Cross education is a neurophysiological phenomenon where an increase in strength is witnessed within an untrained limb following unilateral strength training in the opposite, contralateral limb. [1]
Cross education can also be seen in the transfer of skills from one limb to the other.
A resistance trainer witnesses strength gains in her left and right biceps after participating in a strength training program for only her right biceps. This phenomenon is due to factors at the muscular, spinal and neural levels.
A basketball player learns to dribble a basketball with his right hand and then successfully performs the task with his left hand even though he had undergone no previous training with his left side.
Calisthenics or callisthenics (/ˌkælɪsˈθɛnɪks/) is a form of strength training that utilizes an individual's body weight as resistance to perform multi-joint, compound movements with little or no equipment.
Tetraplegia, also known as quadriplegia, is defined as the dysfunction or loss of motor and/or sensory function in the cervical area of the spinal cord. A loss of motor function can present as either weakness or paralysis leading to partial or total loss of function in the arms, legs, trunk, and pelvis; paraplegia is similar but affects the thoracic, lumbar, and sacral segments of the spinal cord and arm function is spared. The paralysis may be flaccid or spastic. A loss of sensory function can present as an impairment or complete inability to sense light touch, pressure, heat, pinprick/pain, and proprioception. In these types of spinal cord injury, it is common to have a loss of both sensation and motor control.
The biceps or biceps brachii is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is at the elbow where it flexes the forearm and supinates the forearm. Both these movements are used when opening a bottle with a corkscrew: first biceps screws in the cork (supination), then it pulls the cork out (flexion).
Alien hand syndrome (AHS) or Dr. Strangelove syndrome is a category of conditions in which a person experiences their limbs acting seemingly on their own, without conscious control over the actions. There are a variety of clinical conditions that fall under this category, which most commonly affects the left hand. There are many similar terms for the various forms of the condition, but they are often used inappropriately. The affected person may sometimes reach for objects and manipulate them without wanting to do so, even to the point of having to use the controllable hand to restrain the alien hand. Under normal circumstances however, given that intent and action can be assumed to be deeply mutually entangled, the occurrence of alien hand syndrome can be usefully conceptualized as a phenomenon reflecting a functional "disentanglement" between thought and action.
The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness. A greater intensity of light causes the pupil to constrict, whereas a lower intensity of light causes the pupil to dilate. Thus, the pupillary light reflex regulates the intensity of light entering the eye. Light shone into one eye will cause both pupils to constrict.
Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain, a deficit in attention and awareness towards the side of space opposite brain damage is observed. It is defined by the inability of a person to process and perceive stimuli towards the contralesional side of the body or environment. Hemispatial neglect is very commonly contralateral to the damaged hemisphere, but instances of ipsilesional neglect have been reported.
The withdrawal reflex is a spinal reflex intended to protect the body from damaging stimuli. The reflex rapidly coordinates the contractions of all the flexor muscles and the relaxations of the extensors in that limb causing sudden withdrawal from the potentially damaging stimulus. Spinal reflexes are often monosynaptic and are mediated by a simple reflex arc. A withdrawal reflex is mediated by a polysynaptic reflex resulting in the stimulation of many motor neurons in order to give a quick response.
The crossed extensor reflex or crossed extensor response or crossed extension reflex is a reflex in which the contralateral limb compensates for loss of support when the ipsilateral limb withdraws from painful stimulus in a withdrawal reflex. During a withdrawal reflex, the flexors in the withdrawing limb contract and the extensors relax, while in the other limb, the opposite occurs as part of the crossed extensor reflex. Besides shifting the body weight to the other side, the reflex pathway is also associated with leg coordination when walking by flexing muscle on one side, while extending muscle on the other side. This crossed extensor response is properly part of the withdrawal reflex.
A squat is a strength exercise in which the trainee lowers their hips from a standing position and then stands back up. During the descent, the hip and knee joints flex while the ankle joint dorsiflexes; conversely the hip and knee joints extend and the ankle joint plantarflexes when standing up. Squats also help the hip muscles.
Todd's paresis is focal weakness in a part or all of the body after a seizure. This weakness typically affects the limbs and is localized to either the left or right side of the body. It usually subsides completely within 48 hours. Todd's paresis may also affect speech, eye position (gaze), or vision.
Hoover’s sign of leg paresis is one of two signs named for Charles Franklin Hoover. It is a maneuver aimed to separate organic from non-organic paresis of the leg. The sign relies on the principle of synergistic contraction.
Extinction is a neurological disorder that impairs the ability to perceive multiple stimuli of the same type simultaneously. Extinction is usually caused by damage resulting in lesions on one side of the brain. Those who are affected by extinction have a lack of awareness in the contralesional side of space and a loss of exploratory search and other actions normally directed toward that side.
Amorphosynthesis, also called a hemi-sensory deficit, is a neuropsychological condition in which a patient experiences unilateral inattention to sensory input. This phenomenon is frequently associated with damage to the right cerebral hemisphere resulting in severe sensory deficits that are observed on the contralesional (left) side of the body. A right-sided deficit is less commonly observed and the effects are reported to be temporary and minor. Evidence suggests that the right cerebral hemisphere has a dominant role in attention and awareness to somatic sensations through ipsilateral and contralateral stimulation. In contrast, the left cerebral hemisphere is activated only by contralateral stimuli. Thus, the left and right cerebral hemispheres exhibit redundant processing to the right-side of the body and a lesion to the left cerebral hemisphere can be compensated by the ipsiversive processes of the right cerebral hemisphere. For this reason, right-sided amorphosynthesis is less often observed and is generally associated with bilateral lesions.
Normal aging movement control in humans is about the changes in the muscles, motor neurons, nerves, sensory functions, gait, fatigue, visual and manual responses, in men and women as they get older but who do not have neurological, muscular or neuromuscular disorder. With aging, neuromuscular movements are impaired, though with training or practice, some aspects may be prevented.
Asomatognosia is a neurological disorder characterized as loss of recognition or awareness of part of the body. The failure to acknowledge, for example, a limb, may be expressed verbally or as a pattern of neglect. The limb may also be attributed to another person, a delusion known as somatoparaphrenia. However, they can be shown their limb and this error is temporarily corrected. Some authors have focused on the prevalence of hemispatial neglect in such patients.
Power training typically involves exercises which apply the maximum amount of force as fast as possible; on the basis that strength + speed = power. Jumping with weights or throwing weights are two examples of power training exercises. Regular weight training exercises such as the clean and jerk and power clean may also be considered as being power training exercises due to the explosive speed required to complete the lifts. Power training may also involve contrasting exercises such as heavy lifts and plyometrics, known as complex training, in an attempt to combine the maximal lifting exertions with dynamic movements. This combination of a high strength exercise with a high speed exercise may lead to an increased ability to apply power. Power training frequently specifically utilises two physiological processes which increase in conjunction with one another during exercise. These are deep breathing, which results in increased intra-abdominal pressure; and post-activation potentation, which is the enhanced activation of the nervous system and increased muscle fibre recruitment. Power training programmes may be shaped to increase the trainee's ability to apply power in general, to meet sports specific criteria, or both.
Achiria, also referred to as "Simple Allochiria", is a neurological disorder in which a patient is unable to recognise or perceive one side of their body. It is oftentimes associated with dyschiria, also known as a form of unilateral neglect or hemispatial neglect. The term achiria is seldom used in modern scientific literature.
Dyschiria, also known as dyschiric syndrome, is a neurological disorder where one-half of an individual's body or space cannot be recognized or respond to sensations. The term dyschiria is rarely used in modern scientific research and literature. Dyschiria has been often referred to as unilateral neglect, visuo-spatial neglect, or hemispatial neglect from the 20th century onwards. Psychologists formerly characterized dyschiric patients to be unable to discriminate or report external stimuli. This left the patients incapable of orienting sensory responses in their extrapersonal and personal space. Patients with dyschiria are unable to distinguish one side of their body in general, or specific segments of the body. There are three stages to dyschiria: achiria, allochiria, and synchiria, in which manifestations of dyschiria evolve in varying degrees.
Unilateral training involves the performance of physical exercises using one limb instead of two. Such exercises should be considered as being distinct from bilateral, two limbed, exercises. For example, unilateral squats use one leg, and bilateral squats use two legs. A unilateral bench press uses one arm and a bilateral bench press two arms. Depending on the exercise, this may also entail using different equipment i.e. a dumbbell instead of a barbell. Unilateral exercise is commonly involved in comprehensive training regimes and especially those of professional sports people and athletes. Usually it is used in addition to bilateral training as opposed to instead of it. Unilateral training can yield numerous benefits including improving a person's muscle balance between the left and right sides of their body, improving their sense of balance, and helping to avoid or rehabilitate injury.