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.