Does a brief biofeedback exercise minimise the impact of acute stress on gastric function?

Participants will be required to attend a single 2-hour session at Alimetry Ltd. The study involves a simple test, "like an ECT for the gut" that will run continuously for the duration of the session. Individuals will also have additional cutaneous electrodes and sensors placed on their hand and shoulders to capture heart rate variability, breath rate, temperature and perspiration. Recording for HRV and associated parameters will run continuously for the duration of the session. This process is painless and non-invasive, although participants are asked to minimise movement. Participants will be asked to fast (not eat or drink anything including tea and coffee) from midnight the evening prior to their session and asked not to smoke or vape in the morning of their test. They may also be asked to refrain from taking some medications for 48 hours before their test. These medications include: drugs that affect gastric emptying (metoclopramide, domperidone, erythromycin), antispasmodics, pain medications which contain opiates (codeine, oxynorm, morphine, and tramadol), or sedatives. This is because these medications affect normal stomach actions. Upon arrival, eligibility will be reviewed and confirmed. Participants will be asked if they have any questions or concerns about the studies. Once these are satisfied, they will be required to sign an informed consent form and randomly assigned to either the intervention group (HRVB) or control group (sham procedure) The Body Surface Gastric Mapping (BSGM) recording will then be set-up: --A guide will be used to locate the array in a personalised manner. A portable ultrasound may be used to verify this positioning system is accurate. --Excess hair will be removed and participant’s skin will be prepped using NuPrep, which reduces skin impedance for enhanced test results. --A 64-channel electrode array (28 cm x 17 cm) will be non-invasively placed over the abdominal skin and connected to a portable data logger. The HRV Biofeedback equipment will also be set-up. - A respiratory belt will be placed firmly above the midline of the chest to measure breath rate. - An ECG electrode will be placed on each shoulder to capture heart rate variability. . - A PPG will be connected to the middle finger of the left hand for heart rate and blood pressure. - A temperature probe will be attached to the left thumb to measure temperature. - Skin conductors will be attached to the index and ring finger of the left hand to measure perspiration. Around 15 minutes of baseline BSGM and HRV data will be captured. During this time participants will complete standard participant information (e.g. demographics) and the Alimetry Gut-Brain Wellbeing Survey. A baseline measurement of how stressed and relaxed the participant feels will also be recording using a visual analogue sale (VAS). Participants will then be asked to consume a standardised meal of 425kCal. This includes a nutritional shake and protein bar. Suitable dietary options will be available for diabetics, people with dairy or gluten sensitivities, or people who are vegan. A 10-minute window is provided for meal consumption and participants will be asked to use this full time. Once the meal has been consumed, participants will then be guided through HRVB training (the intervention) or sham procedure for approximately 20-minutes. HRVB Training - involves determining resonance frequency (RF) for the individual which typically falls between 4.5 breaths per minute (bpm) and 7 bpm. - Participants are directed to view their real-time HRV signal (and other parameters as outlined above) on the screen. - They will see a tracking ball following the curves of a sine wave. They will then be asked to breath in as the ball ascends and breath out as the ball descends. - To determine optimal RF, participants will engage in breathing at different rates ranging from 5 to 7 bpm - The researcher and participant will discuss which rate is the most comfortable that produces the highest respiratory sinus arrhythmia (RSA). - Once RF has been determined, there will be a 10-minute wash-out period. The Cold Pressor Test - After the 10-minute wash-out period, participants will be asked to engage in HRVB or the sham procedure for the following 20 to 25 minutes. This will be the same condition they were orignally asssined to. - Within the first 10 minutes, they will be asked to indicate how relaxed and stressed they feel using a visual analogue scale (VAS) - At 10-minutes, they will be asked to immerse their right hand fully into a cold bath of approximately 10 degrees Celsius. They will be directed to hold it there for at least 1 minute and then are able to extract their hand thereafter with a ceiling time of 3-minutes observed. During this time pain intensity will be measured using a numerical rating scale (NRS). A third VAS will also be administered when the hand is extracted from thd cold bath. Post-Cold Pressor Test - Participants will be asked to continue with the initial treatment they were assigned to (either HRVB or sham procedure) for a further 20-minutes after the cold-pressor test. Additional note: The researcher(s) are present for the duration of the observation period to monitor process and adherence to intervention. .