Comparison of incremental and steady state tests of endurance training

To compare the results obtained by incremental or constant work load exercises in the evaluation of endurance conditioning, a 20-week training programme was performed by 9 healthy human subjects on the bicycle ergometer for 1 h a day, 4 days a week, at 70-80% VO2max. Before and at the end of the training programme, (1) the blood lactate response to a progressive incremental exercise (18 W increments every 2nd min until exhaustion) was used to determine the aerobic and anaerobic thresholds (AeT and AnT respectively). On a different day, (2) blood lactate concentrations were measured during two sessions of constant work load exercises of 20 min duration corresponding to the relative intensities of AeT (1st session) and AnT (2nd session) levels obtained before training. A muscle biopsy was obtained from vastus lateralis at the end of these sessions to determine muscle lactate. AeT and AnT, when expressed as % VO2max, increased with training by 17% (p less than 0.01) and 9% (p less than 0.05) respectively. Constant workload exercise performed at AeT intensity was linked before training (60% VO2max) to a blood lactate steady state (4.8 +/- 1.4 mmol.l-1) whereas, after training, AeT intensity (73% VO2max) led to a blood lactate accumulation of up to 6.6 +/- 1.7 mmol.l-1 without significant modification of muscle lactate (7.6 +/- 3.1 and 8.2 +/- 2.8 mmol.kg-1 wet weight respectively). It is concluded that increase in AeT with training may reflect transient changes linked to lower early blood lactate accumulation during incremental exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sleep and Sleepiness of Fishermen on Rotating Schedules

Seafaring is a hazardous occupation with high death and injury rates, but the role of seafarer fatigue in these events is generally not well documented. The International Maritime Organization has identified seafarer fatigue as an important health and safety issue. Most research to date has focused on more regularly scheduled types of operations (e.g., merchant vessels, ferries), but there is relatively little information on commercial fishing, which often involves high day‐to‐day and seasonal variability in work patterns and workload. The present study was designed to monitor the sleep and sleepiness of commercial fishermen at home and during extended periods at sea during the peak of the hoki fishing season, with a view to developing better fatigue management strategies for this workforce. Sleep (wrist actigraphy and sleep diaries) and sleepiness (Karolinska Sleepiness Scale [KSS] before and after each sleep period) of 20 deckhands were monitored for 4–13 days at home and for 5–9 days at sea while working a nominal 12 h on/6 h off schedule. On the 12 h on/6 h off schedule, there was still a clear preference for sleep at night. Comparing the last three days at home and the first three days at sea showed that fishermen were more likely to have split sleep at sea (Wilcoxon signed ranks p<0.001), but the median sleep/24 h did not differ significantly by location (5.9 h at sea vs. 6.7 h at home). However, on 23% of days at sea, fishermen obtained<4 h total sleep/24 h, compared to 3% of days at home (p(χ²)<0.01). Sleep efficiency, mean activity counts/min sleep, and subjective ratings of sleep quality did not differ significantly between the last three days at home and the first three days at sea. However, sleepiness ratings remained higher after sleep at sea (Wilcoxon signed ranks p<0.05), with fishermen having post‐sleep KSS ratings ≥7 on 24% of days at sea vs. 9% of days at home (Wilcoxon signed ranks p<0.01). This work adds to the limited number of studies that objectively monitored the sleep of seafarers. It has the strength of operational fidelity but the weakness that large inter‐ and intra‐individual variability in sleep, combined with the small sample size, limited the power of the study to detect statistically significant differences between sleep at home and at sea. The clear preference for sleep at night during the 12 h on/6 h off schedule at sea is consistent with the expectation that this 18 h duty/rest cycle is outside the range of entrainment of the circadian pacemaker. High levels of acute sleep loss, and residual sleepiness after sleep, were much more common at sea than at home. The longer duration of trips during the peak of the fishing season increases the risk of performance impairment due to greater cumulative sleep loss than would be expected on typical three‐day trips. Key fatigue management strategies in this environment include that fishermen report to work as well rested as possible. Once at sea, the day‐to‐day variability in activities due to uncontrollable factors, such as fishing success, repairing gear, and weather conditions, mean that contingency planning is required for managing situations where the entire crew have experienced long periods of intensive work with minimum recovery opportunities.     

某大型综合医院护理人力资源配置研究

?????? 目的 从目前护理人员承担的工作量出发,探讨临床科室护理人员配置理想床护比,为医院护理人力配置提供依据。方法 以工作量测算法作为核心研究方法,采用工现场观察法对西安市某大型综合医院42个临床科室护士的工作量进行测算,并使用Excel、SPSS17.0统计软件进行公式运算和统计分析。结果 （1）临床科室护理人员的工作时间超过标准工作时间6小时;（2）所调研科室现有床护比仅为1: 0.46,缺编41.50%;（3）依据目前的工作量需要,内科病房的床护比应为1:0.62,外科病房床护比应为1:0.63,监护科室为1:2.08,平均床护比1:0.78。结论 临床科室医师人员配备亟待补充,医院应根据实际工作量进行合理测算后配置护理人员,通过工时测定提出了的理想床护比可为其他医院提供参考。     

When mental fatigue maybe characterized by Event Related Potential (P300) during virtual wheelchair navigation

The goal of this study is to investigate the influence of mental fatigue on the event related potential P300 features (maximum pick, minimum amplitude, latency and period) during virtual wheelchair navigation. For this purpose, an experimental environment was set up based on customizable environmental parameters (luminosity, number of obstacles and obstacles velocities). A correlation study between P300 and fatigue ratings was conducted. Finally, the best correlated features supplied three classification algorithms which are MLP (Multi Layer Perceptron), Linear Discriminate Analysis and Support Vector Machine. The results showed that the maximum feature over visual and temporal regions as well as period feature over frontal, fronto-central and visual regions were correlated with mental fatigue levels. In the other hand, minimum amplitude and latency features didn’t show any correlation. Among classification techniques, MLP showed the best performance although the differences between classification techniques are minimal. Those findings can help us in order to design suitable mental fatigue based wheelchair control.     

Individual variation in parental workload and breeding productivity in female European starlings: is the effort worth it?

We analyzed individual variation in work load (nest visit rate) during chick‐rearing, and the consequences of this variation in terms of breeding productivity, in a highly synchronous breeder, the European starling (Sturnus vulgaris) focusing on female birds. There was marked (10‐ to 16‐fold) variation in total, female and male nest visit rates, among individuals, but individual variation in female nest visit rate was independent of environment (rainfall, temperature) and metrics of individual quality (laying date, clutch size, amount of male provisioning help), and was only weakly associated with chick demand (i.e., day 6 brood size). Female nest visit rate was independent of date and experimentally delayed birds provisioned at the same rate as peak‐nesting birds; supporting a lack of effect of date per se. Brood size at fledging was positively but weakly related to total nest visit rate (male + female), with >fivefold variation in nest visit rate for any given brood size, and in females brood size at fledging and chick mass at fledging were independent of female nest visit rate, that is, individual variation in workload was not associated with higher productivity. Nevertheless, nest visit rate in females was repeatable among consecutive days (6–8 posthatching), and between peak (first) and second broods, but not among years. Our data suggest that individual females behave as if committed to a certain level of parental care at the outset of their annual breeding attempt, but this varies among years, that is, behavior is not fixed throughout an individual's life but represents an annually variable decision. We suggest females are making predictable decisions about their workload during provisioning that maximizes their overall fitness based on an integration of information on their current environment (although these cues currently remain unidentified).     

A plasma global metabolic profiling approach applied to an exercise study monitoring the effects of glucose, galactose and fructose drinks during post-exercise recovery

A global metabolic profiling methodology based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) for human plasma was applied to a human exercise study focused on the effects of beverages containing glucose, galactose, or fructose taken after exercise and throughout a recovery period of 6 h and 45 min. One group of 10 well trained male cyclists performed 3 experimental sessions on separate days (randomized, single center). After performing a standardized depletion protocol on a bicycle, subjects consumed one of three different beverages: maltodextrin (MD)+glucose (2:1 ratio), MD+galactose (2:1), and MD+fructose (2:1), consumed at an average of ～1.25 g of carbohydrate (CHO) ingested per minute. Blood was taken straight after exercise and every 45 min within the recovery phase. With the resulting blood plasma, insulin, free fatty acid (FFA) profile, glucose, and GC-TOFMS global metabolic profiling measurements were performed. The resulting profiling data was able to match the results obtained from the other clinical measurements with the addition of being able to follow many different metabolites throughout the recovery period. The data quality was assessed, with all the labelled internal standards yielding values of <15% CV for all samples (n=335), apart from the labelled sucrose which gave a value of 15.19%. Differences between recovery treatments including the appearance of galactonic acid from the galactose based beverage were also highlighted.     

A Comparison of Two Recorders for Obtaining In-flight Heart Rate Data

Measurement of mental workload has been widely used for evaluation of aircraft design, mission analysis and assessment of pilot performance during flight operations. Heart rate is the psychophysiological measure that has been most frequently used for this purpose. The risk of interference with flight safety and pilot performance, as well as the generally constrained access to flights, make it difficult for researchers to collect in-flight heart rate data. Thus, this study was carried out to investigate whether small, non-intrusive sports recorders can be used for in-flight data collection for research purposes. Data was collected from real and simulated flights with student pilots using the Polar Team System sports recorder and the Vitaport II, a clinical and research recording device. Comparison of the data shows that in-flight heart rate data from the smaller and less intrusive sports recorder have a correlation of.981 with that from the clinical recorder, thus indicating that the sports recorder is reliable and cost-effective for obtaining heart rate data for many research situations.     

Determination of the cost of worker reproduction via diminished life span in the ant Diacamma sp

Workers of social Hymenoptera can usually produce male offspring, but rarely do so in the presence of a queen despite the potential individual fitness benefit. Various mechanisms have been hypothesized to regulate worker reproduction, including avoiding the colony-level cost of worker reproduction. However, firm quantitative evidence is lacking to support that hypothesis. Here, we accurately quantified this cost by studying an ant species (Diacamma sp.) in which worker reproduction is rare in the presence of the gamergate (the functional queen). A series of experiments to manipulate worker-gamergate contact revealed that short-term brood-production efficiency is not changed by the presence of worker reproduction. However, when workers reproduce, their average life span is reduced to between 74% and 88% of that in the absence of reproduction, indicating a long-term cost to the colony. In theory, this cost can explain the policing of worker reproduction under a queen-single mating system, but the cost does not appear to be high enough to stop worker reproduction. When contact with the gamergate is lost, it is only the nonreproductive workers whose life span was reduced; the reproductive workers lived as long as nonorphaned workers. We suggest that an increased workload can account for the reduction in life span better than a trade-off between reproduction and longevity.     

Efficiency and demographics of a high-yield dairy ewe farm with two managing systems involving five or 10 lambings per year

This study assessed milk productivity, demographic characteristics and workload distribution on a single high-yield dairy ewe farm in Spain (Avila, Spain; continental climate, latitude of 40.90 N, altitude of 900 m) over a 7-year period considering a transition from a herd management system involving five lambings per year (5LY) to a system involving 10 lambings per year (10LY). The 5LY system was practiced on the farm from 2010 to 2012 and the 10LY system from 2014 to 2015, with 2009 and 2013 being considered transition years. During this period, 27 415 lactations were recorded from an average of 3746 Lacaune sheep/year. Several productivity parameters were higher in 2014 to 2015 than in 2010 to 2012: milk yield/lactation (370±156 v. 349±185 l), lactation length (218±75 v. 192±75 days) and dry period length (53.5±38.3 v. 69.1±34.8 days) (all P<0.0001). During 2014 to 2015, investment in new lambing facilities was possible, workload was distributed more uniformly throughout the year, workload per worker was smaller, rate of ewe culling was lower (35.39±0.53% v. 42.51±7.51%), ewe longevity was greater and higher-order lactations were more numerous (P<0.0001). On the other hand, during 2010 to 2012, daily production was higher (1.73±1.66 v. 1.70±0.62 l/day; P=0.038), the interlambing period was shorter (283±50 v. 302±44 days; P<0.0001) and lambings/ewe per year were greater (1.42±0.01 v. 1.30±0.01; P<0.05). These results suggest that a 10LY herd management system can be compatible with profitability, productivity and good animal and worker’s welfare on a high-yield dairy farm, and may even be associated with better outcomes than a 5LY system.     

运动负荷对青年学生和运动员心脏功能的影响

用无创法(阻抗法)测量了40名青年学生和40名运动员在两种运动负荷(50W和150W)运动前、运动后即刻和恢复时程的收缩时间间期(STI)和心率(HR)。在静态时,“运动员组”的心率较缓(P<0.01)、QS_1较长(P<0.05)、PEP/LVET比值较大(P<0.05和P<0.01)、LVETc较短(P<0.001)。运动后即刻,“学生组”和“运动员组”都表现为QS_z、LVET、PEP、IVCT、QS_1缩短、PEP/LVET比值减小、心率增速和LVETc延长。但“运动员组”QS_2、LYET的缩短和心率增速的程度较少,而PEP/LVET比值的减小和LVETc延长的程度较大。除PEP/LVET比值外,其余各项指标的恢复速度均与负荷量有关。“运动员组”的恢复速度较快,尤其在150W时更为明显。本文指出:1)用阻抗法测算动态下的STI更为实用;2)系统训练可提高心脏活动的潜力,改善泵功能,促进心脏活动的调节速度。