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This study will evaluate the effects manipulating ingested fluids can have on hydration status and cycling performance. There will be 4 different conditions.
Being dehydrated can decrease endurance exercise performance. The investigators wish to test which of three drinks is most effective at re-hydrating cyclists and if this affects performance. Subjects will undertake 4 tests: once dehydrated, once hydrated with water, once hydrated with a sports-specific drink, and once with an altered sports drink. Blood samples will be taken and expired gasses will be sampled at various time points throughout the tests for later analysis. A small amount of labelled water will be consumed with each drink, a technique which will allow us to quantify the absorption of each of the drinks.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Dehydrated | Experimental | 90 minutes cycling, without the ingestion of any fluids, followed by a 15 minute cycling time trial test |
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| Hypotonic | Experimental | 90 minutes cycling, with the ingestion of six 250 ml carbohydrate (6g sucrose, 3g glucose) drinks, followed by a 15 minute cycling time trial test |
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| Isotonic | Experimental | 90 minutes cycling, with the ingestion of six 250 ml carbohydrate (6g glucose, 3g fructose) drinks, followed by a 15 minute cycling time trial test |
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| Placebo | Experimental | 90 minutes cycling, with the ingestion of six 250 ml taste-matched water drinks, followed by a 15 minute cycling time trial test |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Hypotonic | Dietary Supplement | N/A: see arm description |
| |
| Isotonic |
| Measure | Description | Time Frame |
|---|---|---|
| Absorption of fluid through the gut | Absorption of drinks through the gut will be measured using 2 boluses of deuterated water. This will be consumed alongside 2 of the drinks, and blood samples will be used to quantify enrichment. Total body water calculations are required to provide corrections in equations related to D2O. H218O will be consumed in order to quantify total body water: this will be provided in a single bolus before each trial. | To begin 10 minutes after the completion of the 90 minute steady-state cycle |
| Measure | Description | Time Frame |
|---|---|---|
| Work done (kJ) during 15 minute cycling time-trial | Subjects will perform a cycle ergometer protocol that has been shown to be reproducible in athletes. Subjects will complete the time trial on a Lode Excalibur cycling ergometer. Software linked to this software will record work done and power output. | Throughout the 90 minute steady-state cycle & the 15 minute time trial. |
| Measure | Description | Time Frame |
|---|---|---|
| Substrate utilisation | Substrate utilisation will be calculated from data collected through a metabolic cart and its software. It will be measured during the 90-minute steady-state cycle for 4 periods of 3 minutes. Carbohydrate and lipid oxidation rates will be calculated using equations by Jeukendrup & Wallis (2005). | Throughout the 90 minute steady-state cycle |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Andrew D Davenport, MSc | The University of Exeter | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| School of Sports and Health Sciences | Exeter | Devon | EX1 2LU | United Kingdom |
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Doubly-blinded & randomised using an online randomisation website.
| Dietary Supplement |
N/A: see arm description |
|
| Placebo | Dietary Supplement | N/A: see arm description |
|
| Dehydrated | Other | N/A: see arm description |
|
| Plasma metabolites | A cannula will be used to draw blood from subjects at several time points. Whole blood samples will be analysed immediately for plasma glucose, plasma lactate, haemoglobin content, haematocrit and plasma volume. Remaining whole blood will be centrifuged immediately and its plasma split into aliquots and stored in a -20°C freezer. At the end of the trial, plasma samples will be moved to a -80°C freezer for later analysis for sodium, glycerol, and NEFA. | Throughout the 90 minute steady-state cycle and time-trial |
| Heart rate | Heart rate will be measured throughout with the use of a heart rate monitor. | Throughout the 90 minute steady-state cycle and time-trial |
| RPE (rating of perceived exertion) | RPE will be measured using the Borg Scale. | Throughout the 90 minute steady-state cycle and time-trial |
| Core body temperature | Core temperature will be measured throughout with the use of an ingestible core-body temperature pill (HQ Inc, FL, USA). | Throughout the 90 minute steady-state cycle and time-trial |