Engaging in outdoor activities like hiking and mountain biking does not only give you the opportunity to enjoy the Great Outdoors, it also gives you a chance to stay fit and healthy. However, being in an ideal physical condition doesn't mean you are invincible. To maintain a good energy level, you'll need a steady supply of water.

You can always take a water jug or a sports bottle with you when you hike or cycle in the mountains, but the weight of a jug or bottle can slow you down, not to mention consume your time as you have to retrieve the item from your backpack. Meanwhile, a hydration pack can quench your thirst and all you have to do is drink the water from a built-in tube.

These hydration packs, though, come in numerous types, including those which have pockets for your trusty cell phones and iPods. Most hydration packs are made of durable plastic materials. In addition, there are some that don't only stand up well to the elements but also keep your water at an ambient temperature—not too hot and not too cold.