What’s the most important body part an athlete needs on the field? A strong throwing arm? Legs of steel? All of these things help, but it may just be the brain. According to a recent study of mental fatigue published in Medicine & Science in Sports and Exercise, mental fatigue may significantly affect your physical endurance. Although your muscles may still be somewhat fresh, exercise simply feels harder when your brain is tired, forcing you to quit earlier.

Scientists from the University of Kent in England and the French Institute of Health and Medical Research decided to see how well male volunteers’ bodies would perform after tiring their brains with a mentally demanding computer word game. The computer test was known to induce mental fatigue.

Scientists found that mental fatigue significantly affected the men’s endurance. In fact, the volunteers tired about 13 percent faster after the computer test than after watching a serene, calming documentary for the same amount of time. Volunteers also reported that the workout felt more exhausting after the computer test than after the documentary.

Another pre-workout practice to avoid is cold stretching. Stretching muscles when they’re cold can lead to injuries and poor performance. Instead warm up with a few minutes of light cardio, such as jogging outside the gym or dancing to your favorite workout playlist.

Also avoid chugging water and eating too much. Although it is important to hydrate during your workout, drinking too much water can lead to cramping, feeling sluggish and an overall bad workout. The same goes for eating too much or eating the wrong kinds of foods before a workout.

So, before your next challenging workout session put down your copy of Moby Dick and just let your brain relax. Just know, in many instances, your body may be stronger than your mind realizes.