Postural stability after whole-body vibration exposure

Fall injuries to operators of heavy mobile equipment are more frequent during egress rather than while climbing onto the equipment. One possible contributing factor is a loss of postural stability during egress. Because many of these operators are exposed to prolonged periods of whole-body vibration (WBV) while controlling the equipment, a study was conducted to determine if postural stability is impaired by WBV exposure. Subjects were tested for a difference in standing postural sway before and after seated WBV exposure. The WBV consisted of 40 minutes of vertical vibration generated by a motion platform, which emulated actual vibration levels of an operating under-ground shuttle car. Two independent variables, each at two levels, consisted of vibration and vision. The measured dependent variables were postural sway amplitude and velocity of sway. No significant difference between the vibration and no vibration conditions were found. Based on the results of this study, it cannot be concluded that WBV at the exposed frequencies influences postural stability. The results suggest that other factors may be the primary contributors to fall injuries while exiting the vehicle, such as problems with foot placement accuracy or egress system design.     

Evaluation of responses to broad-band whole-body vibration

Abstract

The experiment was aimed at investigating the human response to different modes, frequencies and intensities of whole-body vibration (WBV), in order to check the evaluation procedures currently recommended. Six male seated subjects were exposed to sinusoidal (SIN) and octave-band-wide vibration (OWV) in the z axis with the frequencies or centre frequencies, respectively, of 2,4, 8 and 16 Hz at two intensity levels (except for 2 Hz), in accordance with the frequency weighting of ISO 2631 (ISO 1978 a). The 14 exposure conditions were compared by means of a slightly modified, complete paired comparison, the total number of exposures amounting to 1044. Subjective judgements of the severity of WBV, annoyance and the ability to control a constant sitting posture were obtained along with the bioelectrical activity of trunk muscles, transmissibility and impedance. An integral assessment of the exposures was rendered possible by the complex evaluation of different human responses. OWV and SIN with identical a_zw r.m.s. values (ISO 1978 a) produced almost identical effects. The results clearly speak in favour of the weighting procedure. This procedure was also supported by an additional pilot study with two-octave-band-wide vibration. The superiority of the weighting procedure suggests lower limits for broad-band vibration than those recommended at present (ISO 1978 a). Human response to WBV in the range near 4 Hz was more pronounced than that of equivalent exposures with other frequencies. Generally, higher intensities induced stronger effects. The biomechanical data exhibited a non-linearity for the WBV levels of intensity investigated. The patterns of myoelectric and biomechanical reactions depended on both anatomical and exposure conditions. The individual responses in discriminating the exposure conditions significantly agreed, but the extent of agreement between the individual responses varied for the effects investigated.     

Inter-individual postural variability in seated drivers exposed to whole-body vibration

Long-term occupational exposure to whole-body vibration (WBV) is a cause of low back pain for seated drivers. Poor and long-term seated postures are considered as a cofactor in the risk. It depends on the vehicle's ergonomics and tasks. Differences in posture may also be observed between operators doing identical tasks. An experiment has been performed in order to simultaneously measure posture and WBV for 12 drivers in 3 vehicles (loader, dumper and excavator) during controlled tasks. The inter-individual postural variability has been evaluated. The positions and movements of the body were measured with the CUELA system (computer-assisted recording and long-term analysis of musculoskeletal loads). Significant differences were observed between the three vehicles in the WBV, positions and movements of the body. Significant postural differences were observed between drivers (EN 1005-4 2005). Individual strategies for performing a task were also identified.     

Equally moved and not really sick from viewing 2D and 3D motion stimuli on a TV screen

ObjectiveVisually induced motion sickness (VIMS) and increased postural sway are two adverse side effects that may occur when viewing motion stimuli. However, whether these effects are elevated to a greater extent when viewing stereoscopic 3D motion stimuli, compared to 2D stimuli on a TV screen, has not been investigated under controlled circumstances. Therefore this study aimed at investigating VIMS and postural sway before, during, and directly after viewing 2D and 3D motion stimuli, on a commonly available TV screen.Method16 Participants were exposed to an aviation documentary shown in 2D and in 3D on separate occasions. Before, during, and after exposure, VIMS and postural sway were measured. VIMS was quantified by a rating scale giving a single number, and by a multi-symptom questionnaire that assessed multiple VIMS symptoms separately. Sway path length, standard deviations and short-range and long-range scaling components of the center of pressure were calculated as measures of postural sway.ResultsVIMS symptom severity, as obtained with the single rating scale, did not show a significant increase to either 2D or 3D exposure. The multi-symptom questionnaire did reveal significant increases in VIMS symptom severity to both 2D and 3D exposure. However, VIMS was not significantly more increased in case of 3D exposure compared to 2D exposure. All postural sway measures (sway path length, standard deviation in mediolateral and anteroposterior direction, as well as the short-range scaling components) increased significantly as a result of exposure. None of the postural sway measures was differentially affected to 3D as compared to 2D exposure.ConclusionViewing 3D motion stimuli did not cause more serious VIMS symptoms, compared to viewing motion stimuli in 2D. We attribute this lack of difference to the fact that the 3D effects in this documentary were optimized for viewing in a cinema, the projection on the TV-screen thus causing quarantining of the visual input. The increase in postural sway, irrespective of image type, may reflect exploratory behavior, allowing the participant to gain more information about self-orientation with respect to the virtual environment.     

Low-back disorders in agricultural tractor drivers exposed to whole-body vibration and postural stress

The occurrence of low-back pain (LBP) was investigated in a population of 1155 tractor drivers exposed to whole-body vibration (WBV) and postural stress (response rate 91.2%) and in a control group of 220 office workers (response rate 92.2%). The subjects were questioned about several types of low-back symptom (LBP, sciatic pain, acute LBP, transient and chronic LBP) and various work- and individual-related risk factors, by using a standardized questionnaire. Vibration measurements were performed on a representative sample of the vehicles driven by the tractor drivers in the last ten years. Vibration magnitude and duration of exposure were used to calculate a vibration dose for each tractor driver. Perceived postural load was assessed in terms of frequency and/or duration of awkward postures at work. The prevalence of LBP was found to be greater in the tractor drivers than in the controls. After controlling for potential confounders by logistic modelling, low-back disorders were found to be significantly associated with both vibration dose and postural load. Back accidents and age were also significant predictors for LBP. Quantitative regression analysis indicated that vibration exposure and postural load were independent contributors to the increased risk for LBP according to a multiplicative model. The exposure levels for WBV recently recommended by a proposal of European Directive on physical agents seem to be more adequate to prevent long-term health effects on the lower back than the exposure limits suggested by the International Standard ISO 2631/1.     

Association of Risk Factors with Musculoskeletal Disorders among Male Commercial Bus Drivers in Malaysia

A national study in Malaysia was conducted with the main objective being to determine the prevalence of musculoskeletal disorders (MSDs) and the association between risk factors and MSDs among Malaysian bus drivers. Cross‐sectional data were collected from 1,181 male commercial bus drivers in Malaysia using questionnaires to determine demographic, working characteristics and a translated Nordic questionnaire to determine MSD complaints. A Human Vibration Meter was used to measure whole body vibration (WBV) exposure, and postural analysis was used to evaluate awkward working posture. To assess psychological factors, the validated Profile of Mood States (POMS) was used. The overall prevalence of MSD was 81.8% and, by body parts, low back pain was reported to be the highest complaint of lifetime MSD (58.5%) compared to other body parts. The levels of WBV acceleration magnitude A(8) exceed the European Union Directive (0.54 m/s² root‐mean‐square [r.m.s.] acceleration), and only 1.2% of the bus drivers adopt more than 40% of awkward postures while driving. Logistic regression analysis, controlling for age, income, education level, and work activities, revealed that factors such as lack of seat adjustability, uncomfortable seat, seat's material, seat contour and design, WBV exposure, smoking, frequency of daily trips, duration of daily driving, prolonged sitting, working part time, and psychological factors (namely, feeling stress, feeling worried, feeling fatigued) were important risk factors of MSDs among Malaysian bus drivers. As a conclusion, bus drivers are exposed to a combination of risk factors that may lead to an increased risk of developing MSDs. © 2012 Wiley Periodicals, Inc.     

Effects of BMI and task parameters on postural sway during simulated small parts assembly

Postural stability is critical for ensuring a safe workplace. Employees with poor stability are more prone to falls and injuries while at work. In this study, postural sway of participants in different obesity categories was evaluated while performing an assembly workstation task. The study included three workstations: those designed for the 5th, 50th and 95th percentile workers based on anthropometric data tables. Force plates were used to study the differences in postural sway in both the medial–lateral and anterior–posterior directions. The results revealed that the obese class 1 and obese class 2 groups’ anterior–posterior sway was significantly larger than that of the normal weight groups while performing assembly work tasks. Also, pace type (self-paced or time-paced) and workstation (5th, 50th and 95th percentile) significantly affected the postural sway. The postural sway was not affected by gender differences. Workstations should be designed to accommodate the increased postural sway of obese workers.     

Surface slope effects on shingling frequency and postural balance in a simulated roofing task

The purpose of this study was to investigate the influence of surface slopes (18 degrees , 26 degrees , 34 degrees ) on the maximum acceptable roof shingling frequency for males performing a simulated roof-shingling task. The psychophysical roof shingling frequency was also compared to the postural sway and trunk motion values. The maximum acceptable roof shingling frequency and selected trunk motion decreased significantly with an increase in slope. Postural sway however increased significantly with an increase in slope. The study also revealed that workers were experiencing a greater postural sway at the earlier phase of task on the steeper surface. This suggests that there might be an adaptation period associated with working on a slope and the body's ability to compensate for a loss of balance. Therefore, more emphasis should be given to the workers in this adaptation period, with additional monitoring and cautionary measures. Collectively, the findings of the study could be utilized for improving work practices on roofs, while reducing the potential risks of falls in roofing construction.     

Motion in images is essential to cause motion sickness symptoms,but not to increase postural sway

ObjectiveIt is generally assumed that motion in motion images is responsible for increased postural sway as well as for visually induced motion sickness (VIMS). However, this has not yet been tested. To that end, we studied postural sway and VIMS induced by motion and still images.Method15 Participants were exposed to motion- and still images in separate sessions. Motion images consisted of video clips taken from a first person shooter game. Still images consisted of stills taken every 10 s from these same clips. Before, during, and after exposure, VIMS was rated and postural sway was measured. Sway path length, standard deviation and short- and long-term scaling components of the centre of pressure were calculated as measures of postural sway.ResultsVIMS scores obtained during and after exposure to motion images were significantly higher compared to scores obtained before, and directly after exposure to still images. The sway path length, standard deviation in anteroposterior direction and short-term scaling components in mediolateral and anteroposterior direction increased significantly during exposure to motion and still images.ConclusionIn this experiment motion- and still images caused different levels of VIMS, but comparable increases in postural sway. We assume VIMS was caused by a mismatch between visual and vestibular motion cues. The increase in sway during exposure to still images can be explained by visual effects present in still images. The lack of vection in the motion images may explain why sway was not larger when viewing these motion images as compared to viewing the still images.     

Whole-body vibration in underground load-haul-dump vehicles

Abstract

Whole-body vibrations (WBV) were measured at the seatpan of load-haul-dump (LHD) vehicles of 3.5-, 5-, 6- and 8-yard capacity at two underground mines. Twenty-two sets of measurements were made involving 11 vehicles, 8 operators and 4 work locations. In each set frequency-weighted rms and peak accelerations were measured in the x, y and z directions, as defined by the ISO (1982), during mucking, driving full, dumping and driving empty. Significant differences in rms accelerations were found between vehicle sizes and between operational tasks (≤0.05). The smallest (3.5 yd) vehicle produced the greatest accelerations in the x and z directions. Accelerations in the x and z directions were also greater when driving full and empty than when mucking and dumping. The highest frequency-weighted rms accelerations of 2.0 to 2.8 m/s^-2 were recorded in the z (longitudinal) direction. Peak accelerations ranged from 1.2 to ≥20 m/s², resulting in crest-factor ratios in excess of six. The exposure periods for each task were used to calculate mean daily acceleration exposures (m/s²). Of the 22 sets of measurements, 20 exceeded the International Standards Organization (ISO) six-hour daily exposure limit in the z direction.of acceleration, and 9 exceeded the six-hour daily exposure limits in all three directions. Acceleration exposure ratios calculated using resultant acceleration vectors as described in ISO (1982), were found to exceed the ISO exposure limit for health or safety in all 22 cases. One-third octave band frequency analysis of the weighted signals indicated that the dominant frequencies were usually 1.6 to 3.15 Hz, except when the vehicles were idling and higher frequencies predominated.     

Walking on ballast impacts balance

Railroad workers often perform daily work activities on irregular surfaces, specifically on ballast rock. Previous research and injury epidemiology have suggested a relationship between working on irregular surfaces and postural instability. The purpose of this study was to examine the impact of walking on ballast for an extended duration on standing balance. A total of 16 healthy adult males walked on a 7.62 m × 4.57 m (25 ft × 15 ft) walking surface of no ballast (NB) or covered with ballast (B) of an average rock size of about 1 inch for 4 h. Balance was evaluated using dynamic posturography with the NeuroCom^® Equitest System^? prior to experiencing the NB or B surface and again every 30 min during the 4 h of ballast exposure. Dependent variables were the sway velocity and root-mean-square (RMS) sway components in the medial–lateral and anterior–posterior directions. Repeated measures ANOVA revealed statistically significant differences in RMS and sway velocity between ballast surface conditions and across exposure times. Overall, the ballast surface condition induced greater sway in all of the dynamic posturography conditions. Walking on irregular surfaces for extended durations has a deleterious effect on balance compared to walking on a surface without ballast. These findings of changes in balance during ballast exposure suggest that working on an irregular surface may impact postural control.     

Evaluation of circumferential pressure as an intervention to mitigate postural instability induced by localized muscle fatigue at the ankle

Pressure application via taping reportedly improves proprioception, and localized muscle fatigue (LMF) increases postural sway, which may be due to a loss of position sense acuity (PSA). This exploratory study investigated the effects of circumferential pressure (CP) and induced ankle LMF on sway. Fourteen young participants performed fatiguing sub-maximal isotonic plantarflexion exercises. Ankle PSA was determined, and used to categorize participants (i.e. high and low groups). Postural sway during quiet standing was assessed using a force platform, both pre- and post-LMF. CP was applied unilaterally to the dominant leg above the ankle joint. Both CP and LMF resulted in greater sway in the low PSA group. CP did not mitigate LMF effects on sway in the low PSA group, but reduced sway among the high PSA group. Reduced PSA may thus indicate less reliance on somatosensation for balance maintenance.

Relevance to industry

Potential benefits of circumferential pressure were indicated. Specifically, CP at the ankle led to improved postural control in certain individuals, which suggests that pressure application might thereby improve balance maintenance and help reduce occupational fall incidents. Results might help to design occupational interventions (specifically CP or taping) differently for individuals with low vs. high PSA.     

Estimating reduced oxygenation levels in the erector spinae lumbar muscle region during seated whole-body vibration

Previous research has demonstrated deficiency in blood supply to lumbar muscles in the form of decrease in oxygenation and blood volume during short duration of exposure to seated whole-body vibration (WBV). However, it is not clear if these WBV-induced lumbar muscle responses are comparable, for example, to that of an endurance exercise-induced oxygenation and blood volume responses?On a separate day, eight healthy participants performed a seated arm cranking exercise until volitional exhaustion. On three separate days, participants were exposed to 3, 4.5, and 6 Hz on a vibration simulator for a period of 16 min. During the fifth minute of WBV ‘with’ and ‘without’ backrest support, participants performed rhythmic handgrip contractions for 1 min. Oxygenation and blood volume responses from the lumbar region were measured utilizing Near-infrared spectroscopy.A percent change in oxygenation and blood volume responses during WBV was expressed as a function of spectroscopy-derived minimum (at the exhaustion) and maximum (during recovery from WBV) responses obtained from the arm cranking exercise. Highest decrease in spectroscopy-derived responses (represented in mean values) was observed: at 4.5 Hz; sitting ‘without’ backrest support; and handgrip contractions during exposure to WBV.Spectroscopy-derived hemodynamic responses obtained during the endurance exercise were significantly lower than the corresponding values measured at different WBV conditions, implying that although the spinal resonance frequency of 4.5 Hz decreases oxygen saturation considerably, progress of oxygen depletion is further evidenced during an endurance exercise.Relevance to industryEstablishing fully oxidized and reduced physiologic states for the lumbar muscle by occluding arterial blood flow is difficult. However, by utilizing an aerobic protocol until volitional exhaustion, lumbar oxygenation and blood volume responses for a variety of WBV-related exposures can be compared. It was concluded that WBV-induced lumbar hemodynamic responses fall well within the reduced and oxidized conditions established through the endurance arm cranking exercise.     

All-terrain vehicle use in agriculture: Exposure to whole body vibration and mechanical shock

Whole body vibration (WBV) and mechanical shock were measured in 12 New Zealand farmers during their daily use of all-terrain vehicles (ATVs). As per the International Organization for Standardization (ISO) guidelines for WBV exposure, frequencies between 0 and 100 Hz were recorded via a seat-pad tri-axial accelerometer during 20 min of ATV use. The farmers were also surveyed to estimate seasonal variation in daily ATV usage as well as 7-day and 12-month prevalence of spinal pain. Frequency-weighted vibration exposure and total riding time were calculated to determine the daily vibration dose value (VDV). The daily VDV of 16.6 m/s^1.75 was in excess of the 9.1 m/s^1.75 action limit set by ISO guidelines suggesting an increased risk of low back injury from such exposure. However, the mean shock factor R, representing cumulative adverse health effects, was 0.31 indicating that these farmers were not exposed to excessive doses of mechanical shock. Extrapolation of daily VDV data to estimated seasonal variations of farmers in ATV riding time demonstrated that all participants would exceed the ISO recommended maximum permissible limits during the spring lambing season, as compared to lower exposures calculated for summer, autumn and winter. Low back pain was the most commonly reported complaint for both 7 day (50%) and 12 month prevalence (67%), followed by the neck (17% and 42%) and the upper back (17% and 25%) respectively. The results demonstrate high levels of vibration exposure within New Zealand farmers and practical recommendations are needed to reduce their exposure to WBV.     

Evaluating worker vibration exposures using self-reported and direct observation estimates of exposure duration

The objective of this study was to compare objective and subjective methods of collecting exposure time data for hand arm vibration (HAV) and whole-body vibration (WBV), and to evaluate the impact of inaccurate exposure times’ on the calculation of the average vibration exposure over an 8 h working day A(8).The study was carried out in the engineering services and maintenance departments of a construction and property management company. Worker exposure time data was collected using three methods, questionnaire surveys, daily worker interviews and 8 h direct workplace observations. Vibration magnitudes (m/s²) were measured for a range of hand tools and vehicles, and daily vibration exposure estimates A(8) were calculated using exposure times observed, reported in interview and self reported in the questionnaire.Results from the study showed that self-reported exposure time estimates from the questionnaire survey were a factor of 9.0 (median value) times greater for HAV and a factor of 6.0 (median value) times greater for WBV when compared with direct observation estimates. Exposure times reported in interview were higher, than those observed, but more reliable than those self reported in the questionnaire; a factor of 2.1 (median value) times greater for HAV and a factor of 1.4 (median value) times greater for WBV. A(8) values calculated using questionnaire exposure times were up to 66% and 75% greater for sources of HAV and WBV respectively when compared to A(8) values calculated using observed exposure times.For the purposes of carrying out a reliable risk assessment, results from this study indicate that direct measurements of worker exposure time are not recommended over questionnaires especially where work is highly variable for example in construction and property management. Worker interviews or direct workplace observation methods were found to be reliable alternative methods for collecting exposure time.     

Evaluating worker vibration exposures using self-reported and direct observation estimates of exposure duration

The objective of this study was to compare objective and subjective methods of collecting exposure time data for hand arm vibration (HAV) and whole-body vibration (WBV), and to evaluate the impact of inaccurate exposure times’ on the calculation of the average vibration exposure over an 8 h working day A(8).The study was carried out in the engineering services and maintenance departments of a construction and property management company. Worker exposure time data was collected using three methods, questionnaire surveys, daily worker interviews and 8 h direct workplace observations. Vibration magnitudes (m/s²) were measured for a range of hand tools and vehicles, and daily vibration exposure estimates A(8) were calculated using exposure times observed, reported in interview and self reported in the questionnaire.Results from the study showed that self-reported exposure time estimates from the questionnaire survey were a factor of 9.0 (median value) times greater for HAV and a factor of 6.0 (median value) times greater for WBV when compared with direct observation estimates. Exposure times reported in interview were higher, than those observed, but more reliable than those self reported in the questionnaire; a factor of 2.1 (median value) times greater for HAV and a factor of 1.4 (median value) times greater for WBV. A(8) values calculated using questionnaire exposure times were up to 66% and 75% greater for sources of HAV and WBV respectively when compared to A(8) values calculated using observed exposure times.For the purposes of carrying out a reliable risk assessment, results from this study indicate that direct measurements of worker exposure time are not recommended over questionnaires especially where work is highly variable for example in construction and property management. Worker interviews or direct workplace observation methods were found to be reliable alternative methods for collecting exposure time.     

The effect of occupational whole-body vibration on standing balance: A systematic review

Adverse health effects from exposure to occupational whole-body vibration (WBV) are common among drivers. In particular some researchers consider that there is kinaesthetic and balance disturbance from WBV exposure in the workplace and this might be one of the aetiological factors responsible for occupational low back pain in drivers. The purpose of this study was to undertake a critical review of the literature to determine whether exposure to seated occupational WBV can affect standing balance performance in an actual or simulated occupational environment. Specific keywords and MeSH terms for three major areas included WBV, balance and occupation. These were used to conduct a systematic search of the following databases; PubMed, EMBASE (Ovid), Medline (Ovid), CINAHL (EBSCO), Academic Search Complete (ASC), AMED, Scopus, Web of Science, Science Direct, Proquest, Cochrane library(OVID), IEEExplore and ProQuest Dissertations and thesis, Google Scholar, WorldCat and related conference proceedings. Five articles met the inclusion criteria and were assessed for quality. Two were field studies conducted on actual vehicles (a long haul freight truck and a bulldozer), while the other three were laboratory studies simulating the characteristics of the following vehicles; long-haul-dump vehicle, underground mine shuttle car, and helicopter. The systematic review scored the methodological quality of the included articles with an average and standard deviation of 76 ±12.3% (range 59- 93%) indicative of high quality. Three of the five studies (two field and one laboratory) found evidence for seated WBV decreasing standing balance performance while two laboratory studies did not find such effects. Thus there is modest evidence to suggest there is a decrease in standing balance performance following exposure to seated occupational WBV.

Relevance to industry

This systematic review suggests that balance deficits may exist immediately following exposure to occupational seated WBV and may predispose driver/operator to low back injury during manual material handling tasks immediately post driving.     

Predictors of whole-body vibration levels among urban taxi drivers

To identify a set of important WBV predictors that could be used to develop a statistical instrument for exposure assessment in a large epidemiologic study, a total of 432 WBV measures were taken from a sample of 247 male drivers in Taipei City, Taiwan. In accordance with the ISO 2631-1 (1997) methods, we measured the frequency-weighted vertical acceleration (z-axis) over drivers' seat surface, under conditions representing different types of rides (vacant vs. short vs. long) assigned to random destinations. Mixed effect models were used to analyse the WBV data including repeated measures. For this group of urban taxi drivers regularly exposed to WBV of low intensity (mean = 0.31 ms ^-2, ranging from 0.17 to 0.55 ms ^-2 r.m.s.), our analyses indicated that average driving speed was the primary predictor (p < 0.0001). As average driving speed increased, measured vertical acceleration increased in a quadratic-linear manner (p < 0.0001). Other WBV predictors, after adjusting for the effects of other covariates, included automobile manufacturer (p = 0.02), engine size (p = 0.04), body weight (p = 0.002), age (p = 0.02), use of seat cushion (p = 0.03), and traffic period (p = 0.02). Our study suggests that a similar statistical approach could be employed in future studies to improve the quality and efficiency of WBV exposure assessment in professional drivers.     

A survey of expert opinion on the effects of occupational exposures to trunk rotation and whole-body vibration

We present a review of current expert opinion on the effects of combined exposures to trunk rotation and whole-body vibration (WBV), commonly experienced by operators of agricultural machinery. We evaluate the level of agreement between academic experts in the field of ergonomics, human response to WBV and agricultural operators, on the effects of exposure to WBV and trunk rotation. A total of 83 individuals responded to the paper-based questionnaire, which included questions on risk levels from individual and combined exposures, discomfort development, exposure duration limits and tasks within agriculture. The results showed that all groups considered exposure to WBV and trunk rotation as risk factors for the development of back pain. The experts were not in consensus regarding acceptable exposure durations, areas of discomfort experienced or recommendations for cab developments.     

Effects of agricultural quad bike driving on postural control during static,dynamic and functional tasks – A field study

BackgroundDriving a quad bike in a rural occupational setting is likely to expose the driver to various physical stimuli including whole-body vibration (WBV). These exposures may be linked to post-driving postural alterations which in turn could lead to an increased risk of spinal injury while undertaking manual material handling activities immediately following driving or falls while exiting from a vehicle.PurposeThe purpose of this study was to use a battery of postural tasks namely; bipedal and unipedal stance, limits of stability (LOS) and lifting task to assess how quad bike driving alters the postural control (PC) in a group of rural workers.MethodsThe PC, determined from centre of pressure (COP) displacements in a group of rural workers (n = 34), was evaluated at three time (T) periods, once (T-I) before the 30 min quad bike driving session on a typical New Zealand farm terrain and twice (T-II and T-III) immediately following driving, each time period lasted approximately 10 min later.ResultsThe results demonstrated a significant (p < 0.05) increase and decrease in the magnitude of the COP measures for the lifting task and unipedal stance respectively during both T-II and T-III periods. However significant (p < 0.05) increase in the magnitude COP measures of bipedal stance, and increase in the maximal stability limits (LOS) were demonstrated only in the T-III.ConclusionsThese results demonstrate both immediate and sustained alterations in the PC following a period of occupational vehicle driving. Also, the results demonstrate both a worsening and improvement in postural control during the performance of a battery of tasks. Observed adverse or facilitatory postural effects will require further laboratory based investigations in order to determine how such disparity can best be explained or challenged.Relevance to industryThe findings will inform ergonomists about the potential risk involved in carrying out physically demanding occupational tasks following vehicle driving. This putative situation could be prevented by adopting behavioural strategies by drivers, and engineered interventions designed to reduce WBV exposure.