Muscular Tension The degree of muscular tension during the performance of an activity affects the energy requirement of the task, the rate of movement of body parts, and the onset of fatigue. Muscular tension during manual work can be measured by recording grip pressure of the idle hand and of the used hand, by recording the pressure of the point of the pencil in writing, by recording muscular action potentials, and by observations of increases of blood lactic acid. The level of muscular tension habitually exhibited by an individual during muscular activity characterizes him as a tense or relaxed person. Too much tension makes movement jerky, awkward, and often painful. Too little tension makes movement weak and unsteady. The level of muscular tension is determined by the intensity of the activity of the central nervous system, particularly the cortical and subcortical centers. Impulses from the sensory nervous system received by these centers elicit a discharge of motor impulses which stimulate skeletal muscles, causing a general increase in tension. Mental and emotional experiences affect tension. States of sadness and depression diminish tension and result in slouched posture and "halfhearted" movements. States of happiness and confidence elevate tension and result in more erect posture, alertness, and movements which are more direct and leas fatiguing. Fear and intense excitement can increase tension to the point of incapacitating contracture ("scared stiff") and resultant muscular fatigue. Such spasticity during excitement interferes with coordination and often results in fumbles and inaccurate performances during an athletic event. Thinking about muscular performance has been shown to produce an increase in the tension of the muscles which would participate in actual performance. This phenomenon suggests that learning and perfection of skills can proceed through reading and thinking about the technique of the event. Thus, a golfer during the winter season may improve his swing by studying texts written on the subject. Divers commonly repeat in their imagination the movements of a new dive before attempting to perform it off the springboard or platform. Just as thinking about muscular performance increases muscular tension, increased muscular tension during activity also increases the activity of the central nervous system. Clenching the fists exaggerates the knee-jerk reflex response. Muscular relaxation reduces the amplitude of the knee-jerk response. In one experiment the rate of learning various tasks was improved by induced tension achieved by gripping a hand dynamometer. Restlessness and incidental activity such as clenching a fist while writing an examination may conceivably contribute sufficiently to the stimulation of cortical activity so as to improve the student's score.		Home Components of Physical Fitness Clinical Examination Differences Between Fit and Unfit Men Physiological Elements of Fitness The Step Test The Effects of Training on the Physiological Systems Work Output Physical Condition of Muscle Application of Muscular Force Maintaining Optimum Strength Tests of Muscular Strength Strength and appearance Strength as a measure of physical fitness Strength as affected by organic problems Strength as prophylaxis Role of inactivity in production of disease Lack of Sociability in Work Lactic Acid System Muscular Form Capillary Growth Heart Size Heart Rate Training produces physicochemical changes Muscular Strength Nervous Stimulation and Muscular Strength Quality of Champions Factors Which Limit Skill Kinesthesis Balance Reaction Time Muscular Tension Visual Aim Skill Center in the Brain Endurance for Exhaustive and Moderate Work Distribution of Energy