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PubMed2000

Study on work load of matrons under shift work in a special nursing home for the elderly.

In order to find out the work load of matrons under shift work in a special nursing home for the elderly (SNH), six healthy female matrons volunteered to participate in the present study. For each subject, care working time, heart rate, walking steps, estimated energy expenditure and working time in different postures were determined during day shift work (540 min) and night shift work (960 min). Although the time on duty, working and recess were significantly longer in night shift work than day shift work, the percentages of working and recess time to duty time were nearly the same regardless of shift work. The longest care work in each shift work was individual care of residents in the SNH. The maximum, minimum and mean heart rate and percentages to estimated maximal heart rate were similar in each shift work. Although total walking steps in night shift work were significantly larger than those in day shift work, steps per hour did not differ between them. The estimated total energy expenditure (kcal) was significantly higher in night shift work than in day shift work; however, the work intensity (kcal/kg/min) was significantly higher in day shift work. The longest length and larger percentage of working time were observed in standing posture in each shift work. These findings suggest that physical activity and energy expenditure of matrons under either shift work in the SNH seem to be high. Further studies are needed to clarify the work load of matrons engaged in SNH to formulate countermeasures.

Adult↗
PubMed1992

Effect of low and high intensity exercise on circulating growth hormone in men.

We hypothesized that circulating GH would increase only if a threshold of work intensity [corresponding to the anaerobic or lactate threshold (LT)] was exceeded. Ten healthy male volunteers (18-35 yr) first performed ramp-type progressive cycle-ergometer exercise to determine the LT and the maximal oxygen uptake. On subsequent mornings after an overnight fast, each subject performed bouts of 1, 5, and 10 min constant work rate exercise of either high intensity (above LT) or low intensity (below LT). A 1-h interval separated exercise bouts. Gas exchange (breath-by-breath), GH, immunoreactive insulin, glucose, lactate, pyruvate, and epinephrine and norepinephrine were measured at regular intervals. After the 10-min bouts of high compared with low intensity exercise, lactate was 7.2 +/- 3.7 mmol/L vs. 1.4 +/- 1.3, P less than 0.05; epinephrine was 1,113 +/- 519 pmol/L vs. 496 +/- 273, P less than 0.05; and norepinephrine was 7.89 +/- 3.45 nmole/L vs. 2.83 +/- 1.34, P less than 0.05. GH did not increase significantly from preexercise baseline during low intensity exercise (e.g., GH after 10-min low intensity exercise changed from baseline values by 1.5 +/- 2.0 micrograms/L, NS). Although lactate was elevated after 5-min of high intensity exercise, peak GH was significantly elevated (mean increase above baseline of 7.7 +/- 2.4 micrograms/L, P less than 0.05) only after 10 min of high intensity exercise (increases in 9 of 10 subjects). The GH increase occurred despite simultaneous increases in both IRI and glucose. A minimum duration of 10 min, high intensity exercise consistently increased circulating GH in adult males.

Adolescent↗
PubMed2002

Competition between internal and external sources of information during exercise: influence on RPE and the impact of the exercise load.

BACKGROUND: The purpose of this study was to investigate the influence of the exercise setting on perceived exertion during sustained low and high intensity cycling exercise. METHODS: Thirteen untrained males completed 4 15-min cycling sessions at 50% VO(2peak) and at 80% VO(2peak) under each of the following conditions: control, sensory deprived, video, and music. Ratings of perceived exertion (RPE) from Borg's 6-20 scale and heart rate (HR) were recorded at 5 min intervals during all sessions. RESULTS: RPE increased with exercise duration at both intensities and, as expected, was substantially higher at the harder workload. Exercising to music resulted in significantly lower RPE when compared to all other conditions at both the low and high workloads, while RPE was higher in the sensory deprived condition when compared to the other 3 conditions. However, RPE was similar for the control and video conditions at both workloads. A significant ordinal interaction existed between conditions and exercise duration during the low but not the high workload. While HR was higher for the harder workload and increased during each workload as a function of exercise duration, it was not different among the 4 conditions at either workload. CONCLUSIONS: Varying the type of sensory information available to the exercising individual did influence perceptual responses to the exercise with the degree of influence dependent on the intensity and duration of the exercise. These results are consistent with information processing models that suggest a limited capacity to attend to the information available. The type of information available, the work intensity, and the work duration were important elements influencing perceptual responses to exercise.

Adult↗
PubMed1982

Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle.

The influence of intensity and daily duration of exercise on cytochrome c concentration in the three muscle fiber types was assessed in rats that were treadmill trained for 8 wk (5 days/wk) by 1 of 19 protocols. The importance of exercise duration was determined at six running intensities (10, 20, 30, 40, 50, and 60 m/min). Daily run times resulted in a maximal adaptive change for each running intensity. The general pattern of cytochrome c change, caused by increasing daily run times, followed a first-order manner in all fiber types. The final time-independent asymptotic values were dependent on the intensity of running. In addition, as running intensity was increased, the length of daily run time required to achieve the peak adaptive response was shortened. The intensity influence was very different between fiber types. In the fast-twitch red fiber, the maximal time-independent response at each work intensity was altered by exercise intensity at only submaximal work loads (i.e., the adaptation from 19 to 29 nmol/g was not further increased at 50 and 60 m/min). In contrast, the adaptive response in the fast-twitch white fiber began at 30 m/min (approx 80% VO2max) and increased exponentially as intensity was increased (200% increase at 60 m/min). Whether this different adaptive response between fiber types is due solely to the ordered recruitment of motor units remains to be determined.

Animals↗
PubMed1998

A simplified assay for screening of drug resistance of cell-associated cytomegalovirus strains.

BACKGROUND: Conventional phenotypic drug resistance determination of cell-free clinical human cytomegalovirus (HCMV) isolates is usually very laborious and may take 8-12 weeks, since serially passages of slowly growing viral isolates in tissue cultures are required to obtain a sufficient viral titer for an appropriate inoculum. Rapid screening of a large number of samples would therefore only be possible if simplified, less work-intensive methods are employed. OBJECTIVE: The aim of this work was to develop an assay which speeds up the whole procedure of phenotypic drug resistance determination. Steps of the classical plaque reduction assay should be simplified or omitted, but on the other hand, the assay should be reliable and reproducible. STUDY DESIGN: Twenty-six clinical HCMV isolates from 20 immunocompromised patients (ten pre-treatment and 16 post-treatment with ganciclovir) were tested for drug susceptibility with the simplified plaque reduction assay. Most isolates were tested at least twice in independent assays. Virus titration could be avoided by using four different doses of cell-associated virus from the secondary culture for coculture susceptibility testing. Drug susceptibility values were determined by plaque titration and Probit analysis. RESULTS: All clinical HCMV isolates tested showed a mean ganciclovir ID50 value of 1.98 microM, (range 0.2-12.2; median 0.95) and a mean foscarnet ID50 value of 92.4 microM (range 35.7-181; median 81). All except one isolate were classified ganciclovir sensitive when compared to ID50 values of two ganciclovir resistant control stains (53.7 +/- 6.4 and 12.7 +/- 0.9 microM) and the sensitive laboratory strain Towne (2.1 +/- 0.8 microM). Repeated tests of individual isolates were reproducible, although the infectivity of the inoculum has not been determined prior of the assay. The mean time which elapsed between receipt of the clinical specimen and read-out of the assay was circa 4 weeks. CONCLUSIONS: Phenotypic resistance testing of HCMV isolates following to this protocol drastically reduces expenditure of time and work. The assay allows reliably the discrimination of HCMV isolates as drug resistant or sensitive according to the recent classification criteria of the AIDS Clinical Trials Group (ACTG). The simple handling and uncomplicated calibration of this assay facilitates the screening of large specimen numbers and renders drug susceptibility determination of HCMV more accessible to diagnostic routine use.

Antiviral Agents↗
PubMed1982

Effect of training specificity on maximal treadmill and bicycle ergometer exercise.

Sixteen competitive athletes in long-distance running (n = 8) and cycle racing (n = 8) performed three maximal exercise tests on the treadmill as well as on the bicycle ergometer. The test protocol for both ergometers was similar in work intensity and duration. The results obtained at the maximum work load were compared between and within the two groups of athletes. Comparing treadmill to bicycle exercise, the oxygen uptake was 14% higher on treadmill in the long-distance runners, but equal in the cycle racers. The work efficiency on both types of ergometers showed a clear relationship with the training activity: the cycle racers worked more efficiently on the bicycle ergometer while the results of the long-distance runners were better on the treadmill. Heart rate and minute ventilation reached similar values in the cycle racers on both ergometers, but treadmill exercise induced higher values in the long-distance runners as compared to cycling. Opposite results were found in the variables of the acid-base balance: lactate concentration and base excess reached similar values (13 and -14 mmol l-1, respectively) in the long-distance runners on both ergometers, but in the cycle racers bicycle exercise induced higher values than running. From these results it can be concluded that congruence between the mode of ergometer exercise and the sport activity improves the validity of the test result.

Acid-Base Equilibrium↗
PubMed1998

Limits for oxygen and substrate transport in mammals.

Environmental oxygen is transported by the respiratory cascade to the site of oxidation in active tissues. Under conditions of heavy exercise, it is ultimately the working skeletal muscle cells that set the aerobic demand because over 90 % of energy is spent in muscle cells. The pathways for oxygen and substrates converge in muscle mitochondria. In mammals, a structural limitation of carbohydrate and lipid transfer from the microvascular system to the muscle cells is reached at a moderate work intensity (i.e. at 40-50 % of VO2max). At higher work rates, intracellular substrate stores must be used for oxidation. Because of the importance of these intracellular stores for aerobic work, we find larger intramyocellular substrate stores in 'athletic' species as well as in endurance-trained human athletes. The transfer limitations for carbohydrates and lipids at the level of the sarcolemma imply that the design of the respiratory cascade from lungs to muscle mitochondria reflects primarily oxygen demand. Comparative studies indicate that the oxidative capacity of skeletal muscle tissue, and hence maximal oxygen demand, is adjusted by varying mitochondrial content. At the level of microcirculatory oxygen supply, it is found that muscle tissue capillarity is adjusted to muscle oxygen demand but that the capillary erythrocyte volume also plays a role. Oxygen delivery by the heart has long been recognized to be a key link in the oxygen transport chain. In allometric variation it is heart rate and in adaptive variation it is essentially stroke volume, and hence heart size, that determines maximal cardiac output. Again, haematocrit is an important variable that allows the heart of athletic species to generate higher flux rates for oxygen. The pulmonary gas exchanger offers only a negligible resistance to oxygen flux to the periphery. However, in contrast to all other steps in the respiratory cascade, the lungs have only a minimal phenotypical plasticity and appear, therefore, to be built with considerable structural redundancy in all but the most athletic species. Because of the lack of malleability, the lungs may ultimately become limiting for VO2max when adaptive processes have maximized O2 flux through the malleable downstream elements of the respiratory system: the heart, microcirculation and muscle mitochondria.

Animals↗
PubMed1977

Cardiorespiratory and metabolic responses to positive, negative and minimum-load dynamic leg exercise.

Cardiorespiratory and metabolic responses to steady-state dynamic leg exercise were studied in seven male subjects who performed positive and negative work on a modified Krogh cycle ergometer at loads of 0, 16, 33, 49, 98, and 147 W with a pedalling rate of 60 rpm. In positive work, O2 uptake increased with the ergometric load in a parabolic fashion. Net O2 uptake averaged averaged 220 ml-min-1 at 0 W (loadless pedalling), and was 75 ml-min-1 lower at the point of physiological minimum load which occurred in negative work at approximately 9 W. The O2 cost of loadless pedalling is for one-third attributed to the work of overcoming elastic and viscous resistance, the remaining part being due mainly to the work of antagonistic muscle contraction in the moving legs. Although at a given VO2, work rate was much higher in negative than in positive work, corresponding values for VE were similar, suggesting that the mechanical tension in working muscles is of little or no importance in the control of ventilation in steady-state exercise. Heart rate increased linearly with VO2 in both positive and negative work, with a steeper slope in negative work. Evidence is presented that none of the current definitions of muscular efficiency yields the true efficiency of muscular contraction in cycle ergometry, net efficiency calculation resulting in too low estimates, and work and delta efficiency calculations in overestimated values in the low-intensity work range, and in underestimated values in the high-intensity range.

Adolescent↗
PubMed1999

Breathing during exercise in subjects with mild-to-moderate airflow obstruction: effects of physical training.

In this study we explored the effects of physical training on the response of the respiratory system to exercise. Eight subjects with irreversible mild-to-moderate airflow obstruction [forced expiratory volume in 1 s of 85 +/- 14 (SD) % of predicted and ratio of forced expiratory volume in 1 s to forced vital capacity of 68 +/- 5%] and six normal subjects with similar anthropometric characteristics underwent a 2-mo physical training period on a cycle ergometer three times a week for 31 min at an intensity of approximately 80% of maximum heart rate. At this work intensity, tidal expiratory flow exceeded maximal flow at control functional residual capacity [FRC; expiratory flow limitation (EFL)] in the obstructed but not in the normal subjects. An incremental maximum exercise test was performed on a cycle ergometer before and after training. Training improved exercise capacity in all subjects, as documented by a significant increase in maximum work rate in both groups (P < 0.001). In the obstructed subjects at the same level of ventilation at high workloads, FRC was greater after than before training, and this was associated with an increase in breathing frequency and a tendency to decrease tidal volume. In contrast, in the normal subjects at the same level of ventilation at high workloads, FRC was lower after than before training, so that tidal volume increased and breathing frequency decreased. These findings suggest that adaptation to breathing under EFL conditions does not occur during exercise in humans, in that obstructed subjects tend to increase FRC during exercise after experiencing EFL during a 2-mo strenuous physical training period.

Adult↗
PubMed1997

Predictors of return to work following carpal tunnel release.

Little is known about factors that predict return to work following carpal tunnel release. Patients enrolled in a prospective, community-based study of carpal tunnel syndrome in Maine were evaluated with standardized questionnaires preoperatively and 6 months following carpal tunnel release. Univariate and multivariate analyses were performed to identify baseline factors associated with work disability 6 months following surgery. Thirty-one of 135 patients (23%) were out of work because of CTS 6 months following surgery. The predominant preoperative variables associated with work absence due to CTS 6 months postoperatively in logistic regression analyses were Workers' Compensation, work absence preoperatively, and worse mental health status (p < or = 0.01 for each). In analyses that considered postoperative as well as preoperative variables, persistence of symptoms following surgery was the most striking predictor of failure to return to work due to CTS (p < 0.0001). Preoperative correlates of less complete relief of symptoms in multivariate models included involvement of an attorney, milder preoperative symptom severity, preoperative work absence (p < 0.005 for each) and exposure to hand intensive work (p = 0.04). These data indicate that economic and psychosocial variables have a strong influence upon both return to work and the extent of symptom relief 6 months following surgery for carpal tunnel syndrome.

Adult↗
PubMed1999

Skeletal muscle substrate metabolism.

Endurance power of muscles is determined largely by the capacities to oxidize substrates in mitochondria in the process of making ATP by oxidative phosphorylation. This review explores physiological and morphological factors that may cause limitation of carbohydrate and fat utilization by muscle cells. The pathways for oxygen and substrates converge in muscle mitochondria. In mammals, a structural limitation of carbohydrate and lipid transfer from the microvascular system to muscle cells is reached at a moderate work intensity (that is, at 40-50% of VO2max). At higher work rates intracellular substrate stores must be used for oxidation. Because of the importance of these intracellular stores for aerobic work we find larger intramyocellular substrate stores in endurance trained athletes. The transfer limitations for carbohydrates and lipids on the level of the sarcolemma implies that the design of the respiratory cascade from lungs to muscle mitochondria reflects primarily oxygen demand.

Animals↗
PubMed1988

Effect of exercise on cardiac cyclic AMP.

The effect of one bout of intense swimming caused significant increases in the cyclic AMP content of fast-twitch white skeletal muscle, liver, and heart. Further investigation of the exercise-induced increase in myocardial cyclic AMP indicates that the nucleotide content remained elevated long after (24 h) termination of exercise. This increase in cyclic AMP was time dependent, with the level increasing gradually throughout the work bout. The increase in cardiac cyclic AMP seemed to be independent of work intensity, provided that work time was of sufficient duration (greater than or equal to 30 min). Increases in cardiac cyclic AMP were also seen when rats were exposed to 2 degrees C for 1-7 d. The increases in cyclic AMP seen following exercise and cold exposure were accompanied by an increase in cardiac cyclic AMP phosphodiesterase (PDE) activity. Our working hypothesis was that prolonged elevations in cyclic AMP produced an induction and/or activation of one or more of the PDE isozymes. When we administered dibutyryl cyclic AMP to rats, cardiac PDE activity was increased. This increase was inhibited by cycloheximide, suggesting that the elevated enzyme activity is mediated by the synthesis of new protein. These data support the concept that cyclic AMP is involved in the regulation of its own metabolism during physiological stress.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

[Report of experiences with AIDS education in schools by the public health service].

AIDS information work is very work-intensive if it is to be pursued with consequence and effect. This is a report on the work done in the course of one year at 47 schools and on the experience collected: --Many evening events have to be visited (parents' evenings and get-togethers, meetings of the parent councils). Such events are absolutely imperative if work at the schools should be meaningful and effective. --Working in Small groups (class groups) is much more time-intensive but also clearly more effective and should therefore always be preferred to large-scale events. --Working at different types of schools with different age levels makes great demands on the flexibility and intuitive abilities of the AIDS expert.

Acquired Immunodeficiency Syndrome↗
PubMed1992

[Relation between the change of slope of heart rate and second lactic and ventilatory thresholds in muscular exercise with large load].

The time-course of heart rate, blood lactate, and ventilatory gas exchange was studied during an incremental exercise test on cycloergometer in order to ascertain whether heart rate deflection occurred at the same load as the second lactate S[La]2) and ventilatory (SV2) thresholds. Twelve moderately trained subjects, 22 to 30 years old, participated in the study. The initial power setting was 30 W for 3 min with successive increases of 30 W every min except at the end of the test where the increase was reduced to 20 and 10 W.min-1. Ventilatory flow (VE), oxygen uptake (VO2), carbon dioxide production (VCO2, ventilatory equivalents of O2 (EO2 = VE/VO2) and CO2 (ECO2 = VE/VCO2), and heart rate (HR) were determined during the last 20 s of every min. Venous blood samples were drawn at the end of each stage of effort and analyzed enzymatically for lactate concentration ([La]). The HR deflection, S[La]2, and SV2 were represented graphically by two investigators using a double blind procedure. Following the method proposed by Conconi et al. 1982, the deflection in HR was considered to begin at the point beyond which the increase in work intensity exceeded the increase in HR and the linearity of the work rate/HR relationship was lost. S[La]2 corresponded to the second breaking point of the lactate time-course curve (onset of blood lactate accumulation) and SV2 was identified at the second breaking point in the increase in VE and ventilatory equivalent for O2 uptake accompanied by a concomitant increase in ventilatory equivalent for CO2 output. We observed that the deflection point in HR was present only in 7 subjects. The work load, VO2, HR, and [La] levels at which heart rate departed from linearity did not differ significantly from those determined with S[La]2 ans SV2. The VO2 and HR values at HR deflection point were significantly correlated with those measured at S[La]2 and SV2. It is concluded that deflection in heart rate does not always occur, and when it does, it coincides with the second lactate and ventilatory gas exchange thresholds. It can thus be used for the determination of optimal intensity for individualized aerobic training.

Adult↗
PubMed2006

Employment experience in relation to alcohol, tobacco, and betel nut use among youth in Taiwan.

The aim of this study is to assess the association linking employment experience with alcohol, tobacco, and betel nut involvement among youth in Taiwan. In 2004, an outreach program was conducted during weekdays to recruit youth sample in seven major geographic regions. A total of 5886 youth aged 12-18 years drawn from 26 cities or towns were assessed by a two-page anonymous self-administered questionnaire, including sociodemographic characteristics, employment-, development-, and drug-related experiences. In Taiwan, youthful experience of alcohol, tobacco, and polydrug use varies by employment status, work intensity, and job type. Holding a full-time job and working in certain settings (e.g., grocery, restaurants) were found associated with an excess of drug-using behaviors. With taking age, male gender, family context, disposable allowance, and school attendance into account, working youths were two to four times as likely to have recent drug involvement than their non-working counterparts, especially for tobacco and polydrug (OR=3.32, 95% CI: 2.58-4.27, p<0.001; OR=3.76, 95% CI: 2.76-5.13, p<0.001). Youths in the labor force emerge as a subgroup experiencing greater use of alcohol, tobacco, betel nut, and polydrug. Future prevention programs may target this high-risk group to reduce possible drug-related negative consequences in developmental and health domains in Taiwan.

Adolescent↗
PubMed1989

[Bases of measures aimed at improving working conditions for women employed in manufacturing of television sets].

Proceeding from hygienic, physiologic and ergonomic studies, a complex assessment of working conditions of female workers engaged in TV-set manufacture is presented. Major unfavourable occupational factors have been identified, among them there are work intensity, insufficient lighting of workplaces, their inadequate organization, induced posture during work at a conveyer with regulated movement rhythm. Profound computer-based studies of temporary disability rates have revealed a number of occupations for which temporary disability rates depend on female's length of service. The results obtained provide the basis for the development and introduction of health measures intended for further improvement of working conditions that promote reduction of temporary disability rates and have significant economic effect.

Adult↗
PubMed1987

Responses to dynamic leg exercise in man as influenced by changes in muscle perfusion pressure.

The influences of induced alterations in muscle perfusion pressure on the physiological responses to rhythmic exercise in man were investigated. The experiments were carried out in healthy subjects performing leg exercise on a cycle ergometer at light to exhaustive work intensities. Increased muscle perfusion pressure was brought about by exposing the working legs of the supine subject to a subatmospheric pressure of -50 mm Hg (Lower Body Negative Pressure, LBNP), decreased perfusion pressure by instead applying a supraatmospheric pressure of 50 mm Hg (Leg Positive Pressure, LPP). In this way, the perfusion pressure in dynamically exercising large muscle groups could be altered in a controlled fashion. The influences of such manipulation of the perfusion pressure on the physiological adjustments to incremental-load exercise were studied and analysed. The main results and conclusions were as follows: (1) Exercise-induced increases in cardiac output were attenuated by LBNP, an effect caused by curtailment of stroke volume secondary to suction-induced sequestration of blood volume in capacitance vessels not affected by the action of the leg muscle pump. This situation resembles that of dynamic leg exercise in the upright body position. Thus, supine exercise with LBNP at -50 mm Hg seems to be a valid model of upright leg exercise, not only in that it increases perfusion pressure in working muscles but also by causing similar changes in the central circulation as a shift from supine to upright leg exercise. (2) Exercise-induced increases in systolic arterial pressure were markedly exaggerated by LPP, an effect attributable to increased exercise responses in both cardiac output and total peripheral resistance. The exaggerated pressor response supports the notion of a muscle chemoreflex drive in response to flow-restricted exercise tending to reduce the existing flow error. (3) Exercise-induced increases in O2 uptake and blood lactate concentration were both attenuated by LBNP and exaggerated by LPP. The changes in blood lactate levels are attributable to perfusion-pressure dependent variations in muscle blood flow, resulting in opposite changes in the share contributed by anaerobic metabolism to the energy release. Possible explanations for the fact that impaired muscle perfusion was associated with increased O2 uptake at given external work loads are discussed. (4) Exercise-induced responses of the pulmonary ventilation were attenuated by LBNP and markedly exaggerated by LPP.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

A comparison of two noninvasive methods in the determination of the anaerobic threshold in children.

Seventy children, ranging in age from 7 to 14 years, performed a maximal exercise test on a treadmill with determination of the anaerobic threshold (AT) by two methods: (1) with the gas exchange method the ventilatory anaerobic threshold (VAT) was identified by the increase in the ventilatory equivalent for O2 uptake without a concomitant increase in the ventilatory equivalent for CO2 output and (2) with the method proposed by Conconi, the AT was taken at the point beyond which the increase in work intensity exceeded the increase in heart rate and the linearity of the work rate/heart rate relationship was lost. The AT values measured with the two methods were correlated (r = 0.80, P less than 0.001). This result confirms, also in children, the validity of the simple Conconi method: It can be used particularly for the determination of the individual optimal intensity of training.

Adolescent↗