Recently I was asked: How often should a triathlete drink during the bike and run while racing an Ironman 70.3?

This is a massive topic, but here are my 10 key points for optimal race day hydration:

  1. Don’t load up on fluid the day before the race (and this includes electrolyte drinks).
  2. Eat dinner prior to 6pm the night before to allow at least 12 hrs of transit time to digest and eliminate your food. Practice eating dinner early for at least two days prior to race day – not just the night before.
  3. Go light on alcohol the night before: one glass of beer or wine, OR none at all.
  4. Eat your normal breakfast but err on the lighter side if you’ve experienced GI issues in previous races.  Be sure to finish breakfast 2.5 hrs before the gun goes off.
  5. If you sweat heavily, consider taking in 800 -1200mg of salt 30min prior to race start.  Practice this in training.
  6. If your race duration is longer than 2.5 hour, then take a Fluid Replacement Drink (FRD) or 1/2 gel about 12-15min before the start of the swim – not to exceed 80 calories.

During the race:

  1. Don’t drink for the first 10-20min at the outset of the bike. Definitely avoid guzzling something in T-1.  Allow your sweat, breathing and heart rate to level off, then sip FRD every 8-12 minutes.
  2. Race-day calorie needs are dependent upon “like” workloads in training, the speed that you’re riding or running, and lean body weight.  Even the fastest pros rarely eat more than 350 calories/hr. Most amateurs should aim between 125-250 calories/hr.  The first hour should be about 20-30% less.
  3. Generally you’ll consume less calories/hr while running than when cycling.  This is due to the intensity and fatigue during the run.
  4. You’re not a camel; don’t overdrink!  Fluid intake might exceed 40 oz/hr in extreme conditions, but most athletes only need 12–28 oz/hr.