Running 101 - Hydration

This posting provides basic information for determining your proper hydration needs and strategy. As with all running related recommendations there are no fixed rules; everything depends on each individual athlete.

Before introducing recommendations on running hydration, it is important to remember:

1. It is unwise to seek weight loss through body fluid loss.
2. Hydration needs are dependent on each person’s specific physiology, weather conditions, and training intensity and duration.
3. While we are all familiar with the concept of dehydration, hyponatremia is the other side of the coin. Too much liquid ingestion can cause an electrolyte imbalance, creating a life threatening condition.

DEHYDRATION

Dehydration is the loss of fluids and salts essential to maintain normal body function. Dehydration occurs when the body loses more fluids than it takes in.

HYPONATREMIA

1. Over ingestion of liquid can cause hyponatremia. This risk increases in novice runners whose marathon time is over 4 hours. Novice runners are prone to ingest more liquid than faster runners, and their slower speed facilitates liquid ingestion.
2. Time- or distance-based approaches to hydration (drink x amount of liquid per hour / every ten miles) does not considers the specific condition of your run or your hydration status when you start exercise.

GENERAL RECOMMENDATION

a) If you are a novice runner: Aim to minimize weight loss (1-3% of body weight) during a bout of exercise your exercise

1. In the recommended readings, you can find the USTAF guidelines for calculating your suggested liquid ingestion based on sweat rate
2. Most recommendations aim at zero weight loss from body fluid during a race or training session; this implies same weight before and after racing or training. However, not all body fluid lost impacts dehydration. The body “combusts” carbohydrates and in the process produces water. This water evaporates through sweat causing acceptable weight loss.

b) If you are an experienced runner, learn to drink according to your thirst

1. The main objective is to drink as your body “requests” fluids through your thirst (ad libitum). In the past the recommendation has been to drink before thirst appeared or drink as much as you can

A key part of your training is to understand your hydration needs, but in order to hydrate you need to have access to liquid.  So, we recommend that you carry your own liquids when you run.

Additional sources
Podcast:

• Interview with Dr. Tim Noakes: Hydration, The Role of the Brain in Racing, and His Latest Findings on Carbohydrates for Runners

Recommended reading:

• Proper Hydration for Distance Running- Identifying Individual Fluid Needs – A USA TRACK & FIELD Advisory
• IMMDA ADVISORY STATEMENT ON GUIDELINES FOR FLUID REPLACEMENT DURING MARATHON RUNNING Written by Tim Noakes MBChB, MD, FACSM
•    Opposite to general belief, there are no reported cases of dehydration causing death (Marathoners Warned About Too Much Water ,NYT October 20, 2005)
• Experts debate dehydration finding in Chicago Marathon death

Disclaimer: As expressed on the blog description I used this media to summarize my research on subjects of interests. By no means I claim that the information shared is expert advice on every subject but my own personal conclusion after reading / listening those that claim to be experts.