The right running shorts can make your break your workout. A crotch that rides up, tight waist bands and insufficient coverage can send you running home, rather than for miles on the trail as you planned. Women's bodies differ, so not every running short works for everyone -- but the best models do share specific features.
The best running shorts include an internal liner that acts as underwear. Save your lingerie for after your workout. This liner should be made of wicking material, such as Collmax Alta Crepe or TechniFine mesh. The liner fits over your cheeks, so you don't get the unpleasant flossing effect as you run.
Look for shorts made for women, rather than unisex models, as they are sewn to fit you optimally through the waist, hips and thighs. The best running shorts are made of a technical fabric and fit relatively closely to the body. They don't have to be skin tight, but long, baggy shorts are not recommended. The extra material creates wind resistance and can rub, causing chafing.
The Long and Short of It
The length of the inseam is a matter of personal preference. Women with more generous thighs may prefer a little more coverage for modesty and comfort -- thigh skin rubbing against thigh skin definitely makes for an unpleasant run. Women with thin gams may like the freedom that a short-short provides, especially if they are going for short distances or sprints.
The best shorts will have a small, unobtrusive pocket for your key or credit card. Some even feature a zip pocket on the back of the waist for a gel pouch or a small MP3 player. Although these pockets aren't essential, they are convenient.