Effect and length of the overflow principle in proprioceptive neuromuscular facilitation: electromyographic evidences

Objective: To investigate the occurrence and irradiation/overflow amount on the muscular activity of healthy individuals submitted to proprioceptive neuromuscular technique Design: Experimental study with convenience sample Setting: Physiotherapy university rehabilitation centre. Subjects: Sixteen volunteers dexterous, healthy (8 men and 8 women), with 18 to 24 years (21± 1.61) were evaluated. Procedures: Bilateral electromyography of the upper limbs and trunk muscles (anterior deltoid, posterior deltoid, pectoral major and external obliquus) were recorded during the proprioceptive neuromuscular facilitation exercise in left lower limb (diagonal of flexion/adduction/internal rotation). Electromyography were obtained in 5 conditions: (1) rest; (2) right upper limb concentric movement of extension-adductioninternal rotation; (3) left lower limb diagonal of flexion, adduction and internal rotation (4) left lower limb diagonal with contralateral upper limb having an attachment point; (5) right upper limb performing free diagonal 3, 6, and 9 seconds after irradiation technique. Results: The lower limb isometric diagonal (condition 3) had the highest muscle activity of the posterior deltoid, external obliquus (right side) and anterior deltoid, posterior deltoid, pectoral and external obliquus (left side) compared to condition 2 (p<0.05). The exercise made with an attachment point (condition 4) was the most favorable to the majority of the muscles, followed by condition 3. Conclusion: Based on the present data, irradiation technique is detectable in healthy subjects, considering the positioning to elicit muscle response at distance, ipsilateral and contralateral to the stimulus. Clinically, its use allows muscle contraction when there is some impediment in exercising a body segment directly. Key-words: Electromyography, facilitation, physical therapy, skeletal muscle. International Journal of Therapies and Rehabilitation Research electromyographic records (EMG) of the anterior tibialis, rectus and biceps femoris muscles of 11 healthy subjects during isokinetic tests.11 There was overflow of the anterior tibialis muscle for the ipsilateral and contra lateral rectus femoris. Moreover, the EMG evoked through overflow was directly dependent of the angular speed of the exercised joint. Similarly, Shimura and Kasai (2002) compared EMG and evoked potentials of seven healthy subjects during movements initiated in neutral position versus PNF position.12 The findings had been favorable to the PNF proposals, since the electromyographic activity increased and the reaction time and the latency of the evoked potentials decreased. The overflow or irradiation is defined as the propagation of synergic muscle co-activations proceeding from a resisted movement.11 Such propagation could result in facilitation or inhibition during specific movements.3,4,13 In the facilitation sense, Adamson et al. (2008) suggested that the overflow migrates through the strongest muscle groups to the homologous muscles or any another body segment from proprioceptive inputs.14 Manual resistance is the most powerful and effective to produce overflow increasing the muscle recruitment and conscience of movement and strength.3,15 Of the biomechanical point of view, the overflow would be resulted of a body persecution to stability, having as consequence a broad variability of motor behaviors, according to individual conditions.16 Few studies are devoted to overflow in comparison to the popularity of its use in the clinical practice. The majority of the scientific basis about overflow with the PNF has been produced about thirty years ago.13,16 In those studies, exercises made without resistance do not result overflow in healthy individuals. Pink (1981) submitted ten women to the PNF and verified increase of EMG in the non-exercised segment. It was not found predilection of activation to agonists or antagonistic muscles. The increase of EMG was understood as a stabilizing activity, mainly of the latissimus dorsi muscle.16 For hemiparetics condition, the overflow was observed after resisted exercises in the non-paretic side evoked EMG in the paretic side,17 but this is not observed in recently study.18 So, it is possible to note the importance to test and discover more about the overflow phenomena because of its clinical potential. The findings of such a study could contribute as an insight to the treatment of several injuries, in which, some part of body or even some muscles, are not possible to move or contract by themselves. In the present study, it was tested the hypothesis that healthy subjects present electromyographic activity in unexercised upper limbs during the PNF irradiation technique applied in contralateral lower limb. Also, we hypothesized that contralateral upper limb muscle recruitment would be rise above free voluntary movement. Therefore, the aim of this study was to investigate the occurrence and duration of the overflow from lower to upper limbs. Material and Methods The study involved a convenience sample with sixteen young volunteers subjects (8 men and 8 women), dexterous, healthy, age 18 to 24 years (21± 1.61). The healthy definition was an individual that no history of the musculoskeletal or neuromuscular diseases, no pain or other symptoms, which could affect of the motor control. As inclusion criteria, all subjects should be between 15 and 30 years and considered sedentary. Exclusion criteria were the presence of any orthopedic, cardiovascular, vestibular, psychiatric, neurological, and any other condition that would interfere in the results and/or not allow the execution of the technique. The research was analyzed and approved by the Ethics Committee in Research of Ribeirao Preto University (protocol number 044/05) and volunteers were informed about procedures used in the study and had signed informed consent forms.