Does the Timing of When High Intensity Intermittent Exercise is Undertaken Matter?

The Effect of Multiple Exercise Bouts During the Same Day (Continuous and High Intensity Intermittent Exercise), on Gastrointestinal Function, Appetite and Metabolic Response in Healthy Males: a Randomised Cross Over Trial

The participants will visit the laboratory on 3 occasions, once for a preliminary visit and a further two occasions to complete experimental trials in a randomised order. The experimental trials will consist of cycling under two conditions; HIIE-First followed by Continuous (Trial-A) or Continuous-First followed by HIIE (Trial-B). Participants will be asked to standardise their diet for 24-hours and complete an overnight fast prior to visiting the laboratory. Participants will then complete 60-min of cycling split throughout the day into two 30-min bouts, HIIE or continuous cycling before breakfast followed by a 3.5 hour rest period before completing their remaining 30-min HIIE or Continuous cycling before lunch. Each experimental trail will last approximately 8 hours and begin at 08:00am. Throughout the trial measurements of subjective feelings of appetite, gastric emptying rate, substrate utilisation and regular blood samples will be taken. Post-trial nutritional and well-being questionnaires will be collected at 24-h post.

Study hypothesis

1. The order in which continuous and HIIE is undertaken will result in differences in gastric emptying rate after ingesting a semi-sold lunch?
2. Depending on which mode of exercise is undertaken first will result in different gastrointestinal hormone responses, metabolic responses and appetite responses throughout the trial day?
3. Will the order in which different modes of exercise, undertaken within the same day effect nutritional intake and well-being 24-h after both exercise bout have been completed?
4. Is substrate oxidation effected by the order in which multiple exercise bout of different modes are undertaken within the same day.

There is a growing amount of literature committed to understanding if becoming more active will have beneficial effects on metabolic health; secondly do the traditional physical exercise and dietary approaches to managing obesity result in prolonged weight loss. The purpose of this study is to determine whether high intensity intermittent exercise (HIIE) and continuous exercise carried out in differing sequences within a day will have a beneficial health impact.

Participants will complete two 8h experimental trials in a randomised cross-over design. Each participant will complete 60-min of exercise in both trial arms; HIIE-First or Continuous-First separated by a minimum of 7 days. One trial will consist of a 30-min HIIE cycling session (10 x 1min of peak power output followed by 2min rest). After completion of this bout of exercise, participants will ingest a standardised breakfast. Following a rest period of 3h before completing the remaining 30-min of exercise (50% peak maximal oxygen uptake), before consuming a standardised semi-sold lunch meal. The second trial will be identical other than participates will undertake the continuous exercise first followed by the HIIE. Regular appetite, breath and blood samples will be taken throughout the trials. In The 24 hours following the end of each trial, participants will be asked to record their dietary intake and record their feeling of well-being documented on a questionnaire. There will be no long-term follow up following completion of the study.

Therefore, the aim of this research project is to identify whether the order of HIIE and continuous exercise separated within the day results in changes to gastrointestinal health, appetite, and metabolic responses.

Inclusion Criteria:

1. Healthy males
2. Age between 18-40 years
3. Body mass index = <29.9 kg/m2
4. Non-smokers
5. No history of GI symptoms
6. Not consuming prescription medication, or no other relevant medical conditions assessed by a medical screening questionnaire.
7. Not vegan or lactose intolerant
8. Subsequently be physically active, in order to complete the trials.

Exclusion Criteria:

1. Not healthy
2. Female
3. Under 18 years
4. Over 40 years
5. Body mass index = >29.9 kg/m2;
6. Smokers
7. History of GI symptoms or disease,
8. Consuming prescription medication
9. Lactose Intolerant
10. Vegan
11. Subsequently not physically active, in order to complete the trials