You can appreciate what you're putting your body through if we take a brief look inside it. What's more, it's easier to listen to your body when you understand what it's doing.
A quick anatomy lesson about marathon muscles: There are two groups of muscles that are important to your training, slow twitch and fast twitch. Slow twitch muscles are the most important of all. These muscles are good for endurance events because the fibers contract (get tense and tighten, thereby becoming smaller) slowly. Fast twitch muscles contract much faster, which makes them ideal for speed events, like sprinting. Elite marathoners might have a physiological edge over other runners. Some studies have shown that they have a significantly larger proportion of slow twitch to fast twitch muscles [source: BBC]. But, you can train your muscles to work for you -- no matter your proportions. You develop your slow twitch muscles through endurance training, like your weekly long runs. And you build fast twitch muscles through your speedwork.
Nearly all training programs advocate days of rest in your regimen. On a rest day, you abstain from running to give your muscles time to heal. When you tax muscles, they rip and tear. Don't worry -- they're designed to do this. When your muscles repair these tiny tears, they grow back even stronger than before. If you're feeling particularly sore after a grueling workout, your body is probably giving you a cue to take it easy.
In addition to getting your muscles ready for the run, you're also prepping your lungs for the race. Running is an aerobic exercise -- it relies on your body's ability to use oxygen efficiently. When you're running, your muscles are working overtime. They need oxygen to support them. You supply this to them by simply breathing; your body does the hard work by sending the oxygen to your heart and lungs, where it's transported by the circulatory system to your muscles [source: Bloch]. But it takes time to gain aerobic fitness -- and if you don't start training slowly or at your level, you'll be sucking wind.
So how do you know if your body is working hard enough or too hard? You can gauge your activity level by using a heart rate monitor. Gordon Bakoulis Bloch offers a formula for determining your ideal training heart rate (beats per minute or BPM) when running: 220 (-) your age (x) 0.6 and 0.9 [source: Bloch]. For instance, a 25-year-old's BPM would fall into a range between 117 and 175.5.
But if you don't have a heart rate monitor, you can use the talk test. In your ideal training zone, you should be able to speak. If you're working too intensely, you won't be able to eke out more than a couple of words. And if you're not working hard enough, you'll find that you can talk -- and even sing.
You're training not only your body but also your mind for the race. Many sports advocate the practice of visualization before the big event. Visualization refers to imagining yourself in the act of the event and accomplishing your goal. Jeff Galloway advocates a practice called positive brainwashing. You can make yourself think positively by repeating "magic words" to spur yourself onward. The words Jeff recommends ("relax, power and glide") address complications that runners face on the course [source: Galloway].
Even if you've trained properly, you can't anticipate all the difficulties of the race. In the next section, we'll learn about running the marathon.