Exercise, Damage Muscle, Nutrition
Conditions
Keywords
eccentric exercise, 13C-glucose, exercise mode
Brief summary
This study compares fuel selection during eccentric and concentric cycling, with (placebo) or without glucose ingestion during exercise. After a 2-week familiarization and habituation with the ergometers, subjects will complete four experimental conditions in a randomized order: concentric with placebo, eccentric with placebo, concentric with glucose, eccentric with glucose.
Detailed description
Cycling on a cycle ergometer typically requires repeated concentric muscle contractions to push on the pedals and produce mechanical work. An eccentric cycling ergometer has a motor that rotates the cranks with a predetermined torque, the cyclist needs to resist to the movement of the cranks. This leads to eccentric muscle contractions, the work is thus produced while the muscle is lengthening (negative work). This mode of exercise is known to produce a lower oxygen consumption (energy cost) for the same mechanical power output and also leads to muscle damage which can interfere with fuel selection.
Interventions
DIETARY_SUPPLEMENTSolution ingestion
Two ingestion modalities will be attributed (participant is blinded) in random order: a placebo and a glucose solution. The placebo contains water and a non-caloric sweetener (stevia) in order to reproduce the taste of the glucose solution. The glucose solution contains 6% glucose per volume, labelled with 13C. Both solutions will be administered in 8 doses: a bolus (333 mL) at rest, 30 minutes before the start of exercise, 167 mL immediately before exercise, 167 mL every 15 minutes during arm cranking, 125 mL immediately before concentric or eccentric pedalling and at 15 and 25 minutes of this last exercise period. In total, 1250 mL of solution will be administered during the experimental protocol.
BEHAVIORALConstant load arm cranking
The participants will perform 45 minutes of arm cranking on a specialized ergometer at a power output corresponding to 30% of their concentric cycling VO2max, previously measured.
PROCEDUREExpired gas sampling
Subjects will be asked, twice, to provide a forced expiration into a 10 mL plastic tube in order to collect a sample expired gases. This procedure will be done immediately before blood sampling and ingestion of the solution.
PROCEDUREIndirect respiratory calorimetry
A mouthpiece and nose plug will be placed on the subject and expired gases will be analyzed by a metabolic cart during 3 minutes. This procedure will be done immediately before expired gas collection, blood sampling and ingestion of the solution.
PROCEDUREBlood sampling
A catheter will be inserted in an antecubital vein and a saline solution will be continuously perfused to maintain vein open. 10 mL of blood will be collected immediately before ingesting the solution for a total of 80 mL.
BEHAVIORALMeasure of maximal voluntary contraction force production
Maximal voluntary bilateral knee extensions (3 trials of 3-4 seconds each) will be performed on a chair equipped with force sensors to measure peak force production. These measurements will be done before the first ingestion, immediately before exercise, during the transition between arm cranking and concentric or eccentric cycling, and at the end of the exercise protocol.
DIAGNOSTIC_TESTMeasure of muscle electrical activity (EMG)
Surface electrodes will be placed on the biceps and quadriceps to measure EMG throughout the exercise protocol.
DIAGNOSTIC_TESTMeasure of central and cutaneous temperatures
Wireless sensors will be placed on the skin of the arm, chest, back, abdomen, thigh and calf using adhesive tape. A wireless thermometric pill will be ingested the morning of the experiment. These will allow the measurement of skin and central temperatures throughout the exercise protocol.
DIAGNOSTIC_TESTMeasure of perceived exertion, pain perception and affective response
100 points scales (CR100) will be used to measure perceived exertion and pain perception immediately before ingesting the gas sampling. At the same time, affective responses will be assessed using the Feeling scale.
PROCEDUREMeasure of sweat and urine production
Sweat production and sampling will be performed by measuring body weight before and after exercise, after voiding the bladder. Mass loss through the urine and gases will be accounted for in order to compute sweat production. A sweat sample will be collected using a cotton gauze placed into a plastic collector affixed in the upper back of the participants. A urine sample will be taken from the urine collected at the end of the exercise period. Urine and sweat volumes along with respective urea concentrations will be used to compute protein oxidation during exercise.
Sponsors
Université de Montréal
Study design
Allocation
RANDOMIZED
Intervention model
SEQUENTIAL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Masking description
Opaque bottles to administer beverages with similar sweet taste.
Eligibility
Sex/Gender
MALE
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Low alcohol consumption (\<3 drinks/week) * Non-smokers * Not regularly taking medication for a known pathology * Regularly practices endurance sports (cycling, running, etc.)
Exclusion criteria
* Intolerant to glucose (according to WHO standards) * Musculoskeletal injury or illness affecting exercise performance * Failure to respect protocol guidelines (diet, exercise prior to experimentation, etc.)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Exogenous glucose oxidation | Average over the 35 minutes of eccentric or concentric exercise | Measured by indirect respiratory calorimetry combined with tracer techniques. |
| Maximal voluntary force production | Change between baseline and end of exercise | Measured using isometric bilateral knee extensions |
| Central and skin temperature | Average over the 35 minutes of eccentric or concentric exercise | Measured using a thermometric pill and skin-surface electrodes |
| Perceived exertion | Average over the 35 minutes of eccentric or concentric exercise | Measured using a Category Ratio scale on 100 points (CR100), 0 signifies no exertion and 100 being maximal effort. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Total carbohydrate, fat and protein oxidation | Average over the 35 minutes of eccentric or concentric exercise | Measured by indirect respiratory calorimetry corrected for urea excretion in sweat and urine |
| Blood insulin concentration | For 0 minutes corresponds to the beginning of exercise, at -31, -1, 14, 29, 44, 49, 59 and 69 minutes | Blood is sampled using a venous catheter over about 60 seconds. Following centrifugation to extract the plasma, a small sample is used to measure insulin concentration. |
| Affective response | Average over the 35 minutes of eccentric or concentric exercise | Feeling scale, ranging from -5 to +5, reporting the mood (Hardy & Rejeski, 1989). -5 corresponds to very bad and +5 to very good. |
| Pain perception: VAS | Average over the 35 minutes of eccentric or concentric exercise | Visual analogue pain scale of 25 cm, relative distance converted to score on 100 points. Higher values correspond to greater pain sensation. |
| Blood glucose concentration | For 0 minutes corresponds to the beginning of exercise, at -31, -1, 14, 29, 44, 49, 59 and 69 minutes | Blood is sampled using a venous catheter over about 60 seconds. Following centrifugation to extract the plasma, a small sample is used to measure glucose concentration. |
| Blood free-fatty acid concentration | For 0 minutes corresponds to the beginning of exercise, at -31, -1, 14, 29, 44, 49, 59 and 69 minutes | Blood is sampled using a venous catheter over about 60 seconds. Following centrifugation to extract the plasma, a small sample is used to measure free-fatty acid concentration. |
| Blood lactate concentration | For 0 minutes corresponds to the beginning of exercise, at -31, -1, 14, 29, 44, 49, 59 and 69 minutes | Blood is sampled using a venous catheter over about 60 seconds. Following centrifugation to extract the plasma, a small sample is used to measure lactate concentration. |
Countries
Canada
Outcome results
None listed