Muscle Isometric Exercise

An isometric exercise involves a muscle contraction in which the length of the muscle remains constant while tension develops toward a maximal force against an immovable resistance. The muscle should generate a maximal force for 10 seconds at a time, and this contraction should be repeated 5 to 10 times per day. Isometric exercises are capable of increasing muscular strength; strength gains are specific to the joint angle at which training is performed. At other angles, the strength curve drops off dramatically because of a lack of motor activity at that angle.

Another major disadvantage of isometric exercises is that they tend to produce a spike in blood pressure that can result in potentially life - threatening cardiovascular accidents. This sharp increase in blood pressure results from holding one's breath and increasing intrathoracic pressure. Consequently, the blood pressure experienced by the heart is increased significantly. This has been referred to as the Valsalva effect. To avoid or minimize this effect, it is recommended that breathing be done during the maximal contraction to prevent this increase in pressure.