Monday, 9 April 2012

Some thoughts on race nutrition

Through my training and racing I tried many approaches to my nutrition and through readings and trial and error I have come to follow the following guidelines. In my mind there seems to be two approaches to race nutrition, the first working to tap into your fat burning system and train your body to maintain energy levels while burning fat and the second by keeping carbohydrate levels stocked at consistent levels through your entire run.

Both systems require you to start your workout or race fully stocked with a good meal pre event and at that point they go their separate ways. The fat burning system focuses on consuming non carb based sports drinks and consuming protein up until the mid point in the event before switching over to carbohydrates while the second method focuses primarily on carbohydrates.

In this post I am focusing on the second method, keeping in mind that both systems work well, but both require training to adapt, i.e. if you aim to use the fat burning system you would need to do several of your long runs in a depleted state by not having a pre-workout meal and only consuming water during the run.

At the core of the second system is to consume small amounts of carbs every 15mins and to start each workout or race fully loaded and not getting behind in calories. Also the longer the event the more calories needed. For myself having a bowl of porridge pre-event has been magic using this system where as a breakfast of eggs and salmon was a better option when using the fat burning system.

In my readings by Trent Stellingwerff and Asker's Jeukendrup, Trent drives home the point of 15grams of carbs every 15mins in 150ml of fluids and Asker has some specific ideas based on distance.

Asker showed some interesting data showing a pronounced trend that faster times were correlated with higher carb intake per hour in ultra events and suggests that ultra-endurance athletes should aim for up to 90 g/hr of carbs, and he showed some data from Ironman triathlete Chrissie Wellington who set a new Ironman world record in 2010 using this approach.

He offers these guidelines with my suggestions based on Trent's "rule of 15"
(Trent's rule of 15 is adjusted slightly when moving to the ultra marathon)
  • less than 1hr: no carbs needed
  • 1-2 hr: up to 30 g/hr, any type of carb
    • 10 grams of carbs every 15mins
  • 2-3 hr: up to 60g/hr, carbs that are oxidized rapidly like glucose or maltodextrin
    • 15 grams of carbs every 15mins
  • 3-20 hrs: up to 90g/hr, combination of carbs
    • glucose or maltodextrine combined with fructose at a 2:1 ratio
    • 22.5 grams of carbs every 15mins
In terms of tolerating high carb intake, it’s definitely an individual thing, but you do get better at tolerating high loads with practice. In his example of triathlete Chrissie Wellington, she was consuming 86 g/hr in 2007 and in 2011 was apparently taking quite a bit more than that, because she’s managed to train her system to tolerate it. Another change Wellington made was that she takes just carbs, no protein. In Asker’s opinion he found no benefit from adding protein — so eliminating the protein might make it easier on the gut. 

Also he noted that his recent studies have found no difference in absorption rate for bars, gels and  fluids, so you can mix and match to find what your stomach tolerates best. He makes no reference to non sport nutrition products in terms of absorption rate but I would think that certain foods such as cooked sweet potato would also be a good addition to your mix of foods. The thing that stands out here for me is that when you consume food like soups, potatoes etx in an ultra event be very careful to keep to the rule of 15 in that you do not consume more than 25grams of carbs in 15mins as your body will not be able to tolerate the large increase in calories, i.e. do not come into transition and sit down and consume a pizza, have the pizza cut up into small pieces in a zip lock and consume in small portions as you walk on the hills.

It takes a about an hour for the rate of carb uptake to reach maximum. So if you only start taking carbs after an hour, there will be a delay before those carbs are being fully utilized, so it is best to start right from the start utilizing the rule of 15 deciding how you want to consume the calories utilizing gels, bars, sports drink and in what combination. 

For myself, I tend to lean toward more liquid nutrition in shorter events with watered down gels and more solid food in longer events using a combination of sports drinks, gels, bars, sweet potatoes, soups and many combinations there in.

Given all this, the thing that strikes you the most, is how am I going to carry all these calories so that I can consume them in such small amounts throughout the event. This is where a little planning can go a long way and breaking down the legs and deciding how long each leg will take and how many calories  you will need using any number of hydration packs and hand helds. In marathon events,  I tend to carry my calories and use the aid stations for water where as with ultras I decide on size of bladder and food combination based on the length of the leg as I need to carry both the water and calories. For the longer legs I put more emphasis on having enough calories on board than having enough water. Also I look for calorie options that have electrolytes combined just in case I run low on sports drink.

As a side note there did not seem to be direct link between nutrition and cramping, the studies seemed to indicate that cramping was more in line with starting too fast or not going into the event fully rested.

The take home message in my mind is not so much what you use as fuel but how you consume that fuel and if you can take small sips, small bites and start early you will stay well stocked and energy levels will remain even throughout your event. The same can be said in your daily nutrition, small meals consistently through the day so that you start your workouts fully stocked putting more focus on consumption early in the day and less focus latter in the day, i.e large breakfast and a small dinner.

Hope that helps.