Human Physiology is coordinated by a circadian timing system that synchronises daily cycles of light-dark, wake- sleep, activity-rest and feeding-fasting. The alignment of these behavioural patterns with underlying biological rhythms is closely linked to physiological function, with misalignment linked to chronic metabolic diseases.
The vast majority of evidence about rhythms in metabolism comes from studies of rodents, which is remarkable given that rodents differ fundamentally from humans in both behaviour and metabolic regulation. Moreover, almost no research in any species has examined the effects of muscle contractile activity on 24-h rhythms in metabolism. Skeletal muscle is a key site of metabolic regulation and contractile activity is a powerful stimulus to increase metabolism. The researchers have established a novel protocol for serial muscle sampling throughout 24 hours and pilot work completed in preparation for this grant revealed diurnal transcriptomic and lipidomic rhythms in human skeletal muscle. Further development of that protocol has used enteral feeding via a tube which delivers nutrient directly to the stomach to enable constant nutrient delivery (including during sleep), with preliminary data indicating that underlying rhythms in metabolism are responsive to nutrient availability patterns.
The researchers will now capitalise on those findings by incorporating multiple isotope tracers within the protocol, thus finally documenting the nature of rhythmic flux in carbohydrate metabolism and protein turnover in human skeletal muscle, and how those rhythms are aligned with timing and patterns of exercise. In summary, participants will stay in the laboratory for 36 hours with 24 hours of constant feeding via nasogastric tube, and muscle and blood sampling. Participants will be allocated to either the early or late exercise group (involving 1 hour of cycling at either 0800 or 2000 h, respectively) or the control group who will rest for the 24 hours.
Who can participate
Age range
18 Years – 50 Years
Sex
ALL
See this in plain English?
AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Inclusion Criteria:
* Women and men - with targeted recruitment to encourage females to volunteer given previous recruitment rates; anticipating fewer women than men, sex will also be included as a strata in the randomisation plan to favour the few who do volunteer being relatively evenly distributed between conditions.
* A body mass index of \>18 and \<35 kg•m-2.
* Minimum absolute body mass of 67 kg (to accommodate the required dose of lidocaine for 7 biopsies, plus additional for pre-incisions)
* be between 18-50 years of age
* Premenopausal women
* Metabolically healthy (free from diagnosed metabolic illness or family history of type II diabetes
* be able and willing to give informed oral and written consent,
* complete and meet the defined criteria of pre-study questionnaires and screens
* have a regular sleep cycle with a sleep duration between 6 and 8 h
* do not exhibit extreme morning or evening preference (Horne and Ostberg, 1976)
* agree to keep a constant sleep/wake cycle with a self-selected 8-h duration in bed/dark trying to sleep (from which it cannot be deviated by more than 30 minutes) for one week prior to the lab study
* obtain 15 minutes of sunlight within 1.5 hours of waking up and agree to nap only within a 4 h designated nap window for one week prior to the lab study
* allow confirmation of compliance to these instructions by wearing ActiHeart and light monitors continuously and complete daily sleep and event diaries for one week before the study sessio…
Questions worth asking your doctor
Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.
1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?
Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.
Questions for the trial coordinator
The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.
1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?
A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.