Monara Nunes, Diandra Martins e Silva, Rayele Moreira1, Fernanda Sousa, Lysnara Lial, Kaline Rocha, Fernando Silva-Junior, Marco Orsini, Gildário Dias, Silmar Teixeira and Victor Hugo Bastos.
The concepts of Proprioceptive Neuromuscular Facilitation (PNF) are followed rigorously worldwide. Originally, PNF was used in the treatment of patients with poliomyelitis and with the progress of studies; it was shown that the PNF promotes effective results in diseases that compromise the musculoskeletal system . The method combines concentric, eccentric and isometric contractions with the gradual application of a resistance and facilitatory procedures such as cutaneous, visual and auditory stimulus, which improve control and neuromuscular function [2,3].
Basic procedures of PNF were influenced by the works of Sir Charles Sherrington, a pioneer in research on spinal cord and motor control [4,5]. Among the basic procedures for facilitation, the Motor Irradiation (MI) allows that weak and impaired muscles are activated by strong muscles and preserved . The spread of the motor response is proportional to the intensity, the duration of the stimulus and independent of sex, age or the presence of activity in untrained muscle or in the muscle group of application of PNF. Irradiation is governed by the principle of training specificity (isometric or dynamic), and eccentric contractions cause greater strength gains when compared to concentric contractions [7,8]. This strength gain can be propagated to the ipsilateral agonist muscle, to contralateral limb  or having origin in trunk and irradiate for the lower and / or upper limbs .
Studies support that motor irradiation is due to neuromuscular adaptations that reorganize the motor control in the contralateral limb through adaptive changes in neural circuits that involve planning and motor execution in the frontal cortex  and temporal lobe . Possibly voluntary contraction produces activation in the cortex corresponding to executed movement and slight contralateral facilitation via the corpus callosum. The strong unilateral voluntary contractions may also affect the excitability of spinal motor pathways and the electrical impulses directed to the muscles that are receiving the PNF application are conducted to the muscles agonists or antagonists of the contralateral limb .
Biomechanical mechanisms may also be related to MI, since on unstable surfaces, irradiation is most notable . Changes in limb positions cause modifications in muscle activation limit. This body rearrangement triggered by the Central Nervous System (CNS) possibly seeks to recover the information’s from predetermined circuits for human development. In this way, the irradiation would act as a compensatory mechanism in order to ensure the best individual functional performance .
Several authors used electromyography (EMG) to evaluate the irradiation produced by PNF because is possible to record the activity of motor units that are recruited during muscle contractions [7,14,9]. The effects of PNF in the brain is evaluated using the Functional magnetic resonance imaging (fMRI), a tool also a lot highlighted in the studies of PNF .
The load cell is another instrument used to measure the motor irradiation for allow to assess strength and deformation of materials. In the case of muscular contractions, the load cell can be used to indicate the amount of force the limb is doing from the stress or strain generated by muscle activity that therefore, generates limb movements. The use of a load cell, showed to be an efficient quantifier of the motor irradiated during the application of manual resistance to flexion and extension of the trunk. The study demonstrated significant motor irradiation of trunk flexors to dorsiflexors and the extensors to plantar flexors .
Future studies may use the electroencephalogram (EEG) to better understand the neural mechanisms related to the principle of motor irradiation. With this tool it is possible to compare the electrical activity between two counterparts electrodes positioned on the scalp of the individual and assess the existence of a connection between two cortical areas and thus, point out which are involved with the task being performed . Authors reported in their study the successful use of EEG to evaluate the bilateral cortical activity after the execution of liabilities, assets and imagined movements, whether unilateral or bilateral. They noted that the EEG is a promising resource in the seek to understand the irradiation principle observed in the PNF techniques .
- Shimura K, Kasai T (2002) Effects of proprioceptive neuromuscular facilitation on the initiation of voluntary movement and motor evoked potentials in upper limb muscles. Rev Human Movement Science 21: 101-113.
- Witt D, Talbott N,Kotowski S (2011) Electromyographic activity of scapular muscles during diagonal patterns using elastic resistance and free weights. The International Journal of Sports Physical Therapy 4: 322-332.
- Kabat H, McLeod M, Holt C (1959) The practical application of proprioceptive neuromuscular facilitation. Physiotherapy 45:87-92.
- Molnár Z, Brown RE (2010) Insights into the life and work of Sir Charles Sherrington.Nat Rev Neurosci 11: 429-436.
- Sherrington Cs (1947) The integrative action of the nervous system. Yale University Press.
- Alencar RF, Cordeiro TGF, Anjos PGS E Cavalcanti PL (2011) Facilitação Neuromuscular Proprioceptivaemtatamenareaquisição de funçõesnalesãomedular. Rev Neurocience 3:512-518.
- Oliveira AS, Brito Silva P, Farina D, Kersting UG (2013) Unilateral balance training enhances neuromuscular reactions to perturbations in the trained and contralateral limb.Gait Posture 38: 894-899.
- Clark DJ, Patten C (2013) Eccentric versus concentric resistance training to enhance neuromuscular activation and walking speed following stronke. Neurorehabilitation and neural repair 27: 335-344.
- Abreu R, Lopes AA, Sousa ASP, Pereira S, Castro MP (2015) Force irradiation effects during upper limb diagonal exercises on contralateral muscle activation. Journal of Eletromyography and Kinesiology 25:292-297.
- Gontijo LB, Pereira PD, Neves CDC, Santos AP, Machado DCD, et al. (2012) Evaluation of Strength and Irradiated Movement Pattern Resulting from Trunk Motions of the Proprioceptive Neuromuscular Facilitation. Rev. Rehabilitation Research and Practice.
- Farthing JP, Borowsky R, Chilibeck PD, Binsted G, Sarty GE (2007) Neuro-physiological adaptations associated with cross-education of strength.Brain Topogr 20: 77-88.
- Hendy AM, Spittle M, Kidgell DJ (2012) Cross education and immobilisation: mechanisms and implications for injury rehabilitation.J Sci Med Sport 15: 94-101.
- Duecker F, de Graaf TA, Jacobs C, Sack AT (2013) Time- and task-dependent non-neural effects of real and sham TMS.PLoS One 8: e73813.
- Chiou SY, Wang RY, Roberts RE, Wu YT, Lu CF, et al. (2014) Fractional anisotropy in corpus callosum is associated with facilitation of motor representation during ipsilateral hand movements.PLoS One 9: e104218.
- Storti SF, Formaggio E, Manganotti P, Menegaz G (2015) Brain Network Connectivity and Topological Analysis During Voluntary Arm Movements.Clin EEG Neurosci .
- Formaggio E, Storti SF, Galazzo IB, Gandolfi M, Goroin C, et al. (2013) Modulation of event-related desynchronization in robot-assisted hand performance: brain oscillatory changes in active, passive and imagened. Journal of neuroengineering and rehabilitation 10: 24.