The volleyball libero is a back-row defensive specialist who cannot block or attack balls above net height and cannot serve in international play. The libero's job is to receive serves, dig hits, pass and occasionally set. The position emerged internationally in 1998 to improve defense and ball movement. "

If wrestling isn't the most difficult sport in the world, it's one of the most exhausting. To succeed at the highest levels in wrestling, you need a combination of physical power, speed, technical skill, mental toughness and endurance.

Cyclists seeking a rough, off-road riding bike may end up deciding between the Trek 4300 or Trek 3900. While the Trek 4300 suits riders who enjoy attacking rugged trails with rocks, logs or other obstacles, the Trek 3900 may appeal to commuters who get in a weekend trail ride.

Playing soccer can give your body an intense workout, especially your legs. Soccer involves a lot of running -- much of it sprinting. This, combined with the repetitive kicking of the ball, can put your leg muscles -- particularly the quadriceps and hamstrings -- through a rigorous endurance and strength-training test.

Newcomers often are introduced to gymnastics by learning tumbling moves on the floor. This teaches them "air awareness, to know where their body is, what it is doing at all times,"

Freestyle wrestling is a respected sport that has been around since the early 19th century. It is a close cousin of Greco-Roman and Folkstyle wrestling and utilizes throws, locks and leg trips in an attempt to score points and pin the opponent's shoulder blades to the mat.

Golf club heads are attached to the golf shaft with epoxy glue. Epoxy is a thermosetting polymer that is a high strength adhesive. Two parts, the resin and the hardener, are mixed together to create a chemical reaction that cures the epoxy to hardness.

Knowing how to float in the water for long periods of time could save your life in an emergency. Although you often see swimmers floating on their backs, this is just one of many possible positions. Relaxing and staying motionless help you float more easily, regardless of the position.

Track and field relies on speed, agility, quickness and balance more than power and strength. The larger your muscles, the more power and speed you can get from them. However, simply building muscles without training them for the demands of the sport will decrease your chances of success.

The intense workouts associated with competitive gymnastics provide a great source of physical exercise and encourage disciple as well as time-management skills. Gymnastics can be very demanding on competitive athletes, however, and several studies indicate that this sport can impact your child’s growth.

The basic rules of volleyball are well-known in terms of legal and illegal hits. However, there are special situations that have led to the creation of new rules to define what is and is not an acceptable hit.

Sometimes the best part of a workout is winding down afterward. Warming up slowly when you get in the pool lets you ease into an intense workout, and cooling down lets you ease back out. During moderate aerobic exercise, your heart pumps faster and your circulation increases.