When it comes to delivering real performance benefits, very few sports nutrition products step up to the plate (no pun intended!).

However, carbohydrate feeding during longer rides is a scientifically proven strategy to delay fatigue, increase performance and keep the bonk at bay. That’s because carbohydrate is your body’s premium fuel, especially when exercise becomes intense.

Even a slight shortfall of carbohydrate in the body can leave your muscles feeling tired, heavy and leaden. Feeding while on the bike is a sure way to help sustain performance. Ideally, you should start fuelling after 30-60 minutes of riding and throughout the rest of your ride.

But suppose you find yourself out on a long ride without enough carbs; what’s the best way to consume what you have? Should you fuel early and then ride the later stages un-fuelled, or ride on empty and then start fuelling later on in the ride? This exact question has now been investigated.

The science
In the study, a group of fit, recreational cyclists completed four separate trials. Each trial consisted of a two-hour ride at moderate intensity (around 62 per cent of their maximum oxygen uptake), immediately followed by a self-paced 10-kilometre time trial where they rode as fast as possible. 
The trials were all identical except for nutrition consumed.

In one trial, the cyclists received no carbohydrate at all. In another, they were given carbohydrate throughout the trial. In the other two trials, they were either given carbohydrate early or late in the two-hour ride. In all three of the carbohydrate trials, the total amount of carbohydrate given was the same (i.e. only the timing of feeding varied).

Eating later in the ride could give you just the boost you need for those final hard yards

Unsurprisingly perhaps, when carbohydrate was given throughout the trial, the cyclists rode the 10km significantly faster (knocking nearly 26 seconds off) than when none was given. What was unexpected, however, was the results from the early and late feeding trials.

When carbohydrate was given later in the ride, the cyclists rode just as fast as when carbohydrate was given throughout. However, when it was given early in the ride, the 10km time was around 15 seconds slower — a significant difference.
Appl Physiol Nutr Metab. 2014 Jan;39(1):58-63

The bigger picture
Why should the same amount of carbohydrate taken later in a ride enhance performance to a greater degree than when taken earlier?

One explanation is that, by feeding later, the muscles were forced to use more energy from fat stores during the early part of the ride, leaving more carbohydrate in reserve for the intense riding at the end. This corresponds to what we already know from previous studies. Although consuming carbohydrate drinks and snacks boosts performance, the resultant rise in blood sugar and insulin significantly reduces the proportion of muscular energy derived from burning fat (1,2).

This is also the rationale of the ‘train low, race high’ approach, whereby some training is conducted without carbohydrate fuelling — to help muscles ‘learn’ how to burn fat for energy, thereby conserving precious carbohydrate (glycogen) and extending endurance.

Apply the science
For riders undertaking an unusually long ride, make sure you have enough carbohydrate drinks and snacks (supplying at least 60g of carbohydrate per hour) to get you through your ride. If your access to carbohydrate is limited, you should try and conserve your drinks/snacks so you can take them later in the ride, when they are more likely to benefit you.

For experienced trainers doing 2-3 hours riding, try riding the first hour or so without carbohydrate, which can help improve your fat-burning capacity. But ensure you consume plenty of carbohydrate after that point, right up until the end of your ride.

1. J Sports Sci. 2003 Dec;21(12):1017-24
2. Appl Physiol Nutr Metab. 2008 Jun;33(3):441-9