Running can be hard on your muscles, especially when you go out for a long haul.

Working out for more than an hour can tax your system. Muscles can hold only so much fuel. Once that fuel is depleted, your muscles begin to tire, slow you down, and wear you out.

If you're familiar with this fatigue -- "bonking" or "hitting the wall" -- you may want to try any of the sports energy gels that have entered the market recently.

Most gels contain simple sugars, as well as electrolytes and often caffeine. These gels are absorbed directly into the bloodstream and provide energy right away. Most companies produce a pudding-like gel, which is easy to suck down while you're in motion.

So why not just eat an energy bar or have a drink? Bars are fine, but they don't digest as easily, and they're hard to eat while running. Bars also slow down the absorption process and tend to suck water out of your system. Drinks don't give you as many carbohydrates. Go with gels for the quick, short-term boost.

To get the most out of your performance and avoid the bonk zone, suck down a gel packet every 30 minutes into the haul. Wash them down with water to help prevent dehydration and to move the fuel into the bloodstream faster.

Try several flavors to see what works best for you.