Schoolbag weight and musculoskeletal symptoms in New Zealand secondary schools.

The weight of schoolbags and the prevalence of musculoskeletal symptoms 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. Schoolbag weight for third form students (mean age 13.6 years) was 13.2% of their body weight, while for sixth form students (mean age 17.1 years) it was 10.3% of their body weight. These weights may exceed the recommended guideline load limits for adult industrial workers. Musculoskeletal symptoms were reported by 77.1% of the students. Symptoms were most prevalent in the neck, shoulders, upper back and lower back. Although musculoskeletal symptoms are believed to be multifactorial in origin, the carriage of heavy schoolbags is a suspected contributory factor and may represent an overlooked daily physical stress for New Zealand secondary school students.

How safe is cycling with a schoolbag?

This study was undertaken as a preliminary investigation to compare cycling errors and sudden stopping distance in secondary students traversing an obstacle course on their bicycle with and without a schoolbag, to determine if further studies of cycling accident aetiology amongst children were warranted. Twenty children cycled as fast as they could around an obstacle course. Each child undertook two separate trials, about an hour apart on a morning of the same day. The children traversed the course one at a time in turn using their own bicycle and wearing their own usual school clothes. For the first trial they did not carry a schoolbag. On the second trial they carried a schoolbag weighing 6 kg. There were no significant differences in the number of cycling errors made by the children when traversing the obstacle course with and without a schoolbag. However, the children generally took longer to complete the course when carrying the schoolbag and stopping distances were greater. It was not possible to be certain that these findings were genuine or whether the effect of carrying the schoolbag was reduced by increased familiarity with the course, since all of the children first traversed the course without a schoolbag and then with one. It is concluded that there is some justification for conducting further studies to explore the implications of carrying schoolbags on cycling accident aetiology amongst children.

Subjective perceptual methods for comparing backpacks in the field.

Subjective perceptual methods have provided useful information in the laboratory about small differences in backpack design when physiological and biomechanical comparisons are ineffective, but have never been used in the field. This study therefore evaluated, in a controlled field trial with 10 male participants, the suitability of quantitative and qualitative subjective perceptual approaches to distinguish between subtle design differences in two backpacks, each loaded to 15 kg. In addition, initial quantitative subjective impressions about the two backpacks during a 15 min simulated 'in-shop' trial were compared with post-field trial backpack preference. In the simulated 'in-shop' trial the participants 'tried out' the backpack in a manner that was very similar to the way that they would normally try out a backpack as if they were considering buying one in an 'outdoor' shop. It included donning and doffing the pack several times and walking around the room wearing the backpack. In the controlled field trial, participants carried the two backpacks for approximately 15 min around a 1313 m hilly outdoor track at a self-selected walking pace which elicited a moderate exercise intensity. Seven participants preferred backpack A. Three preferred backpack B. The qualitative approach, which required participants to provide free-format written responses to semi-structured open-ended questions immediately after the field trial, successfully identified specific reasons underlying participants' preferences. The main reasons for preferring backpack A were better balance, weight distribution, stability up and down hill and over obstacles, fewer pressure points on their back and easier strap location and adjustment. The quantitative approach, which involved participants responding to written post-field trial questions on visual analogue or category ratio rating scales, was generally unsuccessful in distinguishing between backpacks. Thus, qualitative subjective perceptual methods appeared to be more useful than quantitative ones in distinguishing between backpacks and in identifying positive and negative design features under controlled field conditions in which participants carry a backpack at a moderately intense self-selected exercise level. However, since the quantitative approach had been successful in distinguishing between backpacks in an earlier similar study, in which participants exercised more intensely by walking uphill on a treadmill at a fixed pace, it is possible that the quantitative subjective perceptual approach may be capable of distinguishing between backpacks in the field if a fixed pace eliciting higher exercise intensity were to be used. Finally, since quantitative responses to questions about the backpacks after a short simulated 'in-shop' trial closely agreed with participants' post-field trial overall backpack preference, it is concluded that initial subjective impressions may be a good guide to backpack preference after limited field usage.

Prediction of foaling using mammary secretion constituents.

AIMS: To test published models for predicting time of foaling using data derived from prepartum mammary secretions and to develop a new model based on concentrations of mammary secretion constituents that accurately predicts time of foaling in Thoroughbred mares. METHODS: Concentrations of sodium, potassium, calcium, citrate and lactose were measured in prepartum mammary secretions of 20 Thoroughbred mares in the 2 weeks before expected date of foaling. Models to predict time of foaling were fitted to data based on absolute concentration, change in concentration, and percentage change in concentration of mammary secretion constituents in relation to actual intervals to foaling. RESULTS: Concentrations of potassium, calcium, citrate and lactose increased, and concentration of sodium decreased as foaling approached but variation between mares was large. Models to predict time of foaling based on percentage change in electrolyte concentrations were less accurate than those based on absolute concentration and change in concentration. When data from this study were fitted to two previously published models, the statistical sensitivity, specificity, and positive and negative predictive values of both models were lower than those originally reported. CONCLUSIONS: The use of prepartum equine mammary secretion electrolyte concentrations for prediction of time of foaling is unreliable, due to large variation in both absolute concentrations and change in concentrations between mares. Models that use a combination of mammary secretion electrolytes and physical and behavioural factors may better predict foaling than those based on mammary secretions alone.

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.

A comparison of bacterial adherence to bare hands and gloves following simulated contamination from a beef carcass.

One of the risks for contamination of edible product in the pre-inspection area of processing lines in meat plants is cross contamination. This can occur directly as a result of carcass-to-carcass contact or indirectly via knives or the hands of butchers. Standard procedures require that operators rinse their hands and knives to remove any visible contamination. In New Zealand, protective gloves are not allowed in the pre-inspection area because they are considered a potential risk for cross contamination until the carcasses have passed the final meat inspection. However, the risk of injury to the bare hands is as high in this area as in other parts of the plant, where such gloves are permitted. There is therefore a need to evaluate the risk of bacterial cross contamination via bare hands and via protective gloves. The present study compared bacterial adherence to bare hands and to gloves after rinsing for 5 s in a shower of water at 40 degrees C and after rinsing gloves in hotter water (60 degrees C) following simulated contact with the hide of a recently slaughtered animal. Under laboratory conditions there were no statistically significant differences between bacterial adherence to bare hands or to gloves rinsed in water at 40 degrees C or 60 degrees C.

Development of reference intervals for the large intestinal transit of radiopaque markers in dogs.

Ten healthy dogs were fed 30 1.5 mm and 10 5 mm radiopaque markers (BIPS, MedID, Grand Rapids) mixed with sufficient quantities of a high fibre diet to meet 25% of their estimated daily caloric requirements. Abdominal radiographs were made at two hour intervals until 90% of the small and large markers had left the colon. The mean residence times (MRT) of each size of marker in the proximal, distal and total colon were calculated using kinetic analysis. The MRT's of the small markers were 4.9 hours (SD 4.4), 7.1 hours (SD 3.3) and 12.0 hours (SD 7.1) respectively. The MRT's of the large markers were not significantly different from the small markers except in the proximal colon where they were significantly shorter (3.2 hours, SD 2.3). Reference colonic filling and colonic transit curves for both sizes of markers were constructed. These may be useful to detect abnormal colonic transit in dogs.

Acute effects on mood and cognitive performance of breakfasts differing in fat and carbohydrate content.

Sixteen subjects consumed low-fat/high-carbohydrate (LFHC), medium-fat/ medium-carbohydrate (MFMC), high-fat/low-carbohydrate (HFLC) iso-energetic breakfasts and no breakfast in a counterbalanced order on four separate days. The LFHC breakfast was similar in macronutrient composition, though not in meal size (more kcal) and types of foods offered, to the habitual breakfast of the subjects. A battery of cognitive performance tasks together with mood and appetite ratings were completed before and during the 3 h following breakfast. Results showed no clear differences in performance between the four dietary conditions, but significant effects on mood were observed. Mood improved (a decline in fatigue/dysphoria) following the LFHC breakfast compared to the other meals. The findings show that the macronutrient content of breakfast, independent of energy value and oro-sensory qualities, can exert small but reliable effects on subsequent mood, and suggest that deviation from habitual meal composition can produce a relative decline in mood state. These conclusions are supported by results from a previous study of the effects of lunch which found very similar relationships between meal composition, habitual choices and postprandial mood changes.