 Dear students, in this topic, we shall discuss the two types of muscle contractions, that is, isotonic and isometric contractions. Dear students, in a muscle contraction, two variables, that is, the force or tension and the length, that is, shortening or lengthening of muscle fiber during contraction, are important parameters or variables which can be measured. Based on these two variables, muscle contractions are categorized into two types, that is, isotonic contractions and isometric contractions. First we shall discuss the isotonic contractions. Tension means same or constant and tonic means tension, that is, such contractions in which the tension remains constant. During these types of contractions, the tension remains constant but the length changes. These isotonic contractions occur when the muscle exerts force, that is greater than the external force acting on it. The change in length of the muscle results in the movement of body parts, particularly the bones. So such contractions are produced during the movement of body parts and locomotion. Dear students, based on how the length changes, the isotonic contractions are classified into two types. Number one, the concentric contractions. Number two, eccentric contractions. Concentric contractions happen when a muscle generates tension and shortens. When a muscle force generates and shortens, then such contractions are called concentric contractions. When we lift any weight, then our bicep muscles show concentric contractions. Here students, when a muscle generates force, attention and becomes lengthened, such contractions are called eccentric contractions. When we have to return an lifted weight, that is, we are lowering of weight, then our bicep muscles generate force but they lengthen. This is an example of eccentric contractions. Dear students, a contraction in which the muscle increases tension but no change in the length of the muscle, then such contractions are called isometric contractions. Isometric contractions occur when the force exerted by muscles is equal to the opposing external force. Dear students, these isometric contractions are important in maintaining the posture and stabilizing a joint. When we hold on to something and stand calmly and there is no movement of the arm, then during this time, the muscles of the arm are contacted so that they can force the force against the gravity but no change in the length of the muscles. Such contractions are called isometric contractions.