Red dot trace prep

Surface electromyography (EMG) data were collected bilaterally using bar bipolar active surface electrodes applied over the lumbar erector spinae (LES) muscles at the L4–L5 and L2-L3 levels, approximately 3 cm from the mid-line (electrodes were applied in-line with muscle fiber direction). Electrode material was 99.9% Ag and the interelectrode distance was fixed at 10 mm. A ground electrode was placed on the left anterior superior iliac spine. Skin impedance was reduced by (1) shaving body hair, (2) gently abrading the skin with fine-grade sandpaper (Red Dot Trace Prep, 3M, St. Paul, MN, USA), and (3) wiping the skin with alcohol swabs. EMG activity was recorded using a single differential Delsys Surface EMG sensor with a common mode rejection ratio of 92 dB at 60 Hz, a noise level of 1.2 μV, a gain of 10 V/V ± 1%, an input impedance of 10¹⁵ Ω, a bandwidth of 20–450 ± 10% (Model DE2.1, Delsys Inc., Boston, MA, USA) and sampled at 1000 Hz with a 12-bit A/D converter (PCI 6024E, National Instruments, Austin, TX, USA). The EMG data were filtered digitally by a 10- to 450-Hz bandpass, zero-lag, fourth-order Butterworth filter. Data were collected using LabView (National Instruments, Austin, TX, USA) and processed by Matlab (R2007b MathWorks, Natick, MA, USA).

The EMG electrodes were attached over RF and BF muscles of the dominant leg of participants. The location of the RF’s electrode was at the midway between the anterior superior iliac spine and the upper edge of patella (Figure 1a). The location of the RF’ electrode was at the midway between gluteal fold and knee crease (Figure 1b). The location of the ground electrode was over tibial tuberosity (Figure 1c). The required skin areas were shaved, handled with abrasive material (3M Red Dot Trace Prep) and cleaned with alcohol swab (70%isopropyl). For the bony landmarks of (1) greater trochanter of femur, (2) lateral epicondyle of femur and (3) lateral malleolus, markers of 3cm in diameter were attached (Figure 1d) and covered with tegaderm (Smith and Nephew Flexifix Opsite Transparent Adhesive Film Roll 4” x10.9 Yard, model66000041) for kinematic tracking.

On the experimental day, one pig was brought into the experimental room and allowed to acclimatize for approximately 30 minutes before being placed into an on-purpose made sling. A local anaesthetic cream (EMLA, 5%, Anesderm, Pierre Fabre, Switzerland) was applied to the auricular vein and artery, and over the coccygeal artery, ensuring complete coverage, and left acting for at least 45 minutes before catheters placement. During this period, a six leads wireless device (Televet 100, Engel Engineering Services GmbH, Germany) was applied to continuously record electrocardiographic activity. The area between the frontal and the occipital bone, over the tibialis cranialis muscle and over the right metatarsus was clipped, cleaned with a warm antiseptic soap solution and shaved with a razor. Once dried, the skin was rubbed with abrasive paper (Red Dot Trace Prep, 3M Health Care, Canada) and benzinum medicinale (Benzinum Medicinale, Hänseler AG, Switzerland) was applied to the skin to remove excess fat. During the whole experimental period, the following clinical variables were continuously assessed and reported on an anaesthesia record sheet every 5 minutes: heart rate (HR), respiratory rate (RR), diastolic (DAP), mean (MAP) and systolic (SAP) invasive blood pressure, as well as palpebral reflex and jaw tone, that were scored as “0” = absent, “1” = reduced or “2” = as awake.

Surface electromyography (sEMG), consisting of bipolar disposable surface Ag/AgCl electrodes (Bortec Biomedical, Calgary, Alberta, Canada), was used to register muscle activation strategy for lumbar erector spinae at L3 and at vastus lateralis. Skin was prepared to reduce skin impedance by shaving body hair, gently abrading with fine-grade sandpaper (Red Dot Trace Prep; 3M, St. Paul, Minnesota) and wiping with alcohol swabs. Electrodes were then placed bilaterally, and a ground was positioned on the left ASIS completed the setup. A Delsys sEMG sensor recorded data with a common mode rejection ratio of 92dB at 60Hz and an input impedance of 10¹⁵ Ω (model DE2.1; Delsys, Inc., Boston, Massachusetts). Data were sampled at 1000Hz with a 12-bit A/D converter (PCI 6024E; National Instruments, Austin, Texas). After the data collection with LabView (National Instruments, Austin, Texas), the sEMG signals were processed by Matlab (MathWorks, Natick, Massachusetts).

Two bipolar surface electrodes (Model DE2.1, Delsys Inc., Boston, MA, USA) were used to record EMG activity during the baseline and post-intervention MVCs, and during the muscle fatigue task. Electrodes were positioned on the upper trapezius and the middle deltoid muscles on the dominant arm, following the muscle fibers orientation, at the level of the most prominent part of the muscle belly, according to SENIAM recommendations (41 (link)). Electrodes’ material was 99.9% Ag, and the inter-electrode distance was fixed at 10 mm. A reference electrode was positioned on same side acromion. Skin impedance on these three areas was reduced with: (1) shaving body hair, (2) gently abrading the skin with fine-grade sandpaper (Red Dot Trace Prep, 3 M; St. Paul, MN, USA) and (3) wiping the skin with alcohol swabs.
Bipolar EMG signals were amplified (DE2.1 model; Delsys, Inc., Boston, Massachusetts) by a factor of 1,000, sampled at 2,048 Hz and converted to digital form by a 12-bit A/D converter. Data were collected and processed with OT Bioelettronica (64-channel surface EMG amplifiers, SEA 64, LISiN-OT Bioelettronica; Torino, Italy; −3 dB bandwidths 10–500 Hz).