Omer C. Jenkins

Factors affecting minimum push and pull forces of manual carts.

The minimum forces needed to manually push or pull a 4-wheel cart of differing weights with similar wheel sizes from a stationary state were measured on four floor materials under different conditions of wheel width, diameter, and orientation. Cart load was increased from 0 to 181.4 kg in increments of 36.3 kg. The floor materials were smooth concrete, tile, asphalt, and industrial carpet. Two wheel widths were tested: 25 and 38 mm. Wheel diameters were 51, 102, and 153 mm. Wheel orientation was tested at four levels: F0R0 (all four wheels aligned in the forward direction), F0R90 (the two front wheels, the wheels furthest from the cart handle, aligned in the forward direction and the two rear wheels, the wheels closest to the cart handle, aligned at 90 degrees to the forward direction), F90R0 (the two front wheels aligned at 90 degrees to the forward direction and the two rear wheels aligned in the forward direction), and F90R90 (all four wheels aligned at 90 degrees to the forward direction). Wheel width did not have a significant effect on the minimum push/pull forces. The minimum push/pull forces were linearly proportional to cart weight, and inversely proportional to wheel diameter. The coefficients of rolling friction were estimated as 2.2, 2.4, 3.3, and 4.5 mm for hard rubber wheels rolling on smooth concrete, tile, asphalt, and industrial carpet floors, respectively. The effect of wheel orientation was not consistent over the tested conditions, but, in general, the smallest minimum push/pull forces were measured with all four wheels aligned in the forward direction, whereas the largest minimum push/pull forces were measured when all four wheels were aligned at 90 degrees to the forward direction. There was no significant difference between the push and pull forces when all four wheels were aligned in the forward direction.

Behavioral responses of mares to short-term confinement and social isolation

Thirty-six mares, blocked by age and temperament score, were assigned to one of three treatment groups: pasture (P); confinement stalls (C), allowing social contact; isolation stalls (ISS), allowing no contact with conspecifics. After 48 h on treatment, the mares were observed in situ for 1 h. Medium temperament and highly reactive ISS mares spent more time eating grain (P<0.01) and exhibited more grain-eating bouts (P<0.03) than P and C mares. Calm P mares had longer forage-eating bouts than C and ISS mares (P<0.02). During a 15 min open-field test in a 23 m × 23 m pen after 72 h on treatment, ISS mares traveled farther (P<0.005) than C and P mares, spent more total time trotting (P<0.01) than C and P mares, and exhibited a greater number of trotting bouts (P<0.01) than both C and P mares. Isolated mares spent less total time standing during the open-field test than C (P<0.05) and P (P<0.01) mares, but exhibited a greater number of standing bouts than C (P<0.05) and P (P<0.01) mares. Isolated mares also exhibited a greater number of total activity bouts (P<0.01) during the open-field test than both C and P mares; P mares also exhibited fewer activity bouts than C mares (P<0.1). Results indicate that mares kept in confined and isolated environments showed greater motivation for movement and performance of a greater number of activities than those maintained on pasture with conspecifics.

The effect of handle height and cart load on the initial hand forces in cart pushing and pulling

The objective of this study was to measure the three-dimensional hand forces people exert to initiate a cart push or pull for two cart loads: 73 and 181 kg, and three handle heights: knuckle, elbow, and shoulder heights. The cart used was equipped with 15.24 cm (6 in) diameter wheels. The floor was covered with carpet tiles. The laboratory-measured hand force exertions were compared to the minimum forces needed to push/pull the cart under the same conditions and to the psychophysical initial push/pull force limits. For pushing and pulling, the measured anterior-posterior hand forces were 2–2.4 times the minimum required forces. For the heavier cart load, lower forces were applied as handle height increased. Pull forces were 7% higher than push forces. The smallest vertical forces were measured at elbow height. Strength capability and gender did not have an effect on the applied forces. The mean strength percentile for the male sample was 64%, while the mean strength percentile for the female sample was 13...

Effects of restricted nursing on physiological and behavioral reactions of Brahman calves to subsequent restraint and weaning1

The influence of restricted nursing on physiological and behavioral reactions to later restraint and weaning was examined in Brahman (Bos indicus) calves. The calves were blocked for sex and randomly assigned at birth to one of two treatments: restricted nurse (RN), or ad libitum nurse (ALN). The RN calves were separated from their dams at 21 days of age and allowed to nurse once daily (2-h duration) for 19±3 days. The ALN calves remained with their dams from birth until weaning. The ALN calves were brought in and worked through handling facilities for the same amount of time each day as the RN calves. At 192±4 days of age each calf was restrained while blood samples (5) were taken and heart rate monitored via telemetry. Two weeks later, the calves were weaned and blood samples and behavioral observations were taken. Mean plasma cortisol concentration (MC) increased over time for both treatments (P<0.004) in response to restraint, but was greater for RN than for ALN calves after 15 min of restraint (P<0.03). In response to restraint, RN calves had overall greater heart rates than did ALN calves (P<0.02). In response to weaning, ALN calves tended to travel more (P<0.07), and included more calves who ate (P<0.05), and vocalized (P<0.05). The effects of the restricted nursing regimen, which inherently includes handling, appears to alter the calfs later response to restraint and weaning. However, due to the lack of a uniform response further research is required to determine the meaning of and causal factors for this alteration.

A Prospective Field Study of the Relationship of Potential Occupational Risk Factors with Occupational Injury/Illness

Twenty-one occupationally related risk factors were measured and prospectively evaluated for statistically significant relationships with occupational injury/illness in 442 manual material handlers, working for three different companies, at nine U.S. locations, and encompassing 15 different job descriptions. OSHA 200 logs were used to ascertain evidence of occupational injury/illness (dichotomous) within this population for 1 year after the testing and measurement were completed. The present study demonstrated evidence of a subset of critical variables significantly related to occupational injury/illness occurrence through the significantly related occupational risk factors presented in the univariate and multivariate models. Higher occurrences of injury/illness were significantly associated with nine risk factors in the univariate model, with odds ratios ranging from 1.11-2.27. The significantly (p<0.05) related risk factors in the univariate model were lifting frequency; weight lifted per day; weight lifted per hour; number of trunk flexions per hour; number of trunk twists per hour; number of trunk motions per hour; number of knee flexions per hour; number of shoulder flexions per hour; and static shoulder flexion. In the multivariate analysis two risk factors were associated with occupational injury/illness. The significantly (p<0.05) related risk factors in the multivariate model were lifting frequency (p=0.0010, odds ratio [OR]=4.47, 95% confidence interval [CI]=[2.38-8.40], and average weight of lift (p=0.0001, OR=1.71, 95% CI=[1.29-2.25]).

The influence of supporting the Oxylog instrument on estimated maximal aerobic capacity during a step test and heart rate in a lifting test

This study investigated the influence of wearing, an Oxylog mask and heart rate monitor while the Oxylog instrument was supported in a stand versus that of wearing the Oxylog mask, heart rate monitor, and the Oxylog instrument, on oxygen consumption (VO2) and heart rate response during a graduated submaximal step test protocol. Also, the predicted maximal aerobic capacities ( VO2max) produced by the two graduated step tests were compared. In addition, differences in the working heart rates in a submaximal lifting test were analyzed in two lifting tests, one with the participant wearing the Oxylog mask, heart rate monitor, and Oxylog instrument and the other required the participant to only wear a heart monitor. Seventeen experienced male manual materials handlers participated in the study, and each treatment was seen by each participant in a randomized Latin Square design. Results from the two investigations indicate that there was no significant difference in the estimated maximal oxygen consumption (p = 0.1384) and no significant difference in the heart rate between the two lift tests. The analysis did show that the 4th stage (participants reaching their physiological limits) of the step tests indicated a statistically significant difference (p = 0.0259 for oxygen consumption, and p = 0.0465 for heart rate).

Blood buffering in sedentary miniature horses after administration of sodium bicarbonate in single doses of varying amounts

SUMMARY Blood acid-base and electrolyte status was studied in four sedentary Miniature Horses treated with 200, 300, 400 and 500 mg of sodium bicarbonate (NaHCO 3 ) per kg of body weight (BW). Arterial blood was collected before treatment with NaHC0 3 and each hour for 5 h after treatment. All treatments resulted in an increase in blood pH, bicarbonate (HCO 3 − ) concentration and base excess (BE) by 1 h post-dosage, which continued through the 5th hour (P 3 /kg BW resulted in less elevated blood HCO 3 − concentrations (P 3 , plasma Na + concentrations increased among all treatments but declined to initial values by 3 h post-treatment. The 200 mg NaHCO 3 /kg BW dosage resulted in the smallest increases in plasma Na + concentrations (P + and Ca ++ concentrations were lower (P .05) among treatments. All NaHCO 3 dosages increased blood buffering capacity as indicated by increased blood pH, HCO 3 − concentration and BE. Maximum blood pH, HCO − 3 concentration and BE was reached using a dosage of 300 mg NaHCO 3 /kg BW. Also, all treatments altered the plasma electrolyte concentrations.