There is no conflict of interest.
Highlights
- The study’s objective was to examine the impact of seat suspension systems on health and safety outcomes.
- The study was a randomized controlled trial conducted in a laboratory setting. The authors examined differences in whole body vibration (WBV) exposure, reported discomfort and motion sickness across three different seat conditions with different suspension systems.
- The study found that seats with active suspension were significantly more effective in reducing WBV exposure compared to the static seats.
- This study receives a high evidence rating. This means we are confident that the estimated effects are attributable to seat suspension systems, and not to other factors.
Intervention Examined
Features of the Study
The study used a laboratory experiment to assess whole body vibration (WBV) exposure. The authors created 5 minutes of vibrations collected and replicated from a passenger van during a regular commuting route. To test WBV exposure, the authors used three seats with different suspension systems:
- Seat 1: a conventional static suspension-less seat (ST)
- Seat 2: a seat with vertical active suspension (VA)
- Seat 3: a multi-axial (vertical and lateral axis) active suspension seat (MA)
Study participants included 18 healthy adults (9 men and 9 women) with an average driving experience of 10.4 years. The average age of the sample was 27.5 years. All participants had no pain in the week leading up to the study and did not have any history of musculoskeletal issues in their upper limbs or lower back.
The study occurred over the course of three days. The authors randomly assigned three seat conditions to participants, so each participant experienced the three conditions in a random order. The order of the seat conditions and testing were counterbalanced to minimize any potential bias due to order of testing. The authors used laboratory-collected data of WBV measured as Average Weighted Vibration (Aw), Vibration Dose Value (VDV), and daily Static Spinal Compression Dose (Sed) and Seat Effective Amplitude Transmissibility (SEAT) for the X, Y and Z axes. In addition, they collected self-reported discomfort and motion sickness before and after sitting on each seat using validated scales. The authors used statistical analyses to assess the impact of various seat suspension systems on WBV reduction, reported discomfort, and motion sickness.
Findings
Health and safety
- The study found that active suspension seats (VA and MA) significantly reduced the vertical (z-axis) WBV by about 50%, whereas the static seat (ST) increased vertical WBV by about 110%.
- The study found that the mean lateral (y-axis) VDV on the MA seat was lower than the other seats (VA and ST), but there was no significant difference in mean lateral (y-axis) Aw between the seats. There were also no significant differences in the fore-and-aft (x-axis) Aw and VDV measures across the seats.
- Active suspension seats (VA and MA) significantly reduced SEAT floor vibration by about 40% for Aw and 50% for VDV. In contrast, the static seat (ST) increased the SEAT floor vibration by 108% for Aw and 161% for VDV.
- The study found that the daily static spinal compression dose (Sed) values for the active suspension seats (VA and MA) were significantly lower than the static seat (ST).
- However, the study found no significant differences in self-reported discomfort and motion sickness score across the three seat conditions.
Considerations for Interpreting the Findings
The authors did not explicitly provide information to calculate attrition. However, the authors conducted the experiment in a laboratory setting where all 18 participants completed the three conditions, implying no attrition. Also, the vibrations were only simulated from a passenger van and the findings might not be directly translated to other types of passenger vehicles.
Causal Evidence Rating
Research Guidelines
Review Protocol: Living Systematic Annual Search and Review Protocol
Review Guidelines: Causal Evidence Guidelines