Speaker
Description
Manual handling in forestry and nursery work involves repetitive low postures, trunk bending, and short-distance load carriage, all of which can elevate the risk of musculoskeletal disorders (MSDs). Passive exoskeletons are sometimes suggested as a practical way to reduce postural exposure and strain, but their effectiveness varies depending on the job. Their effectiveness depends heavily on the activity required movements (i.e., the task pattern) and the weight of the load being handled.
So far, either the kinematics of movement or the ergonomic risks associated with work performance and specific tasks are examined. In this laboratory study, we compared the two methods simultaneously by quantifying the influence of different passive exoskeleton models on kinematic exposure metrics and ergonomic risk indicators during two simulated manual task sets.
The first, Task Set A, simulated tree planting and included low-load repetitive handling, repeated trunk flexion and kneeling, as well as upright walking over 20 meters while placing small items (0.5 kg every 2 meters; 1 kg every 4 meters). Task Set B (Moderate-Load Handling and Carriage) simulated plant seeding and included repeated lifting of loads with deep squatting, short-distance walking, and lifting/carrying loads of 5, 10, and 15 kg over 4 meters.
Participants performed the protocol both with and without an exoskeleton (two models for Task Set A and three models for Task Set B). Whole-body motion was digitally recorded at 60 Hz samples using Inertial Movement Units-based motion capture and converted into 3D ergonomic joint angles and movement acceleration.
To provide a comparable assessment, we analyzed several kinematic exposure outcomes, including: (i) time spent in trunk flexion/extension, (ii) trunk flexion/extension dose (time × depth in degrees), (iii) relative flexion/extension between lower extremity segments and pelvis, (iv) upper arm positions and flexion/extension dose, and (v) trunk sway, pelvis movement, and knee position as a stability-related proxy during walking/carrying. We contextualized kinematic exposures using ergonomic risk evaluation frameworks, including ISO 11226 (angle–time postural loading) and EN 1005-4 (repetition characteristics). We complemented these with time-based distributions consistent with OWAS/RULA logic for identifying high-risk postures. Condition effects were summarized as within-participant differences versus the no-exoskeleton condition, with confidence intervals.
The results show that the effects of passive exoskeletons vary across the equipment × task combinations. In the low-load pattern, which is dominated by bending and kneeling, the main potential benefits are reducing the movement dose and improving walking and activity stability. These are closely related to body strain and performance in repetitive tree nursery activities. In the moderate-load pattern, 'effectiveness' is better judged by whether the exoskeleton allows efficient squatting and stable carrying without increasing demands for upper-arm elevation or trunk sway/rotation, rather than by reducing trunk bending alone. In practice, these findings support the selection of exoskeleton models based on dominant task patterns and expected load ranges. They also emphasize the need for field testing on uneven terrain and with full protective equipment and working tools before operational implementation.
| Keywords | Exoskeletons; Movement&Kinematics; Ergonomics; Health&Safety |
|---|
