Sunglasses should be worn during any activity that exposes you to sunlight, but sports, particularly, depend on extended time spent in the sun over many months or years. The right sunglasses can also provide the wearer with less eye fatigue and clearer sight. It's crucial that sunglasses are worn while participating in sports, but the physical activity involved in sports creates a dilemma when looking for sunglasses.
The first step is ensuring that the sunglasses won't fall off during activity. They should be close fitting and could have a rubberized coating so that they don't become slippery when wet. If sunglasses were to fall off during sports, it could cause distraction to the wearer, damage to the sunglasses, and even injury to other players if stepped on. Quite a lot to pay for not having the right sunglasses.
Many sports also have a possibility of bodily injury. Just as well as your body can be hurt, your sunglasses can be as well. Of course it's not ideal if your brand new pair of Choppers sunglasses break from a basketball to the face, but the real concern is the damage that those breaking sunglasses can do to your face. Glass lenses can do the most damage when not manufactured specifically for sports, so it's best to stick with plastic lenses for sports sunglasses.
Since the first priority in any sunglasses is that they sufficiently protect your eyes, it's important to choose sunglasses with the particular conditions you will be exposed to in mind. This will determine the tint of the lens you need, as well as special lens treatments like polarization. For the most part, lighter lenses will block less glare, but have their own benefits.
Snow sports require good depth perception and also subject participants to very high glare from snow reflecting the sunlight. Yellow or orange tinted lenses balance these conditions. Brown tinted sunglasses are especially useful in increasing contrast against green or blue backgrounds, so they're suitable for most outdoor sports, especially field sports and water sports. Red tinted sunglasses are best for indoor sports because they increase visibility in low light conditions. Gray tinted sunglasses are the most versatile, and are suitable to any sport.
For added protection from glare, tinted sunglasses can be treated with a reflective mirror coating as well. Every sport is different, and there's a different pair of sunglasses for every occasion. X-Loop sunglasses are especially suited to sports because they were designed with that in mind. Buying cheap sunglasses in bulk can make it more affordable to own several pairs of sunglasses for each sport you participate in.