Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “work intensity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources
PubMed1990

Effects of pyrogen administration on temperature regulation in exercising rats.

To study the mechanism of rise in body temperature during exercise, endogenous pyrogen was administered to exercising rats. At rest and at a neutral ambient temperature (Ta) of 24 degrees C, intravenous injection of recombinant human interleukin 1 (IL-1, 40 micrograms/kg) produced a 0.5 degree C rise in rectal temperature (Tre) from 37.4 degrees C. At Ta of 34 degrees C, at which Tre was 38.6 degrees C, Tre rise in response to IL-1 was only 0.2 degree C greater than when saline was used. In the first series of exercise experiments, rats ran on a treadmill after IL-1 or saline injection at two different work intensities (estimated at 40 and 60% of maximal oxygen uptake) at 24 degrees C Ta. At either work intensity, the magnitude of Tre rise after IL-1 injection was approximately 0.5 degree C higher than after saline injection. Threshold Tre for tail vasodilation increased when IL-1 was injected. The difference in the threshold Tre between the IL-1 and saline conditions was 0.5 degree C at either work intensity. Evaporative heat loss was also suppressed and metabolic heat production facilitated when IL-1 was injected. In a second series of experiments, IL-1 was injected after Tre reached a steady state (38.5 degrees C) during exercise. After IL-1 injection Tre increased another 0.5 degrees C, but after saline injection Tre did not change. These results suggest that body temperature rise during exercise is not induced merely by an insufficient capability of dissipating heat and that the thermoregulatory set point is reset during exercise.

Animals↗
PubMed2004

Overshoot in VO2 following the onset of moderate-intensity cycle exercise in trained cyclists.

We have previously observed that following the onset of moderate intensity cycle ergometry, the pulmonary O2 uptake (VO2) in trained cyclists often does not increase towards its steady-state value with the typical mono-exponential characteristics; rather, there is a transient "overshoot". The purpose of this study was to systematically examine this phenomenon by comparing the VO2 responses to two moderate-intensity work rates and one high-intensity work rate in trained and untrained subjects. Following a ramp exercise test to the limit of tolerance for the determination of the gas exchange threshold (GET) and VO2(peak), seven trained cyclists [mean (SD); VO2(peak) 66.6 (2.5) ml x kg(-1) x min(-1)] and eight sedentary subjects [VO2(peak) 42.9 (5.1) ml x kg(-1) x min(-1)] completed six step transitions from baseline cycling to work rates requiring 60% and 80% GET and three step transitions from baseline cycling to a work rate requiring 50% of the difference between GET and VO2(peak) (50%delta). VO2 was measured breath-by-breath and modelled using standard techniques. The sedentary subjects did not overshoot the steady-state VO2 at any intensity. At 60% GET, six of the seven cyclists overshot the steady-state VO2 [by an integral volume of 164 (44) ml between approximately 45 and 125 s]. At 80% GET, four of the seven cyclists overshot the steady-state VO2 [by an integral volume of 185 (92) ml between approximately 55 and 140 s]. None of the cyclists showed an overshoot at 50%delta. These results indicate that trained cyclists evidence an overshoot in VO2 before steady-state is reached in the transition to moderate-intensity exercise. The mechanism(s) responsible for this effect remains to be elucidated, as does whether the overshoot confers any functional or performance benefit to the trained cyclist.

Adult↗
PubMed2004

Further evidence on adolescent employment and substance use: differences by race and ethnicity.

In an on-going debate over the consequences of adolescent employment, there is growing agreement that work intensity (i.e., longer hours) fosters underage drinking and other substance use. The current study furthers our understanding of the relationship between hours of employment and substance use in adolescence by testing whether it is evident across racial/ethnic groups. Based on data from two waves of the National Longitudinal Study of Adolescent Health, the study finds that the effects of work intensity on substance use is mostly limited to whites. Work intensity is not consistently related to alcohol, cigarette, and marijuana use among minority adolescents.

Adolescent↗
PubMed1995

Regulation of glucose fluxes during exercise in the postabsorptive state.

The increase in glucose utilization by the working muscle would lead to hypoglycemia were it not accompanied by an increase in hepatic glucose production. Although the increase in glucose uptake is normally driven by mechanisms that are primarily independent of the action of insulin and other hormones, the response of the liver appears to be closely controlled by the endocrine system. Although considerable progress has been made in understanding the bases for the increases in glucose utilization and production, the means by which these two processes are coordinated to form the exercise response are unclear (e.g. feedback or central feedforward control). Work intensity affects the mechanisms by which glucose fluxes are regulated. For example, during moderate-intensity exercise, the glucoregulatory response resembles glucoregulation in the basal state in that under both conditions, glucose release from the liver is controlled by glucagon and insulin, and blood glucose levels are tightly controlled. The response to high-intensity exercise, on the other hand, takes on characteristics of the stress response, as described by Cannon (13). That is, the catecholamine response increases disproportionately for a given increment in work intensity, and glucose levels are no longer closely regulated, but increase. The specific factors that turn exercise into stress at higher work intensities are not well defined. Determining factors involved in the regulation of glucose fluxes are limited in some respects because the body is more sensitive than are experimental detection methods to various stimuli (glucose, hormones, neurotransmitter release). More complete delineation of mechanisms involved in the regulation of glucose fluxes will require the development of improved techniques and unique experimental models. The trend in the physiological sciences is for more study at the level of the gene. Technical limitations will be overcome or circumvented as knowledge of gene regulation and the development of genetically engineered animal models provide new avenues with which to address basic questions regarding the control of glucose fluxes during exercise.

Blood Glucose↗
PubMed2005

Spinal kinematics in elite oarswomen during a routine physiological "step test".

INTRODUCTION: Biomechanical measures of movement are being used increasingly to understand injury mechanisms and enhance performance. Frequently, rowing injuries are attributed to poor rowing technique. This suggests a need to understand technique and its influencing factors. This study aimed to quantify rowing technique in terms of lumbopelvic motion, force production, and work done at different work intensities. METHODS: An electromagnetic motion measuring device in conjunction with a load cell was used to determine the ergometer rowing kinematics of 12 elite international oarswomen during a routine step test. This test comprised six steps at a series of different stroke ratings starting at 18 strokes per minute and ending at maximal-output rowing. RESULTS: As work intensity increased, force output increased significantly (P < 0.0001). Stroke length remained relatively consistent throughout the steps, although there was a nonsignificant shortening from 136.5 cm (+/-6.4 SD) at 18 strokes per minute to 130.6 cm (+/-8.1) at maximal testing. Changes in kinematics were also observed, particularly at the catch and finish positions. There was a trend towards less anterior pelvic rotation occurring at the catch with an associated reduction in lumbar rotation and greater extensions occurring in both at the finish at the higher rating. Overall, rowers underutilized pelvic rotation to achieve these positions relying predominantly on lumbar rotation. CONCLUSION: This study quantified the spinal kinematics of elite rowers at different incremental work intensities and noted subtle but important changes to lumbopelvic and spinal kinematics at increasing work levels, particularly at maximal intensity. Such changes particularly are thought to be important with respect to the development of low-back pain.

Adult↗
PubMed2000

[Hardiness, coping and quality of life of nurses working in intensive care units].

The goals of the study are two-folds: on the one hand, to examine the relations between hardiness, coping strategies and quality of life at work of french nurses working in the intensive care units; on the other hand, to examine the mediating effect of coping strategies between hardiness and quality of life at work. Data was collected using a self-administered questionnaire, anonymously filled by 137 nurses which represented 60% participation from the initial sample population. Maddi & Kobasa's theory (1984) of Hardiness is the foundation for the present study and Baron & Kenny's statistical model (1986) was used to determine the mediating effect of the coping strategies. Regression analysis demonstrated that positive reevaluation/problem solving strategies had a mediating effect between a sense of commitment, a sense of mastery and quality of life at work. These results prompted various propositions in order to improve nurses quality of life at work.

Adaptation, Psychological↗
PubMed2003

Stressors, emotional exhaustion and aversion to patients in residents and chief residents - what can be done?

QUESTIONS UNDER STUDY: The goal of the study was to identify (1) specific stressors in the work of residents and chief residents (R and CR) and their consequences, and (2) possibilities for improvement. METHODS: Written questionnaire of 80 physicians at a Swiss public primary and secondary referral center and teaching hospital surveying stressors and resources in the working conditions as well as associated subjective strains. Selective observation of work activities of 14 representative R and CR. RESULTS: Stressors: R and CR reported a deficit in 6 out of 10 expectations regarding their work (greatest deficits: lack of time off, lack of future career prospects and of clear management). The deficits for the R/CR group differed in part highly significantly from deficits reported by directing physicians and medical directors. Work intensity was experienced as high or too high in 72% of R and 67% of CR. Strains: 41% of R and 43% of CR met criteria for emotional exhaustion, and 34% of R and 14% of CR reached critical values for aversion to patients. These strains correlated significantly with the stressors "overburdened through heavy workload", "subjective work intensity", "inadequate leisure time", and "lack of a right to a say in important matters" (all p between <0.001 and <0.01). CONCLUSIONS: Work-related emotional exhaustion and aversion to patients reached a critical mass in R and CR and was underestimated by both physicians and hospital management. The significant correlations between stressors and strains point to the main areas for improvement: reduction in work intensity and workload, change in style of leadership and management, development of new work models.

Burnout, Professional↗
PubMed1978

[The effect of oxyfedrine and intervall training in intermittent claudication (author's transl)].

In 23 patients suffering from intermittent claudication due to chronic occlusions of the femoral artery proved on angiography, a double-blind study was performed to compare the effects of treatment with oxyfedrine and interval-training and of interval-training alone. The claudication distance, physical work capacity and physical work intensity were measured on the treadmill before, during and after 10-weeks training period in each case. After training, the walking ability improved in both groups, however, quantitatively being more pronounced in the oxyfedrine group. In the placebo group, the increase in physical work intensity was mainly caused by the improvement of walking ability in patients with higher levels of performance at the beginning of the training. In the oxyfedrine group, on the other hand, a continuous and regular increase in physical work intensity was found at all levels of performance and during the whole training period. For the differences found, blood supply lowering mechanisms after physical training and improvement of collaterals after combination oxyfedrine and physical training are discussed. The possibility of additive action of the pharmacologic treatment and physical training are pointed out.

Aged↗
PubMed1989

A review of blood lactate and ventilatory methods of detecting transition thresholds.

As far back as the 1930s exercise physiologists recognised the existence of critical levels of work intensity above which lactate accumulation increased drastically and energy production was affected. Investigation of these transition points (thresholds) both invasively and non-invasively has led to much recent controversy. Respiratory exchange variables such as Ve, Ve/VO2, VCO2, excess CO2 and blood lactate have been monitored for simple, double and exponential breakaway points to elucidate these critical work intensities. A number of studies have produced high correlations between endurance performance and anaerobic threshold calculations, further demonstrating the potential existence of critical work intensities. Much of the controversy surrounding these phenomena has centered on mechanisms and nomenclature. The term 'anaerobic threshold' has been severely criticised because in addition to the tissues being oxygen insufficient, an imbalance in the energy systems may have resulted. The anaerobic condition or lactate accumulation may be due to changes in lactate production and removal. Muscle fibre type and the fibre type recruitment patterns may also be important factors in threshold transitions. Further examination is made in this review of non-invasive measures for determining transition thresholds and protocols for elucidating the critical points.

Anaerobic Threshold↗
PubMed1990

Circadian variation of thermoregulatory responses during exercise in rats.

Rats exercised on a treadmill at daytime lows and nighttime highs of circadian change in body temperature at two different work intensities [40 and 60% of maximal oxygen uptake (VO2max)] with the ambient temperature (Ta) at 24 degrees C. Immediately before exercise at 60% VO2max, rectal temperature (Tre) was 0.7 degrees C higher at night than during the day. During the exercise, Tre rose more during the day than at night, and Tre at the end of exercise was the same in the day as at night. Threshold Tre for tail vasodilation did not differ between day and night. Similar tendencies of Tre change and tail vasomotor response were observed at a work intensity of 40% VO2max, except that the rise in Tre was smaller than at the higher work intensity. On the other hand, threshold Tre for tail vasodilation spontaneously occurring in resting rats in a warm environment (Ta of 28 degrees C) was 0.7 degrees C higher at night than during the day. In conclusion, exercise in rats attenuates the differences in deep body temperature and threshold Tre for tail vasodilation seen between day and night.

Animals↗
PubMed1979

The significance of the aerobic-anaerobic transition for the determination of work load intensities during endurance training.

Anaerobic and aerobic-anaerobic threshold (4 mmol/l lactate), as well as maximal capacity, were determined in seven cross country skiers of national level. All of them ran in a treadmill exercise for at least 30 min at constant heart rates as well as at constant running speed, both as previously determined for the aerobic-anaerobic threshold. During the exercise performed with a constant speed, lactate concentration initially rose to values of nearly 4 mmol/l and then remained essentially constant during the rest of the exercise. Heart rate displayed a slight but permanent increase and was on the average above 170 beats/min. A new arrangement of concepts for the anaerobic and aerobic-anaerobic threshold (as derived from energy metabolism) is suggested, that will make possible the determination of optimal work load intensities during endurance training by regulating heart rate.

Adult↗
PubMed2004

Medical hegemony in decision-making--a barrier to interdisciplinary working in intensive care?

BACKGROUND: Health care policy in the United Kingdom identifies the need for health professionals to find new ways of working to deliver patient-focussed and economic care. Much debate has followed on the nature of working relationships within the health care team. AIM: This paper reports on an ethnographic study that examined the nursing role in clinical decision-making in intensive care units. This was chosen as a case for analysis due to the close doctor-nurse relationships that are essential in this acute and complex care setting. METHODS: Data were collected during two-stages of fieldwork using participant observation, in-depth ethnographic interviews and documentation across three clinical sites. FINDINGS: The findings revealed the different types of knowledge used for, divergence of roles involved in and degree of authority in clinical decision-making. Furthermore, conflict arose between doctors and nurses due to these differences and in particular because medicine dominated the decision-making process. CONCLUSIONS: The nursing role, whilst pivotal to implementing clinical decisions, remained unacknowledged and devalued. Medical hegemony continues to render nurses unable to influence substantially the decision-making process. This has fundamental ramifications for the quality of team decision-making and the effectiveness of new ways of inter-professional working in intensive care.

Decision Making↗
PubMed1990

Changes in insulation of body tissue and wet suits during underwater exercise at various atmospheric pressures.

To clarify the independent changes of insulations of body tissues (Itissue) and wet suit (Isuit) in the wet-suited subject during underwater exercise, overall heat flow from the skin (Htissue) and wet suit (Hsuit) and esophageal (Tes), skin (Tsk), and wet suit temperatures were measured at 1, 2, and 2.5 atmospheres absolute (ATA) at critical water temperature (Tcw). The average Tcw in nine wet-suited men (23-38 yr) was 22.3 +/- 0.2, 26.3 +/- 0.2, and 28.0 +/- 0.4 degrees C (SE) at 1, 2, and 2.5 ATA, respectively. At Tcw of each pressure male volunteers wearing 5-mm neoprene wet suits completed three 2-h experiments while immersed up to the neck. During one experiment the subjects remained at rest, and in the other two they exercised on an underwater ergometer at two different intensities (2 and 3 met). Tes significantly declined (P less than 0.05) over 2 h from 37.1 to 36.5 degrees C during rest in each pressure. The 2-met exercise prevented Tes from falling in all pressures, and the 3-met exercise elevated Tes by 0.2-0.3 degrees C. There was no exercise-dependent difference in Isuit, but a pressure-dependent difference was remarkable. The Itissue at rest was identical for all pressures; however, it progressively decreased as a function of exercise intensity. It is concluded that overall Itissue is entirely determined by work intensity at Tcw, but not by atmospheric pressure. On the contrary, Isuit at Tcw is solely dependent on the pressure, but not on the work intensity.

Adult↗
PubMed1984

[Ischemic heart disease among men engaged in intense mental work (results of a repeat examination 6 years later)].

A follow-up study (in 6.4 years) of a group of men aged 40-49 years (an average of 46.9) and engaged in strenuous mental work detected a large number of coronary heart disease (CHD) patients (28.9%) which exceeds the CHD incidence in the corresponding age groups of population threefold. Essential hypertension, hyperlipoproteinemia, smoking and stressful situations were shown to be valuable predictors of CHD. One of the major risk factors of CHD in the 40-49-year-old men studied was intensity of mental work.

Adult↗
PubMed1998

Functional neuromuscular stimulator for short-distance ambulation by certain thoracic-level spinal-cord-injured paraplegics.

BACKGROUND: Functional Neuromuscular Stimulation (FNS) for unbraced short-distance ambulation by traumatic complete/near-complete T4 to T12 paraplegics is based on work by Graupe et al (1982), Kralj et al (1980), Liberson et al (1961), and others. This paper discusses methodology, performance, training, admissibility criteria, and medical observations for FNS-ambulation using the Parastep-I system, which is the first and only such system to have received FDA approval (1994) and which emanated from these previous works. METHOD: The Parastep system is a transcutaneous non-invasive and microcomputerized electrical stimulation system built into a Walkman-size unit powered by eight AA batteries that is controlled by finger-touch buttons located on a walker's handbars for manual selection of stimulation menus. The microcomputer shapes, controls, and distributes trains of stimulation signals that trigger action potentials in selected peripheral nerves. Walker support is used for balance. The patient can don the system in under 10 minutes. At least 32 training sessions are required. RESULTS: Approximately 400 patients have used the Parastep system, essentially all achieving standing and at least 30 feet of ambulation, with a few reaching as much as 1 mile at a time. Recent literature presents data on the medical benefits of using the Parastep system-beyond the exercise benefits of short distance ambulation at will-such as increased blood flow to the lower extremities, lower HR at subpeak work intensities, increased peak work capability, reduced spasticity, and psychological benefits. CONCLUSIONS: We believe that the Parastep FNS system, which is presently commercially available by prescription, is easily usable for independent short-distance ambulation. We believe that its exercise benefits and its other medical and psychological benefits, as discussed, make it an important option for thoracic-level traumatic paraplegics.

Blood Pressure↗
PubMed1984

Cardiodynamic variables and ventilation during treadmill exercise in ponies.

We assessed the relationship of ventilation (VE) to cardiodynamic variables and CO2 transport in seven normal ponies during treadmill exercise. At 1.8, 3, and 6 mph, respectively, VE increased from 15 l/min at rest to 43, 51, and 86 l/min by 1 min and 48, 68, and 125 l/min by 8 min. In three ponies at the same work loads, cardiac output (Qc) increased from approximately 12 l/min at rest to 19.7, 28.1, and 40.3 l/min between 30-60 s (P less than 0.05) and then decreased by about 20% to a steady state by 3-4 min. Heart rate (HR) shows a similar biphasic response during exercise. Mean right ventricular pressure (MRVBP) increased from 9.9 to 15.9 Torr at 1.8 mph, 15.2 Torr at 3 mph, and 23.5 Torr at 6 mph by 1 min (P less than 0.05) and then decreased to 11.8, 12.2, and 15.8 Torr by 8 min of the three respective work intensities. At all work loads, VE increased proportionately faster than these cardiovascular variables in the 1st min. For example, at 6 mph VE increased 470%, whereas Qc and HR increased only 230%. Thereafter, VE generally continued to increase at 3 and 6 mph, whereas MRVBP, Qc, and HR decreased. Therefore, the basic assumption of a cardiodynamic hyperpnea that VE and Qc are equivalently coupled at the exercise onset is rejected for this species. Mixed venous CO2 content (C-vCO2) at 3 and 6 mph, respectively, decreased slightly from 61.6 and 62.3 vol% at rest to 59.6 and 61.9 vol% by 45 s and then increased to 63.3 and 63.5 vol% by 7 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

A comparative study on different methods for the determination of energy expenditure.

In order to determine energy expenditure, the Douglas Bag technique (DB) and Kofranyi-Michaelis respirometers (KM) have been widely used under field conditions for several decades. Some years ago the Oxylog (OX) method was developed, measuring simultaneously the difference of partial oxygen pressure in inspired and expired air (PO2 diff.) by two polarographic oxygen sensors. In order to compare these three methods laboratory experiments (3 test subjects, 5 different bicycle ergometer work loads, 180 measurements per apparatus) were performed. Oxygen uptake (VO2) varied between about 0.9 to 3.0 l/min. The VO2 data obtained by the DB method, which were used as a reference, and those obtained by the KM method agreed fairly well. The recorded data of OX underestimated VO2 up to 21%, with the deviation increasing with work intensity. A sufficient accuracy of recorded VO2 was observed only up to moderate work intensity. OX data calculated from ventilation volume of inspired air per minute (VI) and PO2 diff., measured by OX, were always about 19% higher than those recorded by OX. This means that the calculated VO2 values of the OX corresponded fairly well with DB values at heavy work loads. The reason for the differences between recorded and calculated OX data is still unknown. Further research is urgently needed.

Adult↗