NUTRITION – Fluids

Summer – time to think Fluids

EVERYONE knows the importance of fluids to sports performance, particularly those involved in endurance events. We have all had that experience of running well for 80% of the course, but fading in those last few controls towards the end. We lack concentration and energy, tending to make errors which seem impossible when we look over our performance in hindsight with a fully hydrated brain!

There are really only three very simple rules to follow: 1. Start the event well hydrated 2. Keep up the fluid intake throughout the run 3. Replenish fluids adequately after the event

How do you know you are well hydrated?

There are two main ways to tell. One involves knowing your normal weight, the other is to visually assess the colour of your urine.

It is known that a 2% loss in body weight due to sweating is enough to impair performance considerably. So if you know that your normal body weight is 70 kg, and you hop on the scales before a training session or event and see you are 69.6 kg, then you are dehydrated by 2% (normal body weight less 2%). Now I realise that it is difficult to carry scales to Orienteering events and find a place flat (and secluded) enough to step on them! So perhaps the second method is more practical.

Look at the colour of your urine if you manage to beat the queue at the portaloo! If it is just a pale yellow colour, then you are probably fairly well hydrated. The darker it is, the more dehydrated you are. So if it is bright or dark yellow in colour you really need to have time to rehydrate well before your run starts. The darker the urine colour, the more concentrated your urine. In other words, the more your kidneys are trying to conserve what limited fluid your body does hold.

Be careful not to over-hydrate. This can cause problems too. If you have been drinking excessively and are producing large quantities of very dilute, very clear urine, you may be over-hydrated. It is unnecessary and potentially dangerous to drink at rates that are far greater than sweat losses. This can cause a dilution of blood sodium levels (hyponatraemia). Symptoms include headaches, disorientation, coma, and in severe cases, death.

What is the best fluid to use?

In the past, the advice would have been that water was sufficient for most sports lasting less than an hour in duration. However, with the invention of sports drinks and the subsequent research into their usage, advice on this has changed. It is now known that even in events lasting only 30 minutes, an athlete’s performance can be improved by consuming sports drinks rather than water only.

Sports drinks of course replace not only fluid, but also carbohydrate and electrolytes, all of which are important to be maintained for best body function. They are specifically designed to contain carbohydrate at a concentration which allows the liquid to be emptied rapidly from the stomach and absorbed quickly from the intestine, allowing better hydration than water alone.

Will sports drinks improve performance?

Generally, yes. All types of effort will benefit from the fluid provided by sport drinks. Carbohydrate intake during exercise has been shown to enhance performance in the following situations: • Prolonged (more than 90min) sessions of constant lower intensity (60-80% of max) • Prolonged periods (more than 60min) of intermittent highintensity exercise (80-100% max) • High intensity exercise (80-100% max) lasting 60 minutes or more • Any athlete who has heavy sweat losses

Orienteering would certainly fit in under several of these categories. The slower steady runners who are out there in the bush for 90 minutes might need sports drinks just as much as the faster elites who perform at greater intensity for a shorter time, covering the same ground in 60 minutes or less.

When should sports drinks be used?

1. Before: Sports drinks are ideal in the last hour before an event. The carbohydrate tops up muscle glycogen fuel levels, while the added sodium reduces urine losses before exercise begins. The flavour also helps the athlete to drink a higher volume compared to drinking water. 2. During: Sports drinks are primarily designed for use during exercise, for optimal fluid and fuel delivery so this is where they really come into their own. They will allow the athlete to perform for longer and more effectively in training and competition. Just what the orienteer needs – energy for both mind and body for the duration of the whole event. 3. Recovery: Sports drinks can be of great assistance in rehydration. However, don’t rely on the sports drink alone for complete recovery. It is best to consume them in conjunction with foods that provide carbohydrate, protein, vitamins and minerals. High GI carbohydrate foods like watermelon, and other tropical fruits, can be helpful here.

In summary for a successful summer in Orienteering, plan your hydration strategy well and stick to this plan, adjusting it to hotter conditions where necessary. Experiment on training runs, using various quantities and types of sports drinks, until you find the best volume and product for you. Everyone’s needs are individual, so discovering what suits you best is the key.

TRAINING – continued

greatly reduced risk of coronary heart disease which is about 1/7th that of non-smoking, non-athletic controls6. So although no-one is completely free of the risk of cardiovascular disease, we are certainly loading the dice in our favour by participating in our Orienteering. Furthermore, in addition to benefiting our cardiovascular health, leisure activities such as Orienteering can have positive benefits upon our mental health as well as our social life.

Conclusions

Ageing is inevitable and will affect our Orienteering performance. It may be impracticable therefore to directly compare our running speeds as we get older. However, given that the average rate of decline is around 0.6 – 1.0% per year in road running and 1.0 – 1.5% in Orienteering we should consider factoring this into our comparisons. So if our rate of decline proves to be equal or less than this, we could congratulate ourselves on maintaining our level of performance. Furthermore, Orienteering fulfils the criteria of a health enhancing physical activity, and therefore we should keep active and aim to stay fit for the good of our health as well as our sport.

References

1. Bird, S., Balmer, J., Olds, T., & Davison, RCR (2001). Differences between the sexes and age-related changes in orienteering speed Journal of Sports Sciences, 19, 243-252. References continued page 47