Visual Aim The accuracy of aim in directing an object toward a distant target is enhanced if a closer object is used as a reference point. The Spot System in bowling utilizes this principle. Instead of taking aim on the pins, aim is taken on or near a spot on the alley about sixteen feet ahead of the foul line. On account of the defects in the optical system of the eye, visual acuity is greatest when the pupil is fairly constricted. In the act of accommodation the pupil is constricted for near vision and dilated for far vision. For objects near at hand the visual acuity is remarkable. Most persons can see the width of the finest hair at arm's length. The width of the retinal image of the hair is 0.0049 mm., and this is practically the diameter of a single cone in the fovea. The lens is flattened when viewing objects at least twenty feet away and must bulge for clear vision of objects closer titan twenty feet (in the normal eye). Associated with the accommodation reflex when an object is viewed at close range is the convergence reflex by which the two eyes are turned in towards the nose through contraction of the internal recti and simultaneous relaxation of the external recti of each eye. The kinesthetic impressions from the converging eye muscles provide an estimate of the distance, the convergence becoming greater as the distance is shortened. Near objects (within twenty feet) viewed with the eyes naturally converged are seen with stereoscopic vision which allows an estimate of the length, width and thickness of the object. This spatial discrimination is diminished when the object is viewed from afar. When near objects are viewed with only one eye, spatial discrimination is also lost. The appreciation of the size and shape in three dimensions improves the accuracy of aim and the judgment of distance.		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