The physical strain of dairy farming

The aim of this study was to estimate the physical stress and strain in dairy 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 ([Vdot]O₂ max) of female farmers (26 ± 3 ml/min/kg) was below average, and their work required over 50% of [Vdot]0₂ max during most of the tasks. The [Vdot]0₂ max of male fanners (32±10 ml/min/kg) was moderate, and most work tasks required below 50% of [Vdot]0₂ 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 men 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 [Vdot]0₂ max of women. Special attention should be paid to these factors in the occupational health services for farmers.     

Oxygen uptake and muscle activity limitations during stepping on a stair machine at three different climbing speeds

Abstract

This laboratory study examined human stair ascending capacity and constraining factors including legs’ local muscle fatigue (LMF) and cardiorespiratory capacity. Twenty-five healthy volunteers, with mean age 35.3 years, maximal oxygen uptake (VO_2max) of 46.7?mL·min^?1·kg^?1 and maximal heart rate (HR) of 190 bpm, ascended on a stair machine at 60 and 75% (3?min each) and 90% of VO_2max (5?min or until exhaustion). The VO₂, maximal heart rate (HR_max) and electromyography (EMG) of the leg muscles were measured. The average VO_2highest reached 43.9?mL·min^?1·kg^?1, and HR_highest peaked at 185 bpm at 90% of VO_2max step rate (SR). EMG amplitudes significantly increased at all three levels, p?<?.05, and median frequencies decreased mostly at 90% of VO_2max SR evidencing leg LMF. Muscle activity interpretation squares were developed and effectively used to observe changes over time, confirming LMF. The combined effects of LMF and cardiorespiratory constraints reduced ascending tolerance and constrained the duration to 4.32?min.

Practitioner Summary: To expedite ascending evacuation from high-rise buildings and deep underground structures, it is necessary to consider human physical load. This study investigated the limiting physiological factors and muscle activity rate changes (MARC) used in the muscle activity interpretation squares (MAIS) to evaluate leg local muscle fatigue (LMF). LMF and cardiorespiratory capacity significantly constrain human stair ascending capacities at high, constant step rates.     

Evaluation of three methodologies to estimate the VO2max in people of different ages

Aging and gender are factors that affect the variation of physical work capacity. The present paper highlights the importance of the metabolism used by ergonomics to establish the appropriate limits of loads at work. This study compares the aerobic capacity of people from 20 to 71 years old split in 5 different groups. The laboratory experiment tested 33 volunteers (19 women and 14 men). A submaximal step test was used to measure the VO₂ using a portable breath by breath metabolic system and a telemetric heart rate monitor. Three methods to estimate the VO_2max were compared: 1) a direct measurement of VO₂, 2) estimation by heart rate, and 3) a step test method using predetermined charts. Significant difference was encountered among the estimation methods as well as among the age ranges (F_2,92 = 6.43, p < 0.05 y F_4,92 = 7.18, p < 0.05 respectively). The method of direct measurement and the method of predetermined charts were different for the estimation of the VO_2max with a confidence level of 95%. The method of predetermined charts is better adapted for males and people younger than 30 years. The estimation through non invasive heart rate apparatus was a good appraiser of the maximal oxygen consumption considering both genders and all the age groups.     

A comparison of circadian rhythms in work performance between physically active and inactive subjects

This study compared circadian rhythms in physiological, subjective, and performance measures between groups exhibiting different levels of habitual physical activity. Fourteen male subjects, aged 19–29 years, were assigned to a physically active (group I, n=7) or a physically inactive (group II,n= 7) group on the basis of leisure–time physical activity. Rectal temperature, oral temperature, resting pulse rate, subjective arousal and sleepiness were measured at 02:00,06:00, 10:00, 14:00, 18:00 and 22:00 in a counter–balanced sequence for each subject. Whole–body flexibility, back and leg strength, grip strength (right and left), flight time in a vertical jump, PWC₁₅₀ and self–chosen work–rate were also recorded at each time point. At least 8h separated each test session. Subjects avoided exercise 48h prior to, and during the experiment. Data were subjected to the group cosinor method. Group I evidenced 1·5–2·5 times greater rhythm amplitudes than Group II for oral temperature, subjective arousal, sleepiness, flexibility, left and right grip strength, submaximal heart rate, and self–chosen work–rate (p<0·05). Oral temperature and arousal for Group I were lower than Group II only at 06:00. Early morning troughs in most of the performance measures were significantly greater for Group I (p<005). The groups did not differ with respect to phasing of the rhythms (p<005). These results confirm with physical performance measures that rhythm amplitudes are higher for physically fit subjects. This could be attributed to greater early–morning troughs in the measures for active individuals. Since the subjects were sedentary immediately prior to testing, it is plausible that these findings are training effects of physical activity.     

Evaluation of three methodologies to estimate the VO2max in people of different ages

Aging and gender are factors that affect the variation of physical work capacity. The present paper highlights the importance of the metabolism used by ergonomics to establish the appropriate limits of loads at work. This study compares the aerobic capacity of people from 20 to 71 years old split in 5 different groups. The laboratory experiment tested 33 volunteers (19 women and 14 men). A submaximal step test was used to measure the VO₂ using a portable breath by breath metabolic system and a telemetric heart rate monitor. Three methods to estimate the VO_2max were compared: 1) a direct measurement of VO₂, 2) estimation by heart rate, and 3) a step test method using predetermined charts. Significant difference was encountered among the estimation methods as well as among the age ranges (F_2,92 = 6.43, p < 0.05 y F_4,92 = 7.18, p < 0.05 respectively). The method of direct measurement and the method of predetermined charts were different for the estimation of the VO_2max with a confidence level of 95%. The method of predetermined charts is better adapted for males and people younger than 30 years. The estimation through non invasive heart rate apparatus was a good appraiser of the maximal oxygen consumption considering both genders and all the age groups.     

The metabolic consequences of reduced habitual activities in patients with muscle pain and disease

Abstract

Activities of mitochondrial enzymes have been measured in percutaneous muscle biopsies obtained from 23 patients with non-specific muscle pains (e.g. effort syndromes and post-viral fatigue syndromes), in biopsies obtained from eight patients with McArdle's disease (myophosphorylase deficiency), an enzyme defect known to lead to muscle pain during exercise, and, for comparison, in biopsies obtained from 14 untrained controls. Exercise performance was studied during incremental cycle ergometry in six typical patients with non-specific muscle pains and in six patients with McArdle's disease. The patients in general had a lower content of mitochondria in their muscles than the controls. The patients with nonspecific pain studied during cycle ergometry could not exercise at high intensities and showed decreased endurance, tachycardia, a high degree of exercise stress and an increased dependence on glycolysis at low exercise intensities. Many of the biochemical changes during exercise and many of the symptoms of these patients could be a consequence of their reduced habitual activities. The patients with McArdle's disease also could not exercise at high intensities because of their metabolic defect. The most ‘active’ patients had a normal content of mitochondria in their muscles and performed better during cycle ergometry. Furthermore, in contrast to the others they managed to remain successful in their profession. This study appears to suggest that the physical and mental well-being of patients with muscle pain and disease could be improved by the enhancement of their habitual activity.     

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.     

The Aerobic Capacity of Forty British Women Aged 17-27 Years

Maximum oxygen intake ([Vdot] _{o 2}max), lung ventilation, heart rate, skinfolds, haematocrit and haemoglobin concentration were measured in 40 British women aged 17-27 years during 5?min maximum ergometer exercise. Repeatable values were obtained in 2 or 3 attendances. [Vdot] _{o 2}max for 20 subjects preparing for Alpine skiing was 43.3 ml/kg min (range 37.8-50.8 ml/kg min). [Vdot] _{o 2}max for 20 laboratory technicians was 36.5 ml/kg min (range 30.9-42.2 ml/kg min). The variation in [Vdot] _{o 2} max in subjects followed over 6-12 weeks ranged from + 3 to + 30%. The variation in [Vdot] _{o 2} max in 6 skiers followed over 2-6 years ranged from — 10 to +45%. The results are compared with other series on British women and with published results from other countries.     

Older females in the workforce – the effects of age on psychophysical estimates of maximum acceptable lifting loads

Abstract

The number of older workers in the workforce is increasing substantially, and advanced age is associated with factors that could influence musculoskeletal injury risk and work capacity. This study’s goals were to test whether psychophysical estimates of maximum acceptable weight of lift (lift_max) differed between younger and older workers, and to examine potential explanatory factors. Twenty-four female workers (half 50 + years; half 20–32 years) self-adjusted a box’s mass to their perceived lift_max during four lifting tasks. Older workers’ lift_max values were significantly lower (by approximately 24%) than their younger counterparts. There were no age-related differences in resting heart rate, or peak joint angles and final heart rate during the lifting trials. However, the older group demonstrated lower grip strength (by 24%), and lower heart rate reserve during the trials (by 18%). These results question whether current maximum acceptable lifting weights based on psychophysical information are appropriately protective for female workers greater than 50 years of age.

Practitioner Summary: This psychophysical study demonstrated that older female workers (aged 50–63 years) selected maximum acceptable lift masses that were (on average) 24% lower than younger workers (aged 20–32 years), which corresponded with lower grip strength and heart rate reserve. Current maximum acceptable lifting weights based on psychophysical information may not protect female workers greater than 50 years of age.     

A worksite physical activity program and its association with biopsychosocial factors: An intervention study in a footwear factory

ObjectiveThe objective of this study was to evaluate the effect of a worksite physical activity program on psychophysiological and social factors.MethodsA worksite physical activity program included 1113 workers from a footwear factory in northeastern Brazil. The participants were classified based on their frequency of attendance in the program. The dependent variables were psychophysiological factors, including the relief of musculoskeletal pain, the improvement of physical and psychological well-being, perceived difficulty in performing tasks, and willingness to work; and social factors related to interpersonal relationships among employees. The obtained data were processed, and the analysis of the correlations between the variables was modeled using ordinal logistic regression.ResultsThe frequency of physical activity was a determining factor for the effectiveness of the intended outcomes for all analyzed variables. The participants who attended more weekly exercise sessions were twice as likely to experience relief of musculoskeletal pain, 74% more likely to report psychophysiological well-being, 30% less likely to have difficulties in performing tasks, and 87% more likely to perceive improved interpersonal relations.ConclusionsRegular physical activity is associated with consistent benefits for work dynamics and the health status of employees and effectively and rapidly improves the desired outcomes.Relevance to industryWorksite physical activity programs are used as strategies to prevent diseases and address complications caused by exposure to occupational risk factors. However, data on the effects of these interventions that consider the frequency of physical activity and work-related social factors are inconsistent.     

非合作面部晃动情况下的心率检测

目的 心率是直接反映人体健康的重要指标之一,基于视频的非接触式心率检测在医疗健康领域具有广泛的应用前景。然而,现有的基于视频的方法不适用于复杂的现实场景,主要原因是没有考虑视频中目标晃动干扰和空间尺度特征,使得血液容积脉冲信号提取不准确,检测精度不尽人意。为了克服以上缺陷,提出一种抗人脸晃动干扰的非接触式心率检测方法。方法 本文方法主要包含3个步骤：首先,针对目标晃动干扰人脸区域选择的问题,利用判别响应图拟合检测参考图像的人脸区域及主要器官特征点,在人脸跟踪时首次引入倾斜校正思想,输出晃动干扰抑制后的人脸视频;然后,结合空间尺度的差异,采用颜色放大方法对晃动干扰抑制后的人脸视频进行时空处理,提取干净的血液容积脉冲信号;最后,考虑到小样本问题,通过傅里叶系数迭代插值的频域分析方法估计心率。结果 在人脸静止的合作情况以及人脸晃动的非合作情况下采集视频,对心率检测结果进行定量分析,本文方法在两种情况下的准确率分别为97.84%和97.30%,与经典和最新的方法相比,合作情况准确率提升大于1%,非合作情况准确率提升大于7%,表现了出色的性能。结论 提出了一种基于人脸视频处理的心率检测方法,通过有效分析人脸的晃动干扰和尺度特性,提取到干净的血液容积脉冲信号,提高了心率检测的精度和鲁棒性。     

Initial training as a stimulus for optimal physical fitness in firemen

Abstract

In this investigation the physical fitness of 34 recruits to the UK Fire Service was assessed before and after their initial training (tests 1–2) and on three occasions (tests 3–5) during the first 18 months of their service (n=34+6=40). The initial training (test 2-test 1) resulted in an increase in maximum aerobic power (11% p<0·05), body mass (2 kg, p<0·001), lean body mass (2·02 kg, p<0·001), grip and lifting strengths (/><0·001), and in calf girth (p<0·05). But no change in waist girth, maximum anaerobic power or measures of lung function was noted. There was evidence therefore that the men became physically fitter. In the first eighteen months of their service, subjects' maximum oxygen consumption declined to pre-training levels, while body mass continued to increase with a decrease in lean body mass (p<0·001). Strength remained unaltered or tended to fall with a decrease in calf girth (p<0·05). These changes reflected a return towards pre-training physical fitness levels. It is suggested that the initial training, while ill-matched to the firemen's habitual activity, produced levels of physical fitness which may approximate more closely to the infrequent peak requirements experienced by the men during actual fire fighting. Consequently it is concluded that the physical training during service was insufficiently intense and that a more effective programme could be designed to maintain an appropriate level of physical fitness     

Spinal loading in static and dynamic postures: EMG and intra-abdominal pressure study

Abstract

The difference in physiological stress between static posture loading and dynamic lift is poorly understood. Therefore, the quantitative pattern of gradual increase and decrease of stress as measured by EMG of erectores spinae at T₁₂ and L₃ and intraabdominal pressure (IAP) due to steady progressive loading and unloading in static stooping posture was studied and compared with that of stoop lifting of the same weight. For dynamic loading and unloading a steady flow of 25 kg of water into or out of a plastic tub held in the hand while maintaining a stooping posture was used. The subjects also performed stoop lifting weights of 15 and 25 kg. In static posture loading the mean EMG at T₁₂ was approximately 50% of the L₃ level. During unloading in that posture it was reduced to 33%. The level of electromyographic activity at T₁₂ for loading was not significantly different from unloading. At L₃ however, the magnitude increased significantly for unloading. The EMG and intraabdominal pressure responses of static posture were between 33 and 50% of the corresponding phases during stoop lifting of the same weight. An insignificant difference in IAP and heart rate between static posture loading and stoop lifting indicates a less critical role of IAP and no difference in cardiac stress in less stressful tasks.     

Reducing the physical work load and strain of personal helpers through clothing redesign

This study assessed the effects of redesigning clients’ clothing on the physical work load and strain of personal helpers. Five women, aged 18–54 years, who helped persons with physical disabilities were measured at their worksites before and after development of the clothes worn by clients. The physical work load and strain of the helpers’ dressing/undressing of clients were determined from their hand and back movements, work time, muscular activity, heart rate (HR), percentage of heart rate range (%HRR), and rating of perceived exertion (RPE). The muscular activity of the right (p=0.05) and left (p=0.02) trapezius muscles, HR (p=0.03), and %HRR (p=0.03) of the helpers were lower when the new outerwear was used in place of traditional outerwear. Four helpers reported lower perceived exertion, and three had shorter work time with the new outerwear. This study showed that redesigning clients’ clothing can help reduce the physical work load and strain of personal helpers.     

Validation and adjustment of the mathematical prediction model for human rectal temperature responses to outdoor environmental conditions

Abstract

Models to predict rectal temperature (T_re ) have been based on indoor laboratory studies. The present study was conducted to validate and adjust a previously suggested model for outdoor environmental conditions. Four groups of young male volunteers were exposed to three different climatic conditions (30°C, 65% rh; 31°C, 41% rh; 40°C, 20% rh). They were tested both in shaded and open field areas (radiation: 80 and 900 W-m^?2, respectively) at different work loads (100, 300 and 450 watt). Exercise consisted of two bouts of 10 minutes rest and 50 minutes walking on a treadmill, at a constant speed (1.4m ? s^?1) and different grades. The subjects were tested wearing cotton fatigues and protective garments. Their T_re and heart rate were monitored every 5 min and skin temperature every 15 min, oxygen uptake was measured towards the end of each bout of exercise; concomitantly, ambient temperature, relative humidity and solar load were monitored. We concluded that: (a) the corrected model to predict rectal temperature overestimates the actual measurements when applied outdoors; ( b) radiative and convective heat exchanges should be considered separately when using the model outdoors; ( c) radiative heat exchange should also be considered separately for short-wave radiation (solar radiation) and long-wave emission from the body to the atmosphere. Finally, an adjusted model to be used outdoors was suggested.     

Walking Works Wonders: a tailored workplace intervention evaluated over 24 months

This article presents longitudinal data from 1120 participants across 10 worksites enrolled in Walking Works Wonders, a tailored intervention designed to increase physical activity and reduce sedentary behaviour. The intervention was evaluated over 2 years, using a quasi-experimental design comprising 3 conditions: tailored information; standard information and control. This study explored the impact of the intervention on objective measures (BMI, %Fat, waist circumference, blood pressure and heart rate) and self-reported measures of physical activity, sedentary behaviour, physical and psychological health. Interventions tailored to employees’ stage of change significantly reduced BMI and waist circumference compared to standard and control conditions. Employees who received either a standard or tailored intervention demonstrated significantly higher work ability, organizational commitment, job motivation, job satisfaction and a reduction in intention to quit the organization. The results suggest that adopting a tailored approach to interventions is particularly effective in terms of improving health in the workplace.

Practitioner Summary: This study describes Walking Works Wonders, a tailored intervention, which aims to encourage physical activity in the workplace. The study evaluated Walking Works Wonders over a 2 year period and demonstrated that interventions are more effective in improving health outcomes where the information is tailored to employees’ stage of change.     

Analysis on the variations of atmospheric CO2 concentrations along the urban–rural gradients of Chinese cities based on the OCO-2 XCO2 data

Anthropogenic CO₂ emissions contribute the most to the growth of atmospheric CO₂ concentrations. These emissions are largely concentrated in urban areas where human activities are intense. Studies have been conducted to explore the urban and rural difference in CO₂ concentrations based on ground-based measurements. The launch of NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite provides a new opportunity to monitor CO₂ concentrations and their spatial and temporal variations at city scale. The objective of this study is to analyse the spatial and temporal distributions of CO₂ concentrations along the urban–rural gradients of Chinese cities, using the column averaged CO₂ dry air mole fraction (XCO₂) data derived from OCO-2. We used both conceptual and physical urban–rural gradients to analyse variations in CO₂ concentrations over space. The results show that the urban and rural difference in CO₂ concentrations of these cities can be monitored. And, the seasonal variations of CO₂ concentrations in these cities can also be detected using the XCO₂ data. Moreover, the variations in CO₂ concentrations along the urban–rural gradients have four main types with significant enhancements of CO₂ concentrations were observed in urban areas, urban–rural transitional areas, rural areas, and without regular patterns, respectively. The results are generally different from the common assumption that CO₂ concentrations peak in central urban areas and decline in rural areas. In conclusion, the XCO₂ data can be used to analyse the spatial-temporal variations of CO₂ concentrations along the urban–rural gradients of Chinese cities, and the results have important policy implications for mitigating CO₂ emissions.     

Comparison of swimming with running as training stimuli

Abstract

The cardiovascular training effect was compared between swimming and running. Twenty-two healthy young adult women trained for 6 weeks either swimming or running with the same frequency,.duration and intensity (as judged by heart rate). Both groups showed significant improvement in cardiovascular fitness after training, assessed on a bicycle ergometer, with no significant difference between the two groups before or after training.     

The physical and physiological workload of refuse collectors

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (F_max) and the maximal aerobic power( [Vdot]O_2max of 23 refuse collectors were measured in the laboratory. F_max was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (± 127)N. VO_2max was measured running on a treadmill; the mean value was 43-3 (±0-8) ml O₂ per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fm? and a mean energy expenditure of 30% VO_2max and an energy expenditure of 50% VO_2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.     

Physical,mental, emotional,and subjective workload components in train drivers

This study, using 12 train drivers on a high speed track and 11 drivers on a mountain track, tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work. With the simultaneous recording and on-line analysis of heart rate and physical activity, the emotional component in terms of the so-called additional heart rate was separated from the physical component. Mental workload was calculated by the heart rate variability and by shifts in the T-wave amplitude of the ECG. Speed of the train, mode of driving, and stress of the situation were rated by two observers who accompanied the drivers in the cabin. During speeds up to l00km/h as compared to standstills no heart rate changes occurred, but with speeds from l00km/h up to 200 km/h heart rate decreased indicating a monotony effect. However, heart rate variability, and T-wave amplitude indicated higher mental load during driving in most speed categories. Starting the train and coming to a halt showed greater emotional workload as compared to moving. Observer ratings of stress and subjective ratings of stress by the drivers revealed several discrepancies. Discrepancies were also seen between workload as indicated by the physiological parameters, and corresponding stress ratings by the observers or by the drivers.