Examining the Acute Glycemic Effects of Different Types of Structured Exercise Sessions in Type 1 Diabetes in a Real-World Setting: The Type 1 Diabetes and Exercise Initiative (T1DEXI)

Abstract

Objective: Maintenance of glycemic control during and after exercise remains a major challenge for individuals with type 1 diabetes. Glycemic responses to exercise may differ by exercise type (aerobic, interval, or resistance), and the effect of activity type on glycemic control after exercise remains unclear.

Research design and methods: The Type 1 Diabetes Exercise Initiative (T1DEXI) was a real-world study of at-home exercise. Adult participants were randomly assigned to complete six structured aerobic, interval, or resistance exercise sessions over 4 weeks. Participants self-reported study and nonstudy exercise, food intake, and insulin dosing (multiple daily injection [MDI] users) using a custom smart phone application and provided pump (pump users), heart rate, and continuous glucose monitoring data.

Results: A total of 497 adults with type 1 diabetes (mean age ± SD 37 ± 14 years; mean HbA1c ± SD 6.6 ± 0.8% [49 ± 8.7 mmol/mol]) assigned to structured aerobic (n = 162), interval (n = 165), or resistance (n = 170) exercise were analyzed. The mean (± SD) change in glucose during assigned exercise was -18 ± 39, -14 ± 32, and -9 ± 36 mg/dL for aerobic, interval, and resistance, respectively (P < 0.001), with similar results for closed-loop, standard pump, and MDI users. Time in range 70-180 mg/dL (3.9-10.0 mmol/L) was higher during the 24 h after study exercise when compared with days without exercise (mean ± SD 76 ± 20% vs. 70 ± 23%; P < 0.001).

Conclusions: Adults with type 1 diabetes experienced the largest drop in glucose level with aerobic exercise, followed by interval and resistance exercise, regardless of insulin delivery modality. Even in adults with well-controlled type 1 diabetes, days with structured exercise sessions contributed to clinically meaningful improvement in glucose time in range but may have slightly increased time below range.

Graphical abstract

Figure 1

Boxplots of change in glucose during study exercise by exercise type and insulin modality (N = 2,756 exercise sessions from 497 participants). Black lines in the middle of colored boxes represent medians; solid black dots in the middle of boxes represent means. Whiskers outside of the colored boxes represent the 10th and 90th percentiles. The number above each box indicates the number of exercise sessions.

Figure 2

N = 398 participants. A: Scatterplot of participant-level exercise versus sedentary day percent time 70–180 mg/dL. B: Boxplots of day-level percent time in range 70–180 mg/dL on exercise versus sedentary days. Black lines in the middle of colored boxes represent medians; solid black dots in the middle of boxes represent means. Whiskers outside of the colored boxes represent the 10th and 90th percentiles. The number above each box indicates the number of days. C: Cumulative distribution of participant-level percent time 70–180 mg/dL on exercise versus sedentary days.