External Workload Research Articles

Institution of Veno-arterial Extracorporeal Membrane Oxygenation Does Not Lead to Increased Wall Stress in Patients with Impaired Myocardial Function.

The effect of veno-arterial extracorporeal membrane oxygenation (VA ECMO) on wall stress in patients with cardiomyopathy, myocarditis, or other cardiac conditions is unknown. We set out to determine the circumferential and meridional wall stress (WS) in patients with systemic left ventricles before and during VA ECMO. We established a cohort of patients with impaired myocardial function who underwent VA ECMO therapy from January 2000 to November 2013. Demographic and clinical data were collected and inotropic score calculated. Measurements were taken on echocardiograms prior to the initiation of VA ECMO and while on full-flow VA ECMO, in order to derive wall stress (circumferential and meridional), VCFc, ejection fraction, and fractional shortening. A post hoc sub-analysis was conducted, separating those with pulmonary hypertension (PH) and those with impaired systemic output. Thirty-three patients met inclusion criteria. The patients' median age was 0.06years (range 0-18.7). Eleven (33%) patients constituted the organ failure group (Gr2), while the remaining 22 (66%) patients survived to discharge (Gr1). WS and all other echocardiographic measures were not different when comparing patients before and during VA ECMO. Ejection and shortening fraction, WS, and VCFc were not statistically different comparing the survival and organ failure groups. The patients' position on the VCFc-WS curve did not change after the initiation of VA ECMO. Those with PH had decreased WS as well as increased EF after ECMO initiation, while those with impaired systemic output showed no difference in those parameters with initiation of ECMO. The external workload on the myocardium as indicated by WS is unchanged by the institution of VA ECMO support. Furthermore, echocardiographic measures of cardiac function do not reflect the changes in ventricular performance inherent to VA ECMO support. These findings are informative for the interpretation of echocardiograms in the setting of VA ECMO. ECMO may improve ventricular mechanics in those with PH as the primary diagnosis.

Calculating acute:chronic workload ratios using exponentially weighted moving averages provides a more sensitive indicator of injury likelihood than rolling averages

ObjectiveTo determine if any differences exist between the rolling averages and exponentially weighted moving averages (EWMA) models of acute:chronic workload ratio (ACWR) calculation and subsequent injury risk.MethodsA cohort of 59...

Quantification of Training and Competition Loads in Endurance Sports: Methods and Applications.

Training quantification is basic to evaluate an endurance athlete's responses to training loads, ensure adequate stress/recovery balance, and determine the relationship between training and performance. Quantifying both external and internal workload is important, because external workload does not measure the biological stress imposed by the exercise sessions. Generally used quantification methods include retrospective questionnaires, diaries, direct observation, and physiological monitoring, often based on the measurement of oxygen uptake, heart rate, and blood lactate concentration. Other methods in use in endurance sports include speed measurement and the measurement of power output, made possible by recent technological advances such as power meters in cycling and triathlon. Among subjective methods of quantification, rating of perceived exertion stands out because of its wide use. Concurrent assessments of the various quantification methods allow researchers and practitioners to evaluate stress/recovery balance, adjust individual training programs, and determine the relationships between external load, internal load, and athletes' performance. This brief review summarizes the most relevant external- and internal-workload-quantification methods in endurance sports and provides practical examples of their implementation to adjust the training programs of elite athletes in accordance with their individualized stress/recovery balance.

Within-Season Distribution of External Training and Racing Workload in Professional Male Road Cyclists.

To describe the within-season external workloads of professional male road cyclists for optimal training prescription. Training and racing of 4 international competitive professional male cyclists (age 24 ± 2 y, body mass 77.6 ± 1.5 kg) were monitored for 12 mo before the world team-time-trial championships. Three within-season phases leading up to the team-time-trial world championships on September 20, 2015, were defined as phase 1 (Oct-Jan), phase 2 (Feb-May), and phase 3 (June-Sept). Distance and time were compared between training and racing days and over each of the various phases. Times spent in absolute (<100, 100-300, 400-500, >500 W) and relative (0-1.9, 2.0-4.9, 5.0-7.9, >8 W/kg) power zones were also compared for the whole season and between phases 1-3. Total distance (3859 ± 959 vs 10911 ± 620 km) and time (240.5 ± 37.5 vs 337.5 ± 26 h) were lower (P < .01) in phase 1 than phase 2. Total distance decreased (P < .01) from phase 2 to phase 3 (10911 ± 620 vs 8411 ± 1399 km, respectively). Mean absolute (236 ± 12.1 vs 197 ± 3 W) and relative (3.1 ± 0 vs 2.5 ± 0 W/kg) power output were higher (P < .05) during racing than training, respectively. Volume and intensity differed between training and racing over each of 3 distinct within-season phases.

Evaluation of the horizontal movement distance of elite female beach volleyball players during an official match

The purpose of this study was to evaluate distances and durations of horizontal movement of elite female beach volleyball players during matches. Four teams (n: 8; age: 28.6±5.8 years; height: 178.1±5.7 cm; body mass: 66.5±5.3 kg; mean±SD, respectively) were analysed by 3D kinematic analysis. 106 rallies (368 distances) were analysed. The average duration of a rally was 7.27±3.4 s. 83.7% of rallies lasted less than 10 s (63% lasted between 4 and 8 s and 27 % lasted longer than 8 s). The average distance of horizontal movement in all rallies was 9.39±5.67 m (in one set it was 287.5±19.7 m). 45.7% of measured distances ranged between 5 and 10 m. In total, 85.3% of distances measured less than 15 m, 14.7% measured more than 15 m. The field position of players (blockers and diggers) did not affect the covered distance during the game (t366 = 0.73, p = 0.47). Evaluation of player movement during performance is beneficial for assessing the crucial part of external workload and provides feedback in terms of tactical and conditional preparation. Results yielded information about external load and movements during the match.

External Match Workloads During the First Week of Australian Open Tennis Competition.

With a view to informing athlete preparation leading into tournament play, this study examined external hitting and movement workloads during the first week of the 2012-2016 Australian Open tournaments. Using Hawk-Eye, on-court movement and stroke data were captured for 39 players (21 women, 18 men) during the first 4 rounds of singles competition. Hitting and movement workloads were compared between sexes and rounds of competition. On average, men traversed approximately 4 km greater distance and hit 785 more shots than women hit across the first 4 rounds of the Australian Open. Women hit significantly more first serves, forehand returns, and backhand groundstrokes per game than men did. Total distance covered per game did not exhibit a significant sex effect, although men covered a significantly greater proportion of that distance at speeds greater than 3 m/s. Game-level hitting and movement workloads, and effective playing time, increased significantly between rounds 1 and 4 of the tournament in both sexes. When preparing athletes for competition, tennis practitioners should be aware that men may need to withstand aggregated hitting and movement (specifically, high-speed exertion) workloads that are 52% and up to 281% greater than women, respectively. Moreover, the evidence demonstrated that these workloads increased as players progressed deeper into the tournament. These novel insights can be used to improve the specificity of training prescription and physical-testing protocols in professional tennis.

Effects of Continuous and Interval Training on Running Economy, Maximal Aerobic Speed and Gait Kinematics in Recreational Runners.

The purpose of this study was to evaluate the effects on running economy (RE), V[Combining Dot Above]O2max, maximal aerobic speed (MAS), and gait kinematics (step length [SL] and frequency, flight and contact time [CT]) in recreational athletes, with 2 different training methods, Interval and Continuous (CON). Eleven participants were randomly distributed in an interval training group (INT; n = 6) or CON training group (CON; n = 5). Interval training and CON performed 2 different training programs (95-110% and 70-75% of MAS, respectively), which consisted of 3 sessions per week during 6 weeks with the same external workload (%MAS × duration). An incremental test to exhaustion was performed to obtain V[Combining Dot Above]O2max, MAS, RE, and gait variables (high speed camera) before and after the training intervention. There was a significant improvement (p ≤ 0.05) in RE at 60 and 90% of MAS by the CON group; without changes in gait. The INT group significantly increased MAS and higher stride length at 80, 90, and 100% of MAS and lower CT at 100% of MAS. As expected, training adaptations are highly specific to the overload applied with CON producing improvements in RE at lower percentage of MAS whereas INT produces improvements in MAS. The significantly increased stride length and decreased CT for the INT group are an important outcome of favorable changes in running gait.

Aerobic Fitness Modulates Whole‐body Heat Loss Responses in Young Adult Males during Exercise in Hot Dry Conditions

It is well established that aerobic fitness (as defined by peak oxygen uptake) improves the body's ability to dissipate heat during exercise in hot conditions. However, it currently remains unclear at what level of heat stress differences in aerobic fitness may alter the body's physiological capacity to dissipate heat. Therefore, in this pilot work, we examined whole‐body heat loss using direct calorimetry in endurance (n=4, 63.5±1.5 mlO2/kg/min) and non‐endurance trained (n=4; 37.3±0.3 mlO2/kg/min, P=0.002) healthy young adult males (22±4 years) matched for body surface area (endurance: 1.89±0.14; non‐endurance: 1.87±0.16 m2, P=0.104). Participants performed three 30‐min bouts of semi‐recumbent cycling at fixed rates of metabolic heat production equal to 300 (Ex1), 400 (Ex2), and 500 W (Ex3) (an equivalent external workload of approximately 45, 75 and 100 W, respectively), each separated by a 15‐min recovery period in dry heat (40°C, 14% relative humidity). These fixed rates of heat production were employed to ensure a similar stimulus for whole‐body sweating. The rates of whole‐body heat loss (evaporative heat loss and dry heat exchange) and metabolic heat production were measured by direct and indirect calorimetry, respectively. Whole‐body heat content was measured as the cumulative summation of heat production and heat loss. We show that the rate of dry heat gain (i.e., from the environment), and therefore the net heat load (i.e., metabolic heat production plus dry heat gain), was similar between groups throughout the intermittent exercise protocol (Ex1, Ex2, Ex3, all P≥0.207). Although not statistically significant at all exercise bouts, the rate of whole‐body evaporative heat loss tended to be lower in the non‐endurance males during Ex1 (non‐endurance: 357±17 vs. endurance: 378±9 W, P=0.047), Ex2 (non‐endurance: 438±17 vs. endurance: 481±18 W, P=0.059), and Ex3 (non‐endurance: 513±29 vs. endurance: 573±26 W, P=0.113) compared to their endurance trained counterparts. Consequently, whole‐body heat content trended towards being greater in the non‐endurance group during Ex1 (non‐endurance: 127±50 vs. 112±36 kJ, P=0.163), Ex2 (non‐endurance: 138±38 vs. 86±25 kJ, P=0.038), and Ex3 (non‐endurance: 227±47 vs. 157±34 kJ, P=0.122) relative to the endurance trained group. Our early findings demonstrate that aerobic fitness may modulate the body's physiological capacity to dissipate heat at metabolic heat loads ≥300 W in young adult males differing in peak oxygen uptake by as much as ~26 mlO2/kg/min. Therefore, our data supports that maintaining a high level of aerobic fitness may facilitate an enhanced capacity to dissipate heat and thereby minimize the incidence of experiencing heat related illness during exercise in the heat.Support or Funding InformationThis study was supported by grants from the Natural Sciences and Engineering Research Council of Canada (Discover grant, RGPIN‐06313‐2014; Discovery Grants Program ‐ Accelerator Supplement, RGPAS‐462252‐2014; funds held by Dr. Glen P. Kenny).

Influence of Yo-Yo IR2 Scores on Internal and External Workloads and Fatigue Responses of Tag Football Players during Tournament Competition.

The purpose of this study was to: a) identify changes in jump height and perceived well-being as indirect markers of fatigue, b) determine the internal and external workloads performed by players, and c) examine the influence of Yo-Yo IR2 on changes in jump height, perceived well-being and internal and external workloads during a tag football tournament. Microtechnology devices combined with heart rate (HR) chest straps provided external and internal measures of match work-rate and workload for twelve male tag football players during the 2014 Australian National Championships. Jump height and perceived well-being were assessed prior to and during the tournament as indirect measures of fatigue. Changes in work-rate, workload and fatigue measures between high- and low-fitness groups were examined based on players’ Yo-Yo IR2 score using a median split technique. The low- and high-fitness groups reported similar mean HR, PlayerloadTM/min, and distance/min for matches, however the low-fitness group reported higher perceived match-intensities (ES = 0.90–1.35) for several matches. Further, the high-fitness group reported higher measures of tournament workload, including distance (ES = 0.71), PlayerloadTM (ES = 0.85) and Edwards’ training impulse (TRIMP) (ES = 1.23) than the low-fitness group. High- and low-fitness groups both showed large decreases (ES = 1.46–1.49) in perceived well-being during the tournament, although jump height did not decrease below pre-tournament values. Increased Yo-Yo IR2 appears to offer a protective effect against player fatigue despite increased workloads during a tag football tournament. It is vital that training programs adequately prepare tag football players for tournament competition to maximise performance and minimise player fatigue.

Heart Rate, Time-Motion, and Body Impacts When Changing the Number of Teammates and Opponents in Soccer Small-Sided Games.

The purpose of this study was to determine the internal (heart rate) and external load (body load, distance covered, and exertion index) during different types of unbalanced soccer small-sided games (SSGs) in professional (PRO) and amateur (AMA) players. In 2 separated sessions (PRO and AMA), participants played 3 SSG formats (4vs3, 4vs5, and 4v7). Data were analyzed from the fixed team's perspective (4vsX) according to the number of opponents (3, 5 and 7) and from the variable team (3 + Xvs4) according to the teammates (without teammates, 2 and 4 teammates). The time-motion and body impact data were collected using a nondifferential global positioning system with integrated heart rate measurement. Differences in internal and external workload between the game formats were compared using Cohen's dunb effect sizes with 95% confidence intervals. Results reveal that the higher the number of players involved in the task, the lower the internal and external workload. The analysis also showed different teammates and opposition-related trends that need to be considered when planning and monitoring training performance. Playing in low-inferiority (4vs3 and 4vs5) had higher physiologic impact to players than the other higher unbalanced situations. This evidence was similar to both PRO and AMA players; however, the PRO presented higher physical and lower physiological responses across games. Our results suggest that coaches should consider the usage of unbalanced SSG formats to simultaneously facilitate the emergence of defensive and offensive proficient scenarios also representing opportunities to increase the practice workload.

The influence of body morphology on changes in core temperature during exercise in an uncompensable environment

Evidence demonstrates that for unbiased comparisons of changes in core temperature (ΔTcore) between groups unmatched for body morphology, exercise should be performed using a fixed heat production (Hprod) per unit mass in physiologically compensable environments [1]. In uncompensable conditions, it has been suggested that a fixed external workload is the primary determinant of ΔTcore [2], however in addition to not accounting for differences in Hprod relative to mass, such an approach excludes the influence of differences the surface area-to-mass ratio on the absolute maximum rate of evaporative heat loss (Emax). We examined the best method for performing unbiased comparisons of ΔTcore between groups unmatched for body morphology during exercise in an uncompensable environment.

Celebrating diversity: a mixture of experts approach for runtime mapping in dynamic environments

Matching program parallelism to platform parallelism using thread selection is difficult when the environment and available resources dynamically change. Existing compiler or runtime approaches are typically based on a one-size fits all policy. There is little ability to either evaluate or adapt the policy when encountering new external workloads or hardware resources. This paper focuses on selecting the best number of threads for a parallel application in dynamic environments. It develops a new scheme based on a mixture of experts approach. It learns online which, of a number of existing policies, or experts, is best suited for a particular environment without having to try out each policy. It does this by using a novel environment predictor as a proxy for the quality of an expert thread selection policy. Additional expert policies can easily be added and are selected only when appropriate. We evaluate our scheme in environments with varying external workloads and hardware resources.We then consider the case when workloads use affinity scheduling or are themselves adaptive and show that our approach, in all cases, outperforms existing schemes and surprisingly improves workload performance. On average, we improve 1.66x over OpenMP default, 1.34x over an online scheme, 1.25x over an offline policy and 1.2x over a state-of-art analytic model. Determining the right number and type of experts is an open problem and our initial analysis shows that adding more experts improves accuracy and performance.

Comparing Changes In Core Temperature Between Groups Differing Greatly In Body Morphology During Exercise In An Uncompensable Environment

It has been recently demonstrated that changes in core temperature during exercise in a physiologically compensable environment are primarily determined by the total rate of metabolic heat production per unit body mass (W/kg). In an uncompensable environment it has been suggested that an absolute intensity will induce similar changes in core temperature; however such an approach does not account for the biophysical influence of body morphology. PURPOSE: To assess different methods of exercise prescription on changes in core temperature in an uncompensable environment in participants that greatly differ in body morphology. METHODS: Seven participants separated into a small (SM; 66.9±8.0 kg, 1.8±0.1 m2, 271±21 cm2/kg; n=4) and large (LG; 93.1±8.3 kg, 2.2±0.1 m2, 233±9 cm2/kg; n=3) body size group were recruited. Firstly, the maximum potential for evaporation (Emax) for each participant was assessed using a humidity ramp protocol. On separate occasions, participants then completed 75 min of upright cycling in a 35°C and 70%RH environment at i) a fixed external workload of 100W; and ii) a fixed heat production per kilogram above their Emax (3W/kg>Emax). RESULTS: Absolute Emax was greater in LG (611±58 W) compared to SM (540±48 W), but Emax was similar relative to body surface area (LG: 286±35 W/m2; SM: 300±35 W/m2). Change in rectal temperature (ΔTre) was greater in SM (1.7±0.3°C) than LG (1.3±0.2°C) at 100 W; however ΔTre was similar at 3 W/kg>Emax (SM: 1.5±0.3°C, LG: 1.6±0.1°C). Total heat production per unit mass was greater for SM compared to LG at 100 W (SM: 8.2±1.9 W/kg; LG: 6.1±1.1 W/kg) and at 3 W/kg>Emax (SM: 7.7±0.8 W/kg; LG: 6.4±0.5 W/kg). CONCLUSION: Preliminary data indicate that ΔTre of morphologically different groups exercising in an uncompensable environment is determined by the amount heat production exceeds Emax per unit mass, and not total heat production per unit mass or absolute workload.

Influence of playing standard and physical fitness on activity profiles and post-match fatigue during intensified junior rugby league competition.

BackgroundThe aim of this study was to determine whether the fatigue responses to the same intensified rugby league competition differed depending on playing standard and physical fitness.MethodsPlayers from a high-standard (n = 15) and a low-standard (n = 16) junior rugby league team had lower body neuromuscular fatigue, perceptual wellbeing, and blood creatine kinase (CK) assessed over an intensified competition. Global positioning system units measured match activity profiles and rating of perceived exertion-assessed internal loads. Players were divided into high- and low-fitness groups across the two standards based on Yo-Yo intermittent recovery test performance.ResultsPlaying intensity increased with playing standard and fitness levels (high-standard = 92 ± 6 m·min−1 vs. 88 ± 6 m·min−1; low-standard = 88 ± 2 m·min−1 vs. 83 ± 6 m·min−1). Despite greater internal and external loads, high-fitness players showed smaller reductions in lower body power (high-standard effect size [ES] = −0.74; low-standard ES = −0.41). High-standard players had smaller increases in blood CK (77% ± 94% vs. 113% ± 81%; ES = −0.41), primarily due to very small increases in the high-fitness group (50% ± 45%).ConclusionsIncreased fitness leads to greater internal and external workloads during intensified competition, smaller increases in blood CK, and less neuromuscular fatigue. Maximising player fitness should be a primary goal of coaches in order to increase match workloads and reduce post-match fatigue during intensified competition.Key PointsIncreased physical fitness results in greater relative and absolute match workloads.Increased physical fitness results in less fatigue and muscle damage during an intensified competition.Coaching staff should aim to maximise physical fitness in order to optimise match performance and reduce player fatigue.

Reduced Exercise Endurance after Repeated Long‐Duration Oxygen Dives — Do Ventilatory Parameters Hint at a Cause?

Running endurance decreases after repeated long-duration dives with oxygen partial pressure 1.3 atm. Physiological clues for the mechanism were sought from non-invasive ventilatory and metabolic measurements during endurance exercise. Three groups of nine male Navy divers completed five days of 6-hour dives breathing air or O2 in 15 feet of water or O2 at equivalent pressure dry while resting in a hyperbaric chamber. Several days before the first (Pre) and one day after the final dive (Post), they ran to their voluntary endurance limits on a treadmill at 85% of VO2 max. Breath-by-breath data (Cosmed K4b2) were compared Pre – Post using one-minute averages at the run time matching the last minute of the shorter of the two runs. Endurance times decreased with O2 (wet:–29%, p<0.01; dry: –41%, p< 0.01), but did not change with air (–16%). Relative to Pre, Post for O2 dives had higher minute ventilation (V’E) (wet: +12%, p < 0.01; dry: +25%, p <0.001) and lower end tidal CO2 partial pressure (PETCO2) (wet:–5%, p<0.05; dry: –13%, p=0.01), and changes were more pronounced after dry than wet exposures. Wet but not dry O2 increased respiratory quotient (R) Post relative to Pre (+7%, p < 0.03). Air dives caused no significant changes (V’E: +1%; PETCO2: –2%; R: –4%). Oxygen breathing but not immersion during five days of 6-hour dives caused post-dive metabolic changes during heavy endurance exercise. The increase in V’E and decrease in PETCO2 at the same external workload suggests increased lactate production after repeated mildly-hyperoxic exposures. Funding: ONR, and NAVSEA Deep Submergence Biomedical Program

Variability of PlayerLoad, Bowling Velocity, and Performance Execution in Fast Bowlers Across Repeated Bowling Spells.

The use of wearable microtechnology to monitor the external load of fast bowling is challenged by the inherent variability of bowling techniques between bowlers. This study assessed the between-bowlers variability in PlayerLoad, bowling velocity, and performance execution across repeated bowling spells. Seven national-level fast bowlers completed two 6-over bowling spells at a batter during a competitive training session. Key dependent variables were PlayerLoad calculated with a MinimaxX microtechnology unit, ball velocity, and bowling execution based on a predetermined bowling strategy for each ball bowled. The between-bowlers coefficient of variation (CV), repeated-measures ANOVA, and smallest worthwhile change were calculated over the 2 repeated 6-over bowling spells and explored across 12-over, 6-over, and 3-over bowling segments. From the sum of 6 consecutive balls, the between-bowlers CV for relative peak PlayerLoad was 1.2% over the 12-over bowling spell (P = .15). During this 12-over period, bowling-execution (P = .43) scores and ball-velocity (P = .31) CVs were calculated as 46.0% and 0.4%, respectively. PlayerLoad was found to be stable across the repeated bowling spells in the fast-bowling cohort. Measures of variability and change across the repeated bowling spells were consistent with the performance measure of ball velocity. The stability of PlayerLoad improved when assessed relative to the individual's peak PlayerLoad. Only bowling-execution measures were found to have high variability across the repeated bowling spells. Player- Load provides a stable measure of external workload between fast bowlers.

Modalités ou charge de réentraînement : quelle modalité choisir pour améliorer l’aptitude aérobie du patient coronarien en seulement 4 semaines ?

ObjectiveThe aim of this study was to compare the effects of 4 weeks of CT and AT, which training impulse (total external workload and perceived exertion), are similar on power associated at VO2peak (pVO2peak) and cardiorespiratory responses of patient with CAD. MethodEighteen male with CAD (62±7 years, 175±2cm, 84±16kg, fraction of ejection=0.49±0.16) performed 4 weeks of CT (n=9) or AT (n=9). pVO2peak, maximal and first ventilatory threshold values of oxygen uptake (VO2peak, VO2-vt) and heart rate (HRmax, HR-vt) were measured before and after training session. Total training impulse (exercise rehabilitation and other paramedical actions) were evaluated and harmonized between AT and CT according to Foster et al. formula (1996) ResultsNo significant difference were found in training impulse between AT and CT (3650±220 vs 3497±190 U, P=NS). VO2pic increased after AT (16.9±4.4 vs 18.9±4.9mLO2/min/kg, P<0.05) and remained unchanged after CT (17.7±7.8 vs 17.8±7.2, P=NS). Four weeks of training induced significant increase in pVO2peak, VO2-vt and FC-vt, expressed in absolute or relative value (P<0,05), without any difference between AT and CT modalities (P=NS). ConclusionsImproving pVO2pic following an exercise training does not necessarily preclude an improvement in coronary VO2pic. pVO2 peak was not improved with the same cardiorespiratory adaptations between AT and CT. Thus, there seems important to measure gas exchanges of subject with CAD during the incremental test and identify the respective part of muscular and cardiorespiratory functions in exercise exhaustion.

Mean-field analysis of hybrid Markov population models with time-inhomogeneous rates

We consider a hybrid extension of population continuous time Markov chains (PCTMC)—a class of Markov processes capturing interactions between large groups of identically behaved agents. We augment the discrete state space of a PCTMC with continuous variables that evolve as integrals over the population vector and that can simultaneously provide feedback to the rates of transitions in the PCTMC. Additionally, we include time-inhomogeneous rate parameters, which can be used to incorporate real measurement data into the models. We extend mean-field techniques for PCTMCs and show how to derive a system of integral equations that approximate the evolution of means and higher-order moments of populations and continuous variables in a hybrid PCTMC. We prove first- and second-order convergence results that justify the approximations. We use a moment closure based on the normal distribution which improves the accuracy of the moment approximation in case of proportional control where transition rates depend on the amount a continuous variable is above or below a fixed threshold. We demonstrate how this framework is suitable for modelling feedback from globally-accumulated quantities in a large scale system, such as energy consumption, total cost or temperature in a data centre. We present a model of a many server system with temperature management and external workload that varies with time. We show how to use real data to represent the workload within the framework. We use stochastic simulation to validate the example and an earlier example of a hypothetical heterogeneous computing cluster.

Micro- and macroergonomic changes in mental workload and medication safety following the implementation of new health IT

Health information technology (IT) is a promising way to achieve safer medication management in the delivery of healthcare. However, human factors/ergonomics dictates that in order to make the complex, cognitive work of healthcare delivery safer, health IT must properly support human cognition. This means, for example, that new health IT must reduce, not increase, workload during safety-critical tasks. The present study was the first to quantitatively assess the short- and long-term impact of bar coded medication administration (BCMA) IT on nurses' mental workload as well as on perceived medication safety. One-hundred seventy registered nurses across 3 dissimilar clinical units at an academic, freestanding pediatric hospital in the Midwest US participated in surveys administered before, 3 months after, and 12 months after the hospital implemented BCMA. Nurses rated their external mental workload (interruptions, divided attention, being rushed) and internal mental workload (concentration, mental effort) during medication administration tasks as well as the likelihood of each of three medication safety events: medication administration errors, medication errors on the clinical unit, and clinical unit-level adverse drug events. Clinical unit differences were assessed. Findings generally confirmed the hypothesis that external but not internal mental workload was associated with the perceived likelihood of a medication safety event. Comparisons of mental workload from pre- to post-BCMA revealed statistically significant changes in the critical care unit only. Medication safety appeared to improve over the long term in the hematology/oncology unit only. In the critical care and medical/surgical units, medication safety exhibited short-term improvements that were eliminated over time. Changes in mental workload and medication safety, two classically microergonomic constructs, were deeply embedded in macroergonomic phenomena. These included the fit between the BCMA system and the nature of nursing work, the process of BCMA implementation, and BCMA interactions with concurrent changes occurring in the hospital. Findings raise questions about achieving sustainable performance improvement with health IT as well as the balance between micro- and macroergonomic approaches to studying technology change. Relevance to industryDesigners must consider how technology changes cognitive work, including mental workload. Hospitals and other implementers of technology must ensure that new technology fits its users, their tasks, and the context of use, which may entail tailoring implementation, for example, to specific clinical units. Evaluators must look over time to assess both changes in cognitive work and implementation issues. Healthcare practitioners must also recognize that new technology means a complex transformation to an already complex sociotechnical system, which calls for a macroergonomic approach to design and analysis.

Acute metabolic, hormonal and psychological responses to cycling with superimposed electromyostimulation.

The purpose of the present study was to evaluate the effects of superimposed electromyostimulation (E) during cycling on the acute hormonal and metabolic response, as E might be a useful tool to intensify endurance training without performing high external workloads. Thirteen subjects participated in three experimental trials each lasting 60 min in a randomized order. (1) Cycling (C), (2) cycling with superimposed E (C + E) and (3) E. Human growth hormone (hGH), testosterone and cortisol were determined before (pre) and 0', 30', 60', 240' and 24 h after each intervention. Metabolic stimuli and perturbations were characterized by lactate and blood gas analysis (pH, base excess, bicarbonate, partial pressure of oxygen, partial pressure of carbon dioxide). Furthermore, changes of the person's perceived physical state were determined. C + E caused the highest increases in cortisol and hGH, followed by C and E. Testosterone levels showed no significant differences between C + E and C. Metabolic stress was highest during C + E, followed by C and E. C + E was also the most demanding intervention from an athlete's point of view. As cortisol and hGH are known to react in an intensity dependent manner, the present study showed that superimposed E is a useful method to intensify endurance training, even when performing low to moderate external workloads. Even at lower exercise intensities, additional E may allow one to induce a high (local) stimulus. It can be speculated, that these acute hormonal increases and metabolic perturbations, might play a positive role in optimizing long-term training adaptations, similar to those of intense training protocols.