The half marathon is one of the trickier distances to get right from a hydration perspective - Precision Hydration's Andy Blow shows you how...

What they used to tell you

Around 100 years ago nutrition and hydration advice for athletes followed the theme characterised in this quote attributed to James Edward Sullivan (Secretary of the Amateur Athletic Union in the USA 1888 to 1906):

"Don’t get in the habit of drinking and eating in a marathon race; some prominent runners do, but it is not beneficial."

These days, and certainly for marathons, this advice would be considered borderline crazy. Scientific studies and a wealth of anecdotal evidence have shown that taking in a decent amount of carbohydrates and some fluids can definitely boost performance over 26.2 miles and help to lessen the impact of the dreaded ‘wall’ that many athletes smash into around mile 18.

The 90 minute rule?

The half marathon, at 13.1 miles, however is a different animal to a full distance. Depending on the speed you go at and the environmental conditions encountered, it’s right on the borderline between the longest distance you can race without taking in any energy or fluid, and the point at which supplementation will start to make a noticeable difference to performance.

For most people the point at which intake of fluids and carbs starts to make a real impact is around the 90 minute mark. Whilst it’s impossible to call this as a definitive ‘threshold’ beyond which you need to start eating and drinking (there are just too many confounding variables), it’s a good rule of thumb.

So a decent place to start with planning your nutrition and hydration strategy is to estimate your likely finishing time. If it’s well under 90 minutes you’re likely to be okay without any in-race intake, but if you’re drifting out towards two hours or beyond it’s highly likely you’ll need to consume something to perform at your best.

Getting your nutrition right

Because it’s on the cusp of what you can do without fuelling mid race, for the half marathon there is a great emphasis on getting your pre-race nutrition and hydration nailed down correctly, as the better hydrated and fuelled you are on the start line, the further you can realistically go without needing to take anything on board.

Minimising your intake during the run itself is very helpful as it reduces the time and energy you waste carrying, picking up, consuming and digesting fluid and foods when all you want to be doing is concentrating on staying on target pace.

If you are going to take in some energy during the run then the key is to use simple sources that are easily absorbed. Energy gels are designed for this and one or two taken in the period from 45 to 90 minutes in should give you enough of a boost to make a positive difference.

A more low-tech (and cheaper) alternative are jelly babies or similar sweets (six jelly babies contain about the same carbohydrate content - around 28g - as an average energy gel).
 

Pre-race hydration

As far as hydration goes, the principles are very similar to the management of energy levels. The aim is to start well topped up and then you can probably get away with very light drinking during the race itself (and potentially no drinking for the really fast sub 90 minutes folks).



A big danger with pre-race drinking however is overdoing it.

Many people take in lots and lots of extra water in the last few days pre-event and this can have very negative consequences if you’re not careful. In a nutshell what happens when you over-consume water is that eventually you just have to start peeing it out, and this can flush valuable minerals (mainly sodium) out too.

In the extreme, this can lead to a dangerous condition called hyponatremia (low blood sodium levels) as over drinking dilutes your sodium levels. As you lose a lot of sodium in your sweat, this can start to be problematic during the race as your levels drop even further as you sweat.

How to stay hydrated during the race

To counteract the electrolyte losses expected in the race, whilst maintaining good levels of body water, it’s a good idea to top up with a couple of bottles of a strong sodium based electrolyte solution (about two to three times stronger than a standard sports drink) in the last 24 hours before the race.

If you finish the last bottle 90 minutes before the start it tops your fluid tanks up and leaves enough time to empty your bladder before the gun goes.

During the race itself, try to listen to your body and drink if and when you feel you need to.

There is no need to force down fluids if your body is not telling you to drink. If aid stations are plentiful on the route then consider not carrying water yourself, this just costs energy.

If it’s super hot, you are a very heavy sweater or a cramper, taking a couple of sodium based electrolyte capsules (containing 250-500mg sodium) is a good idea. These can be washed down with cups of water at an aid station and help stave off cramps and sore legs late on.

If you’re training for your first half marathon, it’s ideal to test out any new nutrition and hydration strategies in training first, that way you don’t risk ruining the day you’ve been working so hard for!

Best of luck and train hard!

(Images courtesy of Precision Hydration)