Strength, the ability to create and/or maintain force, is perhaps the most important physical quality for success in sports. The main reason for this is that strength is related to many other physical and mental qualities. For example:
1) Strength is needed to assume and maintain static and dynamic posture. In execution of sports skills, the body changes position so that the muscles must constantly make corrections to maintain the body in a safe and effective position.
2) You need strength to hold the spine in its normal, safe curvature. This is needed when executing strength exercises and sports skills and when transferring forces from the legs to the upper body and vice versa.
3) Strength is needed to demonstrate active flexibility.
Athletes often use static stretching in which you hold a position for 30-60 seconds. Such stretching does not prevent injury nor does it prepare the muscles for action, the main purpose of stretching in a warmup. Muscle strength is needed to move the body and limbs through the needed range of motion (flexibility) and provide the force for these movements.
4) Greater strength produces greater speed and force. In general, the more strength you have (up to an optimal amount) the greater the speed and force that you can exhibit in running, kicking, throwing, hitting, etc. When coupled with speed (speed-strength), it is the key to quick, fast and explosive movements.
5) Greater strength gives you better control of your body movements, i.e. neuromuscular coordination, the key element in execution of all sports skills. The strength enables your movements to be executed safely and effectively.
6) With greater strength, you develop a better muscular feel of the various joint actions. This is needed in perfecting your sports technique. Strength allows you to practice a particular movement correctly to develop the necessary neuromuscular (motor) pathway that will feel natural when full adaptation occurs.
7) You need strength to learn a skill (technique).
Strength allows you to execute your sports skills effectively and to learn key actions to improve your sports skill. This is especially evident when first attempting new or different movements. If you do not have the strength to carry out new actions, you develop poor or even potentially dangerous skill patterns that may be extremely difficult to change after solidified.
8) Strength is needed to prevent injury. Effective technique, adequate flexibility, muscle strength and strong tendons and ligaments help prevent injury. When your joints or limbs are stabilized and under control of the muscles, the chances of injury are minimal. Also, since all skills are under neuromuscular control, any dysfunction may create injury.
9) Strength speeds up rehabilitation. If you happen to get injured but have adequate strength levels, you will recover faster. Strength training is one of the primary methods used in rehabilitation of injuries.
10) Strength improves breathing abilities. Breathing plays an important role in the execution of almost all skills and in relaxation. When your respiratory muscles are strong, you are capable of processing more air per breath to get greater amounts of oxygen for energy production, prevent the onset of fatigue and to help in recovery.
11) Greater strength can improve your aerobic capabilities. When you engage in aerobic conditioning, the cardiovascular and respiratory functions improve, but strength does not. By developing greater muscle strength, you will be able to do aerobic activities more effectively and experience greater gains.
12) Strength (and other physical qualities) develops greater confidence, a most important psychological quality you must possess in order to be successful. Confidence is based on your ability to execute the skills needed when necessary. It is the key to consistent and well-executed play.
13) Greater strength develops greater mental abilities. We known that only about 10% of the brain cells participate in mental activities. What is overlooked is that the remaining 90% of the brain participates directly in the work of different organs, including the muscles, during the mental activity. If you deprive the brain of impulses from these organs, you would plunge into a deep sleep.
Thus, the signals from the muscles, tendons, etc., are a necessary prerequisite for successful brain activity. Strength training is best for maximum nervous pulsation in a minimum amount of time to quickly remove psycho-emotional tension and mental fatigue which leads to improved mental abilities.
Related to this is that as you become stronger and more fit, you learn what it takes to overcome difficulties in life. For example, I once had a student who had to swim one mile using any stroke or combination of strokes, without stopping or holding on to the sides of the pool. She had to be in motion at all times but could float when tired.
Of all the girls in the class she was the most poorly coordinated and had hardly participated in physical activities during her elementary and high school years. To pass the class, she practiced almost every day.By the end of the semester, she successfully finished the mile swim.
A few days later she told me that my class did more to change her life than any other experience. She now realized she could accomplish anything she wanted to, both physically and mentally. In her words, this was a turning point in her life. It made her realize that she was capable of much more than she had ever dreamed possible.
The same thing can happen to you. In order to succeed in your sport, you will find that training at times is serious, hard, sometimes miserable, dirty work and not fun and games. As a result, you develop perseverance, tenacity, at times aggressiveness and other psychological qualities to do the work that is needed to succeed. The more you practice, the more accomplished you will become and the greater will be the effect on your mind and body.
14) You need strength for relaxation. When you are under tension, the muscles are in a state of contraction (tension). As a result, before you can relax the tension must be removed. If not, relaxation is impossible. By contracting the muscles during exertion, the muscles relax on the return phase. If not, you must consciously think of relaxation on the return. You must also learn to relax muscles that are not involved in the exercise. This conserves energy, keeps you relaxed and thinking more clearly to adapt to changing situations during game play.
For related information see Biomechanics and Kinesiology of Exercise