Evaluation of Trunk Assistance Exoskeleton

Change in spinal compression

Stadiometer measurements require an electronic comparator (Mitutoyo; model 543-730B) mounted on a height-adjustable structure that allows alignment with the longitudinal axis of the spine. To measure spinal compression, the participant should position themselves face down against the wall, feet shoulder-width apart (template on the floor), knees fully extended, arms at their sides, and the following points in "light" contact with the wall: forehead, nose, pelvis (or navel), and toes (without shoes, with socks). The assessor will be asked to take the measurements (10 measurements) at the end of expiration, where they will be asked to hold their breath for 2-3 seconds. The baseline for the lifting task sessions is measured before all lifting task blocks. This measurement, expressed in millimeters, reflects only the vertical position of the electronic comparator. Measure = Mean after Block X - Session's baseline mean(before block 1).

Change in muscular exertion perception

Participants score their muscular exertion perception in 5 muscle groups (quadriceps, hamstrings, hip extensors, lumbar extensors, thorax extensors) on the Borg CR-10 scale. The baseline for the lifting task sessions is measured before all lifting task blocks. There are 12 levels to this scale(Minimum=0(No exertion) maximum=10(maximal exertion), all integer values, 0.5 is also an option.

Change in maximal lifting strength

Maximal lifting strength is assessed by measuring pulling force on a bar at knee level with a strain gauge. The handle is held firmly by both hands. Participants were asked to bend at the hips and knees so as to keep an extended lower back during the trials, similar to a deadlifting position. During each trial, participants were asked to progressively pull harder on the bar without jerking for 5 seconds. The maximal value expressed in newtons during each trial was used. The baseline measurement is the mean of 3 trials with a 2 minute pause in between trials. Only 1 trial was performed after the last lifting block so as to better assess muscular fatigue by limiting time for recovery.

Exoskeleton assistance score

Participants scored the assistance they felt wearing an exoskeleton on a 5-level Likert scale(min: no assistance= 0, max: considerable assistance = 4).

Number of cycles with parasitic forces score

Participants scored the estimated proportion of cycles where parasitic forces were experienced (min:0% of cycles=0 , max:100% of cycles=4) on a 5-level Likert scale.

Magnitude of parasitic forces score

Participants scored the magnitude of parasitic forces when these were experienced (min: no forces experienced=0 , max: very high forces experienced=5) on a 6-level Likert scale.

Number of cycles with restriction of movement

Participants scored the estimated proportion of cycles where the exoskeleton restrained their movement (min:0% of cycles=0 , max:100% of cycles=4) on a 5-level Likert scale.