Evaluating the effect of exercise and kiwifruit on blood glucose regulation

This is a single-blind, placebo controlled parallel design intervention study that will allow us to evaluate whether exercise has any effect in modifying the reduction in glycaemic response (when consumed with a high GI drink) conferred by kiwifruit. Prospective participants will be asked to attend a familiarisation session where they will meet with the study’s principal investigator (research scientist, PhD). During the session, the principal investigator will explain the study’s objectives and what is required from them as a volunteer. Each participant will be asked to complete a health screening and a Baecke habitual physical activity questionnaires which will be assessed against the study’s exclusion/inclusion criteria. They will also be asked to sign a consent form to confirm their permission to proceed as a volunteer in this study. Participants will be introduced to the Rating of Perceived Exertion (RPE) scale that they will be responding to during the trial days. Finally, participants will be asked to perform an exhaustive cycle exercise test (under the guidance of the principal investigator) to estimate their maximal aerobic capacity that will allow us to estimate the workload they will need to perform on the trial days. Measuring each participant’s aerobic capacity allows us to ensure that participants are exercising at the same intensity relative to their fitness as participant’s fitness levels will vary. All recruited participants will be required to attend an initial Non-Exercise Trial Day where their baseline resting glycaemic response after consuming a glucose drink will be characterised. Participants will arrive on the morning of their trial day in a fasted state (no food for 12 hours) where they will be given a sugar drink (50 g glucose dissolved in 250 mL water) to consume quickly (within two minutes). Their blood glucose will be subsequently measured from finger prick samples at regular intervals for up to 2 hours after consuming their glucose drink. To assess if the exercise has any effect in modifying the modulatory effect of kiwifruit on the glycaemic response, recruited participants will be required to complete two trial days with an exercise (Exercise Trial Days 1 and 2). Participants will be evenly randomly allocated into two treatment groups: (1) kiwifruit and (2) placebo (kiwifruit sugar) group. Exercise Trial Day 1 will involve determining participant’s post-exercise glycaemic response after consuming a glucose drink following a 10 min exercise cycle bout. On Exercise Trial Day 2, the post-exercise glycaemic response after consuming either a kiwifruit or placebo drink (depending on which treatment group a participant has been allocated to) will be assessed following a 10 minute exercise. By implementing this trial design, we will be able to compare how consuming kiwifruit (or kiwifruit sugar) may further affect changes in the glycaemic response induced by exercise and whether these changes (in any) differ between the two treatment groups. On the morning of these exercise trial days, participants will arrive on-site in a fasted state as they did previously. They will then be required to complete a 10 minute exercise cycle at an intensity corresponding to 75% their maximal aerobic intensity. The principal investigator will be present at this time to monitor the participant’s adherence to the exercise and give verbal encouragement to ensure that they perform the exercise to the best of their ability. Five minutes after the completion of their exercise, participants will be required to consume the glucose drink or one of the treatment intervention drinks (i.e. kiwifruit or placebo). The kiwifruit intervention drink will compose of 200 g kiwifruit with added glucose to total of 50 g available carbohydrate made up to a volume of 250 mL with water. In summary, all participants will take part in three trial days which will involve a Non-exercise Trail Day and two Exercise trial days: Non-exercise Trial Day: All participants’ (n=30) resting glycaemic response after consuming a drink containing 50 g glucose will be assessed. Exercise Trial Day 1: All participants’ (n=30) post-exercise glycaemic response after a 10 minute cycle exercise followed by consuming a drink containing 50 g glucose will be assessed. Exercise Trial Day 2: Participants’ glycaemic response after a 10 minute cycle followed by consuming their allocated nutritional intervention – kiwifruit (n=15) or kiwifruit sugar (n=15) will be assessed. As participant’s post-exercise response will be assessed for only one of the nutritional treatment interventions, this is a parallel study. Trial days will be separated by at least 1 week to avoid any training effect from performing the exercise cycle. No maximum amount of time between exercise trial days is set, but we aim to run our participants through all trial days within 3 months after recruitment.