This report has been compiled by the Motion Analysis Research and Rehabilitation Centre (MARRC), on
behalf of the Manufacturing Advisory Service (MAS).

The Thingy Evaluation

1. Background

Shovelling is an intensive manual activity that is associated with having a high risk of lower-back injury.

"The Thingy" is a novel shovel design with an additional handle intended to improve posture and
ergonomics during the shovelling action. The aim of this project was to provide a biomechanical analysis of The Thingy.

2. Scope
The scope of the project was established and agreed following discussions with Ian Robertson
(Manufacturing Advisory Service) and Jonathan Smith on the 26th March 2008.
The activity to be analysed was the routine action of bending down to scoop up a shovel load then depositing the load into a wheel barrow at the side. A 3D motion capture system acquired the position and movement of key body parts and the shovel. Ground reaction forces were captured using a pair of force plates.

3. Data Collection
Data was collected in the MARRC laboratory on the 21st and 22nd of April.
Movement data was recorded at 60Hz using a 15 camera 3D motion capture system (Vicon MCam2). Retroreflective skin markers were placed on key body and shovel landmarks to determine body segment locations and orientations. The standard MARRC full body marker set was used to identify all limb locations.
Ground reaction forces were measured using Advanced Medical Technology Inc. floor mounted force platesn (AMTI BP400600NC).
Two contrasting subjects were recruited for testing, to give a range of height, weight and shovelling experience;
· Subject 1 - 184 cm, 73.5 kg
· Subject 2 - 160 cm, 58.0 kg
Incremental loads of 0, 2.5, 5 and 10 kg were devised by loading gravel into bags secured by tape.
Subjects were instructed to position themselves in their natural position for shovelling. The loads were positioned so that this resulted in their feet remaining on separate force plates.

Data was captured for each load and both shovel designs in two different actions:
1. Straight lift, with immediate return to start position
2. Drop into wheelbarrow, requiring a twist to the left side before returning to start position.
Each combination was repeated three times, resulting in a total dataset of 96 different trials.
3.1. Accuracy of Data.
It was assumed that the subjects had normal mass distributions for healthy adults, with no clinical
abnormalities of joint position or joint function.
The accuracy of 3D point tracking during the experimental procedures was approximately 0.9 mm RMS error during all trials.

4. Biomechanical Analysis
4.1. Kinematic data
It is well established that the lumbar region and the lower back are particularly vulnerable areas for
injury from manual lifting work such as shovelling. Analysis has therefore concentrated on this
trunk region.
No significant variation or trend in trunk motion was observed with load weight. Similar patterns of
motion were observed with both subjects though there were expected variations in absolute angles and timing of the shovelling action.
Ranges of motion for the hips (left and right), spine, pelvis and thorax were compared in all three
planes. Trends of reduced range of motion with the Thingy were observed across all trials for the
following joint angles:
Joint angle Subject 1 Subject 2 Average Straight Twist Straight Twist Reduction
Left hip flexion 18 % 27 % 27 % 25 % 24 %
Left hip rotation 25 % 45 % 52 % 25 % 39 %
Right hip flexion 25 % 9 % 24 % 19 % 19 %
Spine lateral flexion 21 % 31 % 25 % 32 % 27 %
Pelvic flexion 32 % 34 % 20 % 3 % 22 %
Thoracic flexion 17 % 14 % 20 % 12 % 16 %
Hip flexion is the relative angle between the thigh and pelvis. Pelvic and thoracic angles are absolute and measured with respect to the laboratory space.

Reduced hip, pelvic and thoracic flexion are all coupled together and can be summarised with the
overall observation that there is less bending over with the Thingy. The absence of a change in spine sagittal flexion indicates that the spine-pelvis orientation is largely unchanged.
Reduced spine lateral flexion and hip rotation can be associated with the ‘opening up’ of the hips and pelvis as a result of less bending.
Reduced ranges of motion were observed with the Thingy for other joint angles such as knee and
shoulders flexion. However the trends could not be correlated consistently across all trials actions
and subjects.
Angular velocities were examined across all trials with no significant variations observed.

4.2. Kinetic data
Analysis of the kinetic data showed no significant differences in hip or knee forces or moments
between the Thingy and standard shovel. This was somewhat unexpected given the kinematic
evidence of reduced trunk angles with the Thingy and is believed to be caused by two factors.
Firstly, the increased weight of the Thingy (0.6 kg) could be counteracting the benefits of less
bending. Secondly the positioning of second handle could be positioning the Thingy shovel further
away from the body centre-of-mass compared to a standard grip. This increases the load torque load when using the Thingy again counteracting the more upright trunk.
The mean distance between the sacral point of the pelvis and the junction between the shovel blade and handle was compared across trials:
Distance between LPSI/RPSI midpoint and shovel junction
(mm)
Standard The Thingy
Subject 1 823 ± 30 875 ± 16
Subject 2 712 ± 19 835 ± 16
This confirms that the Thingy shovel is held slightly further away from the body centre-of-mass
during the shovelling action.

5. Summary of Findings
Sagittal (front-back) back flexion has been identified as the highest risk component in the shovelling action [Bridger et al, 1998]. The Thingy shovel design has been found to reduce this bending by around 20% (Average). This is primarily through reduced hip flexion with spine-pelvis orientation staying unchanged.
Other risk factors identified with low back disorders are maximum trunk lateral velocity (rate of
side bending) and average trunk twisting velocities. These were found to similar across both shovel
designs.
Subjects report less perceived effort with two-handled designs compared to standard shovels.