnancy, lactation, or plans to become pregnant during the study period
• Renal insufficiency with estimated GFR <45 mL/min/1.73 m², dialysis dependence, or adrenal insufficiency
• Concurrent participation in another interventional drug or device study within 30 days prior to enrollment
• Inability to comply with study procedures or safety requirements (e.g., inability to achieve target heart-rate zone, attend scheduled visits, or enable required device data access), or otherwise deemed unsuitable by the investigator

Exclusion Criteria: Type 1 Diabetes Group Only

• Use of non-CSII insulin delivery, including long-acting injectable or inhaled insulin, during the study period
• Use of medications with potential to substantially affect glycemia (e.g., SGLT-2 inhibitors, GLP-1 receptor agonists, or GIP agonists), unless on a stable regimen with no planned changes during the study
• Use of systemic corticosteroids within 4 weeks prior to participation
• History of severe hypoglycemia (requiring third-party assistance) or diabetic ketoacidosis within the prior 6 months

Study Plan

How is the study designed?

Design Details

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

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Standard-of-Care (SoC); Participants follow consensus-based guidance for insulin and carbohydrate adjustments around exercise, as outlined in current international standards. These recommendations are applied by study staff in advance of the exercise session.	Behavioral: Standard-of-Care Guidance (SoC); Study staff provide insulin and carbohydrate adjustment advice based on consensus exercise management guidelines (Moer et al., 2024), tailored to the planned activity.; Device: Continuous Glucose Monitoring; Continuous glucose monitoring using an FDA-cleared system (Dexcom G7) for research data collection during and after exercise. CGM data are used to assess glycemic responses and are not used to evaluate device performance or accuracy.; Device: Continuous Ketone Monitoring; A commercially available continuous ketone monitoring (CKM) device will be used for exploratory data collection during and after exercise. Ketone data are collected for research purposes only and are not used for clinical decision-making or to evaluate device performance.
Other: Usual Care (UC); Participants use their own strategies for managing insulin and carbohydrate around exercise.	Behavioral: Usual Care (UC); Participants independently manage their insulin and carbohydrate decisions around exercise, using their routine practices without study-provided guidance.; Device: Continuous Glucose Monitoring; Continuous glucose monitoring using an FDA-cleared system (Dexcom G7) for research data collection during and after exercise. CGM data are used to assess glycemic responses and are not used to evaluate device performance or accuracy.; Device: Continuous Ketone Monitoring; A commercially available continuous ketone monitoring (CKM) device will be used for exploratory data collection during and after exercise. Ketone data are collected for research purposes only and are not used for clinical decision-making or to evaluate device performance.
Experimental: netIOB & Exercise Toolkit (NEXT); Physicians receive personalized, algorithm-informed recommendations for exercise-related insulin and carbohydrate adjustments. Recommendations are generated using the investigational netIOB & Exercise Toolkit based on CGM data, insulin history, and real-time inputs.	Device: netIOB & Exercise Toolkit (NEXT); 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.; Device: Continuous Glucose Monitoring; Continuous glucose monitoring using an FDA-cleared system (Dexcom G7) for research data collection during and after exercise. CGM data are used to assess glycemic responses and are not used to evaluate device performance or accuracy.; Device: Continuous Ketone Monitoring; A commercially available continuous ketone monitoring (CKM) device will be used for exploratory data collection during and after exercise. Ketone data are collected for research purposes only and are not used for clinical decision-making or to evaluate device performance.
Other: Healthy Control; Adults without diabetes complete one supervised moderate-intensity exercise session for physiologic comparison.	Device: Continuous Glucose Monitoring; Continuous glucose monitoring using an FDA-cleared system (Dexcom G7) for research data collection during and after exercise. CGM data are used to assess glycemic responses and are not used to evaluate device performance or accuracy.; Device: Continuous Ketone Monitoring; A commercially available continuous ketone monitoring (CKM) device will be used for exploratory data collection during and after exercise. Ketone data are collected for research purposes only and are not used for clinical decision-making or to evaluate device performance.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Composite Score of Glycemic Safety and Carbohydrate Burden	This composite outcome reflects glycemic risk during exercise and the subsequent post-exercise monitoring period. The score is based on a Magni risk-derived metric computed from continuous glucose monitoring (CGM) data, with the glycemic effects of rescue carbohydrate treatments removed to isolate underlying glycemic risk. Each evaluated timepoint is given a score ranging from 0 to 100, where lower scores indicate lower glycemic risk and higher scores indicate higher glycemic risk. Scores across the defined observation windows are summarized across intervention conditions.	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).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
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	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: %	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.	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.	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.	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	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.	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.	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.	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).
Baseline and Peak Ketone Levels	Baseline and peak ketone concentrations (mmol/L) measured using continuous ketone monitoring during the exercise period. Outcomes will be explored across pre-exercise strategies in participants with type 1 diabetes and relative to healthy control participants.	Baseline (immediately prior to exercise) and Exercise (0 to 90 minutes from exercise).
Ketone Exposure (AUC) During and After Exercise	Ketone exposure quantified as area under the curve (AUC) from continuous ketone monitoring during exercise (0-90 minutes from exercise start) and early post-exercise (0-6 hours after exercise). Outcomes will be explored across pre-exercise strategies in participants with type 1 diabetes and relative to healthy control participants.	Exercise (0 to 90 minutes), Early Post-Exercise (0 to 6 hours after exercise) per visit.

Collaborators and Investigators

• Sponsor: Stanford University
• Collaborators: University College Dublin; The Leona M. and Harry B. Helmsley Charitable Trust
• Investigators: Principal Investigator: Rayhan Lal, MD, Stanford University; Study Director: Dessi dessi@stanford.edu, PhD, Stanford University

Study record dates

Study Major Dates

• Study Start (Estimated): April 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): August 1, 2026

Study Registration Dates

• First Submitted: October 7, 2025
• First Submitted That Met QC Criteria: November 6, 2025
• First Posted (Actual): November 10, 2025

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 11, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Exercise; Continuous Glucose Monitoring; Type 1 Diabetes; T1D; CGM; Insulin Pump; T1DM; closed-loop system; hybrid closed-loop; Insulin Dosing; carbohydrate Intake
• 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; Investigative Techniques; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Blood Chemical Analysis; Clinical Chemistry Tests; Diagnostic Techniques, Endocrine; Monitoring, Physiologic; Continuous Glucose Monitoring
• Other Study ID Numbers: 82224; 2407-07175 (Other Grant/Funding Number: Leona M & Harry B Helmsley Charitable Trust)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

De-identified individual participant-level data will be shared, including:

• Continuous glucose monitoring (CGM) metrics from the Dexcom G7 (e.g., time in range, time below/above range, mean glucose, glucose variability)
• Carbohydrate treatment data (timing, amount, type)
• Insulin delivery data (e.g., pump settings, suspensions, automated adjustments)
• Demographic information (e.g., age range, sex, diabetes duration)

IPD that will not be shared includes:

• Direct identifiers (e.g., names, exact dates of birth, addresses)
• Free-text responses or notes containing potentially identifiable information
• Any raw data not essential to the reported outcomes or secondary analyses

• IPD Sharing Time Frame: Data will be available beginning 18 months after article publication and ending 5 years following article publication.
• IPD Sharing Access Criteria: Proposals should be directed to dessi@stanford.edu. To gain access, data requestors will need to sign a data access agreement.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No