This protocol demonstrates appropriate guidelines by explaining essential parts and how they're carried out in conducting a sit-to-stand experiment with the assistance of arm support and functional electrical stimulation. This technique helps manage the complexity of having a few sets up, including the instrumentation of a standing frame, functional electrical stimulation, and mechanomyography. This method can be applicable to other populations that require the setup of sit-to-stand with arm assistance.
Demonstrating the procedure will be Khairul, an assistant in handling the MMG and FES setup. Adhli, an assistant in Vicon setup, and Musfirah a PhD candidate under Dr.Nur Azah Hamzaid's supervision. Begin the sit-to-stand experiment set up by arranging a chair and standing frame.
To do so, design an armless chair with a height of 45 centimeters without a back rest according to the dimension of a force plate 1 embedded in the floor of the motion analysis laboratory. Next, instrument each SF leg at the bottom with an independent force sensor with a sensitivity range from 0 to 12 kilograms. Position a portable and foldable SF in front of the chair within arm's reach, and position four legs of the SF outside of force plate 2 to avoid double measurements.
For motion analysis set up, enter the participant's details such as leg length, ankle width, and knee width in the system. Then, place 16 reflective markers on the participant's lower limbs with double-sided tape directly over the bilateral, anterior, and posterior of the superior iliac spine. Attach the marker over the lateral surface of the bilateral thigh and shank, and on the lateral left and right malleolus.
Next, place markers over the left and right of the second metatarsal head, and on the calcaneus at the same height of the second metatarsal head. When done, instruct the participant to be seated barefoot, with the knees flexed at 90 degrees, and both feet positioned on force plate 2. Ensure the participant's head and trunk face forward while sitting upright.
After placing the participant's hands on the handle of the SF, identify the rectus femoris muscle by palpating the middle and bulky area of the thigh, then place one mechanomyography, or MMG sensor per leg at the thigh area of the rectus femoris muscle bilaterally to measure the leg muscles sit-to-stand and stand-to-sit efforts. Secure the sensors with a double-sided tape and strap the sensors around the thigh to reduce the motion artifacts before connecting to the MMG device and the computer. On day one, perform a voluntary sit-to-stand exercise by turning on all setups to record the selected parameters.
At the end of countdown of five seconds timed by an electronic timer, ask the participant to stand up from the stationary sitting position for three seconds before sitting back on the chair. After a rest of five seconds, continue to do sit-to-stand trials until the participant cannot perform the same routine any longer. When done, turn off all the recorded data.
Give a five minute break before continuing the next set of the sit-to-stand routine to provide muscle recovery amongst sets. Once the trial is over, allow the participant to rest for at least 48 hours. On day two, place functional electrical stimulation electrodes on the quadriceps and gluteus maximus muscles to perform the FES assisted sit-to-stand exercise.
For quadriceps muscle, place the first electrode horizontally about two finger widths above the knee, and the second electrode horizontally about a palm width below the hip joint. For the gluteus maximus muscle, instruct the participant to bend forward to place the first electrode vertically, closest to the hip bone, and attach the second electrode vertically, closest to the tailbone, side-by-side from the first electrode. When the electrodes are in place, attach all FES electrodes to the FES device and connect them to the FES software in the computer.
Set up the FES software by selecting the pulse width of 300 and the frequency of 35 hertz. To define the FES current intensity, inquire if the participant can tolerate the current to achieve knee and hip extension. Determine the FES current amplitude through several practices before starting the actual trial.
Next, start the experiment as described earlier by switching the FES on as the participant stands up and switching the FES off to let the participant sit back on the chair. Repeat the trial in sets and collect the data. Throughout the sit-to-stand action in both sessions, participant 1's arm percentage showed a higher contribution to total body weight percentage as compared to his leg percentage.
In participant 1, the electrical stimulation could not provide a full extension in the right knee during the end phase of the sit-to-stand routine. The right knee angle did not reach the normal knee extension range of motion. In contrast, participant 2 exerted more strength onto her legs to bear the full body weight, with a higher contribution of leg percent during the end phase of the voluntary sit-to-stand routine.
In addition, during the final set of voluntary sit-to-stand routine, participant 2 exhibited a smaller knee angle during the early stage of the movement. During event B, when the buttocks lift up was initiated, participant 1 was observed to increase arm strength to lift his upper body from the chair. Meanwhile, for participant 2, the maximum contribution of arms was detected during event B, for FES assisted sit-to-stand routine.
Each step in this procedure is important and should be followed as stated. However, it is necessary to note that there can be flexibility, specifically in the initial posture of the participant. Qualitative feedback can be added in order to measure opinions and views regarding the sit-to-stand routines, stability, and fatigue from the participant's perspective.
By adding this method, researchers will better understand the sit-to-stand technique's behavior with the quantitative results achieved.
