Understanding Artificial Pancreas Systems: Results from a 24-Month Trial

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Blood glucose decreased during high-intensity interval exercise, but the decline was significantly smaller compared to continuous exercise at moderate intensity (1.51 vs 3.00 mmol/L, p=0.024), with similar trends at low and high intensities. This smaller decline is clinically beneficial as it reduces hypoglycemia risk while still allowing exercise participation

Blood lactate was significantly higher during interval exercise compared to continuous exercise at low intensity (1.67 vs 0.96 mmol/L, p=0.006) and moderate intensity (2.08 vs 1.33 mmol/L, p=0.004), but similar at high intensity. This reflects greater anaerobic contribution during interval bursts but steady-state conditions were maintained.

Aerobic interval exercise with 20-second bursts at maximal power output alternating with active recovery periods, matched for average intensity with continuous exercise. Three protocols tested: low intensity (5% below first lactate threshold), moderate intensity (5% above first lactate threshold), and high intensity (5% below second lactate threshold). Total duration 30 minutes.

Blood glucose decreased during continuous exercise, with declines that were significantly larger than interval exercise at moderate intensity (3.00 vs 1.51 mmol/L, p=0.024), with similar trends at other intensities. While the decrease was controlled and did not cause hypoglycemia with insulin adjustments, the larger decline requires more careful glucose management.

No hypoglycemic events occurred during or for 24 hours after continuous exercise when using ultra-long-acting insulin and appropriate mealtime insulin reductions. This demonstrates that continuous exercise can be performed safely with proper insulin management despite larger glucose decreases than interval exercise.

Continuous aerobic exercise at steady workload on cycle ergometer, matched for average intensity and duration with interval exercise. Three target intensities tested: 5% below first lactate threshold, 5% above first lactate threshold, and 5% below second lactate threshold. Total duration 30 minutes.

When combined with intensity-dependent mealtime insulin reductions, ultra-long-acting insulin degludec enabled safe exercise at multiple intensities without hypoglycemia during or 24 hours after exercise in both interval and continuous exercise modes.

Ultra-long-acting basal insulin (Tresiba/Novo Nordisk) administered once daily in the evening subcutaneously at 68% of usual long-acting insulin dose after a 4-week run-in period. This insulin has a flat profile with low intra-individual variability and 4-times lower pharmacodynamic variability than insulin glargine.

High-intensity interval exercise with 20-second bursts causes less blood glucose decline than continuous exercise at matched average intensities

Both interval and continuous exercise can be performed safely without hypoglycemia when using ultra-long-acting insulin and reducing mealtime insulin based on exercise intensity

Hormone responses to exercise are similar between interval and continuous modes despite higher peak workloads in intervals

The findings suggest that high-intensity interval exercise with short bursts may offer advantages over continuous exercise for blood glucose management in type 1 diabetes, causing less overall decline in glucose levels. Both exercise modes appear safe when combined with ultra-long-acting insulin and appropriate mealtime insulin reductions. The similar hormone responses between exercise types despite different peak workloads is notable and suggests the average exercise intensity may be more important than peak intensity for metabolic stress.

Participants performed two types of cycling exercise matched for average intensity and duration. High-intensity interval exercise consisted of 20-second bursts at maximal power alternating with active recovery periods. Continuous exercise involved steady cycling at the target workload. Both modes were tested at three intensity levels: below the first lactate threshold, between lactate thresholds, and near the second lactate threshold. Exercise intensities were individualized based on lactate turn points from preliminary testing.

Moser O, Tschakert G, Mueller A, et al. Effects of High-Intensity Interval Exercise versus Moderate Continuous Exercise on Glucose Homeostasis and Hormone Response in Patients with Type 1 Diabetes Mellitus Using Novel Ultra-Long-Acting Insulin. PLoS One. 2015;10(8):e0136489. doi:10.1371/journal.pone.0136489

Neither exercise mode caused hypoglycemia during or for 24 hours after exercise when mealtime insulin was reduced appropriately. High-intensity interval exercise led to significantly smaller blood glucose decreases at moderate intensity and smaller decreases by trend at low and high intensities compared to continuous exercise. Blood lactate and respiratory exchange ratio were higher during intervals at low and moderate intensities but similar at high intensity. Hormone responses including catecholamines, cortisol, glucagon, and IGF-1 were not significantly different between exercise modes despite higher peak workloads in interval exercise.

Very small sample size (only 7 participants)

Only trained males studied - not generalizable to women or sedentary individuals

Non-randomized exercise sequence may introduce bias

Highly controlled laboratory conditions may not reflect real-world exercise

In a study of 7 trained men with type 1 diabetes, high-intensity interval exercise led to a smaller drop in blood glucose compared to moderate continuous exercise, with no hypoglycemia occurring in either exercise mode when insulin was adjusted appropriately.

The study has several important limitations. The sample size was extremely small with only seven male participants, limiting statistical power and generalizability. Results apply only to trained individuals and may not extend to sedentary or less fit people with diabetes. The study used a specific non-randomized sequence (always starting with low intensity and progressing to higher intensities) which could introduce order effects, though the trained status of participants makes training adaptations unlikely. Results are specific to the ultra-long-acting insulin degludec and may not apply to other insulin regimens. The study only included males, so applicability to females is unknown. Exercise was performed under controlled laboratory conditions with standardized meals and specific insulin reduction protocols that may be difficult to replicate in real-world settings. The 20-second interval protocol is very specific, and results may not generalize to other interval formats. Finally, one subject showed atypical blood glucose response but was still included in analysis.

Blood glucose decrease ↓ (smaller in interval vs continuous exercise)

Hypoglycemia risk → (no events in either exercise mode)

Blood lactate ↑ (higher in intervals at low/moderate intensity)

The American Diabetes Association's annual Standards of Care provide evidence-based clinical practice guidelines for diabetes management, including detailed recommendations for physical activity and exercise in type 1 diabetes. The guidelines address exercise safety, insulin adjustment strategies, and hypoglycemia prevention during different types of physical activity.

ADA Standards of Care in Diabetes - 2025: Physical Activity and Exercise

CDC provides educational resources on the benefits and safety considerations of physical activity for people with type 1 diabetes, including practical guidance on managing blood glucose before, during, and after exercise to prevent hypoglycemia while maximizing the health benefits of regular activity.

International consensus statement providing evidence-based recommendations for exercise management in type 1 diabetes, including insulin dose adjustments, carbohydrate intake strategies, and considerations for different exercise intensities and modalities. Addresses both continuous and high-intensity interval exercise approaches.

Exercise Management in Type 1 Diabetes: A Consensus Statement

Seven trained men with type 1 diabetes completed an incremental exercise test followed by six randomized exercise sessions comparing high-intensity intervals to continuous exercise at three intensity levels. All sessions were matched for average workload and 30-minute duration. Participants used ultra-long-acting insulin degludec and received standardized meals with mealtime insulin reduced by 25-75% based on planned exercise intensity. Blood glucose, lactate, hormones, heart rate, and gas exchange were measured during exercise, with continuous glucose monitoring for 24 hours post-exercise.

High-intensity interval exercise causes less blood sugar drop than moderate exercise in type 1 diabetes

This small study tested two different exercise styles in people with type 1 diabetes: short bursts of intense exercise versus steady moderate exercise. When participants reduced their mealtime insulin based on exercise intensity, the interval-style exercise caused less drop in blood sugar. Neither exercise type caused dangerous low blood sugar during or after workouts.

This is a very small pilot study in a highly specific population (young, trained males). The insulin adjustments and exercise protocols were highly controlled and may be difficult to implement outside research settings. Results apply specifically to ultra-long-acting insulin degludec and 20-second interval protocols. Individual responses to exercise vary considerably, and these group averages may not predict any individual's response. Anyone with diabetes should work with their healthcare team before making changes to insulin dosing around exercise.

Comparison of high-intensity interval versus continuous exercise on blood glucose and hormones in type 1 diabetes

This study examined trained men aged 18-35 years with type 1 diabetes for at least 12 months, good glycemic control (HbA1c <8%), no diabetic complications, and using intensified insulin therapy or insulin pumps. Results may not apply to women, older adults, sedentary individuals, or those with poor glycemic control or diabetic complications.

High-intensity interval exercise causes less blood sugar drop than moderate exercise in type 1 diabetes

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