Nl844

Recordings were made with silver ball electrodes (Ø 250 μm). The signal was passed through a Digitimer NL844 pre-amplifier with a low frequency cut off at 0.1 Hz and gain x1000, connected to the NL820 isolator (Neurolog system, Digitimer) with gain x5. The data were digitized at 1 kHz using CED 1401 mk2 hardware and Spike2 software (Cambridge Electronic Design (CED), Cambridge, UK). The recorded data had a sampling time of 1 ms/1 kHz (Figures 1D and 1E). Local field potential responses evoked by the electrical stimulation of the skin of the forepaw verified that the recording electrode was correctly placed in the forepaw area of the S1. The duration of anesthesia did not exceed 8 h. Once all the recordings were performed the animal was euthanized using a lethal dose of pentobarbital.

Participants sat reclined on a plinth with knees extended and back rest at approximately 30° from vertical. US was recorded in video format with a transducer (M7C, GE Healthcare, Australia) placed in the mid-sagittal plane on the perineum. A foot switch triggered each US recording and was used to synchronise US with IAP and EMG. A naso-gastric pressure transducer (CTG-2, Gaeltec Ltd, UK) recorded IAP. PR and BC EMG was recorded with intramuscular electrodes fabricated from pairs of fine-wires (Teflon coated, stainless steel wire, diameter– 75μm). With US guidance, an experienced colorectal surgeon inserted the electrodes through the perineum into PR in a cranial direction just left of the anus, and into BC in a ventral direction at the base of the penis. SUS EMG was recorded using a transurethral surface electrode[17 (link)] which was self-inserted by the participant after detailed instruction. One participant requested assistance with catheterisation from a supervising urologist. Pelvic floor muscle EMG was amplified 2000x (NL844, Digitimer Ltd, UK), bandpass filtered between 10–2000 Hz (NL125, Digitimer Ltd, UK) and recorded at 10 KHz with a Power1401 analogue to digital converter and Spike2 software (Cambridge Electronic Design, UK).

All measurements were performed on the participant's dominant arm using a custom‐designed transducer. An aluminum device positioned the elbow in 90 degrees of flexion, where the participant was seated in a rigid back chair with the humerus horizontal and the forearm oriented vertically (Figure 1a). The arm was secured firmly into the device with a non‐compliant wrist strap so that a PT4000 200kg S‐Type load cell (PT Ltd., NZ) attached to the posterior side of the device could measure elbow flexion force. From this load cell data, flexion force could be converted to flexion torque based on the distance between the lateral epicondyle and the point of force application at the wrist. Torque data were sampled at 2 kHz via Spike2 (CED Ltd., UK).
Surface EMG was obtained from the biceps brachii and triceps brachii using bipolar 24 mm Ag/AgCl electrodes. Electrodes were aligned in the direction of underlying muscle fibers and had an inter‐electrode distance of 24 mm (Kendall ARBO). Surface EMG signals were differentially amplified 1,000 times (NL844, Digitimer Ltd., UK), bandpass filtered with cut‐off frequencies of 10 and 500 Hz (NL135 and NL144, Digitimer Ltd., UK), and then input into a 16‐bit Power 1,401 data acquisition interface (CED Ltd., UK). Surface EMG was sampled via the same Spike2 arrangement used to collect torque data.