Body processes

Reactive Movements – Function, Task & Diseases

Reactive movements

Reactive movements are motor responses to physical and mental stimuli that are to be distinguished from spontaneous movements. Essentially, reactive movement is based on the stretch-shortening cycle that occurs when muscles actively lengthen . The reactive force is subject to disturbances in neurogenic lesions of the extrapyramidal system.

What are reactive movements?

Neurology knows different types of movement of the neuromuscular musculoskeletal system . Every movement consists fundamentally of muscular strength and contraction , which is initiated via efferent motor nerve pathways from the central nervous system .

Involuntary movements such as fascicular twitching following stimulation of peripheral neurons are called spontaneous movements. The so-called reactive movements must be distinguished from this. A reactive movement is a movement that responds to a physical or mental stimulus. Reactive movements usually correspond to a rapid succession of eccentric and concentric muscle work .

The muscle action form of reactive movement is known as the stretch-shortening cycle. The stretch-shortening cycle occurs when the muscles are actively lengthened, which is immediately followed by a contraction of the corresponding muscles.

The plastic elastic properties of the muscles mean that the contraction occurs immediately after the stretch. So the muscle contracts before adapting to the stretch. The stored energy of the previous movements makes the cycle energy-saving and fast.

The force required to perform reactive movements is referred to as reactive force.

function & task

The combined functioning of the muscles plays a major role in everyday human life. It plays an even bigger role in a sporting context. All reactive movements are characterized by rapidly successive, yielding eccentric and overcoming concentric working of the muscles. In the eccentric phase of a reactive movement, the tendo-muscular system stores the kinetic energy from the movement within its serial-elastic and parallel-elastic structures. In the subsequent concentric phase of the cycle, the stored energy is released. This results in an increase in strength and performance compared to the previous concentric contraction. 

The reactive force depends on various factors, including neuro-muscular factors. In addition, the elasticity of the tendinous structures plays a decisive role. The basis of the increase in performance achieved within a reactive movement is the stretching-shortening cycle, which activates the receptors of the muscle spindle . The activation of the muscle spindle receptors is therefore the stimulus that must precede every reactive movement.

The reactive force is exactly the force that realizes the highest possible force impulse in the stretching-shortening cycle. The stretching-shortening cycle itself is the phase between eccentrically yielding and concentrically overcoming muscle work. Good reactive strength is the result of good maximum strength, reactively appropriate muscle tension and rapid contraction ability. The reactive ability to stretch results from the passive elasticity forces of muscles and tendons .

People need reactive power to carry out forms of movement such as jumps , sprints or throws. All such movements essentially have a reactive character.

The extrapyramidal system is an anatomically critical structure for reactive movement. Motor control processes are then found in this system as soon as they do not run via the pyramidal tracts of the spinal cord . The neural pathways of the system pass from nuclear areas of the cerebral cortex through the subcortical basal ganglia , red nucleus, and substantia nigra in the midbrain . From there they continue into the olivary core of the medulla oblongata and run down the spinal cord.

In primates, the extrapyramidal system has some dominance in motor control. A functionally clear separation of the pyramidal and extrapyramidal systems does not exist in primates either.

Diseases & Ailments

The reactive power can be specifically trained. For example, athletes use so-called plyometric training to train reactive movement sequences and thus develop a higher than average reactive strength. In the stretch-shortening cycle, and thus the basis of all reactive movement, tendons must be stretched to the limit to produce the required movement effects. In this context, high extensibility can have an unfavorable effect on the development of the cycle and thus also show unfavorable consequences for reactive movements. 

Apart from these connections, reactive movements can be affected by neurogenic lesions. For example, a movement disorder that is caused by such lesions is called extrapyramidal syndrome. A drastic increase or decrease in movements occurs due to an increased or reduced state of tension in the muscles.

The extrapyramidal system is mainly unconsciously attributed to involuntary movements that characterize automated movement sequences. In addition, the system makes a significant contribution to the coordination of tone and movement. For example , because of the extrapyramidal system, the arms swing along when walking .

In addition, the exrapyramidal system inhibits and controls voluntary motor activity of the pyramidal tract . Disorders of the system are either hypokinetic-hypertonic, as in Parkinson’s disease, or hyperkinetic-hypotonic, as in chorea or ballism.

Corresponding disorders can also occur as a result of medication such as neuroleptics . The consequences of these disturbances are phenomena such as ataxia , tremor or inhibitions when starting, which correspond to a disturbed initiation of movement.

All reactive movements are reduced in the hypokinetic-rigid form of the extrapyramidal syndrome. In many cases, patients with this symptom suffer from a tendency to fall when walking, since walking is associated with reactive movements. Injuries or other pathological conditions of the muscles can also underlie a reduced reactive force.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.