Each week we will be bringing you the training diary of endurance sport specialist John Feeney.
He is writing a weekly schedule on topics covering everything from running physiology and training to choosing the right footwear, recovery and tapering.
For week eight, Feeney writes: The sunny weather this week certainly makes training more bearable, but it presents some challenges for the marathon which could affect your performance on the day.
When exercising, around 80 per cent of the energy released is given off as heat with only nine to 20 per cent used to fuel your muscles.
To maintain a constant core temperature, the excess heat generated by the muscles is transported to the skin by increased blood flow.
If exercise continues and core temperature increases, the body will begin sweating in order to remove excess heat by evaporation.
Sweating has a limited affect unless it can evaporate or be wicked away from the skin.
If it’s chilly on marathon day, avoid the temptation to wear additional clothes. These will act as insulation and interfere with heat transfer to the skin and sweat evaporation.
This will increase heat storage, which may result in fatigue and reduced performance. Instead, try using a bin liner or something that can be thrown away to keep you warm at the start. Don’t worry, you’ll soon warm up when you start running even in cool and overcast conditions.
Also, be aware that your body uses fuel at higher rates when exercising in the heat. Lactate accumulation is also higher in warmer weather and, when combined with reduced muscle glycogen, could mean you hit the wall earlier than anticipated. Reduce your initial running pace in order to help conserve your fuel stores.
Finally, sweat loss must be matched by fluid consumption in order to avoid dehydration. Dehydration will reduce skin blood flow and sweating responses resulting in an increase in core temperature and early fatigue.
Use the water stations along the route and drink to thirst. Sports drinks will provide you with a source of fuel and help replace lost salts and minerals.