Plain English Summary
Background and study aims
Diabetes mellitus is a life-long condition where a person is unable to control their blood sugar levels. There are two main types of diabetes, type 1 (around 10% of cases) and type 2. In type 1 diabetes (T1DM) the immune system attacks specialised cells in the pancreas called β-cells (which are responsible for producing the hormone insulin). This means that the sufferer is unable to produce enough insulin to effectively control their blood sugar levels and so regularly inject insulin in order to keep their blood sugar levels in a healthy range. T1DM sufferers have a high risk of developing complications from their diabetes, such as heart or blood vessel disease (cardiovascular complications), and so they are advised to maintain a healthy lifestyle with regular physical activity. People with T1DM often develop low blood glucose events when they perform exercise, with uncomfortable side effects such as nausea, palpitations, weakness and, in extreme situations, loss of consciousness. A 4-Step strategy has been developed to maintain blood sugar levels throughout exercise to help avoid these complications. This is effective in continuous exercise, such as running or cycling. However, is well known that the demands of intermittent (stop-start) physical activity are different from continuous exercise. The aim of this study therefore is to find out whether a 4-Step strategy of dietary and therapeutic adjustments leads to a better performance at soccer (an intermittent type of exercise), cognitive function (mental processing) and blood sugar control.
Who can participate?
Adults with T1DM who regularly play soccer.
What does the study involve?
Participants are randomly allocated to take part in two study conditions in a random order. In both conditions, participants complete a series of soccer-based training exercises in two sessions (on day 21 and 42 of the study). The first study condition involves the 4-Step strategy of dietary and insulin adjustments on the days when they are training. This involves eating a meal 60 minutes before they exercise with a 50% insulin dose, a meal 60 minutes after exercising with a 50% insulin dose, a bedtime snack without an insulin dose and a 20% reduction in their basal insulin dose (background level of insulin needed 24 hours a day). Those in the second group follow usual recommendations according to exercise guidelines in diabetes with regards to their diet and insulin regime on the days when they are training. At the start of each condition and after three months, participants have their physical performance assessed. At the same times and immediately after and the day after each training session, participants also complete a range of assessments to measure their cognitive function.
What are the possible benefits and risks of participating?
Participants may benefit from better control of their disease and with the prevention of future cardiovascular complications. There are no notable risks involved for participants.
Where is the study run from?
Costa Rican Association of Diabetes, Endocrinology and Metabolism (Costa Rica)
When is the study starting and how long is it expected to run for?
September 2016 to July 2018
Who is funding the study?
Medtronic Foundation (USA)
Who is the main contact?
Dr Javier Calvo
Dr Javier Calvo
Asociación Nacional Pro Estudio de la Diabetes
Endocrinología y Metabolismo (ANPEDEM)
San Rafael de Escazú
Effect of insulin therapy and dietary adjustments on performance during simulated soccer tests in people with type 1 diabetes: study protocol for a randomized, cross-over, double-blinded, controlled trial
Through a 4-Step strategy of dietary and therapeutic adjustments, a better performance will be observed by persons with Type 1 Diabetes on soccer and cognitive evaluations, as well as a more stable control of glycemic parameters before, during and after exercise execution, indexed by continuos glucose monitoring measurements.
Not provided at time of registration
Randomized cross-over double-blinded controlled interventional trial
Primary study design
Secondary study design
Randomised cross over trial
Patient information sheet
Not available in web format, please use the contact details to request a patient information sheet
Type 1 diabetes
Participants are randomized to receive two interventions in a random order using block-stratified randomization, with random 2-4 sized blocks and stratified by gender. A statistician non-related to the protocol will generate the randomization list using a web-based method (http://www.randomizer.org) that will randomize the order of the interventions assigned. The assessment sessions will occur on two separate days separated by three weeks from each other as wash out period because of the cross over design of the trial.
Real 4-Step Method: Participants consume a 60 min pre-exercise meal with 50% of insulin dose, 60 min post-exercise low GI meal with 50% of insulin dose, bedtime low GI snack before sleep omitting insulin dose, and 20% reduction in basal insulin dose.
Sham 4-Step Method: Participants follow ADA's usual recommendations of care before, during and after exercise. This involves a 60 min pre-exercise meal with 75% of insulin dose, 60 min post-exercise medium GI meal with no reduction in insulin dose, bedtime medium GI snack before sleep omitting insulin dose, and no reduction in basal insulin dose.
Participants in both groups attend 7 study visits in each trial condition. These involve: review of eligibility criteria (pre-screening visit), demographic data, clinical evaluation and BMI measurement and laboratory evaluation (visit 1, day 0), theoretical and practical explanation of training exercises (visit 2, day 14), training sessions with simulated soccer exercises and cognitive evaluations (visits 3 and 6, days 21 and 42), revision of self-monitoring of blood glucose (visits 4 and 7, days 24 and 45) and efficacy of blinding assessment (visits 5 and 7, days 35 and 45).
The assessment sessions will occur on two separate days (visits 3 and 6) and them will be separated by three weeks from each other, and consist of both cognitive and physical activity evaluations. Furthermore, participants will be seen the day following each assessment visit (visits 4 and 7) during which cognitive testing and self-monitoring of blood glucose will be repeated. In the last visit (visit 7) the efficacy of blinding will be assessed by asking participants in which interventional arm they think they were allocated, and how confident they are about their answer.
Primary outcome measure
Physical and technical performance in soccer training sessions will be evaluated using the Loughborough Intermittent Shuttle Test – Prescribed and Self-Paced (LIST-P), the Loughborough Soccer Passing Test (LSPT) and the Loughborough Soccer Shooting Test (LSST) at baseline and 3 weeks in each study condition
Secondary outcome measures
1. Selective attention and mental processing speed are measured using the Stroop Test at baseline and three weeks, and immediately after finishing the soccer exercises and the day after each workout visit in each study condition
2. Sustained attention and psychomotor speed are measured using the Digit Vigilance Test at baseline and three weeks, and immediately after finishing the soccer exercises and the day after each workout visit in each study condition
3. Visuo-spatial short-term memory are measured using the Corsi Block-Tapping Task at baseline and three weeks, and immediately after finishing the soccer exercises and the day after each workout visit in each study condition
4. Visual sustained attention and working memory processes are measured using the Rapid Visual Information Processing task at baseline and three weeks, and immediately after finishing the soccer exercises and the day after each workout visit in each study condition
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Age 18 years and over
2. More than two years of established T1D diagnosis
3. Stable insulin regimen in the past 6 months indexed by a less than 20% of changes in total insulin daily dose
4. HbA1c less than 9.0%
5. Weekly physical activity of 90 min or more
6. Participation in recreational or competitive soccer-related activities, at least four times per month
7. Able to provide informed consent
Target number of participants
Participant exclusion criteria
1. Any treatment regimen different from continuous subcutaneous insulin infusion or multiple daily insulin injections
2. Any use of medications (other than insulin) known to affect glycemic control including oral or parenteral steroids (except for inhaled steroids), metformin, SGLT2 inhibitors, GLP.1 agonists, thiazolidinediones, sulfonylureas, DPP-4 inhibitors, or any other oral antidiabetic therapy
3. Detectable C-peptide in serum
4. Cognitive impairment comprising any substantial decrease in alertness, language reception, or attention that might interfere with understanding instructions for motor and cognitive testing, not including hypoglycemia unawareness
5. Chronic kidney disease (glomerular filtration rate less than 90 ml·min-1)
6. Chronic liver failure (Child-Pugh B or C)
7. Advanced diabetic retinopathy
9. Color blindness
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Asociación Nacional Pro Estudio de la Diabetes, Endocrinología y Metabolismo (ANPEDEM)
Autopista Próspero Fernández San Rafael, Escazú San José, Costa Rica
Asociación Nacional Pro Estudio de la Diabetes, Endocrinología y Metabolismo
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Planned publication in a high-impact peer reviewed journal as Diabetes Care 6 months after trial end.
IPD Sharing plan:
The datasets generated during and/or analysed during the current study are/will be available upon request from Javier Calvo (email@example.com) and Gabriel Torrealba (GTORREALBAACOSTA@partners.org)
Intention to publish date
Participant level data
Available on request
Basic results (scientific)
2017 protocol in: https://www.ncbi.nlm.nih.gov/pubmed/28728559