John Brewer, performance director at the Lucozade Sport Science Academy (LSSA), discusses how to respect the challenge, and fuel for success

It’s been well documented that the late, great Chris Brasher once described running a marathon as “the suburban man’s Everest”. Given that since its inception in 1981, almost half a million people have now completed the London Marathon alone, plus the many thousands who have run in other 26.2 mile events, this is perhaps an over-exaggeration, since fewer than 2,000 people have reached the summit of Everest!

However, it does serve to highlight the magnitude of the accomplishment of completing a marathon; a goal which most of the population would never consider aspiring for. Half marathons however, are slightly more attainable – perhaps more akin to reaching the summit of Snowdon or Ben Nevis than Everest – still a fantastic achievement, but a more acceptable challenge for ‘normal’ individuals, and one that’s less likely to take over their lifestyle during the essential weeks of preparation and training.
Nevertheless, the challenge of running a half marathon must be respected, and taking the 13.1-mile distance for granted, or not preparing properly, runs the risk of disaster and poor performance. This article will set out to examine some of the physiological and metabolic challenges of a half marathon, and aim to provide some general nutritional guidelines to help ensure that preparation, completion and recovery from these events are as successful as possible.

The importance of ‘threshold’

Despite a wealth of scientific data examining the demands of marathon running, there’s surprising little scientific data investigating half marathons. A study published in the British Journal of Sports Medicine remains one of the few to comprehensively examine the demands faced by competitors during a half marathon race.

“A proper training plan is the essential ingredient for successful performance, but this must be supported with a sensible strategy for nutrition and hydration”

They examined 10 recreational standard runners during a competitive race around the university campus, and found that they ran at speeds equivalent to almost 80 per cent of their maximum oxygen uptake (VO2 max). There was a strong correlation between VO2 max and performance – in other words, those runners with the highest VO2 max completed the race in the fastest time but, interestingly, the strongest relationship with performance was seen with those runners who accumulated lactic acid in the blood at the highest rate. Runners whose lactic acid levels quickly rose to a level of four mmol per litre of blood recorded the slowest race times, whereas runners whose lactic acid levels rose slowly had the fastest times. At the end of the race, the average level lactic acid was just over five mmol per litre of blood (compared to values of less than one mmol per litre before the start).

This data emphasises the importance of including ‘threshold’ training in the programmes of half marathon runners. This means training at a pace where lactic acid levels are rising, but not preventing a runner from continuing, perhaps best described as ‘tolerable discomfort’, and quicker than a slow steady run, but not flat out.

The same study also found that the average energy expenditure for the group of runners when completing the 13.1 miles was just under 1,500 calories, the majority of which came from the body’s stores of carbohydrate (in the form of muscle glycogen).

Fuelling the body for race day

Many other studies have shown that the body’s stores of muscle glycogen are generally sufficient to provide around 1,800-2,000 calories of energy, so the need for pre-race carbohydrate loading, to boost muscle glycogen stores, would seem to be far less important than it is during the preparation for a marathon. Nevertheless, the energy expended during a half marathon is significant, and it’s essential that runners stand on the start line with a full complement of muscle glycogen stores. Anything less could mean running out of energy before the race has been completed, so eating plenty of high carbohydrate foods in the build-up to a half marathon, (and to support the pre-race training programme), is crucial.

The fact that carbohydrate stores may not be performance-limiting in a half marathon (unlike a marathon) has been emphasised in another study, which examined the effect of carbohydrate consumption on the performance of 18 highly-trained half marathon runners. They performed two separate half marathons three weeks apart, consuming carbohydrate during one of the races, and a placebo during the other. No significant differences were found in the performance times of the ‘carbohydrate’ and ‘no-carbohydrate’ races.

This again suggests that providing the pre-race carbohydrate stores are high, half marathons are not likely to provoke the same ‘hitting the wall’ energy crisis frequently experienced during marathons, since the body’s glycogen stores provide sufficient energy to complete the distance. Anecdotal evidence would also suggest that this is the same for runners of all abilities and speeds – the total energy required to complete the distance will be broadly similar for runners at a range of paces – it will be the rate of energy expenditure that will differ and be dependent on running speed.

Drink plenty!

As with any running event with a duration of over an hour, hydration will be crucial if performance is to be optimised. Depending on climatic conditions and pace, runners could lose between one and four litres of fluid an hour.

“It is essential that half marathon runners start a race properly hydrated, and wherever possible consume fluid during the race itself”

Since fluid losses equivalent to just two per cent of body weight will soon start to impair physical and mental performance, it’s essential that half marathon runners start a race properly hydrated, and wherever possible consume fluid during the race itself. Most organised half marathon races will have drinks stations on-course. At the Great North Run for example, as well as drinks at the start and finish, there are water stations at the 3, 6, 8 and 12 mile points, and isotonic Lucozade Sport at 4 and 10 miles. Whilst other, smaller events may not always have this amount of fluid on-course, most race organisers are now very aware of the need to provide adequate opportunities for hydration for runners.

As with any long run or intensive race, replacing lost fluid and energy after completion is an essential part of the recovery process. Drinking to regain lost body weight, and to return urine to a clear straw colour is the best way to ensure adequate rehydration, whilst consuming a high carbohydrate snack, meal or drink during the first few hours after a half marathon will kick-start the replacement of the muscle glycogen that has been used during the run.

Topping up the immune system

A further study has found evidence of decreased effectiveness of the immune system after intensive exercise such as a half marathon, and identified a consequent increased risk of upper respiratory track infections. Possible ways of sustaining the immune system after exercise to avoid post-race infections could include eating plenty of carbohydrate, or supplementing the diet with vitamin C and zinc.

In summary, the physiological and metabolic challenges of a half marathon are high, and should not be underestimated. A proper training plan is, of course, the essential ingredient for successful performance, but this must be supported with a sensible strategy for nutrition and hydration before, during and after the event. While ‘hitting the wall’ shouldn’t be a problem during a half marathon, it could be if a proper, high-carbohydrate diet isn’t eaten beforehand and, as with all running events lasting over an hour, staying properly hydrated is essential.

LSSA Top Tips

• Respect the challenge – not preparing properly will lead to poor performance.
• Include ‘threshold runs’ in your training.
• Top-up muscle glycogen stores before getting to the start line by eating plenty of high-carbohydrate foods (e.g. bread, potatoes, pasta).
• Start the race properly hydrated and use the on-course drinks stations.
• Consume a high-carbohydrate snack, meal or drink during the first few hours after the event to replace glycogen lost during the run (e.g. six Jaffa cakes, 400ml milk shake, a tin of rice pudding)

For more expert sports nutrition advice from the LSSA, visit www.thelssa.com. Lucozade Sport has developed a unique Runners’ Training Pack to help you stay properly fuelled and hydrated through a typical month’s training. Enjoy 10 per cent off this and other Lucozade Sport high performance products when you buy online. Simply visit www.lucozadesportshop.com and enter the exclusive Running fitness code RF01.

If you are looking for some extra motivation and expert advice in the final weeks up to the BUPA Great North Run, you can benefit from the host of tools and information on the Lucozade Sport Running website. A runner’s haven, www.lucozade.com/running is dedicated to providing you with top running tips and advice from the LSSA’s team of running experts and sports scientists. From the free online running coach – a sophisticated programme that allows you to develop your own structured personal training diary – to pace bands and the race time predictor, the site is geared towards helping you achieve your running goals.