Hydration and Exercise Performance in Cycling

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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How Does Altering the Composition of Ingested Fluids Affect Hydration Status Whilst Cycling?

Conditions
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Healthy

Intervention / Treatment
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* Dietary Supplement: Hypotonic
* Dietary Supplement: Isotonic
* Dietary Supplement: Placebo
* Other: Dehydrated


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Highly trained cyclists (vo2max >55 ml/kg/min, PPO (peak power output) > 4 w/kg) Training at least 4 times a week Females must be taking an oral contraceptive, or using the contraceptive implant Exclusion Criteria: Recent history of musculoskeletal injury Diagnosed cardiovascular disease Regular use of nutritional supplements that may interfere with the protocol

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Dehydrated<br>90 minutes cycling, without the ingestion of any fluids, followed by a 15 minute cycling time trial test | Other: Dehydrated<br>* N/A: see arm description<br>|
| Experimental: Hypotonic<br>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 | Dietary Supplement: Hypotonic<br>* N/A: see arm description<br>|
| Experimental: Isotonic<br>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 | Dietary Supplement: Isotonic<br>* N/A: see arm description<br>|
| Experimental: Placebo<br>90 minutes cycling, with the ingestion of six 250 ml taste-matched water drinks, followed by a 15 minute cycling time trial test | Dietary Supplement: Placebo<br>* N/A: see arm description<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | 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 | 

Secondary Outcome Measures

| Outcome Measure | 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. |