What is the Best Joint Angle of the Knee and Hip to Optimize the Neuromuscular and Tendinous Adaptations Induced by Neuromuscular Electrical Stimulation of the Femoral Quadriceps? Implications for Rehabilitation

Detailed Summary

Introduction: The muscle contractile effectiveness is influenced by the neural activation of the motor units, as well as its architecture and the elasticity of the myotendinous junction. In addition, tendinous properties also affect the production of muscle strength and function. Neuromuscular electrical stimulation (NMES) is a wide-used tool in rehabilitation for motor relearning, to reduce muscular atrophy, pain control and to improve functional performance. Although studies have demonstrated the efficacy of NMES in various clinical situations, the best joint angle (ideal muscle length) to enhance neuromuscular and tendinous adaptations induced by NMES has to be determined. Objective: To investigate the effect of NMES on different hip and knee angles on knee extensor torque, quadriceps muscle electromyographic activity, architecture, and tendon-aponeurosis complex elongation, and tendinous properties of the patellar tendon. Material and Methods: This is a crossover study with healthy males, aged 18-35 years. The independent variables will be: 1) NMES in different lower limb positions: knee joint angulation at 20º or 60º with hip at 0º or 80º (four combinations). The dependent variables will be: knee extensor torque, surface muscle electrical activity, muscle architecture (muscle thickness, pennation angle and fascicular length), the elongation of the tendon-aponeurosis complex of the quadriceps muscle components, and the properties (stiffness, Young's modulus and cross-sectional area) of the patellar tendon. The descriptive and analytical statistics will be carried out with measures of central tendency and dispersion, inference tests, tables and graphs. The normality of the data will be verified with the Shapiro-Wilk test. For the data that present normal distribution, the Two-Way ANOVA will be applied to verify differences among the measurements, with post-hoc of Bonferroni. The non-parametric option will be the Friedman test. Correlation coefficients will be calculated using the Pearson (parametric) or Spearman (non-parametric) correlation test. The level of statistical significance will be p \<0.05. Expected results: The effect of an NMES session on the neural, muscular and tendon adaptations related to the angular specificity of the hip and knee, indicating greater potential for strength and muscle mass gains, will be shown, which is fundamental in the prescription of electrostimulation in rehabilitation.

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