Stephen Legg

The effect of cell phone type on drivers subjective workload during concurrent driving and conversing.

The effect of three types of cell phones (hand held, hands free with an external speaker and personal hands free) on total subjective workload (including its constituent components; mental demand, physical demand, temporal demand, performance, effort and frustration) and intelligibility was measured using the NASA-task load index (TLX) and the modified rhyme test (MRT), respectively in 13 experienced drivers (nine male, four female, age range 28-65 years), whilst driving on a rural highway. The drivers rated all components of workload for each type of cell phone to be significantly higher than for a control condition in which no cell phone was used. The mean (standard deviation) total workload was lowest for the personal hands free cell phone (7.1(3.65)) and highest for the hands free speaker phone (10.8 (3.63)) (P<0.001). The mean (standard deviation) intelligibility score was highest for the personal hands free cell phone (74.1 (7.9)) and lowest for the hands free speaker phone (55.0 (10.4)) (P<0.001). Frustration was significantly correlated with total workload (0.60, P<0.001) and intelligibility was significantly correlated with frustration (-0.35, P<0.05). Physical demand was not a high contributor to total workload. It is concluded that a personal hands free cell phone would interfere least with the cognitive demands of driving.

The weight and use of schoolbags in New Zealand secondary schools

The weight and use of schoolbags amongst 140 students (70 third form students comprising 35 females and 35 males, and 70 sixth form students comprising 35 females and 35 males) from five New Zealand secondary schools was investigated. Third form students, who were smaller in stature and weight than sixth form students, were found to carry 13.2% of their body weight in schoolbags, while sixth form students carried 10.3% of their body weight. Third form students reported carrying their schoolbags for a longer period of time than sixth form students. Third form students also had less access to lockers to store their schoolbooks and supplies as only one of the five schools investigated provided lockers for third form students, whereas four of the five schools provided lockers for sixth form students. Most students used backpacks to transport their supplies, and these were predominantly carried on two shoulders. Heavy schoolbags, long carriage durations and lack of access to lockers amongst third formers, could contribute to the production or maintenance of musculoskeletal symptoms. This study suggests that third form students may be at a higher risk of developing musculoskeletal symptoms than sixth form students.

Prevalence and risk factors associated with musculoskeletal discomfort in New Zealand veterinarians

A cross-sectional study using a modified Nordic musculoskeletal questionnaire asked 867 New Zealand veterinarians about the presence or absence of musculoskeletal discomfort (MSD). Participants were asked if MSD affected their normal activities and if it required any period(s) of absence from work. Additional questions enquired about work activities, psychosocial factors and workload. A binary logistic regression analysis was used to quantify the association between identified risk factors and the presence of MSD requiring absence from work in the previous 12 months, controlling for the presence of known confounders. The overall period prevalence of MSD was 96%, 67% had normal activities being affected and 18% of participants reported that they had been absent from work due to MSD. The lower back was the body site most commonly reported for MSD (73%). Factors increasing the odds of MSD requiring time off work for clinical veterinarians were 10 year increases in age (OR 1.26, 95% CI 1.05-1.52), work involving awkward grip and hand movements 100% of time (OR 12.91, 95% CI 3.46-4.21) and those who were dissatisfied with the level and difficulty of their work (OR 2.27, 95% CI 1.11-6.56). These findings have implications for health, lifestyle and retention rates for veterinarians.

Investigating risk factors for slips, trips and falls in New Zealand residential construction using incident-centred and incident-independent methods

Slip, trip and fall (STF) incidents, particularly falls from a height, are a leading cause of injury in the New Zealand residential construction industry. The most common origins of falls from a height in this sector are ladders, scaffolding and roofs, while slipping is the most frequent fall initiating event category. The study aimed to provide detailed information on construction industry STF risk factors for high-risk tasks, work equipment and environments, as identified from an earlier analysis of STF claims data, together with information to be used in the development of interventions to reduce STF risk in New Zealand residential construction. The study involved the use of both incident-centred and incident-independent methods of investigation, including detailed follow-up investigations of incidents and observations and interviews with workers on construction sites, to provide data on a wide range of risk factors. A large number of risk factors for residential construction STFs were identified, including factors related to the work environment, tasks and the use and availability of appropriate height work equipment. The different methods of investigation produced complementary information on factors related to equipment design and work organization, which underlie some of the site conditions and work practices identified as key risk factors for residential construction STFs. A conceptual systems model of residential construction STF risk is presented.

Subjective perceptual methods for comparing backpacks.

Subjective perceptual methods may provide useful information about small differences in backpack design when physiological and biomechanical comparisons are ineffective. This study used two subjective perceptual methods, category ratio scale (CRS) ratings of perceived discomfort and written questionnaires for comparing two types of leisure backpack. CRS ratings of perceived discomfort for each of 24 body regions after 30 min of uphill (15% grade) treadmill walking at 3 km h-1 in 10 males, failed to distinguish between a New Zealand designed backpack (Pack A) and a British designed backpack (Pack B), each weighted to 20 kg. A simple pre- and post-walking written questionnaire using either a visual analogue linear scale or free-format responses indicated that more subjects found Pack A easier to adjust but that it had less comfortable shoulder and waist straps. It was considered to be more comfortable with regard to balance and posture and for shoulder, back and leg muscular tension. Pack B was initially more comfortable but required more lumbar support. Pack B was considered more comfortable for waist and shoulder pressure only. Overall preference was for Pack A (seven subjects) rather than Pack B (three subjects). In conclusion, in this study a questionnaire approach was found to be more useful than CRS ratings of perceived discomfort and the New Zealand designed backpack was preferred.

Effect of single and double strap backpacks on lung function

Carrying heavy and moderate military loads in backpacks or as body armour compresses the chest, causing a change in lung function that is typical of a restrictive ventilatory impairment. It is not known if a lighter backpack load of only 6 kg, such as is typical of loads carried by students, will have a similar effect on lung function. There have been no studies examining whether backpacks of different strapping styles have an effect on lung function. Several designs of student backpack have recently been introduced to the market. One of the most popular is a single-strap backpack. This study examined Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1.FVC − 1% and Peak Expiratory Flow (PEF) in 13 participants (4 males, 9 females) wearing each of two 6 kg backpacks, one with two shoulder straps (a Double Strap Backpack (DSB)) and the other with a single strap (a Single Strap Backpack (SSB)) worn across the shoulder and chest. In comparison with the control of no pack (N), SSB significantly reduced FVC (by 3.94%, p = 0.006) but there were no significant differences in FEV1, FEV1. FVC − 1% and PEF. The DSB also significantly reduced FVC (by 1.97%, p = 0.034) but no significant differences were found in FEV1, FEV1. FVC − 1% and PEF measures. In comparison with DSB, the SSB was associated with a significantly lower FVC (by 2.05%, p = 0.049) and FEV1 (by 1.88%, p = 0.029) but there were no significant changes in FEV1. FVC − 1% and PEF. It is concluded that a backpack load of 6 kg could produce a mild restrictive type of ventilatory impairment in lung function. This effect was greater for a single cross-chest strap than for a more conventional double strap harness.

Effect of backpack fit on lung function

Carrying loads close to the trunk with a backpack causes a restrictive type of change in lung function in which Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1 s (FEV1) are reduced without a corresponding decrement in the FEV1.FVC − 1 %. It is not known whether this is due to the weight of the load acting on the chest or to the tightness of fit of the shoulder and chest straps and waist belt of the pack harness. This study examined FVC, FEV1, FEV1.FVC − 1 %, peak expiratory flow (PEF), forced expiratory flow between 0.2 and 1.2 s (FEF0.2 – 1.2) after the start of expiration and between 25 and 75% of each FVC (FEF25 – 75%) in 12 healthy males wearing a 15 kg backpack in which the shoulder and chest straps and hip belt were loosened by 3 cm from a ‘comfort fit’ to achieve a ‘loose pack’ fit (LPF) and tightened by 3 cm from CF to achieve a ‘tight pack’ fit (TPF). In comparison with the control condition of no pack, a loose pack fit significantly reduced FVC (by 3.6%, p < 0.01), FEV1 (by 4.3%, p < 0.01) and FEF25 – 75% (by 8.4%, p < 0.01). A tight pack fit significantly reduced FVC (by 8.1%, p < 0.01) and FEV1 (by 9.1%, p < 0.001). It also significantly reduced FEF0.2 – 1.2 (by 7.3%, p < 0.05) and FEF25 – 75% (by 21%, p < 0.01). In comparison with a loose pack fit, the tight pack fit was associated with a significantly lower FVC (by 4.6%, p < 0.01), FEV1 (by 5.0%, p < 0.01), FEF25 – 75% (by 13.8%, p < 0.01) and a fall in FEF0.2 – 1.2 (by 5.5%). The latter was approaching significance (p = 0.077). There were no significant changes in FEV1.FVC − 1% and PEF. It is concluded that tightening the fit of a backpack significantly affects lung function in a manner that is typical of a restrictive change in lung function and is very similar in pattern to that of wearing a loosely fitted loaded backpack. The effect of tightness of fit is additional to that due to the weight of the load alone and may also reduce expiratory flow at low lung volumes.

The prevalence and characteristics of back pain among school children in New Zealand

A cross-sectional survey among 245 children was conducted to establish the prevalence and characteristics of back pain in school children aged 11–14 years. A self-complete questionnaire was used to ascertain demographic details, pain prevalence, psychosocial parameters, school and leisure activities and family characteristics. In the last month, 58% of children had experienced spinal pain. In total, 31% of children reported that pain occurred in one part of the back, while 28% stated that pain presented in more than one spinal region. Pain in the last month was found to be equally prevalent in the low back (35%) and neck (36%) regions. Low back pain was associated with the most severe pain and pain lasting for the longest duration when compared with the upper back and neck regions. Further research should be directed towards investigating pain in the neck region and understanding the characteristics of symptom co-occurrence. Statement of Relevance:A survey was conducted to establish the prevalence and characteristics of back pain in school children. The results provide additional evidence that back pain is a serious problem in children aged 11–14 years, whilst also indicating widespread co-occurrence of pain in the neck, upper back and lower back spinal regions.

The combined effect of physical, psychosocial/organisational and/or environmental risk factors on the presence of work-related musculoskeletal symptoms and its consequences.

This study assessed the combined effect of physical and psychosocial/organisational and/or environmental factors on the presence of musculoskeletal symptoms (MSS) and its consequences (reduced activities and absenteeism due to MSS) in a random sample of 3003 workers in New Zealand. By telephone interview, participants reported their current workplace exposures and MSS (neck/shoulder, arm/elbow, wrist and low back) and its consequences. Data were analysed using multivariable logistic regression. Combined exposure to physical and psychosocial/organisational and/or environmental factors increased the odds of MSS in the neck/shoulder (OR 3.14, 95% CI 1.79-5.52), arms/elbow regions (OR 4.14, 95% CI 2.21-7.76) and low back (OR 1.74, 95% CI 1.28-2.37) and its consequences, i.e. reduced activities due to neck/shoulder symptoms (OR 5.45, 95% CI 2.28-13.00), absenteeism due to neck/shoulder symptoms (OR 5.19, 95% CI 2.24-12.01) and absenteeism due to low back symptoms (OR 4.37, 95% CI 2.92-6.53). In contrast, favourable psychosocial/organisational work conditions reduced the odds of wrist symptoms due to poor physical work conditions (OR 2.19, 95% CI 1.44-3.34). We conclude that to reduce MSS and its consequences, employers need to adopt a multifaceted approach: concentrate on improving physical conditions as well as the psychosocial/organisational and environmental aspects of the working environment.

The Physical Demands of Olympic Yacht Racing

The primary purpose of this study was to quantify the up wards forces of the feet on the hiking strap and the forces in the mainsheet of four Olympic classes of racing dinghies (Europe, Laser. Finn and 470) during realistic on-water sailing in varying wind conditions. The secondary aim of the study was to measure the joint angles adopted by the sailors and boat heel angles. The tertiary aim was to identify events and sailing conditions associated with large or patterned force production. Forces in the hiking strap and mainsheet of four classes of Olympic sailing dinghies were measured on eleven New Zealand sailors during simulated on-water racing in a range of wind conditions. Up-wind hiking strap forces reached an average of 73-87% of predicted maximal voluntary contraction (pred MVC), with peak forces exceeding 100% pred MVC. Mainsheet forces reached 25-35% pred MVC, with peak forces reaching 40-50% pred MVC. Off-wind hiking strap and mainsheet forces were considerably lower than up-wind forces. Ankle and hip joint angles increased and knee joint angles decreased with increasing wind speed during up-wind sailing. Large forces occurred in the hiking strap and mainsheet when boats reached the tops of wave during up-wind sailing in high wind speeds and when a gust of wind hit the boat. During off-wind sailing large forces were observed in the mainsheet when surfing down waves. It is recommended that the intensities and joint angles found in this study be used as a basis for the development of class specific off-water physical conditioning programmes.