The half marathon is one of the most popular running distances. More of a challenge than a 10k, but not quite the feat of endurance of the full marathon distance, half marathons have all the kudos - with only a fraction of the pain.
Still, at 13.1 miles, it's a distance not to be under-estimated. Survive on water alone and the last three to five miles can be a very painful experience (as many have found out at their peril).
Despite a wealth of scientific data examining physiological and nutritional demands of marathon running, there's surprisingly 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.
They examined ten 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.
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).
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.
As with any running event with a duration of more than 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. 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. Sweating is the body's way of cooling down (the hotter it is, the more likely you are to sweat) but, with the fluid loss, will also be valuable vitamins and minerals - electrolytes - which could impact on performance. Loss of sodium, for example, means the rate at which oxygen, nutrients and carbohydrate is carried to the active muscles decreases. Electrolyte replacement drinks are highly advanced these days and lots of research has gone into their efficacy. But watch out for the imposters that are simply loaded with sugar, and no better than the average soft drink. The electrolyteSHOTZ Tablet, on the other hand, is an effervescent tablet that dissolves in water, is sugar free, has no artificial colours, is simple to use and so amazingly portable that you can stay hydrated for the whole half marathon.
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, while 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.
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: electrolyteSHOTZ should be an integral part of this strategy.