Standing Balance After Whole-Body Vibration Exposure: Differences Between Tiptoeing and Flat-foot Standing

Abstract: Slip, trip, and fall accidents are among the most significant occupational hazards in the land transportation industry. These incidents are assumed to be associated with whole-body vibration (WBV) exposure during vehicle operation. Considered the nature of work postures in this industry, it has suggested that tiptoeing postures may contribute to fall accidents. Thus, this study aimed to investigate the effects of WBV exposure on standing balance ability when assuming a tiptoeing posture or flat-foot standing posture.A laboratory experiment was conducted with five participants to investigate the impact of WBV exposure. The participants underwent a 60-minute virtual driving session using a driving simulator (DS) while being exposed to WBV. Standing balance measurements were performed at four time points: before WBV exposure, immediately after exposure, 2 minutes after exposure, and 4 minutes after exposure. The experimental conditions included two variables: (1) the presence or absence of driving tasks during WBV exposure and (2) two standing postures for balance assessment: flat-foot standing posture and tiptoeing posture. Additionally, a control condition without WBV exposure was included, resulting in a total of six experimental conditions.Following the experiment, standing balance was evaluated using three key parameters: total center of pressure trajectory length (LNG), enveloped area (ENV_AREA), and root mean square area (RMS_AREA). The results indicated that, in the tiptoeing posture, all balance parameters exhibited significantly greater values compared to the flat-foot standing posture. This finding suggests that the tiptoeing posture inherently results in reduced balance stability.Furthermore, an analysis of WBV exposure conditions revealed that standing balance was affected compared to the control condition. In particular, a notable degradation in standing balance was observed under the driving condition. A possible explanation for this finding is that prolonged driving requires continuous operation of the accelerator pedal, using the right leg. This asymmetric muscle activation may lead to differential fatigue between the right and left lower limbs, thereby contributing to increased postural instability immediately after driving.These findings suggest the critical importance of post-driving recovery time. The results show that tiptoeing immediately after prolonged driving causes a high risk of falls and should be considered a hazardous condition. Therefore, sufficient rest time should be implemented to mitigate this risk. Moreover, given that standing balance capacity is generally lower in the tiptoeing posture compared to the flat-foot standing posture, workers required to perform tasks in a tiptoeing position should exercise caution to prevent slip, trip, and fall accidents. This study provides valuable insights into occupational safety in the land transportation industry and highlights the necessity of implementing preventive measures against fall-related accidents. Future research should further explore the physiological mechanisms underlying postural instability following WBV exposure and prolonged driving, as well as the development of effective interventions to enhance worker safety.

Keywords: occupational accidents, transportation industry, driving simulator, standing balance, ISO2631-1

DOI: 10.54941/ahfe1006468

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