Ergonomic evaluation and comparison of wood harvesting systems in Northwest Russia

A comparison of 14 currently applicable wood harvesting systems was assessed with respect to ergonomic point of view. For this purpose, the research method, based on the Hodges–Lehmann rule and the integrated work-severity rate of single machinery, was developed for ergonomic evaluation of cut-to-length, tree-length and full-tree harvesting systems. Altogether, about 130 different parameters of 36 units of equipment that impact on the ergonomics and work conditions were measured and estimated in interviews undertaken directly at forestry harvesting workplaces in 15 logging companies in the Republic of Karelia, Northwest Russia. Then the results were compared to the effective norms, and the degree of compliance with the stipulated values was determined. The estimates obtained for the degree of compliance were combined. This permits a direct comparison of the workload on forestry harvesting workers such as operators, lumberjacks and choker setters. In many respects, the current ergonomic standard is standard, except for the operators of cable skidders, chainsaws and choker settings. Visibility and work postures were considered to be the most critical features influencing the operator's performance. Problems still exist, despite the extensive development of cabs. The best working conditions in terms of harvesting systems were provided by “harvester + forwarder” in cut-to-length harvesting, and “feller–buncher + grapple skidder” in full-tree harvesting. The motor-manual tree-length harvesting performed with cable skidders showed the worst results in terms of ergonomics.     

The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in diary farming, using ambulatory heart rate and oxygen consumption measurements. The rate of perceived exertion was estimated with Borg scale. The maximal oxygen consumption was measured in the laboratory. The study group consisted of eight male and 15 female farmers. The handling of feed and manure was the heaviest work task in dairy farming. The aerobic capacity (VO2 max) of female farmers (26 +/- 3 ml/min/kg) was below average, and their work required over 50% of VO2 max during most of the tasks. The VO2 max of male farmers (32 +/- 10 ml/min/kg) was moderate, and most work tasks required below 50% of VO2 max. The mean heart rate in dairy farming tasks was 99 beats min-1 in men and 116 beats min-1 in women. However, according to the rate of perceived exertion, the mean experienced the same work tasks as subjectively more heavy than did the women. The physical strain of female farmers in dairy farming seems to be too high because of heavy work tasks and relatively low VO2 max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

The influence of speed, grade and mass during simulated off road bicycling

The purpose of this investigation was to examine the effects of bicycle mass, speed, and grade on oxygen consumption (VO2), heart rate (HR), and ratings of perceived exertion (RPE) during a simulated off-road riding paradigm. Nine adult subjects with mean +/- SD age, mass, and VO2 max of 26.1 +/- 5.6 years, 71.7 +/- 7.5 kg, 56.6 +/- 5.2 ml x kg(-1) x min(-1) respectively, were trained to ride a fully suspended Trek Y-22 mountain bike on a treadmill with a 3.8 cm bump affixed to the belt. Riders completed a maximum of nine separate trials encompassing three different bike masses (11.6, 12.6 and 13.6 kg), 3 speeds (2.7, 3.6 and 4.5 m x s(-1)), and 3 grades (0, 2.5, and 5%). Throughout a trial, bike mass and speed remained constant while riding grade was increased every 5 min. During simulated off-road riding on a fully suspended mountain bike, increases in speed and grade significantly increased VO2, heart rate, and RPE. Increases in bike mass had no significant effects on VO2, heart rate or RPE. In addition, speed and grade changes interacted to differentially affect VO2, heart rate, and RPE at all speeds and grades.     

Application of the relative summary climatic indices during work in heat for ergonomic purposes

A new method was elaborated for the evaluation of work-heat load. Two indices of heat stress were introduced, the so-called 'climatic heat'--Hcl (a sum of convective, radiation, respiration and maximum evaporation heat), and the 'total heat'--Htot (a sum of metabolic and climatic heat). It is an adapted thermal balance equation in which the evaporation heat was replaced with maximum evaporation heat. This enabled the quantification of climatic load also in the normothermic region, where stored heat S=0. The applicability of these indices is given by the fact that so-called heat heart rate (HRh) is in good correlation with them. The above mentioned indices were used in the relative values of the 'quotient of heat stress' (Qdif,H) and of the 'grade of heat strain' (Gdif,H). These variables are basically a relation between real load and 'permissible' load to which a healthy adult male can be exposed for 8 h without an increase in his body temperature. In this paper, equations for calculation of those relative values according to heat stress indices are introduced. The relative indices show how many times is the real HRh larger (or smaller) than its permissible value (= 20 min(-1)). By joining the relative heat stress indices with the relative work load indices (Qdif,W and Gdif,W, respectively) the index of work-heat load is obtained. The permissible work heart rate (= 30 min(-1)), which corresponds with the energetic output in males (approximately 250 W). The work-heat strain grade (Gdif,WH) can be used for the quantification of load, for the determination of the rest allowance, of the necessary recovery time and for the determination of a suitable regime of work and rest in general. The permissible values of climatic elements under a given physical load, and the admissible duration of exposure under different climatic conditions and different muscle load intensities can be determined.     

Rail system decreases physical strain in milking

The physical strain of milking can be reduced by improving work methods. The aim of this study was to investigate the influence of the rail system (Alfa Line) on the physical strain and work time in tie stall milking. The measurements were performed before the installation of the rail system and after the one year of using the system. The subjects were two male and three female farmers (age 42 ± 2.1 years, mean ± SD), working daily in their barns. The mean heart rate (HR) and heart rate range (HRR) of the four subjects was lower when milking with the rail system. The simultaneous bent and twisted back postures decreased from 29.1% to 10.6% (p < 0.05). Postures with the arms held above shoulder level were reduced to about a half. The proportion of standing with both legs straingt increased and squatting postures diminshed in milking with the rail system. The mean milking time per cow was 3.8 min with the traditional machine milking method and 2.9 min with the rail method. This technical equipment reduced especially the musculoskeletal load in tie stall milking.     

Heart rate strain indices in Greek steelworkers

Abstract

The heart rate strain of 14 Greek steelworkers was assessed during the winter and summer months of 1989 and 1990. Activity sampling was used to establish the pattern of work performed and heart rates were measured throughout work shifts. In addition, maximum aerobic capacity was estimated. The mean heart rate during work was 97 bt. min^?1(±13), while the mean relative heart rate increase was 21% (±15% ). The results indicated that the work performed could be classified as light to moderate.     

Energy cost and physiological responses of males snowshoeing with rotating and fixed toe-cord designs in powdered snow conditions

The purpose of this study was to measure the energy cost and physiological responses of males while snowshoeing with two separate toe-cord designs (rotating toe-cord system vs. fixed toe-cord design) in powdered snow conditions. Eight males snowshoed at self-selected intensity for two, 1600 m trials in two snowshoes, with a rotating toe-cord system and a fixed-toe cord design. It was found that heart rate (HR) (140 vs. 134 beats min(-1)), oxygen consumption (VO(2)) (63.4 vs. 34.0 ml kg(-1)min(-1)), energy cost (56.0 vs. 52.4 kJ min(-1)), and ratings of perceived exertion (RPE) (13 vs. 12) were significantly (p < 0.05) higher while snowshoeing with the fixed toe-cord design than with the rotating toe-cord system. Snowshoeing with the rotating toe-cord system at an average speed of 3.96 km h(-1) produced mean VO(2) values that were 56% of VO(2) max, while snowshoeing with the fixed toe-cord design at 3.86 km h(-1) evoked mean VO(2) values that were 60% of VO(2) max. Mean HR while snowshoeing with the rotating toe-cord system was 70% of HR max, while the mean HR when snowshoeing with the fixed toe-cord design was 74% of HR max. These findings suggest that snowshoeing with a rotating toe-cord system results in lower cardiorespiratory strain in powdered snow conditions compared to snowshoeing with a fixed toe-cord design.     

Comparison of stoop versus prone postures for a simulated agricultural harvesting task

Physical and psychophysical differences between working in the stooped and prone postures were compared while performing a simulated agricultural harvesting task for 30 min. Fifteen male subjects participated. The measures used to compare the two postures included perceived discomfort, electromyography (EMG), and heart rate (HR). Average hamstrings localized discomfort (0-10 scale) was 6.17 (SD=2.9) for the stoop posture and 0.67 (SD=1.29) for the prone posture. Erector spinae and hamstring EMG RMS increased 68% and 18%, respectively, while mean power frequency for the hamstrings decreased 13% for the stoop task. Mean power frequency for the middle trapezius muscle decreased in both postures (stoop 4.13%, prone 3.79%). Average heart rate during the last work cycle was 35% greater than the resting heart rate for the stoop posture while average heart rate was 17% greater for the prone posture. Subjects worked on the prone workstation without rest during the 15 min work simulations with less discomfort, no localized fatigue in the back or leg muscles tested, and lower working heart rates than subjects working in the stoop posture.     

Helmet design to facilitate thermoneutrality during forest harvesting

The purpose of this investigation was to evaluate the ventilatory characteristics of vented and non-vented helmets for use in forestry harvesting operations. A ventilation index developed by Birnbaum and Crockford (1978) was used to determine the ventilation capacity of twelve helmets varying in design and presence, location, and dimension of vents. Helmets with top vents had higher ventilation indices than non-vented, side and side/top-vented helmets. Ten physically fit men participated in a maximal oxygen consumption test and four trials wearing a non-vented, round-side-vented, round-top-vented or rectangulartop-vented helmet. Trials simulated typical summer environmental conditions (28°C, 80% rh) and physiological work loads (40% V O 2 max) experienced during forest harvesting in New Zealand. The temperature and humidity under the helmet was typically lowest when the helmet with the largest vented area (288 mm 2) in the crown was worn, although physiological responses (temperatures at the tympanum, ear and scalp; humidity at the centre of the helmet) of the participants to wearing the helmets differed significantly during some rest periods only. Top-vented helmets (in this experiment measured 288 mm 2) should be worn to minimize temperature and humidity of the head during forest harvesting operations.     

Helmet design to facilitate thermoneutrality during forest harvesting

The purpose of this investigation was to evaluate the ventilatory characteristics of vented and non-vented helmets for use in forestry harvesting operations. A ventilation index developed by Birnbaum and Crockford (1978) was used to determine the ventilation capacity of twelve helmets varying in design and presence, location, and dimension of vents. Helmets with top vents had higher ventilation indices than non-vented, side and side/top-vented helmets. Ten physically fit men participated in a maximal oxygen consumption test and four trials wearing a non-vented, round-side-vented, round-top-vented or rectangulartop-vented helmet. Trials simulated typical summer environmental conditions (28 degrees C, 80% rh) and physiological work loads (40% VO(2)max) experienced during forest harvesting in New Zealand. The temperature and humidity under the helmet was typically lowest when the helmet with the largest vented area (288 mm(2)) in the crown was worn, although physiological responses (temperatures at the tympanum, ear and scalp; humidity at the centre of the helmet) of the participants to wearing the helmets differed significantly during some rest periods only. Top-vented helmets (in this experiment measured 288 mm(2)) should be worn to minimize temperature and humidity of the head during forest harvesting operations.     

Workload assessment in building construction related activities in India

A field study was conducted to highlight the occupational risk factors related to building construction activities in India among female workers. These workers were engaged in eight different types of activities and related work parameters were studied in detail. From field environmental parameters, the calculated WBGT was obtained as 30.26+/-1.52 degrees C, indicated that these workers worked under a positive heat load condition. Whole day work study was conducted on 11 adult female workers performing concreting operation. They were having age of 28-32 years with 5-7 years of work experience. These workers were mainly performing two types of operations in the field: (A) asymmetric lifting during concreting a boundary wall formwork of a lift unit and (B) carrying the concrete mixture. During asymmetric lifting, the average field working heart rate (HR) was calculated as 124.1+/-12.5 beats min(-1), equivalent to 45.03+/-6.93% of VO(2) max level. These working heart rates (HRs) were significantly (p相似文献   

Effects of daytime ingestion of melatonin on short-term athletic performance

The immediate effects of ingesting melatonin in the daytime include decreased alertness and body temperature. To date, no researcher has examined whether daytime ingestion of melatonin leads to impairments in variables relevant to short-term (<10 min) athletic performance. Twelve physically active participants (mean +/- s age = 25.2 +/- 5.0 years, body mass = 81.4 +/- 12.1 kg and chronotype = 33.8 +/- 6.3 units) ingested 5 mg of melatonin or placebo at 11:45 hours in a double-blind experiment. At 13:00 and 17:00 hours, subjective alertness was measured, together with intra-aural temperature, reaction time (two-, four- and eight-choice), short-term memory recall and grip strength. Performance, ratings of perceived exertion (RPE) and heart rate were also recorded during a 4-km cycling time trial. At 13:00 hours, the mean +/- s intra-aural temperature was 0.49 +/- 0.79 degrees C lower after ingestion of melatonin than after placebo (p = 0.015), but this difference was not apparent at 17:00 hours. At both 13:00 and 17:00 hours, melatonin reduced (p < 0.05) alertness, short-term memory and exercise heart rate by 1.5 +/- 1.8 units, 1 +/- 1 digits and 6 +/- 9 beats.min(-1), respectively (mean +/- s). Eight-choice reaction time was also slower at both times of day after ingesting melatonin. Melatonin did not influence time trial performance or RPE (p > 0.05). The effects of 5 mg of melatonin seem more pronounced for mental rather than physical components of short-term athletic performance, although the cardiovascular responses to exercise are affected. Some effects of melatonin were apparent 5 h after ingestion when the hypothermic effects of melatonin had dissipated.     

The Cost of Work on a Vehicle Assembly Line

Abstract

The physiological cost of work on men working on a truck assembly line was measured. Twenty subjects took part in the study: all had their heart rates measured during work, leisure and sleep. Thirteen subjects had their oxygen consumption measured at work using a newly described respirometer (Miser). Results confirmed that such work may be classified as light industrial with an energy expenditure of 120-200 W

Mean heart rates during work were 91 ± SD 8 bt min^-1;, mean relative work load was 24 ± SD 4% and mean relative heart rates were 21 ± SD 7%. The mean of the ratios of work, sleep and leisure: sleep heart rates were 1 -45 ± SD 015 and 1-28 ± SD 012 respectively.     

Intermittent microclimate cooling during exercise-heat stress in US army chemical protective clothing

The effectiveness of intermittent, microclimate cooling for men who worked in US Army chemical protective clothing (modified mission-oriented protective posture level 3; MOPP 3) was examined. The hypothesis was that intermittent cooling on a 2 min on-off schedule using a liquid cooling garment (LCG) covering 72% of the body surface area would reduce heat strain comparably to constant cooling. Four male subjects completed three experiments at 30 degrees C, 30% relative humidity wearing the LCG under the MOPP 3 during 80 min of treadmill walking at 224 +/- 5 W . m(-2). Water temperature to the LCG was held constant at 21 degrees C. The experiments were; 1) constant cooling (CC); 2) intermittent cooling at 2-min intervals (IC); 3) no cooling (NC). Core temperature increased (1.6 +/- 0.2 degrees C) in NC, which was greater than IC (0.5 +/- 0.2 degrees C) and CC (0.5 +/- 0.3 degrees C) ( p < 0.05). Mean skin temperature was higher during NC (36.1 +/- 0.4 degrees C) than IC (33.7 +/- 0.6 degrees C) and CC (32.6 +/- 0.6 degrees C) and mean skin temperature was higher during IC than CC ( p < 0.05). Mean heart rate during NC (139 +/- 9 b . min(-1)) was greater than IC (110 +/- 10 b . min(-1)) and CC (107 +/- 9 b . min(-1)) ( p < 0.05). Cooling by conduction (K) during NC (94 +/- 4 W . m(-2)) was lower than IC (142 +/- 7 W . m(-2)) and CC (146 +/- 4 W . m(-2)) ( p < 0.05). These findings suggest that IC provided a favourable skin to LCG gradient for heat dissipation by conduction and reduced heat strain comparable to CC during exercise-heat stress in chemical protective clothing.     

Promoting children's physical activity in primary school: an intervention study using playground markings

The physical activity levels of 47, 5- to 7-year-old children were assessed before and after a school playground was painted with fluorescent markings. Children's physical activity was measured using heart rate telemetry during three playtimes before and after the markings were laid down. Children in the experimental and control groups spent 27 and 29 min, respectively, in moderate to vigorous physical activity (MVPA) before the intervention, increasing to 45 and 36 min, respectively, during the intervention period. MVPA, vigorous physical activity (VPA) and mean heart rate remained relatively stable in the control group compared to respective increases of 10 and 5% of playtime and 6 beats min(-1) in the experimental group during the intervention period. The ANCOVA analysis revealed significant interactions and main effects for the intervention for MVPA, VPA and mean heart rate. Conversely there were no main effect differences between groups. These results suggest that while playground markings had a significant and positive influence on children's physical activity, factors other than playground markings may also influence children's physically active play.     

Promoting children's physical activity in primary school: an intervention study using playground markings

The physical activity levels of 47, 5- to 7-year-old children were assessed before and after a school playground was painted with fluorescent markings. Children‘s physical activity was measured using heart rate telemetry during three playtimes before and after the markings were laid down. Children in the experimental and control groups spent 27 and 29 min, respectively, in moderate to vigorous physical activity (MVPA) before the intervention, increasing to 45 and 36 min, respectively, during the intervention period. MVPA, vigorous physical activity (VPA) and mean heart rate remained relatively stable in the control group compared to respective increases of 10 and 5% of playtime and 6 beats min ^{- 1} in the experimental group during the intervention period. The ANCOVA analysis revealed significant interactions and main effects for the intervention for MVPA, VPA and mean heart rate. Conversely there were no main effect differences between groups. These results suggest that while playground markings had a significant and positive influence on children's physical activity, factors other than playground markings may also influence children's physically active play.     

Manual lifting load limit equation for adult Indian women workers based on physiological criteria

A comprehensive equation for the evaluation of a maximum load limit for manual load lifting has been developed for the first time for Indian adult female workers, based on a physiological criterion due to the limitation of applicability of the NIOSH (1991) equation. Ten adult female workers, who had been engaged in building construction activities for at least 7 years participated in this study. The cut-off value was selected as the working heart rate corresponding to the 33% level of maximum aerobic power (i.e. V'O2 max.) of this population, which was equivalent to a heart rate of 101.6 beats x min(-1). An equation was developed based on the effects of the following three lifting parameters on working heart rate: vertical height (knee, waist, shoulder and maximum reach height), lifting frequency (1, 4, 7 and 14 lifts x min(-1)), and load weight (5, 10 and 15 kg). The variations of the specific lifting parameter values were selected from field observations. From this equation, the maximum load limit was calculated as 15.4 kg and the workers give this a psychophysical rating as in the moderate to heavy category.     

Physiological strain during kitchen work in relation to maximal and task-specific peak values

Six female and three male subjects from a hospital kitchen volunteered for the study. The subjects were working on a conveyor belt collecting and sorting dirty plates, glasses and cutlery for cleaning. In the study, a medical examination, a maximal clinical exercise test with a 12-lead electrocardiogram (ECG) and a maximal arm cranking test were performed in the laboratory. Further, each subject was studied for 30 min during a normal work shift in the kitchen. Oxygen uptake (VO2) and heart rate (HR) were continuously registered. During the work period, a rating of perceived exertion (RPE) was asked at the 5th, 15th and 30th minute. Physiological responses were measured by a portable system (K4) both in the laboratory and in the field. VO2 and HR measured in the field were proportioned to corresponding maximal values during cycling and to peak values during arm-cranking. The mean VO2 for the male and the female subjects during kitchen work was 0.65 +/- 0.16 l min-1. This corresponded to 24% of VO2max and to 41% of VO2peak during arm-cranking. The difference was significant (p < 0.001). Owing to a magnetic field at the conveyor belt, reliable HR values were obtained only from the female subjects. The mean HR during work among the female subjects was 101 beats min-1. It corresponded to 55% of HRmax and 67% of HRpeak during arm-cranking (p < 0.05). The present study shows that the relative work intensity is markedly higher when it is expressed relative to the corresponding muscle group's VO2peak instead of the VO2max. Similar difference was also seen in the HR response. More task-specific testing of physical capacity may provide improved evaluation of physical strain in a job.     

Physiological mechanism underlying the improvement in visuospatial performance due to 30% oxygen inhalation

This study investigated the effect of 30% oxygen inhalation on visuospatial cognitive performance, blood oxygen saturation, and heart rate. Six male (25.8(mean)+/-1.0(SD) years) and six female (23.8+/-1.9 years) college students participated in this experiment. Two psychological tests were developed to measure the performance level of visuospatial cognition. The experiment consisted of two runs: one was a visuospatial cognition task under normal air (21% oxygen) condition and the other under hyperoxic air (30% oxygen) condition. The experimental sequence in each run consisted of four phases, that were Rest1 (1min), Control (1min), Task (4min), and Rest2 (4min). Blood oxygen saturation and heart rate were measured throughout the course of four phases. The analysis of behavioral performance with 30% oxygen administration when compared to 21% oxygen revealed that the mean performance was improved. When supplied 30% oxygen in the air, the blood oxygen saturation was increased while the heart rate was decreased compared to those under 21% oxygen condition. We conclude that 30% oxygen inhalation enhanced visuospatial performance by the increased the oxygen saturation in the blood.