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PubMed1988

Metabolic and heart rate responses to submaximal arm lever and arm crank ergometry.

Previous studies have shown that arm cranks and arm levers, working as propulsion mechanisms for nonambulatory individuals, may have mechanical and physiologic advantages over standard handrim wheelchairs. This study evaluated physiologic responses to arm lever and arm crank ergometry using identical workloads. An arm lever ergometer (ALE) was constructed and adapted to an arm crank ergometer (ACE) so that equal workloads could be applied with both ergometers. Fifteen able-bodied men and 15 able-bodied women exercised at a low (15 watts) and a high (45 watts) workload, with a three-minute rest interval. While exercising at each level, oxygen consumption (VO2), minute ventilation (VE), and heart rate (HR) were monitored. When low workloads with ALE and ACE were compared, no significant differences (p greater than 0.05) were demonstrated in any of the variables for men or women. For the men, at the high workload, the ALE elicited significantly lower (p less than 0.05) VO2 (by 9.8%), HR (by 6.3%), and VE (by 7.5%), than did the ACE. For the women, at the high workload, VO2 was significantly lower (p less than 0.05) (by 7.6%) with the ALE, as was VE (by 7.5%), but HR, although 3.3% lower with the ALE, was not significantly different (p greater than 0.05) from the ACE. These data suggest that the ALE is physiologically less stressful than the ACE at high workloads. Arm levers may, therefore, provide an advantage for handicapped persons when they propel themselves in wheelchairs.

Arm↗

PubMed1987

[Exercise hypertension: historical, physiologic and clinical aspects of ergometry].

More than a decade before Riva Rocci in 1896 described the principles of blood pressure measurement as still employed today, in 1881 Zadek reported that there is an increase in blood pressure during physical work. The blood pressure increase during physical exercise as well as its extent as a relatively constant physiological response to a given workload were delineated accurately for the first time, however, in the 1950s. There is no significant difference between the blood pressure increase seen in conditioned athletes and untrained individuals at comparable workloads. In healthy male subjects, a comparison was carried out of the reactions of cardiopulmonary and metabolic parameters during five different modes of exercise. The highest values for oxygen uptake as well as the highest heart rates can be observed during treadmill ergometry; with this method, the largest muscle mass is activated. During both treadmill ergometry as well as during step climbing, the blood pressure can be measured only invasively. As compared with bicycle ergometry in the seated position, the stroke volume increase is only relatively small during supine pedaling. Accordingly, to reproduce situations similar to that of everyday activity exercise testing should be carried out in an upright position. Vascular and cardiac catheterization, however, can be performed more easily in the supine than in the seated position. With these facts in mind, the appropriate methods should be chosen according to the needs of the study and the condition of the patient. During continuously increasing workloads, the systolic pressure increases proportionately. Immediately after termination of exercise, this pressure decreases rapidly over two to three minutes. The diastolic pressure measured noninvasively during seated bicycle ergometry is not particularly accurate and should be interpreted with caution. In general, exercise blood pressure should be determined during a standardized test beginning with a workload of 30 watts for three minutes and subsequent workloads incremented 40 watts for three minutes each. The normal ranges for younger and older patients differ substantially. Additionally, body weight exerts an influence on exercise blood pressure. During exercise, patients with hypertension may show one of three different reactions: the increased pressure can be maintained relative to the normal values during the specified workloads, the blood pressure can show normalization and the systolic blood pressure can remain constant or even decrease at higher workloads.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Pressure Determination↗

PubMed1995

[Significance of chronotropic exertion effects on the heart in diagnosing physical fitness in children practising swimming].

Regarding the peculiar character of exercise adaptation in developmental age, two questions have been stated; in what degree heart rate (HR) changes after physical effort reflect and diagnose the physical fitness in children and if these values can be the base of indirect method of maximal oxygen intake (VO2max). The practical problem was to choose the method, which could make the data for the comparative analysis of the heart's chronotropic reaction in children practising swimming professionally and in non-practising ones possible to obtain. The research method should not be connected with excessive workload for children. The heart's chronotropic reaction has been thoroughly analysed in different phases of submaximal progressive effort, according to the methods specific for the PWC170 index estimation; its diagnostic value would determine its differentiation in the age groups of swimmers and non-practising children and correlation between its indexes and real oxygen efficiency estimated using maximal oxygen intake values obtained in direct method (VO2maxEZ). 186 girls and 225 boys aged 10 to 15, practicing systematically since the 10th year of life, were investigated. During six years of the study 1308 exercise trials have been performed, including 654 tests with submaximal workload specific for the PWC170 index estimation (Physical Work Capacity), and 654 spiroergometric tests (TSE) with maximal workload and direct measurement of oxygen intake. Data obtained from the test with submaximal workload were compared with those noted in the same age groups of non-practicing children (246 girls and 256 boys), who formed the control groups for male and female swimmers. Those children from primary school had never practised any organized form of sport apart from obligatory physical exercises at school. Comparative analysis of physical efficiency indexes followed the estimation of basic morphologic features in studied children (body weight, fat-free body weight, body height). The heart's chronotropic reaction has been characterized in a traditional way as PWC170 and PWC150 indexes; it has been also thoroughly analyzed during following stages of the test estimated by workload changes, as well as the resultant for the whole workload dynamics of the HR changes, which has characterized the physiologic chronotropic expense of one watt of the workload applied. In the same time relationship between values obtained directly before the beginning of the exercises (HRW) have been analyzed. Although it has been found that discussed PWC indexes can differentiate in mean falues the groups of practising and non-practising children in the same age, but in significant percentage their values were nearing in both groups; it has been distinctly shown in the value distribution in percentile scores (Fig 1). This situation undoubtedly reduces the diagnostic advantages of the discussed indexes. HRW values have influenced the course of the test and its final result, and especially PWC indexes (significant in some groups of children), which has been emphasized. In the research a problem is discussed: in what degree the changes of the heart rate can describe the general physical fitness of people studies. Comparative analysis of the PWC and TSE tests performed in swimmers show no relationship between physical oxygen efficiency and values of PWC170 and PWC150 indexes. In the longitudinal research the PWC170 test results have significantly fluctuated during progressively increasing values of maximal oxygen intake measured directly, which has been pointed out. Maximal oxygen intake should be evaluated critically on the base of the heart's chronotropic reaction after exercise in children. It seems that more reliable in estimating the exercise adaptation is to describe the heart's chronotropic reaction using its direct indexes. It is possible to use PWC170 results, but it is necessary to regard the initial HR values when starting the exercise.

Adolescent↗

PubMed1995

Development, testing and implementation of an emergency services methodology in Alberta.

Alberta was the first province in Canada to mandate reporting of hospital-based emergency services. This reporting is based on a workload measurement system that groups emergency visits into five discreet workload levels/classes driven by ICD-9-CM diagnoses. Other related workload measurement variables are incorporated, including admissions, transfers, maintenance monitoring, nursing and non-nursing patient support activities, trips, staff replacement, and personal fatigue and delay. The methodology used to design the reporting system has been subjected to extensive testing, auditing and refinement. The results of one year of province-wide data collection yielded approximately 1.5 million emergency visits. These data reveal consistent patterns/trends of workload that vary by hospital size and type. Although this information can assist in utilization management efforts to predict and compare workload and staffing levels, the impetus for establishing this system derived from its potential for funding hospital-based emergency services. This would be the first time that such services would be funded on a systemic, system-wide basis whereby hospitals would be reimbursed in relation to workload. This proposed funding system would distribute available funding in a consistent, fair and equitable manner across all hospitals providing a similar set of services, thus achieving one of the key goals of the Alberta Acute Care Funding Plan. Ultimately, this proposed funding methodology would be integrated into a broader Ambulatory Care Funding system currently being developed in Alberta.

Alberta↗

PubMed2000

Introduction and implementation of the basic treatment equivalent in a Varian-based department.

The increasing popularity of 3-D planning leads to procedural alterations as both workload and resource utilization increase. Although the complexity of the techniques has increased (as well as the set-up and treatment times), the workload statistics must still include the number of fields treated. It is commonly known that machine statistics of fields treated per day do not accurately represent workload because there are major differences between techniques. A mantle treatment technique and an opposed spine technique both have (statistically) two fields, although the set-up requirements and treatment times are very different. A basic treatment equivalent (BTE) formula was reported in early 1999 by Delaney et al. and incorporates a large number of variables inherent in patient treatment. The formula considers different factors that affect overall treatment time, and aims to represent a more accurate treatment time indicator. The aim of introducing the BTE into the Department of Radiation Oncology at Sir Charles Gairdner Hospital was to create a more accurate scheduling system and even out workloads on all treatment units. Therefore the BTE formula was used to assess accuracy of treatment times in order to determine if the values could be relied upon as accurate time indicators. Patients undergoing a variety of treatment techniques were timed for the duration of their treatment procedure, and their treatment times compared to the time estimated using the BTE formula. A few minor alterations were made to the equation for treatment units with multi-leaf collimation (MLC). A trial conducted at Sir Charles Gairdner Hospital found that, using the BTE formula (with a few modifications required for the MLC treatment units), of 60 patients timed for the duration of their set-up and treatment, 85% of values were in the range of +/- 3 min, and 95% were in the range of +/- 5 min of the estimated times. Through the routine use of the BTE equation a more sensitive indication of treatment machine workload can be found. Advantages such as: (i) a more accurate measure of treatment workload (for comparison with other departments) and (ii) increased scheduling accuracy will succeed over the currently accepted system of fields per hour.

Appointments and Schedules↗

PubMed2001

Metabolic response to small and large 13C-labelled pasta meals following rest or exercise in man.

The metabolic response to a 150 or 400 g 13C-labelled pasta meal was studied for 8 h following rest or exercise at low or moderate workload (n 6). Following rest, the 400 g meal totally suppressed fat oxidation (v. 14.1 g following the 150 g meal) and a small amount of glucose was converted into fat (4.6 g), but fat oxidation remained high in subjects who had exercised following both the small (21.8 and 34.1 g) and large meal (14.1 and 32.3 g). Exogenous glucose oxidation was significantly higher in subjects who had remained at rest both following the small (67.6 g v. 60.4 and 51.3 g in subjects who exercised at low and moderate workloads) and large meal (152.2 v. 123.0 and 127.2 g). Endogenous glucose oxidation was similar in the three groups following the 150 g meal (42.3-58.0 g), but was significantly lower following the 400 g meal in subjects who had exercised at low workload (24.2 v. 72.2 g following rest; and was totally suppressed in those who had exercised at moderate workload. As a consequence, a larger positive glycogen balance was observed in subjects who exercised before the large meal (182.8-205.1 g v. 92.4 g following rest; Total fat oxidation calculated from 08.00 hours to 20.00 hours was similar in subjects who exercised at low and moderate workloads. These results indicate that: (1) de novo lipogenesis, which plays only a minor role for the disposal of an acute dietary carbohydrate load, is totally suppressed following exercise, even when a very large carbohydrate load is ingested; (2) the reduction in glycogen turnover as well as a preferential conversion of glucose into glycogen are responsible for the increase in glycogen stores following exercise; (3) for a similar energy expenditure, exercise at low workload for a longer period does not favour fat oxidation when the post-exercise period is taken into account.

Adult↗

PubMed2004

Workplace factors leading to planned reduction of clinical work among emergency physicians.

OBJECTIVE: There is anecdotal evidence that ACEM Fellows are reducing or planning to reduce their clinical workload. We investigated the extent of, and reasons for, these reductions. METHODS: An anonymous, cross-sectional postal survey utilizing a study-specific questionnaire. RESULTS: Three hundred and twenty-three Fellows (63.5%) responded. Most were recently graduated males. In the last 5 years, the mean number of clinical hours worked per week has reduced significantly (P < 0.001) for both junior (40.6-28.9 h) and senior Fellows (30.4-23.1 h). Further significant (P < 0.001) reductions are planned. The most frequently reported reasons for reducing clinical workload were excessive workload, family life and emotional health effects, shift work and work stress. The most stressful aspects of work reported were access block, dealing with management, insufficient staffing, workload pressures and staff supervision. Clinical work reportedly impacts most upon family life, social life and emotional health. CONCLUSIONS: Fellows are significantly reducing their clinical workload largely in response to excessive workload and lack of resources. These findings have important implications for professional longevity and work force planning. Re-evaluation of workplace practice, especially identified stressors, is indicated.

Adult↗

PubMed1996

The impact of cross-training on team functioning: an empirical investigation.

The effects of cross-training (presence vs. absence) and workload (high vs. low) on team processes, communication, and task performance were examined. Eighty male undergraduate students were randomly assigned to one of four training conditions: cross-training, low workload; cross-training, high workload; no cross-training, low workload; and no cross-training, high workload. Results indicated that cross-training was an important determinant of effective teamwork process, communication, and performance. Predicted interactions between cross-training and workload were not supported. Implications for the design and implementation of cross-training as a means to improve team functioning are discussed.

Adult↗

PubMed2000

Head roll compensation in a visually coupled HMD: considerations for helicopter operations.

BACKGROUND: The helmet-mounted display (HMD) research program at the Flight Research Laboratory of the National Research Council of Canada examined the effects of HMD camera platform dynamics on pilot workload. Many currently fielded visually coupled HMD systems do not reproduce head movements in the roll axis which can lead to the presentation of visual information that is not consistent with vestibular and proprioceptive information. HYPOTHESIS: Our hypothesis was that this sensory conflict can induce motion sickness and increase pilot workload. METHODS: To examine this premise, three pilots flew a series of standardized maneuvers with or without roll compensation in the camera platform of a visually coupled HMD system. RESULTS: Increases in motion sickness symptoms and pilot workload were noted during complex, high-workload maneuvers when no roll compensation was present in the camera platform. During the most demanding maneuvers, the lack of roll compensation in the camera platform made it difficult for the evaluation pilot to control the helicopter. CONCLUSIONS: Roll compensation in visually coupled HMD systems reduces pilot workload and' motion sickness during critical flight periods where pilot workload may already be considerable.

Adult↗

PubMed2004

EEG and ECG changes during selected flight sequences.

BACKGROUND: Mental workload has become a critical factor in the design and use of modern aircraft. Because of the complexity of the human-machine system, it is necessary to determine workload, fatigue, and level of performance using noninvasive electrophysiological measures. OBJECTIVE: Our objective was to identify the electrophysiological indicators of mental workload during piloting tasks. METHODS: Electroencephalographic (EEG) and electrocardiographic (ECG) activity was recorded during actual flight, with a profile planned to produce different levels of mental workload. RESULTS: In-flight EEG and ECG recordings enabled us to document mental workload levels. During active segments, delta and theta band activity increased (p < 0.05 or greater); results showed an increase of 22.5% for theta band activity during active flight segments compared with in-flight rest periods. Inversely, alpha band activity diminished: the decrease between ground baseline and all flight sequences was 30% (p < 0.05 or greater). These variations were reversed during the in-flight rest sequences. Instrumental flight caused an increase in the theta and alpha frequency band activity in the parietal-occipital area (p < 0.05 or greater); the alpha/beta ratio also increased. Heart rate increased during the active segments and fell during the in-flight rest periods. The mean difference between active segments and in-flight rest periods was of 8.89 bpm (i.e., an increase of 11.5%; p < 0.01). Heart rate was correlated to the EEG activity of the delta and beta bands in the central area (C3, Cz, C4, p < 0.05). CONCLUSIONS: The electrophysiological measures recorded provide useful indicators of the mental workload required by different flight sequences.

Adult↗

PubMed2001

Increased blood ammonia in hypoxia during exercise in humans.

The effect of acute hypoxia on blood concentration of ammonia ([NH3]b) and lactate (la-]b) was studied during incremental exercise(IE), and two-step constant workload exercises (CE). Fourteen endurance-trained subjects performed incremental exercise on a cycle ergometer under normoxic (21% O2) and hypoxic (10.4% O2) conditions. Eight endurance-trained subjects performed two-step constant workload exercise at sea level and at a simulated altitude of 5000 m (hypobaric chamber, P(B)=405 Torr; P(O2)=85 Torr) in random order. In normoxia, the first step lasted 25 minutes at an intensity of 85 % of the individual ventilatory anaerobic threshold (AT(vent), ind) at sea level. This reduced workload was followed by a second step of 5 minutes at 115% of their AT(vent), ind. This test was repeated into a hypobaric chamber, at a simulated altitude of 5,000 m. The first step in hypoxia was at an intensity of 65 % of AT(vent), ind., whereas workload for the second step at simulated altitude was the same as that of the first workload in normoxia (85 % of AT(vent), ind). During IE, [NH3]b and [la-]b were significantly higher in hypoxia than in normoxia. Increases in these metabolites were highly correlated in each condition. The onset of [NH3]b and [la-]b accumulation occurred at different exercise intensity in normoxia (181W for lactate and 222W for ammonia) and hypoxia (100W for lactate and 140W for ammonia). In both conditions, during CE, [NH3]b showed a significant increase during each of the two steps, whereas [la-]b increased to a steady-state in the initial step, followed by a sharp increase above 4 mM x L(-1) during the second. Although exercise intensity was much lower in hypoxia than in normoxia, [NH3]b was always higher at simulated altitude. Thus, for the same workload, [NH3]b in hypoxia was significantly higher (p<0.05) than in normoxia. Our data suggest that there is a close relationship between [NH3]b and [la-]b in normoxia and hypoxia during graded intensity exercises. The accumulation of ammonia in blood is independent of that of lactate during constant intense exercise. Hypoxia increases the concentration of ammonia in blood during exercise.

Adult↗

PubMed2003

Methodological aspects of maximal lactate steady state-implications for performance testing.

The maximal lactate steady state (MLSS) is the highest blood lactate concentration (BLC) that can be identified as maintaining a steady-state during a prolonged submaximal constant workload. Comparative interpretation of published data about MLSS is complicated by the fact that different methods of testing have been utilized. Thus, three methods, corresponding to the time course of changes in BLC incurred during either 30 min (MLSS I) or 20 min (MLSS II and III) of constant submaximal workload exercise, were compared in 26 male subjects [mean (SD) age 24.6 (5.6) years, height 181.6 (4.9) cm, body mass 74.4 (5.2) kg]. MLSS I [5.1 (1.3) mmol x l(-1)], II [4.9 (1.3) mmol x l(-1)], and III [4.3 (1.3) mmol x l(-1)] were different (P<0.01). The workload corresponding to MLSS III [244.8 (44.0) W] was lower (P<0.01) than that at MLSS I [254.0 (40.8) W] and II [251.9 (40.4) W]. No difference could be confirmed between the workloads established for MLSS I and MLSS II. The differences between MLSS I, MLSS II, and MLSS III and corresponding workloads reflect insufficient contribution to lactate kinetics by testing procedures that depend strongly upon the time course of changes in BLC during the initial 20-25 min of constant-workload exercise. Based on the present findings, constant-load tests lasting at least 30 min and a BLC increase of no more than 1.0 mmol x l(-1) after the 10th testing minute appear to be the most reasonable with respect to valid testing results.

Adaptation, Physiological↗

PubMed2001

Using baseline respiratory function data to optimize cycle exercise test duration.

BACKGROUND: It is often difficult to select an appropriate workload increment for progressive cycle exercise tests in order to achieve optimal test duration (8-12 min). We hypothesize that baseline respiratory function can be systematically used to select appropriate workload increment to optimize test duration in patients referred to the clinical laboratory. METHODOLOGY: One hundred and eighty consecutive exercise tests (with increments of 15 W/min) were retrospectively assessed. Using regression analysis, an equation was generated that predicts the work rate increment that would provide exercise duration of 8-12 min. The validity of this equation was tested prospectively in 231 consecutive tests performed with the calculated workload increment rounded to the nearest 5 watts (W). RESULTS: The best regression equation was: workload increment (W/min)=1.94 x FEV1 (L) + 0.63 x TLCO (mmol/min per kPa) - 0.07 x age + 1.94 x gender (male=1, female=0) + 4.12 (r=0.85, P < 0.0001). Using this equation allowed selection of the most appropriate workload increment in 79% of tests and reduced the number of tests of non-optimal duration from 72% (for a fixed increment of 15 W/min) to 38%. CONCLUSIONS: Utilization of this regression equation allows standardization in the selection of workload increment, and reduces the number of cycle exercise tests of inadequate duration.

Algorithms↗

PubMed1997

The plasma lactate response to exercise and endurance performance: relationships in elite triathletes.

The lactate response to exercise has been studied thoroughly during the last decades and it has been described using a variety of terms and definitions. Numerous investigations observed close relationships between the lactate response and endurance performance. The main question in this study was which of the various lactate responses during incremental exercise described in the literature was the best indicator of endurance performance. The plasma lactate response (PLR) was assessed during an incremental exercise test on 13 male elite triathletes (age 25.5+/-5.8 yrs; HT 179.7+/-5.4 cm; WT 71.3+/-4.7 kg) on a bicycle ergometer. The load was started at 2.5 W/kg and increased by 40 W every 4 min. We evaluated the following PLR-parameters: the workloads at the fixed lactate levels of 2, 3, 4, 5, 6, 7, and 8 mmol/l which were assessed by extrapolation from a workload-lactate-heart rate curve (P2, P3, P4, P5, P6, P7, P8 respectively), the lactate threshold which was defined as the workload at the point at which a non-linear increase of blood lactate occurred (Plt), and the workload at the lactate level that was 1 mmol/l above the baseline (P + 1). Four to seven weeks after the laboratory test, heart rate and lactate levels were assessed during a 40-km long time trial on a bicycle. Two parameters were considered as indicative of athletic performance: the road racing time (Tt), and the workload extrapolated from the workload-lactate-heart rate curve at the heart rate and lactate levels observed during the time trial (Pt). Only P2 showed a significant correlation with Tt (r=-0.65; p < 0.05; se = 72.5 s). Multiple regression analysis with the anthropometric parameters height and weight as additional independent parameters did not change the predictive value. We concluded that for predicting the cycling performance of similarly well-trained subjects the predictive value of PLR is negligible.

Adult↗

PubMed2004

Maximal strength and power, muscle mass, endurance and serum hormones in weightlifters and road cyclists.

Maximal strength, power, muscle cross-sectional area, maximal and submaximal cycling endurance characteristics and serum hormone concentrations of testosterone, free testosterone and cortisol were examined in three groups of men: weightlifters (n = 11), amateur road cyclists (n = 18) and age-matched controls (n = 12). Weightlifters showed 45-55% higher power values than road cyclists and controls, whereas the differences in maximal strength and muscle mass were only 15% and 20%, respectively. These differences were maintained when average power output was expressed relative to body mass or relative to muscle cross-sectional area. Road cyclists recorded 44% higher maximal workloads, whereas submaximal blood lactate concentration was 50-55% lower with increasing workload than in controls and weightlifters. In road cyclists, workloads associated with blood lactate concentrations of 2 and 4 mmol.l-1 were 50-60% higher and occurred at a higher percentage of maximal workload than in weightlifters or controls. Basal serum total testosterone and free testosterone concentrations were lower in elite amateur cyclists than in age-matched weightlifters or untrained individuals. Significant negative correlations were noted between the individual values of maximal workload, workloads at 2 and 4 mmol.l-1 and the individual values of muscle power output (r = -0.37 to -0.49), as well as the individual basal values of serum total testosterone and free testosterone (r = -0.39 to -0.41). These results indicate that the specific status of the participants with respect to training, resistance or endurance is important for the magnitude of the neuromuscular, physiological and performance differences observed between weightlifters and road cyclists. The results suggest that, in cycling, long-term endurance training may interfere more with the development of muscle power than with the development of maximal strength, probably mediated by long-term cycling-related impairment in anabolic hormonal status.

Adult↗

PubMed1998

Cardiorespiratory responses to exercises of equal relative intensity distributed between the upper and lower body.

The principles underlying the cardiorespiratory responses to upper body versus lower body exercise remain unclear. We explored the hypothesis that workloads of the same percentage of maximum strength for a particular part of the body might elicit similar cardiovascular responses. Twelve trained female university rowers (mean +/- s: age, 22.8 +/- 1.3 years; body mass, 66.9 +/- 1.8 kg; height, 169 +/- 6 cm; body fat, 18 +/- 2%; HRpeak, 190 +/- 3 beats min(-1); VO2 peak, 50.7 +/- 2.6 ml kg(-1) min(-1)) performed four 12 min exercise trials on a rowing ergometer. Arm rowing, leg extension and arm rowing + leg extension workloads were set at 20% of the mean of their respective three-repetition maximum (3-RM). The combination of arm rowing and leg extension was also performed in a reciprocal workload fashion; that is, the arm workload was 20% of the mean 3-RM for leg extension, and the leg extension workload was 20% of the mean 3-RM for arm rowing. Analysis of variance and Tukey HSD showed that, although the power output for leg extension was 144% higher than for arm rowing, the mean VO2, VE and heart rate values were not significantly different between exercise modes. Oxygen uptake for reciprocal arm rowing + leg extension, with the arms performing 71% of the total power output, was not significantly different from non-reciprocal arm rowing + leg extension; however, the VE and heart rate values were higher. Our results suggest that, during submaximal exercise, cardiorespiratory responses to upper body exercise do not differ significantly from those to lower body exercise, so long as the upper and lower body workloads are set at an equal relative strength level.

Adult↗

PubMed2006

Psychosocial work characteristics predicting daytime sleepiness in day and shift workers.

Characteristics of work organization other than working time arrangements may contribute importantly to daytime sleepiness. The present study was designed to identify the psychosocial factors at work that predict daytime sleepiness in a sample of day and shift workers. Participants working at a pulp and chemical factory completed an annual questionnaire regarding psychosocial factors at work using the U.S. National Institute for Occupational Safety and Health Generic Job Stress Questionnaire (i.e., quantitative workload, variance in workload, job control, support from supervisor, coworkers, or family/friends, job satisfaction, and depressive symptoms), as well as daytime sleepiness (through the Epworth Sleepiness Scale [ESS]) and sleep disturbances for three years starting in 2002 (response rates, 94.6-99.0%). The present analysis included 55 day workers (11 women) and 57 shift workers (all men) who participated in all three years of the study, worked under the same work schedule throughout the study period, and had no missing data on any of the daytime sleep items. A repeated-measures analysis of covariance (ANCOVA) was used to test the effects of work schedule (day vs. shift work) and psychosocial factors at work in 2002 on the ESS scores in subsequent years, with sleep duration, insomnia symptoms, chronic diseases, and sleepiness levels at baseline as covariates. Given significant and near-significant interactions of work schedules with psychosocial factor or study year, the ANCOVA, with the factors of psychosocial work characteristics and study year, was performed by type of work schedule. The results indicated a significant main effect of psychosocial work characteristics (p = 0.010, partial eng2 = 0.14) and an almost significant main effect of study year (p = 0.067, partial eng2 = 0.06) and interaction between psychosocial work characteristics and study year (p = 0.085, partial eng2 = 0.06) for variance in workload among the day work group. The day workers reporting high variance in workload in 2002 exhibited significantly higher ESS scores in 2003 and 2004 than did those reporting low variance in workload. The ANCOVA for the shift work group showed a main effect of psychosocial work characteristics for job satisfaction (p = 0.026, partial eng2 = 0.10) and depressive symptoms (p = 0.094, partial eng2 = 0.06) with the interaction between psychosocial work characteristics and study year for job satisfaction (p = 0.172, partial eng2 = 0.04) and depressive symptoms (p = 0.035, partial eng2 = 0.07). The shift workers with low job satisfaction and high symptoms of depression in 2002 showed significantly greater ESS scores in 2003 and/or 2004 than did those with opposite characteristics. These results may suggest a potential predictive value of variance in workload for day workers as well as job satisfaction and depressive symptoms for shift workers with respect to daytime sleepiness. The present findings may imply that redesigning these aspects of work environment would be of help in managing daytime sleepiness.

Adult↗

PubMed2006

Efficient on-line setup correction strategies using plan-intent functions.

With the introduction of image-guided radiation therapy (IGRT) delivery systems on-line set-up correction strategies have gained in popularity. Usually, the correction workload of these strategies is high compared to off-line strategies as daily setup corrections have to be performed based on a predefined action level. In this work, it is proposed that on-line strategies must not only be judged in terms of workload but also in terms of efficacy. While workload can be easily predicted for such strategies, the efficacy must ultimately reflect the efficiency with which the original treatment plan intent is met. The purpose of this work is to investigate the tradeoff between workload and efficacy of three different on-line set-up correction strategies: The common fixed action level strategy and two novel on-line setup correction strategies, i.e., a dose-volume histogram (DVH) constraint and an equivalent uniform dose (EUD) score strategy that aim directly for better compliance with original treatment plan intent. All strategies were reformulated in terms of a score function that reflected treatment plan intent. A retrospective study was conducted on 5 prostate patients (7-field conformal, 79.8 Gy, 42 fractions). PTV margins were 10 mm except in the posterior direction (7 mm). The original treatment plan intent for these patients was defined using a set of DVH constraints. The results show that the on-line setup correction strategy based on a fixed action level of 3 mm resulted in a considerable correction workload. For larger action levels, a dose benefit (in terms of EUD) in the rectum and bladder was observed for all patients which is clinically "fortuitous" but difficult to take advantage of. In contrast, the application of the two novel strategies generally resulted in a controlled decrease of the dose to the rectum and the bladder with a smaller workload. It is concluded that using information about target anatomy and the planned dose distribution allows the design of specific correction strategies that are better tailored to the individual patient and that comply effectively with initial treatment plan intent.

Artifacts↗