Your feet will strike the ground 46,000 times. Your heart will thump your chest more than 30,000 times. And over the course of 26.2 miles, your muscles may spasm, your organs may rebel, and your gastrointestinal system may bail on you.

No one questions that running a marathon is a grueling physical task, but striding toward the finish line takes more than muscle and a strong heart. It takes a mighty will.

"Yes, the marathon is a physical act of endurance, but it is also an act of willpower and self-control when our bodies want to give up," said Niels Christensen, a Radford University associate professor of psychology and a marathon runner. Christensen has joined psychology’s growing interest in willpower by teaching a research course on self-control. "Psychologists are discovering new insights into the power – and fragility – of self-control in our lives," he said.

Many of Christensen's insights into self-control were developed over the long stretches of asphalt on which he trains for marathons. The professor, who was inspired to run when his mother completed her first marathon while in her 60s, has completed six 26.2-milers in the past five years, including the Marine Corps Marathon.

His fastest time is 4 hours and 7 minutes in the Richmond Marathon. "I'm what they call a 'back-of-the-packer,'" he joked. The professor's most embarrassing and demoralizing marathon moment, he said, was in that Richmond race.

"People pass you, and that can be so depressing," Christensen recalled. "In Richmond, an older lady passed me, and she was wearing a leopard-skin miniskirt and running top. When she passed me, I was like, 'That is it. It will not get any lower than that.' "

In Philadelphia, he was passed by a man who juggled the entire race, but the professor later overtook the juggler.

Christensen recovered from those dispiriting episodes and willed himself across the finish line in both races. Ahead of preparing for his next big race, he offers these five tips for how you can do the same.

• Habit, habit, habit. If the first three rules of real estate are “location, location, location,” then the first three rules of self-control are “habit, habit, habit.” Psychologists have repeatedly shown that humans are prone to making automatic decisions with little conscious awareness. This is detrimental if we have a habit of eating doughnuts each morning, but the power of automaticity can also be harnessed for our advantage. The power of habit is most important in scheduling training runs in the 15 to 18 weeks leading up to a marathon. Running on the same days and at the same times every week will increase the likelihood that it gets done.
   
• Carbohydrates are good for your muscles … and your willpower. Research suggests that, like muscles, our willpower needs fuel, too. People who use self-control on one task typically showed reduced willpower on subsequent tasks. However, this depletion of self-control can be washed away when participants are given a sugary beverage. Clearly too much sugar or fluctuations in one’s blood glucose are not good. But runners should make sure they are getting sufficient carbohydrates to make good decisions at the end of the marathon. It’s easier to give up when your brain hurts.
   
• Have extra motivation ready when raw willpower gives out. Self-control can only do so much for decision making, especially as it wears down over the course of training or a race. One way to overcome these lows in willpower is to increase motivation. Having reminders of why we are running—especially reminders about other people—can pull us through the difficult times.
   
• Win some, lose some. Over the course of a 16-week training plan, every runner will have some great runs and some stinkers. Success or failure can enhance our determination depending on how we frame the event. Researchers recommend looking forward (Look how far I still have to go!) following success so that we don’t rest on our laurels. After a failure, we’re better focusing on the past (Look how far I’ve come!) to re-energize ourselves.
   
• Practice running…and self-control. Any running coach will tell you that the best performance-enhancing drug for running is, well, running. Increasing training miles each week makes us faster and stronger. Self-control can be improved with practice as well. And the great thing is that willpower appears to generalize from one task to another. So practicing self-control by resisting unhealthy foods can improve future self-control for unrelated temptations, for example, resisting overindulgence in video games.