Angles of Knee and Hip Joints for Optimization of Neuromuscular Electrical Stimulation of the Quadriceps Femoris Muscle
Condition: Electrical Stimulation
Study type: Interventional

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.
    

Detailed description: 
      Neuromuscular electrical stimulation (NMES) is used in various contexts due to its benefits
      related to motor learning, preservation of denervated muscles, training in non-cooperative /
      sedated individuals, pain control and relief, and improvement of athletes, young, and elderly
      functional performance, besides people with severe cardiopulmonary disease. Even with the
      solid accumulated knowledge about NMES, its potential is not fully understood, with questions
      to be clarified for the achievement of greater effectiveness by clinicians and scientists in
      the various possibilities of application.

      The effects of NMES have not been determined yet in quadriceps femoris muscle in different
      lengths, which can be accomplished by changing the angle of the joint or joints it crosses
      (hip and knee). There is probably only one trial (Fahey et al., 1984) addressing this issue.
      In the study, two positions were compared: knee and hip extended versus knee (65º) and hip
      (angle not mentioned) flexed, although the purpose of the study was to evaluate only the
      influence of knee position. Authors found that NMES can increase isometric and isokinetic
      strength, but that it may be more effective to improve isokinetic performance if knee is
      flexed during treatment. Questions are then raised because groups were tested only with knee
      flexed and not also extended, and because the change in hip angle probably influenced the
      results. This study was also the only one found by Bax et al. (2005).

      Justificative: NMES is an established tool applied as the main or an supplementary treatment
      in rehabilitation programs. It is necessary to establish the influence of lower limb position
      in the outcomes. Therefore, this study will address for the first time the effects of NMES on
      quadriceps voluntary and evoked strength, electrical activity, architecture, and tendon
      properties.

      Hypothesis: In healthy young adults, the variation of the hip and knee joint angle for NMES
      may affect the knee extensor torque, quadriceps muscle electromyographic activity,
      architecture, and tendon-aponeurosis complex elongation, and tendinous properties of the
      patellar tendon. These factors will be facilitated when the participants are seated with the
      knee at 60º flexion. On the other hand, when the quadriceps is more elongated (lying with
      knee at 60º) or shortened (dorsal decubitus or sitting with knee extended (0º), such
      adaptations will not be significant.

      Methods: This is a crossover trial with healthy young male subjects. The procedures will be
      performed in the Neuromuscular Performance Laboratory of the Faculty of Ceilândia /
      University of Brasília and in the Force Laboratory of the Faculty of Physical Education /
      University of Brasília. Subjects will perform 5 visits to the laboratory (the first visit
      will be a familiarization session to test NMES in each position), with a minimum interval of
      48 hours between visits. Volunteers will be informed of all the procedures, purposes,
      benefits, and risks of the study and will sign an informed consent form before participation
      (the project was approved by the University Research Ethics Committee N 99221818.9.0000.0029)

        -  Maximal Voluntary Isometric Contraction (MVIC): An isokinetic dynamometer will be used
           for recording torque. The equipment axis will be visually aligned with the axis of the
           knee (lateral epicondyle of the femur). The lever arm of the force transducer will be
           firmly attached 2-3 cm above the lateral malleolus with a strap. Angulations of hip and
           knee will be adjusted with a goniometer. Subjects will be firmly stabilized to the chair
           with belts across the chest and pelvic girdle to minimize body movement. Individuals
           will be instructed to cross their arms with hands on shoulders and extend the knee
           against the strap "by pushing gradually for 3 s (ramping contraction) up to the maximum
           force, maintaining it for 4 s, and then decrease de amount of force gradually for more 3
           s". The number of contractions will correspond to the number of ultrasound evaluations:
           4 muscles (rectus femoris and the three vastus) + proximal patellar tendon + distal
           patellar tendon x 3 measurements for each = 18, each one separated by 1 min of rest.

        -  Neuromuscular electrical stimulation (NMES): NMES will be used to produce a maximal
           electrically evoked isometric torque, which will be assessed in the familiarization and
           will be generated (15-18 times) after the end of the voluntary contractions protocol of
           the subsequent sessions. An electrical stimulator device will be used. Parameters will
           be verified using a digital oscilloscope. The device will be connected to cables that
           will be connected to two pairs of 25 cm2 adhesive electrodes. The first distal electrode
           will be placed at 80% of the line between the anterior superior iliac spine (ASIS) and
           the space where the medial ligament is located. The proximal electrode will be placed in
           the corresponding motor point, identified with a pen type electrode, in the vastus
           medialis. The other distal electrode will be positioned 2/3 of the line that forms from
           the ASIS to the lateral side of the patella, while the proximal electrode will be placed
           at the motor point, identified with a pen type electrode, in the muscular belly of the
           vastus lateralis. It will be used a pulsed current: frequency = 100 Hz, pulse duration =
           400 μs, rise time = 3 s, ON time = 4 s, decay time = 3 s, and off time = 1 min. The
           intensity used will be the one obtained in the familiarization, or greater if tolerated.

        -  Surface electrical activity and activation level: Surface electromyography (EMG)
           activity of vastus lateralis, vastus medialis, and rectus femoris will be recorded
           bipolarly by two rounded electrodes of silver chloride, each measuring 20 mm in diameter
           and having a recording diameter of 10 mm and separated by an inter-electrode distance
           (center to center) of 20 mm. The electrodes will be positioned longitudinally in the
           muscle belly, and a reference electrode will be attached to the patella of the
           contralateral lower limb. As in the case of NMES electrodes, a marking will be made to
           ensure that in the following sessions the electrodes will be placed accordingly. The
           impedance reduction (<5 kΩ) between the two electrodes will be obtained by abrasion of
           the skin with emery paper and cleaning with alcohol. EMG signals will be amplified with
           a bandwidth frequency of 15 Hz to 5.0 kilohertz (common mode rejection rate = 90
           decibels, impedance = 100 milliohms, gain = 1000).

        -  Muscle architecture: Muscle thickness, pennation angle and fascicular length will be
           obtained in rest and during MVIC and NMES using a portable ultrasound in B mode with a
           linear transducer of 7.5 megahertz . Depth, gain, compression and ultrasound settings
           will be kept constant between assessments and from one patient to another. For each
           muscle, three videos will be obtained and the mean values will be used for statistical
           analysis. For better reproducibility, the evaluator will remove and reposition the
           transducer at the marked location. The videos will be stored on the device and then
           transferred to a computer for processing in specific softwares. The videos will be
           obtained with the transducer positioned in the longitudinal plane of the muscle, keeping
           it in parallel with the direction of the fascicles. Proper alignment of the transducer
           will be achieved when multiple fascicles are showed without interruption. Rectus
           femoris, vastus intermedius, vastus lateralis, vastus medialis will be evaluated,
           respectively, in the percentages 50%, 60% and 75% (proximal to distal) of the distance
           between the medial aspect of the anterior superior iliac spine and the superior border
           of the patella, as adapted from Blazevich et al. (2006). The rectus femoris and the
           vastus intermedius will be visualized on the anterior aspect of the thigh, the vastus
           lateralis will be visualized by moving the transducer 5 cm in the lateral direction from
           the midline and the vastus medialis will be visualized with the transducer 3 cm onto the
           medial direction of the thigh. The pennation angle is the angle formed between the echo
           of the deep aponeurosis of the muscles and the echo of the space between the fascicles,
           as measured 3 to 4 mm above the deep aponeurosis of the muscles. The fascicular length
           will be considered as the total length of the muscle fiber, however, because the
           fascicles are too long to be measured from the origin to the insertion, the estimated
           length will be obtained from the formula of Blazevich et al. (2006), which uses as
           variables the muscle thickness, the angle of the fascicle and the angle between the
           superficial and deep aponeurosis.

        -  Tendon-aponeurosis complex elongation: The myotendinous elongation will be estimated by
           the displacement of the deep aponeurosis. For the calculation will be used the
           recordings acquired for analysis of the muscular architecture. However, unlike the
           static nature of the data of the previous topic, this variable uses a dynamic approach,
           since the point (P) will be used as the contact point (insertion) of a fascicle in the
           deep aponeurosis at rest and the displacement of P when considering its final position
           during a maximum contraction. Therefore, the displacement of P (dL) is considered an
           indication of the elongation of the deep aponeurosis and the distal tendon.

        -  Tendon properties: The resting length of the patellar tendon will be measured by tracing
           its path with the ultrasound transducer in the longitudinal (sagittal) plane, starting
           from the patellar insertion to the insertion at the tibia, along the posterior surface
           of the tendon. The central region of the transducer will be placed in each of the tendon
           insertions (considering its posterior surface) and then a mark on the skin will be made
           at that point and a measuring tape will be used for the tendon length measurement. The
           cross-sectional area of the patellar tendon will be calculated from axial plane images
           at 25%, 50% and 75% of its length (at rest). The calculation of tendon force will use
           the ratio of the estimated total knee extension moment (corrected for the activation of
           the biceps femoris muscle obtained by electromyography) by the internal moment arm,
           which will be estimated by individually measuring the length of the femur, according to
           the equation of Visser et al (1990). Tendon stress will be calculated by the force ratio
           applied to the tendon by its cross-sectional area. The strain in the tendon will be
           calculated using the change in length over the original length (ΔL / Lo) and will be
           expressed as a percentage. The Young's modulus, or elastic modulus, will be obtained by
           dividing the stress by the strain. The tendinous stiffness will be calculated by
           dividing the force applied to the tendon by the elongation generated in its length. As
           the length of the transducer does not allow the entire visualization of the patellar
           tendon, a hypoallergenic echo-absorbent adhesive tape will be placed in the center of
           the tendon for reference. Thus, images will be obtained from the tape to the proximal
           insertion and then departing from the tape to the distal insertion. Images will be
           reconstructed for measurement. The deformation will be defined as the change in the
           length between the patella and the tibia, which will be measured frame-by-frame.
    

Intervention name(s): MVIC and NMES with hip at 85º and knee at 20º; MVIC and NMES with hip at 85º and knee at 60º; MVIC and NMES with hip at 0º and knee at 20º; MVIC and NMES with hip at 0º and knee at 60º
Intervention type(s): Other; Other; Other; Other
Intervention description(s): With hip joint at 85º (seated) and knee at 20º (SK20º), subjects will be submitted to maximal isometric voluntary contractions (15-18 per session) and to contractions evoked by neuromuscular electrical stimulation (15-18 per session).; With hip joint at 85º (seated) and knee at 60º (SK60º), subjects will be submitted to maximal isometric voluntary contractions (15-18 per session) and to contractions evoked by neuromuscular electrical stimulation (15-18 per session).; With hip joint at 0º (lying) and knee at 20º (LK20º), subjects will be submitted to maximal isometric voluntary contractions (15-18 per session) and to contractions evoked by neuromuscular electrical stimulation (15-18 per session).; With hip joint at 0º (lying down) and knee at 60º (LK60º), subjects will be submitted to maximal isometric voluntary contractions (15-18 per session) and to contractions evoked by neuromuscular electrical stimulation (15-18 per session).
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: After a familiarization session, there will be four sessions for testing the electrical stimulation at four different combinations of hip and knee angles for isometric contractions. The order of the combinations will be randomized, and a washout period of seven days will be reacquired between each session.
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Other
Keywords: Quadriceps muscle; Electrical Stimulation; Patellar Tendon; Ultrasonography; Electromyography