Isometric exercises: These are those exercises in which no movement takes place while force is exerted against an immovable object. It develops only tension at the joint concerned. It is also called static muscle contraction.
Isokinetic exercises : This is a type of muscle contraction where both the tension and speed are prefixed throughout the range of motion. This process involves development of maximum tension in muscles which shortens at constant speed at all angles.
Methods of strength development:
Isometric: Iso means SAME and metric means LENGTH. A contraction is said to be isometric when tension in the muscle is developed but there is no change in the length of the muscle. This is also called static contraction because the joint angle does not change. For example holding a weight at arm's length, pushing against the wall. So isometric exercises are those in which no movement takes place while force is exerted against an immovable object. It develops tension only at joint concerned. There is neither shortening nor lengthening which results in no visible muscular effort. Such types of contractions are more useful for weightlifters, gymnasts, wrestlers, etc.
For example : (i) Holding half push ups, (ii) Flexed arm hang, (iii) Pushing- against the wall.
Advantages of Isometric Contraction :
1. Isometric exercises need less time. Usually the duration of contraction is 5 to 7 seconds.
2. These exercises need less equipment or do not require costly equipment as exercises can be performed anywhere at home.
3. Isometric exercises help in management of sports injuries.
4. Need of energy requirement is less due to which sportsman does not get tired.
Isotonic : Iso means 'SAME' and tonic means TENSION. In isotonic contraction muscle contracts and shortens under a constant load throughout the entire range of joint. The shortening of a muscle's principle action (length of muscle increases) is called concentric. The lengthening of the muscle (length increases) after contraction is called eccentric. Such types of contractions are commonly used in games and sports. This is also called dynamic contraction. In the initial phase of movement, concerned muscles are stretched and then they contract explosively. Because of shortening and lengthening of muscles there is always a resultant movement at concerned joint. In majority of the cases the dynamic muscle contraction is a specific combination of concentric and eccentric contractions. This happens in all explosive movements like jumps, throws, etc.
Isokinetic : ISO means SAME (constant) and KINETIC means SPEED. This is a special type of muscle contraction where both tension and speed are pre-fixed throughout the range of motion. In isokinetic contraction the muscle applies maximum force throughout the range of movement, e.g., treadmill.
Specially designed machines are necessary for using Isokinetic method for strength development. The speed of contraction can be adjusted according to the individual. This method can be effectively used for developing maximum strength, explosive strength and strength endurance. This process involves development of maximum tension in muscles which shortens at constant speed at all angles.
Advantages of Isokinetic Method :
1. These exercises develop overall strength in the body at all speeds of movement.
2. It is best for improving muscular strength and endurance for sport.
3. Isokinetic exercises are helpful in warming up also.