The Fitness Components in SportsThe fitness components are qualities that athletes must develop to physically prepare for sport competition. They are the building blocks of exercise and physical activity. Sports training programs are designed to build these components in the proper proportions that match the requirements of each sport.Sport fitness component are not mutually exclusive. They all exist to some degree in most sports, but developing certain combinations is important in any given sport (e.g., strength-endurance in rowing). While definitions are assigned to qualities that represent what "fitness" is, it can be operationalized in different ways for each sport. In other words, fitness for one sport is somewhat different for another. Fitness for sports can also be measured in different ways depending upon the energy and movement demands of each sport. 
Endurance is the ability to sustain submaximal activity for extended periods of time. It involves muscular endurance (the ability of a muscle to contract repeatedly) and cardio fitness (the ability of the heart, lungs, and hormonal systems to deliver oxygen and fuel to the muscles). Distance events require exceptional
endurance fitness.
Push ups place greater demands on muscular strength and endurance.
Strength is the ability to move a maximum weight. It can also be described as the maximum amount of force that a muscle can generate in a single effort. When athletes make significant strength gains, muscles fibers (cells) gain size. Weightlifting requires considerable strength, but all sports also require some level of strength fitness. 
Speed is the ability to move quickly. Fast movements involve
reaction time
(from the cue for movement to the beginning of a movement) and movement time (from the beginning to the end of a movement). Speed of movement is necessary for reacting to opponents in open skills. Closed skills, such as discus throwing, also require rapid reactions for skilled execution.
Evan Smith performing the mountain climber Agility Fitness
is the ability to move quickly and change directions under control to execute sport skills. It is a composite of many fitness components--speed, power, strength, balance, flexibility, reaction time, and coordination. Receivers and running backs in football require great agility.
Balance is the ability to maintain a position. Balance can be static or dynamic. Static balance means that the athlete is not moving, such as when performing a handstand. Dynamic balance means that the athlete maintains equilibrium while moving, such as in slalom ski events.
Sources: Powers, S.K. & Howley, E.T. (1990). Exercise physiology: Theory and application to fitness and performance. Dubuque, IA: Wm. C. Brown. Schmidt, R.A. & Wrisberg, C.A. (2000). Motor learning and performance: A problem-based learning approach (2nd ed.). Champaign, IL: Human Kinetics. United States Department of Health and Human Services, President's Council on Physical Fitness and Sports. (2000, March). Definitions: Health, fitness, and physical activity. Retrieved April 23, 2009, from http://www.fitness.gov/digest_mar2000.htm |
Fitness Resources
Handy resource for exercises, muscles used, tips. Great illustrations.
Excellent instructional sources on Olympic weightlifting for building explosiveness for other sports.
Complete reference from the National Strength and Conditioning Association. "...30 expert contributors explore the scientific principles, concepts, and theories of strength training and conditioning..."