Electrical Stimulation Clinical Trial
Official title:
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
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.
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.
;
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