Effects of Acute Glycerol Ingestion on Performance, Metabolic and Biochemical Markers in International Athletes
Condition: Performance Enhancing Product Use; Change, Body Weight; Change, Body Temperature; Antioxidative Stress; Lactate Blood Increase; Thermal Sensation Disorders
MeSH terms: Sensation Disorders; Somatosensory Disorders; Hyperlactatemia; Body Weight; Body Weight Changes; Body Temperature Changes
Study type: Interventional

Summary: 
      This clinical study evaluates the acute effect of glycerol ingestion on performance (power
      output), weight, urine specific gravity, biochemical (antioxidants and lactate) and metabolic
      (indirect calorimetry) markers in international athletes in hot conditions. The investigators
      hypothesized that acute glycerol ingestion can prevent performance loss (power generated at
      submaximal intensity) in hot conditions. To justify this hypothesis, the investigators will
      measure the aforementioned markers, which could establish a cause-effect relationship between
      acute glycerol intake and decreased performance loss in hot conditions.
    

Detailed description: 
      All participants will be informed about the procedures and provide signed informed consent.
      The study will be conducted according to the guidelines of the Helsinki Declaration for Human
      Research and the protocol was approved by the Ethics Committee/Institutional Review Catholic
      University of Murcia (Code: CE091802).

      Study design

      This is a randomized crossover study. There are 3 types of intervention: water intake of 26
      mL/kg/weight at 16°C (CON), 26 mL/kg/weight + placebo at 28°C (PLA) and intake of 1.2 g
      glycerol + 26 mL/kg/weight at 28°C (GLY). In addition, athletes will be instructed to take a
      individualized diet in relation to macronutrients (verified by dietary record) and they will
      follow their adjusted training schedule so that there would be no effect on the tests.
      Participants in both groups will be instructed not to consume supplements 3 weeks prior to
      the start of the study.

      Procedures

      Participants will visit the laboratory on five occasions. Visit 1 consists of a medical
      examination and a blood draw to determine health status. At visit 2, after a dinner the night
      before and a standard breakfast, an incremental test will be performed to determine the
      exercise zones in the rectangular test. At visits 3, 4 and 5, a record of the diet
      (individually set) will be performed regarding the former 7 days, followed by a rectangular
      treadmill test.

      Visit 1:

      Health status blood test: A general blood test will be performed. The blood will be drawn
      through a vein. (Fasting) Medical examination: A medical history of family and personal
      history, an electrocardiogram (ECG) at rest and a medical examination (auscultation, blood
      pressure, etc.) will be carried out to certify that the person is healthy and is not at risk
      to participate in the study. (Fasting)

      Visits 2:

      Incremental test with final ramp test will be performed on a cycle ergometer using a
      metabolic cart (Metalyzer 3B. Leipzig, Germany) to determine maximal fat oxidation zone
      (FatMax), ventilatory thresholds 1 (VT1) and 2 (VT2) and maximal oxygen consumption (VO2max).
      Participants will begin cycling at 35W for 2 min, increasing then by 35W every 2 min until
      RER>1.05, initializing then the final ramp (+35W·min-1) until exhaustion.

      Visits 3:

      The rectangular test will be performed on a treadmill using the speed values obtained in the
      incremental test (15 sets x 2 min at 95% with 2:30 recovery at 85% of maximum speed between
      sets). Cardiorespiratory variables (VO2, VCO2, VO2R, VE/VO2, VE/VCO2, VE/VCO2, respiratory
      coefficient, respiratory frequency, carbohydrate oxidation (CHO), fat oxidation (FAT),
      running economy and energy expenditure) will be determined in the 1st, 5th, 10th and 15th
      series.

      For power measurement, each participant will wear the Stryd power meter, which is an inertial
      sensor (9.1 g) mounted on the foot, firmly attached to the shoe and according to the
      manufacturer's recommendations. The device stores at a sampling rate of 1 Hz the following
      variables: estimated power (PO), pace, cadence, leg sprint stiffness (LSS), form power, form
      power ratio, ground contact time (GCT), vertical oscillation, stride length. These variables
      will then be determined in the 1st, 5th, 10th and 15th series of the rectangular test.
      According to information from the Stryd team, the device is operational out of the box and
      should not require any calibration, accepting a measurement error of 3 percent. Participants
      will fill in their height and body mass prior to use, which is required for PO estimation.
      The firmware version that will be used is 2.1.16 (released in August 2020).

      For lactate and antioxidant measurements, a Lactate Pro 2 meter and eBQC lab will be used on
      finger capillary blood at rest, after the 5th, 10th and after completion of the rectangular
      test.

      For body temperature, the investigators will use an infrared thermographic camera (FLIR) to
      measure heat distribution (head, trunk, lower and upper limbs in both anterior and posterior
      aspects of the body).

      Urine Samples Urine will be collected from the intake of water or water + glycerol or water +
      placebo until the start of the rectangular test and up to one hour after the rectangular
      test. The volume of urine excreted pre and post rectangular test will be recorded and the
      urine specific gravity will be analyzed.
    

Intervention name(s): PLACEBO; GLYCEROL
Intervention type(s): Other; Dietary Supplement
Intervention description(s): Athletes will perform the rectangular test at a temperature of 28°C and ingested 26 mL/kg body weight + placebo one and half hours before the test.; Athletes will perform the rectangular test at a temperature of 28°C and ingested 26 mL/kg body weight + 1.2 g of glycerol one and half hours before the test.
Intervention MeSH terms: Glycerol
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: A randomized crossover study will be conducted, in which 4 international walkers will perform 3 different conditions: CON) water intake of 26 mL/kg/weight at 16°C; PLA) 26 mL/kg/weight + placebo at 28°C and GLY) intake of 1.2 g glycerol + 26 mL/kg/weight at 28°C.
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Power; Performance; Thermography; Metabolism; Endurance Sport; Ergogenic Aids; Oxygen uptake; Hydration; Hyperhydration