A: Build the plan around a regular carbohydrate target you have practised, using any mix of gels, drink and bars that your stomach tolerates. Many runners begin with non-caffeine fuel and save caffeine for later, but there is no single timing that suits everyone. Bars are usually easiest earlier, while gels can be simpler later when chewing feels harder.

Count caffeine from every gel, drink and other source, follow each product label and do not exceed your usual tested intake. Rehearse the full plan on long runs. If you are pregnant, sensitive to caffeine, taking medication or have a medical condition, ask a qualified healthcare professional.