An interventional study of Exercise in Typ 2 Diabetes, sponsored by University of Nis. Completed at 1 site in Serbia. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-10-15.
Sponsored by University of Nis · Not applicable, Interventional, and Treatment
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.
Regular exercise is a cornerstone of type 2 diabetes mellitus (T2DM) management, yet most individuals with T2DM do not meet recommended physical activity levels, with lack of time among the most frequently reported barriers. High-intensity interval training (HIIT) improves glycemic control and cardiorespiratory fitness with a lower time commitment than moderate-intensity continuous exercise (MICT). Exercise snacking, in which brief bouts of vigorous exercise are distributed across the day, has been shown to attenuate postprandial glucose responses acutely. Whether exercise snacking produces chronic adaptations comparable to those of conventional HIIT has not been established.
This was a three-arm, parallel-group randomized controlled trial. Participants were recruited in collaboration with endocrinologists, the Primary Health Care Centre Leskovac, and local diabetes associations. Fifty-one participants were allocated by block randomization (1:1:1 allocation ratio) to exercise snacking group (n = 17), HIIT group (n = 17), or a control group (CON, n = 17). Sample size was calculated a priori for HbA1c (G*Power 3.1; repeated-measures ANOVA, within-between interaction, f = 0.25, α = 0.05, power = 0.80). This required 42 participants, which was increased to 51 to allow for an anticipated 20% dropout.
Both exercise groups trained on cycle ergometers under supervision, two days per week for 12 weeks. Training intensity was prescribed from age-predicted maximal heart rate (HRmax = 208 - 0.7 × age) and monitored continuously with heart rate monitors. Perceived exertion was recorded on the 0-10 RPE scale. The exercise snacking protocol, adapted from Francois et al. (2014), was performed three times per training day, before each main meal. Each session comprised a 5-minute self-paced warm-up, six 1-minute intervals at 90-95% HRmax separated by 1-minute passive or active recovery, and a 3-minute cool-down. The HIIT protocol was performed once per training day in the afternoon or early evening. Each 35-minute session comprised a 5-minute warm-up, four 4-minute intervals at 90% HRmax separated by 3-minute active recovery at 70% HRmax, and a 2-minute cool-down. Workload was progressively adjusted to keep heart rate within the target range. The CON was advised to maintain habitual physical activity and dietary habits. Diet was not controlled in any group, and participants were instructed not to change their usual eating habits. To minimize the risk of hypoglycemia, capillary glucose was measured before and after every session according to established safety recommendations for exercise in diabetes.
All assessments were performed at baseline and after the 12-week intervention in a standardized order. Fasting venous blood samples were collected between 07:00 and 10:00 h after an 8-12 h fast. Fasting glucose was analysed on a Beckman Coulter DxC 700 AU analyser and HbA1c on a HumaNex A1C analyser. Postprandial capillary glucose was self-measured by participants with an Accu-Chek glucometer 180 minutes after breakfast, lunch and dinner. Body composition was assessed by bioelectrical impedance (Omron BF-511), and blood pressure with an automated oscillometric device (Omron HEM-7130). The 6-minute walk test was performed according to American Thoracic Society guidelines on a 30-m outdoor course. Peak oxygen uptake was estimated from walk distance using the Ross et al. (2010) equation and also expressed in absolute terms using body mass. Health-related quality of life was assessed with the WHOQOL-BREF questionnaire.
Intervention effects were analysed using a 3 × 2 mixed-design ANOVA, with the time × group interaction as the main test of intervention-specific effects. Changes from baseline were compared between groups with 95% confidence intervals and Bonferroni-adjusted post-hoc comparisons. Inter-individual variability in response was evaluated using predefined thresholds for clinically meaningful change and the standard deviation of individual responses, with the CON used to account for random variation.
University of Nis is the lead sponsor of 6 studies on the registry; 1 is open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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
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
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.
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
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.
Time frame: 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).
Time frame: 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.
Time frame: 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.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in 6-minute walk distance (6MWT)
Distance (m) covered during the 6 MWT, performed according to American Thoracic Society guidelines on a 30-m outdoor course.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in postprandial glucose after breakfast
Capillary blood glucose (mmol/L) self-measured with an Accu-Chek glucometer 180 minutes after breakfast.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in postprandial glucose after lunch
Capillary blood glucose (mmol/L) self-measured with an Accu-Chek glucometer 180 minutes after lunch.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in postprandial glucose after dinner
Capillary blood glucose (mmol/L) self-measured with an Accu-Chek glucometer 180 minutes after dinner.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in body mass
Body mass (kg) measured by bioelectrical impedance analysis (Omron BF-511).
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in body mass index
Body mass index measured by bioelectrical impedance analysis (Omron BF-511).
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in body fat percentage
Body fat (%) estimated by bioelectrical impedance analysis (Omron BF-511).
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in muscle mass percentage
Skeletal muscle mass (%) estimated by bioelectrical impedance analysis (Omron BF-511).
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in systolic blood pressure
Resting systolic blood pressure (mmHg) measured in a seated position with an automated device (Omron HEM-7130); two measurements separated by 3 minutes.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in diastolic blood pressure
Resting diastolic blood pressure (mmHg) measured in a seated position with an automated device (Omron HEM-7130); two measurements separated by 3 minutes.
Time frame: From enrollment to the end of treatment at 12 weeks.
Change in health-related quality of life
WHOQOL-BREF scores for the physical health, psychological, social relationships and environment domains (0-100; higher scores indicate better quality of life), together with overall quality of life (Q1) and satisfaction with health (Q2).
Time frame: From enrollment to the end of treatment at 12 weeks.
Proportion of clinically meaningful responders
Proportion of participants achieving predefined clinically meaningful changes: ≥0.5% reduction in HbA1c, ≥1.7 mmol/L reduction in fasting glucose, ≥30 m increase in 6-minute walk distance, ≥3.5 mL·kg-¹·min-¹ increase in relative VO₂peak and ≥0.30 L·min-¹ increase in absolute VO₂peak.
Time frame: From enrollment to the end of treatment at 12 weeks.
Inter-individual variability in response
Standard deviation of individual responses (SDIR), calculated as the square root of the difference between the variances of change scores in each exercise group and the control group, for HbA1c, fasting glucose, 6-minute walk distance and relative and absolute VO₂peak.
Time frame: From enrollment to the end of treatment at 12 weeks.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is completed, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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