We aim to establish the impact of pre-exercise CHO availability and exhaustion on maximal fat oxidation (MFO & FATmax) during exercise
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Brief title
Condition
- Other condition
Synonym
Health condition
niet van toepassing (inspanningsfysiologie)
Research involving
Sponsors and support
Intervention
Outcome measures
Primary outcome
The main study parameters are the MFO and FATmax as assessed with indirect
calorimetry (VO2, VCO2) during a graded exercise test (35W/ 3min protocol). In
order to calculate these values oxygen consumption (VO2), and CO2 production
(VCO2) are measured. From these values the RER can be calculated, and fat
oxidation will be quantified according to by the stoichiometric equations
Frayn (1983).
Secondary outcome
Other parameters that can be obtained during the graded exercise test are: peak
sustained power output (expressed in Watt), maximal oxygen consumption
(VO2max), (maximal) heart rate and the respiratory exchange ratio (RER) during
different stages of the graded exercise protocol.
In addition, body composition, training history and dietary intake will be
measured
Background summary
During exercise, energy expenditure increases dramatically, with exercise
intensity as the single most important factor influencing substrate
utilization. It is commonly reported that fat oxidation increases as exercise
intensity increases, up to a certain point. At higher exercise intensities, fat
oxidation declines quite rapidly, despite increased energy requirements, and
carbohydrate becomes the predominant, and finally the only fuel source during
(aerobic) exercise.
The maximal capacity of the human body to oxidize fat during exercise can
quantitatively be described by the so-called *MFO* and *FATmax*. The MFO
(maximal fat oxidation) is the highest absolute level of fat oxidation as
expressed in gram per minute (g/min), while FATmax is the exercise intensity at
which fat oxidation is highest (%VO2max or %HFmax). These concepts may have
importance for endurance training and performance.
It is well known that, even in quite homogenous populations, inter-individual
variability in fat oxidation, in particular MFO, is quite large. Individual
factors like gender, body composition (lean mass) and fitness level do explain
a substantial part of this variation. In addition, genetic factors do underlie
differences between individuals. But also *external factors* like nutritional
status, i.e. a low or high carbohydrate (CHO) availability, and exhaustion are
likely linked to maximal fat oxidation, due to alterations in substrate
availability. The contribution of these external factors to alterations in
substrate utilization is, as of yet, unknown
Study objective
We aim to establish the impact of pre-exercise CHO availability and exhaustion
on maximal fat oxidation (MFO & FATmax) during exercise
Study design
The study consist of two parts. In part I the impact of carbohydrate
availability will be assessed, in part II the impact of exhaustion. Both parts
have a cross-over design.
In part I subjects will perform an graded exercise test to measure maximal fat
oxidation ('fatmax test'). At one occasion with low CHO, the other time with
high CHO. The order will be randomised. One week will be considered in between
conditions.
In part II, subjects will do the graded exercise test twice on a single day,
but now with an exhaustive exercise session ('training') of ~ 90 min in
between, to induce exhaustion
In both parts, the experimental testing will be preceded by a visit in which
body composition is measured and subjects are familiarised to the test
procedures. In addition, a physical activity questionnaire and a 3 day food
record will be taken.
The graded exercise test is the so-called *fatmax test* as described by Achten
and Jeukendrup (2003). Participants start with a warming up at 95W (males) or
60 W (females), after which intensity will be increased every 3 min with 35 W,
till exhaustion. Heart rate as well as oxygen consumption (VO2) and carbon
dioxide production (VCO2) will be monitored, to obtain fat oxidation rates and
maximal aerobic capacity.
Intervention
Part I: In this part of the study the pre-exercise availability of
carbohydrates will be manipulated. Before measuring maximal fat oxidation
during exercise, subjects will be randomly-assigned to a 36 hour period (i.e an
afternoon, a single day plus a breakfast) of either a low CHO / high fat diet
(~65 %en by fat) or an equal energy (isocaloric), high carbohydrate diet (~65
%en by CHO).
Part II: in this part the intervention is a 'training session' of 90 min at 60%
Wmax, with every 15 min a high intensity bout of exercise of 2 min (90%Wmax).
This is to simulate a training session, and induce exhaustion.
The day before the trials, participants have to refrain from exercise
Study burden and risks
The burden associated with participation is as follows:
- the time investment that is required
- The exercise testing/ sessions
- The general rules and guidlines the participants need to obey
- Short term dietary manipulation (part 1)
- X-ray exposure during the DEXA-scan (the amount of radiation which the
participant is exposed to is negligible)
The exercise sessions can induce fatigue and muscle soreness. Muscle soreness
will generally resolve in days. Exercise sessions will be done in the exercise
lab of the Health Research unit of WUR, with adequate medical back-up.
Participants are healthy
The dietary manipulation might cause some discomfort. Especially the low
carbohydrate diet might be burdensome for the participants, as this nutritional
pattern is not something the participants are used to. The participants are
required to follow an altered dietary pattern twice, each for a period approx.
36 hours. This can considered to be a burden for the participant.
The participants will visit the research facility for a maximum of four times
during the study. Total duration of the visits will be 8-9 hours in a period
of 2-3 weeks.
Stippeneng 4
Wageningen 6708 WE
NL
Stippeneng 4
Wageningen 6708 WE
NL
Listed location countries
Age
Inclusion criteria
* Apparently healthy (self-reported)
* aged between 20 and 35
* BMI between 18.5 to 27 kg/m2
* Recreationally active, defined as minimal of 3 hours training per week, and a
maximum of 10 hours a week
* The sport a participant is engaged in should be a game sport, endurance
sport, or should at least contain a major endurance component. Examples of
sports that can be included are: distance running, cycling, triathlon,
crossfit, and game sports like soccer, rugby, handball, hockey,
* For part 2 subjects should be used to prolonged cycling exercise
* Able to be present and participate at all test days and willing and able to
follow prescribed interventions
Exclusion criteria
* Inactive (defined as <3 hours of training per week)
* Non-recreational athlete (>10 hours of training per week)
* active in a sport without a major endurance component
* Smokers, defined as someone who has smoked regularly in the previous year.
* Excessive alcohol consumption (i.e. more than 14 units for males per week; 7
units for females)
* Drug use
* The more *extreme* diets (like veganism, ketogenic diet, raw-food, carnivore
diet etc.)
* Participation in another biomedical study possibly interfering with the study
results within 1 month before the first study visit
* Inability to participate and/or complete the required measurements
* People working for the department of Human Nutrition and Health
not having a GP
Design
Recruitment
Followed up by the following (possibly more current) registration
No registrations found.
Other (possibly less up-to-date) registrations in this register
No registrations found.
In other registers
| Register | ID |
|---|---|
| ClinicalTrials.gov | NCT |
| CCMO | NL72841.081.20 |