Effects of High-Intensity Interval Training and Exercise Snacking on Glycemic Control and Cardiorespiratory Fitness in Adults With Type 2 Diabetes Mellitus

NCT07876180 | Completed

• 1 other identifier: 04-2363/2
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized controlled trial investigates whether two time-efficient forms of high-intensity exercise, high-intensity interval training (HIIT) and exercise snacking, improve glycemic control, cardiorespiratory fitness and other cardiometabolic risk factors in adults with type 2 diabetes mellitus. Over 12 weeks, participants were allocated to HIIT, exercise snacking, or a non-exercise control group. The study addresses two questions: whether each exercise modality improves these outcomes relative to no exercise, and whether accumulating vigorous exercise in brief bouts throughout the day produces adaptations comparable to those of conventional interval training performed in a single session.

Conditions

Typ 2 Diabetes

Keywords

High-Intensity Interval Training; hyperglicemia; exercise snacking; cardiometabolic health

Outcome Measures

Primary Outcomes (4)

• Change in glycated hemoglobin (HbA1c)

  HbA1c (%) measured in venous whole blood (EDTA) using the HumaNex A1C analyzer, sampled between 07:00 and 10:00 h after an 8-12 h overnight fast.

  From enrollment to the end of treatment at 12 weeks.

• Change in fasting blood glucose (FBG)

  Fasting serum glucose (mmol/L) measured in venous blood after an 8-12 h overnight fast using an automated biochemical analyzer (Beckman Coulter DxC 700 AU).

  From enrollment to the end of treatment at 12 weeks.

• Change in estimated relative peak oxygen uptake (VO₂peak)

  Relative VO₂peak (mL·kg-¹·min-¹) estimated from 6-minute walk distance using the Ross et al. (2010) equation: VO₂peak = 0.025 × distance (m) + 4.682.

  From enrollment to the end of treatment at 12 weeks.

• Change in estimated absolute peak oxygen uptake (VO₂peak)

  Absolute VO₂peak (L·min-¹) calculated from estimated relative VO₂peak and body mass.

  From enrollment to the end of treatment at 12 weeks.

Secondary Outcomes (11)

• Change in 6-minute walk distance (6MWT)

  From enrollment to the end of treatment at 12 weeks.

• Change in postprandial glucose after breakfast

  From enrollment to the end of treatment at 12 weeks.

• Change in postprandial glucose after lunch

  From enrollment to the end of treatment at 12 weeks.

• Change in postprandial glucose after dinner

  From enrollment to the end of treatment at 12 weeks.

• Change in body mass

  From enrollment to the end of treatment at 12 weeks.

Other Outcomes (2)

• Proportion of clinically meaningful responders

  From enrollment to the end of treatment at 12 weeks.

• Inter-individual variability in response

  From enrollment to the end of treatment at 12 weeks.

Study Arms (3)

Exercise Snacking

EXPERIMENTAL

Participants performed exercise snacking on a cycle ergometer under supervision, two days per week for 12 weeks. On each training day, three short sessions were performed, one before each main meal (breakfast, lunch and dinner). Each session consisted of a 5-minute self-paced warm-up, six 1-minute intervals at 90-95% of age-predicted maximal heart rate separated by 1 minute of passive or active recovery at minimal resistance, and a 3-minute cool-down (approximately 20 minutes per session). Workload was progressively adjusted to maintain the target heart rate, which was monitored continuously with heart rate monitors. Perceived exertion was recorded using the 0-10 RPE scale.

Behavioral: Exercise

HIIT

EXPERIMENTAL

Participants performed HIIT on a cycle ergometer under supervision, two days per week for 12 weeks. On each training day, one session was performed in the afternoon or early evening. Each 35-minute session consisted of a 5-minute warm-up (4 minutes at 60% and 1 minute at 70% of age-predicted maximal heart rate), four 4-minute intervals at 90% of maximal heart rate separated by 3 minutes of active recovery at 70% of maximal heart rate, and a 2-minute cool-down at 70% of maximal heart rate. Workload was progressively adjusted to maintain the target heart rate, which was monitored continuously with heart rate monitors. Perceived exertion was recorded using the 0-10 RPE scale.

Behavioral: Exercise

Control

NO INTERVENTION

Participants did not take part in any structured exercise program during the 12-week study period. They were advised to maintain their habitual physical activity, dietary habits and usual medical care, and completed the same baseline and post-intervention assessments as the exercise groups.

Interventions

Exercise BEHAVIORAL

Exercise Snacking - interval cycling performed as three short sessions per training day, each completed before a main meal (breakfast, lunch and dinner). Each session comprised six 1-minute intervals at 90-95% of age-predicted maximal heart rate with 1-minute recovery, preceded by a 5-minute warm-up and followed by a 3-minute cool-down (approximately 20 minutes per session). Performed under supervision on a cycle ergometer, two days per week for 12 weeks. HIIT - interval cycling performed as a single 35-minute session per training day in the afternoon or early evening. Each session comprised four 4-minute intervals at 90% of age-predicted maximal heart rate with 3-minute active recovery at 70% of maximal heart rate, preceded by a 5-minute warm-up and followed by a 2-minute cool-down. Performed under supervision on a cycle ergometer, two days per week for 12 weeks

Exercise Snacking; HIIT

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Adults aged 18-65 years
• Diagnosis of type 2 diabetes mellitus for at least 6 months, based on standard criteria (fasting plasma glucose ≥7.0 mmol/L \[≥126 mg/dL\] and/or HbA1c ≥6.5% \[≥48 mmol/mol\])
• Physically inactive according to the International Physical Activity Questionnaire (IPAQ): \<150 min/week of moderate-intensity or \<75 min/week of vigorous-intensity physical activity, or \<600 MET-min/week
• Treated with oral glucose-lowering medication, or with insulin for at least 3 months before enrollment
• Stable pharmacological treatment with no recent changes in the therapeutic regimen
• No musculoskeletal injuries or contraindications to high-intensity exercise
• No chronic conditions that are inadequately controlled by standard medical therapy or that could be aggravated by high-intensity exercise
• No episodes of severe hyperglycemia or hypoglycemia requiring hospitalization within the previous 3 months

You may not qualify if:

• Physically active according to IPAQ criteria (vigorous-intensity activity on ≥3 days/week achieving at least 600-1500 MET-min/week, or ≥5 days/week of any combination of walking, moderate- or vigorous-intensity activity achieving at least 600-3000 MET-min/week)
• Diagnosed nephropathy, liver disease or neuropathy
• Cardiovascular disease, including absolute contraindications to exercise such as unstable angina, recent myocardial infarction or uncontrolled symptomatic heart failure
• Uncontrolled hypertension (systolic blood pressure \>160 mmHg and/or diastolic blood pressure \>90 mmHg)
• History of respiratory disease, including pulmonary hypertension or chronic obstructive pulmonary disease
• Moderate to severe somatic or autonomic neuropathy, retinopathy, or other musculoskeletal or neurological impairments that contraindicate high-intensity exercise
• Electrocardiographic abnormalities judged clinically significant by a specialist physician
• Acute illness with recovery lasting longer than 3 weeks, or recovery from acute illness completed within the 3 weeks preceding the intervention Medical advice to avoid high-intensity or any physical activity due to potential worsening of an existing condition

Sponsors & Collaborators

• University of Nis: lead

Study Sites (1)

Faculty of Sport and Physical Education, University of Niš

Niš, Serbia, 18106, Serbia

Location

MeSH Terms

Interventions

Exercise

Intervention Hierarchy (Ancestors)

Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Research Assistant

Study Record Dates

• First Submitted: October 8, 2026
• First Posted: October 15, 2026
• Study Start: January 20, 2026
• Primary Completion: July 17, 2026
• Study Completion: August 27, 2026
• Last Updated: October 15, 2026

Record last verified: 2026-10

Locations

SE (1)