One-Minute Exercise Snacks and Daytime Glucose in Adults With Type 2 Diabetes

This study was designed as a single-center, randomized, four-condition, four-period crossover trial using a Williams balanced design to evaluate the effects of different daily frequencies of one-minute exercise snacks on glucose regulation in adults with type 2 diabetes who were not treated with insulin.

Study Design and Procedures The study employed four experimental conditions: CON (no prescribed exercise snacks), ES4 (four exercise snacks per day), ES6 (six exercise snacks per day), and ES8 (eight exercise snacks per day). Participants were randomly allocated to one of four Williams balanced intervention sequences, ensuring that each condition appeared once in each experimental period and balancing potential first-order carryover effects.

Before randomization, participants underwent baseline clinical assessments, habitual physical activity monitoring, dietary assessment, and supervised exercise familiarization. Each experimental condition was implemented for two consecutive days, separated by washout periods of at least 72 hours. The four experimental periods were scheduled to be completed over approximately four weeks.

Exercise Snack Interventions Each exercise snack consisted of four consecutive 15-second body-weight exercises, totaling one minute of vigorous physical activity. The exercise combinations included movements such as jumping jacks, squats, high knees, lunges, and modified burpees. Exercise intensity was targeted at 7-9 on the Borg CR-10 rating of perceived exertion scale.

In all three exercise conditions, three exercise snacks were performed approximately 45 minutes after the beginning of breakfast, lunch, and dinner. Additional sessions were distributed across predefined non-postprandial time windows. The ES4 condition included one additional non-postprandial session, ES6 included three, and ES8 included five. Non-postprandial exercise windows were balanced across participants using a Latin-square allocation scheme.

Participants performed the prescribed exercises independently in their usual living or working environments. Exercise adherence and intensity were monitored through electronic exercise logs, Polar H10 heart-rate recordings, mobile reminders, and daily remote follow-up.

Dietary Standardization and Glucose Monitoring During all experimental conditions, participants consumed standardized individualized meals with consistent energy and macronutrient composition. Antidiabetic medication regimens were maintained without changes, and participants were instructed to avoid additional structured exercise.

Glucose concentrations were monitored using a blinded continuous glucose monitoring system (FreeStyle Libre Pro), which recorded interstitial glucose at 15-minute intervals. Participants could not access real-time glucose readings during monitoring.

Outcome Assessment The primary outcome was mean daytime sensor glucose measured from 06:00 to 24:00, averaged across the two observation days of each experimental condition.

Secondary assessments included 24-hour and nighttime mean glucose, non-postprandial daytime glucose, glucose variability, time in predefined glucose ranges, postprandial glucose responses, exercise adherence and intensity, acceptability, habitual physical activity, and adverse events.

Statistical Analysis Linear mixed-effects models were specified to compare glucose outcomes across experimental conditions, accounting for treatment condition, experimental period, randomized sequence, and repeated measurements within participants.

The primary hypothesis was that at least one exercise snack condition would reduce mean daytime glucose compared with the control condition. Additional exploratory analyses examined the shape of the exercise frequency-response relationship and glucose responses following individual exercise snacks performed during postprandial and non-postprandial periods.

The study was intended to provide evidence regarding the optimal daily frequency and practical implementation of brief exercise interventions for improving glucose management in adults with type 2 diabetes.

Participants received four experimental conditions in the following order: CON (no prescribed exercise snacks), ES4 (four 1-minute exercise snacks per day), ES8 (eight 1-minute exercise snacks per day), and ES6 (six 1-minute exercise snacks per day). Each condition lasted two consecutive days, with washout periods of at least 72 hours between conditions.

Behavioral: 1-Minute Exercise Snacks

Participants received four experimental conditions in the following order: ES4 (four 1-minute exercise snacks per day), ES6 (six 1-minute exercise snacks per day), CON (no prescribed exercise snacks), and ES8 (eight 1-minute exercise snacks per day). Each condition lasted two consecutive days, with washout periods of at least 72 hours between conditions.

Behavioral: 1-Minute Exercise Snacks

Participants received four experimental conditions in the following order: ES6 (six 1-minute exercise snacks per day), ES8 (eight 1-minute exercise snacks per day), ES4 (four 1-minute exercise snacks per day), and CON (no prescribed exercise snacks). Each condition lasted two consecutive days, with washout periods of at least 72 hours between conditions.

Behavioral: 1-Minute Exercise Snacks

Participants received four experimental conditions in the following order: ES8 (eight 1-minute exercise snacks per day), CON (no prescribed exercise snacks), ES6 (six 1-minute exercise snacks per day), and ES4 (four 1-minute exercise snacks per day). Each condition lasted two consecutive days, with washout periods of at least 72 hours between conditions.

Behavioral: 1-Minute Exercise Snacks

Participants performed vigorous 1-minute exercise snacks consisting of four consecutive 15-second body-weight movements without rest. Exercises included jumping jacks, squats, high knees, lunges, and modified burpees. Individualized exercise combinations were determined during familiarization and remained unchanged across conditions. Target intensity was 7-9 on the Borg CR-10 scale.

Three exercise frequencies were evaluated: ES4 (4 sessions/day: 3 after meals and 1 non-postprandial), ES6 (6 sessions/day: 3 after meals and 3 non-postprandial), and ES8 (8 sessions/day: 3 after meals and 5 non-postprandial). Postprandial exercise was scheduled approximately 45 minutes after meal initiation. Each condition lasted 2 consecutive days, with washout periods of at least 72 hours. Exercise was performed independently, with adherence monitored using heart-rate recordings and electronic logs.

Time frame: Days 1-2 of each of the four experimental conditions (06:00-24:00 daily), across approximately 4 weeks.

Mean interstitial glucose concentration (mmol/L) measured using a blinded continuous glucose monitoring (CGM) system (FreeStyle Libre Pro). Daytime glucose was defined as the average sensor glucose concentration recorded between 06:00 and 24:00 on each observation day. The primary outcome was calculated as the mean daytime sensor glucose across the two consecutive observation days within each experimental condition (CON, ES4, ES6, and ES8). Glucose measurements were recorded at 15-minute intervals.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Mean sensor glucose concentration (mmol/L) measured using blinded continuous glucose monitoring (CGM) from 00:00 to 24:00, averaged across the two observation days of each condition.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Mean CGM-derived sensor glucose concentration (mmol/L) between 00:00 and 06:00, averaged across the two observation days of each experimental condition.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Mean sensor glucose concentration (mmol/L) during the 12 non-postprandial daytime hours, excluding the three designated 2-hour postprandial windows from 06:00 to 24:00, averaged across two observation days per condition.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Standard deviation (SD) of glucose concentrations (mmol/L) derived from CGM readings during each experimental condition, representing absolute glycemic variability.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Coefficient of variation (CV, %) of CGM-derived glucose, calculated as 100 multiplied by the glucose standard deviation divided by the mean glucose concentration for each condition.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Mean amplitude of glycemic excursions (MAGE, mmol/L) calculated from CGM recordings according to the prespecified Service method to characterize glucose fluctuations.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Percentage of valid CGM monitoring time during which sensor glucose concentrations were within the target range of 3.9-10.0 mmol/L.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Percentage of valid CGM monitoring time during which sensor glucose concentrations were within the tighter glucose range of 3.9-7.8 mmol/L.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Percentage of valid CGM monitoring time during which sensor glucose concentrations exceeded 10.0 mmol/L.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Percentage of valid CGM monitoring time during which sensor glucose concentrations were below 3.9 mmol/L.

Time frame: 0-120 minutes after breakfast, lunch, and dinner on Days 1-2 of each of the four experimental conditions.

Mean CGM-derived glucose concentration (mmol/L) during the 0-120-minute period following the first bite of each meal, evaluated for breakfast, lunch, and dinner.

Time frame: 0-120 minutes after breakfast, lunch, and dinner on Days 1-2 of each of the four experimental conditions.

Maximum CGM-derived glucose concentration (mmol/L) observed within 120 minutes after the first bite of breakfast, lunch, or dinner.

Time frame: 0-120 minutes after breakfast, lunch, and dinner on Days 1-2 of each of the four experimental conditions.

Incremental glucose area under the curve (iAUC, mmol/L × min) from 0 to 120 minutes after meal initiation, calculated by the trapezoidal method using the mean of the readings at meal initiation and 15 minutes before the meal as baseline. Areas below baseline were excluded.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Mean daily number of prescribed exercise snacks reported as completed in electronic exercise logs, calculated separately for the ES4, ES6, and ES8 conditions.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Mean daily number of self-reported exercise snacks verified by synchronized Polar H10 heart-rate records, with matching completion times within ±10 minutes and a heart-rate rise consistent with a 1-minute exercise bout.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Mean daily number of exercise snacks meeting the protocol-defined level-3 verification criteria, requiring heart-rate-confirmed completion and achievement of the prespecified intensity threshold. The count was averaged over the two observation days of each exercise condition.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Percentage of prescribed exercise snack sessions reported as completed in the electronic exercise log, calculated separately for each exercise condition.

Time frame: Each prescribed exercise session on Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Perceived exertion recorded after each exercise snack using the Borg CR-10 scale (0-10), with higher scores indicating greater perceived exertion. The prescribed target was 7-9.

Time frame: Each prescribed exercise session on Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Maximum heart rate (beats per minute) recorded using a Polar H10 chest strap during each exercise snack.

Time frame: Each prescribed exercise session on Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Peak heart rate expressed as a percentage of age-predicted maximum heart rate, calculated using the Tanaka equation: 208 - 0.7 × age (years).

Time frame: Each prescribed exercise session on Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Self-reported enjoyment after each exercise snack on a numerical scale from 0 (not enjoyable at all) to 10 (extremely enjoyable). Higher scores indicate greater enjoyment.

Time frame: Each prescribed exercise session on Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Self-reported muscle soreness after each exercise snack on a 4-level scale: 0 = none, 1 = mild, 2 = moderate, and 3 = severe.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Elapsed time in minutes between consecutive completed exercise snack sessions within each exercise condition, derived from recorded completion times.

Time frame: Days 1-2 of the ES4, ES6, and ES8 conditions, across approximately 4 weeks.

Number of occasions on which consecutive exercise snack sessions were separated by less than the prescribed minimum interval of 60 minutes.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Mean daily step count measured using a waist-worn ActiGraph wGT3X-BT accelerometer during each experimental condition.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Daily sedentary time (minutes per day) measured by accelerometry, using fewer than 100 vertical-axis counts per minute to identify sedentary behavior.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Daily minutes of moderate-to-vigorous physical activity (MVPA) measured by accelerometry, excluding activity recorded from 1 minute before to 1 minute after each prescribed exercise snack.

Time frame: From baseline assessment through the final adverse-event follow-up after the fourth condition (approximately 5 weeks per participant).

Number of symptomatic hypoglycemia episodes confirmed by capillary blood glucose measurements below 3.9 mmol/L. Symptoms included palpitations, sweating, hunger, or dizziness.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Number of CGM-derived hypoglycemic events defined as sensor glucose below 3.9 mmol/L continuously for at least 15 minutes.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Number of CGM-derived level 2 hypoglycemic events defined as sensor glucose below 3.0 mmol/L continuously for at least 15 minutes.

Time frame: From baseline assessment through the final adverse-event follow-up after the fourth condition (approximately 5 weeks per participant).

Number of adverse medical events recorded during the study, regardless of relationship to the intervention, including musculoskeletal injury, cardiovascular symptoms, and other clinical events.

Time frame: From baseline assessment through the final adverse-event follow-up after the fourth condition (approximately 5 weeks per participant).

Number of serious adverse events recorded during the study, including events resulting in death, life-threatening conditions, hospitalization or prolonged hospitalization, or major disability.

Time frame: Days 1-2 of each of the four experimental conditions (approximately 4 weeks in total).

Akaike weights derived from comparisons of seven prespecified dose-response models: linear, log-linear, quadratic, threshold, Emax, unimodal with a peak at six sessions per day, and fully categorical. Weights represent relative model support in the specified candidate set.

Time frame: From 30 minutes before to 120 minutes after each exercise snack during Days 1-2 of ES4, ES6, and ES8 conditions.

Change in CGM sensor glucose (mmol/L) from the exercise completion time (0 minutes) to 60 minutes afterward, separately for postprandial and non-postprandial exercise windows. Glucose trajectories from -30 to +120 minutes were examined, with corresponding clock-time readings from the control condition used as a reference.

Effects of 1-Min Exercise Snacks on Daytime Glucose in Adults With Type 2 Diabetes Not Treated With Insulin: A Randomized Crossover Trial