Assessment
procedures
All described procedures were performed on the dominant leg only.
Active straight leg raise test
The Active straight leg raise test (ASLR) was assessed using a digital
goniometer (BTS Bioengineering, Italy) placed on the front part of the
mid-tibial plateau of the dominant leg and fixed in position with an
elastic band. Participants were instructed to lay supine on a (standard)
therapeutic table, with arms alongside the body. Each was instructed to
flex the hip slowly (full raise in approx. 2 s), while maintaining a
fully extended knee. Once they reached the maximal active range of
motion, they held the final position for approximately 1 second before
slowly (approx. 2 s) returning to the starting position. The
contralateral leg remained straight and in contact with the table at all
times, while the researcher stabilized the pelvis by holding the
anterior superior iliac spine down. The procedure was repeated twice at
each measuring time (PRE, POST, and POST30), and the maximum ASLR angle
(°) at each measuring time was recorded for further analysis.
Tensiomiography (TMG)
Tensiomyography (TMG), which comprises a non-invasive probe-like digital
displacement transducer (TMG-BMC Ltd, Ljubljana, Slovenia), was used to
evaluate the muscle contractile properties of RF, VL, and BF. For
evaluating the RF and VL parameters, subjects were instructed to lie in
a supine position on the therapeutic table, with a triangular cushion
placed below their knee joint to support approximately 30° of knee
flexion. For the BF assessment, subjects were asked to turn over to a
prone position with their head turned to one side and arms alongside
their body. A foam cushion placed underneath the ankle supported five
degrees of plantarflexion. The TMG sensor was placed in contact with the
skin, perpendicular to the tangential plane of the muscle belly for the
selected muscle, held in place by a tripod-mounted mechanical arm
exerting minimal pressure (approx. 1.5 x 10-2N/mm2 – manufacturers data). Correct probe placement
was determined by instructing the subject to slightly contract the thigh
muscles (knee extensors for RF and VL; knee flexors for BF), which
allowed the researcher to visually and manually pulsate the thickest
area of the muscle belly. The probe was additionally adjusted, if
needed, to obtain the greatest mechanical response when the muscle was
electrically stimulated.
TMG evaluation was performed by electrically stimulating the selected
muscles. Two self-adhesive 5x5 cm electrodes were placed equidistant
from the TMG probe sensor and in line with the muscle fibers (Figure \ref{704445}B, \ref{704445}C, and
\ref{704445}D).
The position of the electrodes and the probe sensor were accurately
marked with a medical skin marker to avoid alterations in muscle
response during within days
assessments \cite{Tous_Fajardo_2010} and
to ensure accurate repositioning.
A constant current electrical stimulator (TMG-BMC Ltd, Ljubljana,
Slovenia) was used to deliver a single 1 ms wide stimulation pulse to
elicit a mechanical muscle response. The highest mechanical response for
each muscle was determined at baseline: a small initial stimulation
amplitude (30 mA) was adopted at first and progressively increased by 10
mA increments until the mechanical response reached its maximum.
Electrical stimuli were evoked 10 seconds apart to avoid the phenomenon
of post-activation potentiation or fatigue. As proposed by
\citet{_imuni__2012},
the two highest mechanical responses and related stimulation amplitudes
were recorded and saved during each testing. Stimulation amplitudes used
to elicit the highest mechanical response at baseline were reused later
in the protocol when TMG was assessed after floss band application
(POST, POST30). The highest mechanical responses were generally elicited
at stimulation amplitudes between 60 mA and 90 mA.
Every mechanical response was stored and displayed in the TMG software
and was graphically represented as the change in muscle displacement
over time - displacement curve., The following parameters can be
computed from every displacement curve: contraction time
(Tc - expressed in ms), maximal displacement of
the muscle belly (Dm - expressed in mm) delay
time (Td - expressed in ms), sustained time (Ts - expressed in ms) and
half-relaxation time (Tr - expressed in ms). Since
inter-rater \cite{Tous_Fajardo_2010} and between-day
reliability \cite{_imuni__2012} of Tc and Dm parameters have been shown
to be the most reliable and sufficient for comparison, these two
parameters have been calculated and used for further analysis in this
study.
Maximum voluntary contraction (MVC) assessment
Isometric maximum voluntary contractions (MVC) of knee extensors and
flexors were assessed using a Kineo® dynamometer
(GLOBUS, Codognè, Italy). To assess MVC of knee extensors (extMVC),
participants were instructed to sit on a leg extension machine with
their hips flexed at 80° (0° hip fully extended) and additionally
secured with padded straps around the pelvis. The medial epicondyle of
the femur was aligned with the extension machine’s axis of rotation,
while the knee was flexed at 60° (0° knee fully extended) and a padded
lever arm was placed on the tibia just above the anterior part of the
ankle joint.
For knee flexion MVC (flexMVC), participants were instructed to stand
facing the Kineo® machine, pressing the pelvis into
the pad in front of them, which prevented any compensatory hip flexion
or extension. They were instructed to firmly hold the vertical bar
(fixed on the machine) in front of them to further stabilize their body.
The participants stood on their non-dominant leg on a wooden step
(ranging from 10-25 cm in height) to provide the ground clearance needed
to allow optimal knee alignment with the machine’s axis of rotation. The
dominant leg was fixed at a position of 30° knee flexion, while the padded lever arm was placed on the tibia just above the posterior part
of the ankle joint.
Participants were allowed to perform 3 submaximal isometric knee
extensions of the duration of 5 s to become familiarized with the
testing procedure. The participants were instructed to perform 2 maximal
isometric contractions of 5 s duration each for knee extension and
flexion respectively. A 30 s rest was allowed between trials.
Participants were verbally encouraged to perform the tests with maximal
effort during testing. The maximum peak torque from the two trials was
taken for further analysis.