Picking the right pace for yourself during the marathon is the key to how well you eventually complete the race. First of all it’s important to understand what is happening to your body as you progress through the long marathon distance.
At the start you will be running quite comfortably (hopefully anyway!!), due to your marathon training and your carbohydrate stores (glycogen reserves). However your supply of accessible ‘fuel’ is limited, and as you get to the 17 mile mark and later you need to draw energy from your bodies’ protein and fat just to keep going. At the same time you are also fighting dehydration. You can lose 2 – 3lbs per hour of body weight as you sweat during the run.
Now imagine that it’s a windy day or a hilly course (or both!). Your energy output has to increase if you want to maintain your pace and time goal. However this may well mean that you’ll use up your available energy stores before you even reach the 17-18 mile mark.
The same goes for the temperature and humidity level during the race. If these are high you will sweat more and be more affected by dehydration. This will negatively affect your performance by 10 to 15 %, which translates into about 1 minute per mile. In other words you will be slowing down…
Marathon runners ‘hit the wall’ because their glycogen reserves are depleted and they feel really weak. This feeling will be compounded by the effects of dehydration. At this point many runners have stop and walk just to keep going. Obviously they will be unable to meet their marathon time goal.
So, knowing all this in advance, the wise marathoner will carefully assess the race conditions at the start of the race. If it’s hot it’s best to start slower until you have reached a steady running rhythm. The same goes for running into a headwind. You should also take into account your running form after six miles or so. Are you relaxed and feeling as good as you should at this early point in the run? If not – it’s time to slow down for a while to see if you recover.
To successfully complete a marathon you must run as far as you possibly can within your body’s comfort level. That might sound like an oxymoron when we’re talking about 26.2 miles, – but it is possible! If you can reach the 16 mile mark without a lot of stress then you have a good chance of finishing the race without too much trouble.
The key point is to start out with a target pace range in mind, and not an absolute goal like 3hr 45 m. For example you might pick a pace between 8:30 to 9:00 minutes per mile (for a marathon time in the 3hr 40m to 4 hr range approximately). Then adjust your pace according to the conditions and your own running ability on marathon day. It’s usually better to start at the slower end and then increase the pace as you get further into the race.
Try this and you may well be pleasantly surprised with how well you complete the race.