Relative Workload Research Articles

Pseudo-faeces production in bivalves

Many filter feeders produce pseudo-faeces from selected particles that are filtered; pseudo-faeces does not pass the gut. Food intake can be limited by the filtering (acquisition) as well as the digestion (processing) rate. Its dynamics can be analysed in a straightforward way in the context of the Dynamic Energy Budget (DEB) theory using the closed hand-shaking protocol of Synthesizing Units. The model reveals how food intake depends on the relative size of the filtering and digestion machinery, which can be used to model differentated growth of these structures if allocation is linked to their relative workload. It turns out that non-digestible particles modify the apparent half-saturation coefficient, which makes that estimates for this coefficient can be used to quantify the mean silt load in a given habitat.

Adaptive load distribution algorithms for heterogeneous distributed systems with multiple task classes

A load distribution ( LD) algorithm achieves better system performance by smoothing out any workload imbalance that may exist in a distributed system. This is done by relocating application tasks from busy nodes to lightly loaded (or idle) nodes. Previous studies on LD algorithms allow only one single task to be transferred for each sender–receiver negotiation session. While this approach is effective for a homogeneous system, it is too conservative to be applied to a heterogeneous system where nodes may have drastically different processing speeds. In this paper, we propose a class of LD algorithms that allow a batch of tasks to be transferred during each negotiation session. The core of the algorithms is a protocol that ensures a sender–receiver pair to negotiate and arrive at a suitable batch size. The protocol takes into consideration the processing speeds of the sender and receiver, as well as their relative workload, thus ensuring the maximal benefit for each negotiation session. An additional advantage of the algorithms is that a task batch can be composed according to different performance objectives.

Human temperature regulation during cycling with moderate leg ischaemia

The effect of graded ischaemia in the legs on the regulation of body temperature during steady-state exercise was investigated in seven healthy males. It was hypothesised that graded ischaemia in the working muscles increases heat storage within the muscles, which in turn potentiates sweat secretion during exercise. Blood perfusion in the working muscles was reduced by applying a supra-atmospheric pressure (+6.6 kPa) around the legs, which reduced maximal working capacity by 29%. Each subject conducted three separate test trials comprising 30 min of steady-state cycling in a supine position. Exercise with unrestricted blood flow (Control trial) was compared to ischaemic exercise conducted at an identical relative work rate (Relative trial), as well as at an identical absolute work rate (Absolute trial); the latter corresponding to a 20% increase in relative workload. The average (SD) increases in both the rectal and oesophageal temperatures during steady-state cycling was 0.3 (0.2) degrees C and did not significantly differ between the three trials. The increase in muscle temperature was similar in the Control (2.7 (0.3) degrees C) and Absolute (2.4 (0.7) degrees C) trials, but was substantially lower (P < 0.01) in the Relative trial (1.4 (0.8) degrees C). Ischaemia potentiated (P < 0.01) sweating on the forehead in the Absolute trial (24.2 (7.3) g m(-2) min(-1)) compared to the Control trial (13.4 (6.2) g m(-2) min(-1)), concomitant with an attenuated (P < 0.05) vasodilatation in the skin during exercise. It is concluded that graded ischaemia in working muscles potentiates the exercise sweating response and attenuates vasodilatation in the skin initiated by increased core temperature, effects which may be attributed to an augmented muscle metaboreflex.

Whole‐body fat oxidation determined by graded exercise and indirect calorimetry: a role for muscle oxidative capacity?

During whole-body exercise, peak fat oxidation occurs at a moderate intensity. This study investigated whole-body peak fat oxidation in untrained and trained subjects, and the presence of a relation between skeletal muscle oxidative enzyme activity and whole-body peak fat oxidation. Healthy male subjects were recruited and categorized into an untrained (N=8, VO(2max) 3.5+/-0.1 L/min) and a trained (N=8, VO(2max) 4.6+/-0.2 L/min) group. Subjects performed a graded exercise test commencing at 60 W for 8 min followed by 35 W increments every 3 min. On a separate day, muscle biopsies were obtained from vastus lateralis and a 3 h bicycle exercise test was performed at 58% of VO(2max). Whole-body fat oxidation was calculated during prolonged and graded exercise from the respiratory exchange ratio using standard indirect calorimetry equations. Based on the graded exercise test, whole-body peak fat oxidation was determined. The body composition was determined by DEXA. Whole-body peak fat oxidation (250+/-25 and 462+/-33 mg/min) was higher (P<0.05) and occurred at a higher (P<0.05) relative workload (43.5+/-1.8% and 49.9+/-1.2% VO(2max)) in trained compared with untrained subjects, respectively. Muscle citrate synthase activity and beta-hydroxy-acyl-CoA-dehydrogenase activity were higher (49% and 35%, respectively, P<0.05) in trained compared with untrained subjects. Both lean body mass and maximal oxygen uptake were significantly correlated to whole-body peak fat oxidation (r(2)=0.57, P<0.001), but leg muscle oxidative capacity was not correlated to whole-body peak fat oxidation. In conclusion, whole-body peak fat oxidation occurred at a higher relative exercise load in trained compared with untrained subjects. Whole-body peak fat oxidation was not significantly related to leg muscle oxidative capacity, but was related to lean body mass and maximal oxygen uptake. This may suggest that leg muscle oxidative activity is not the main determinant of whole-body peak fat oxidation.

Immediate impact of ‘penalty points legislation’ on acute hospital trauma services

Road traffic accident (RTA) related mortality and injury may be reduced by up to 40% with the introduction of 'road safety' legislation. Little is known regarding changes in pattern of injury and overall resource impact on acute trauma services. This prospective study examines RTA related admissions, injuries sustained and resultant sub-speciality operative workload in a Level 1 Trauma Centre during the 12 months immediately prior to and following the introduction of 'penalty points' legislation. Eight hundred and twenty RTA related admissions were identified over the 24-month period from 01/11/2001 to 31/10/2003. There was a 36.7% decrease in RTA related admissions subsequent to the introduction of new legislation. Bed occupancy was almost halved. However, the relative Orthopaedic workload increased from 34% to 41% with a 10% increase in relative bed occupancy. The pattern of orthopaedic injury was significantly altered with a >50% absolute reduction in high velocity injuries. Curiously, there was no change in the absolute number of spinal fractures seen. This favourable early Irish experience of 'penalty points' legislation mirrors that of worldwide published literature. Our findings demonstrate that the injury reduction effects were primarily enjoyed by non-orthopaedic sub-specialities. Such findings mandate consideration when allocating vital resources to sub-specialities within busy trauma units.

Complete recovery time after exhaustion in high-intensity work

This study was aimed to investigate complete recovery time (CRT) after exhaustion in high-intensity work. Twenty-four subjects were divided into two groups based on the cardiorespiratory capability index, which was measured in a maximum capacity test. Each subject then performed two cycling tests (at 60% and 70% maximum working capacity). The subject continued cycling until exhaustion in each test and then sat recovering until he/she no longer felt fatigue or until the oxygen uptake (VO2) and heart rate (HR) returned to their baselines, whichever was longer. The results indicated that HR required the longest time to recover and, consequently, HR data were adopted to set the CRT. The CRT was significantly correlated with the cardiorespiratory capability index and the relative workload indices: RVO2 and RHR. The RVO2 was the average elevation in VO2 during work from the resting level as a percentage of maximum VO2 reserve. The RHR's definition was similar to that of RVO2. Based on the obtained CRT-prediction model, the CRT for a high-cardiorespiratory-capability person was 20.8, 22.1, 23.4, and 24.7 min at 50%, 60%, 70%, and 80% RHR levels, respectively. These suggested CRT values should be increased by 10 min for a low-cardiorespiratory-capability person.

Transcriptional basis for exercise limitation in male eNOS-knockout mice with age: heart failure and the fetal phenotype

Endothelium-derived nitric oxide (NO) is pivotal in regulating mitochondrial O(2) consumption (Vo(2)) and glucose uptake in mice. The aim of this study was to investigate the mechanism of age- and genotype-related exercise limitation in male endothelial NO synthase (eNOS)-knockout (KO, n = 16) and wild-type (WT, n = 19) mice. Treadmill testing was performed at 12, 14, 16, 18, and 21 mo of age. Vo(2), CO(2) production, respiratory exchange ratio, and maximal running distance were determined during treadmill running. There were good linear correlations for increase of speed with increase of Vo(2). The difference between KO and WT mice was not significant at 12 mo but was significant at 18 mo. Linear regression showed that KO mice consumed more O(2) at the same absolute and relative workloads, suggesting that Vo(2) was not inhibited by NO in KO mice. KO mice performed 30-50% less work than WT mice at each age (work = vertical distance x weight). In contrast to WT mice, the work performed by KO mice significantly decreased from 17 +/- 1.4 m.kg at 12 mo to 9.4 +/- 1.7 m.kg at 21 mo. Running distance was significantly decreased from 334 +/- 27 m at 12 mo to 178 +/- 38 m at 21 mo, and maximal Vo(2), CO(2) production, and respiratory exchange ratio per work unit were significantly higher in KO than in WT mice. Gene arrays showed evidence of a fetal phenotype in KO mice at 21 mo. In conclusion, age- and genotype-related exercise limitations in maximal work performed and maximal running distance in male eNOS-KO mice indicated that fetal phenotype and age were related to onset of heart failure.

Effects of downstream migration on myosin heavy chain expression and dihydropyridine receptor density in farmed smolt of Atlantic salmon

The expression of myosin heavy chain (MHC) subunits and dihydropyridine receptors (DHPRs) from red and white tail muscles of cultured smolts of Atlantic salmon Salmo salar was analysed from samples taken: (1) before the fish were transferred to the river and (2) after the migration distance of c. 50 km. The relative work load of migrating fish, estimated on the basis of swimming speed of Atlantic salmon and discharge rate of the River Simojoki, Finland, was maximally 1700 times higher than that of fish in culture. The data show that after five migration days the density of DHPRs in the muscles of the smolts was increased already. Furthermore, the results indicated a transition from the fast‐to‐slow MHC isoform. Transfer of fish to a natural environment and downstream migration thus had a significant effect on the expression of muscle proteins.

Estimating relative physical workload using heart rate monitoring: a validation by whole-body indirect calorimetry

Measuring physical workload in occupational medicine is fundamental for risk prevention. An indirect measurement of total and relative energy expenditure (EE) from heart rate (HR) is widely used but it has never been validated. The aim of this study was to validate this HR-estimated energy expenditure (HREEE) method against whole-body indirect calorimetry. Twenty-four-hour HR and EE values were recorded continuously in a calorimetric chambers for 52 adult males and females (19-65 years). An 8-h working period was retained, comprising several exercise sessions on a cycloergometer at intensities up to 65% of the peak rate of oxygen uptake. HREEE was calculated with reference to cardiac reserve. A corrected HREEE (CHREEE) was also calculated with a modification to the lowest value of cardiac reserve. Both values were further compared to established methods: the flex-HR method, and the use of a 3rd order polynomial relationship to estimate total and relative EE. No significant difference was found in total EE when measured in a calorimetric chamber or estimated from CHREEE for the working period. A perfect linear and identity relationship was found between CHREEE and energy reserve values for intensities ranging from 15% to 65%. Relative physical workload can be accurately assessed from HR recordings when expressed in CHREEE between 15% to 65%, and EE can be accurately estimated using the CHREEE method.

Acute Moderate Hypoxia Affects the Oxygen Desaturation and the Performance but not the Oxygen Uptake Response

The purpose of this study was to examine the influence of hypoxia on the O2 uptake response, on the arterial and muscular desaturation and on the test duration and test duration at VO2max during exhaustive exercise performed in normoxia and hypoxia at the same relative workload. Nine well-trained males cyclists performed an incremental test and an exhaustive constant power test at 90 % of maximal aerobic power on a cycling ergometer, both in normoxia and hypoxia (inspired O2 fraction = 16 %). Hypoxic normobar conditions were obtained using an Alti Trainer200 and muscular desaturation was monitored by near-infrared spectroscopy instrument (Niro-300). The mean response time (66 +/- 4 s vs. 44 +/- 7 s) was significantly lower in hypoxia caused by the shorter time constant of the VO2 slow component. This result was due to the lower absolute work rate in hypoxia which decreased the amplitude of the VO2 slow component. The arterial (94.6 +/- 0.3 % vs. 84.2 +/- 0.7 %) and muscular desaturation (in the vastus lateralis and the lateral gastrocnemius) were reduced by hypoxia. The test duration (440 +/- 31 s vs. 362 +/- 36 s) and the test duration at VO2max (286 +/- 53 s vs. 89 +/- 33 s) were significantly shorter in hypoxia. Only in normoxia, the test duration was correlated with arterial and muscular saturation (r = 0.823 and r = 0.828; p < 0.05). At the same relative workload, hypoxia modified performance, arterial and muscular oxygen desaturation but not the oxygen uptake response. In normoxia, correlation showed that desaturation seems to be a limiting factor of performance.

Exercise training increases oxidative capacity and attenuates exercise-induced ultrastructural damage in skeletal muscle of aged horses

Exercise training improves functional capacity in aged individuals. Whether such training reduces the severity of exercise-induced muscle damage is unknown. The purpose of the present study was to determine the effect of 10 wk of treadmill exercise training on skeletal muscle oxidative capacity and exercise-induced ultrastructural damage in six aged female Quarter horses (>23 yr of age). The magnitude of ultrastructural muscle damage induced by an incremental exercise test before and after training was determined by electron microscopic examination of samples of triceps, semimembranosus, and masseter (control) muscles. Maximal aerobic capacity increased 22% after 10 wk of exercise training. The percentage of type IIa myosin heavy chain increased in semimembranosus muscle, whereas the percentage of type IIx myosin heavy chain decreased in triceps muscle. After training, triceps muscle showed significant increases in activities of both citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. Attenuation of exercise-induced ultrastructural muscle damage occurred in the semimembranosus muscle at both the same absolute and the same relative workloads after the 10-wk conditioning period. We conclude that aged horses adapt readily to intense aerobic exercise training with improvements in endurance, whole body aerobic capacity, and muscle oxidative capacity, and heightened resistance to exercise-induced ultrastructural muscle cell damage. However, adaptations may be muscle-group specific.

Endurance training reduces the contraction-induced interleukin-6 mRNA expression in human skeletal muscle.

Contracting skeletal muscle expresses large amounts of IL-6. Because 1) IL-6 mRNA expression in contracting skeletal muscle is enhanced by low muscle glycogen content, and 2) IL-6 increases lipolysis and oxidation of fatty acids, we hypothesized that regular exercise training, associated with increased levels of resting muscle glycogen and enhanced capacity to oxidize fatty acids, would lead to a less-pronounced increase of skeletal muscle IL-6 mRNA in response to acute exercise. Thus, before and after 10 wk of knee extensor endurance training, skeletal muscle IL-6 mRNA expression was determined in young healthy men (n = 7) in response to 3 h of dynamic knee extensor exercise, using the same relative workload. Maximal power output, time to exhaustion during submaximal exercise, resting muscle glycogen content, and citrate synthase and 3-hydroxyacyl-CoA dehydrogenase enzyme activity were all significantly enhanced by training. IL-6 mRNA expression in resting skeletal muscle did not change in response to training. However, although absolute workload during acute exercise was 44% higher (P < 0.05) after the training period, skeletal muscle IL-6 mRNA content increased 76-fold (P < 0.05) in response to exercise before the training period, but only 8-fold (P < 0.05, relative to rest and pretraining) in response to exercise after training. Furthermore, the exercise-induced increase of plasma IL-6 (P < 0.05, pre- and posttraining) was not higher after training despite higher absolute work intensity. In conclusion, the magnitude of the exercise-induced IL-6 mRNA expression in contracting human skeletal muscle was markedly reduced by 10 wk of training.

Patients with classic congenital adrenal hyperplasia have decreased epinephrine reserve and defective glucose elevation in response to high-intensity exercise.

Classic congenital hyperplasia (CAH) is characterized by impaired adrenocortical function with a decrease in cortisol and aldosterone secretion and an increase in androgen secretion. Adrenomedullary function is also compromised due to developmental defects in the formation of the adrenal medulla, leading to decreased production of epinephrine. To examine the response to a natural stressful stimulus in patients with classic CAH, we studied hormonal, metabolic, and cardiorespiratory parameters in response to a standardized high-intensity exercise protocol in nine adolescent patients with CAH and nine healthy controls matched for gender, age, and percent body fat. The same relative workload was applied, based on individual maximal aerobic capacity, and all patients received their usual glucocorticoid and mineralocorticoid replacement. When compared with their normal counterparts, patients with CAH had significantly lower epinephrine levels both at baseline and at peak exercise (P < 0.01), whereas norepinephrine levels did not differ. Blood glucose concentrations were similar at baseline, but the normal exercise-induced rise observed in the healthy controls was significantly blunted in the CAH patients (P < 0.01). Peak heart rate was also lower in CAH patients than healthy controls (P < 0.05). As expected, the normal exercise-induced increase in cortisol was not observed in patients with CAH. No significant differences were found in serum levels of insulin, glucagon, GH, lactate and free fatty acids, blood pressure, or ability to sustain exercise between the two groups. Patients with CAH replaced with glucocorticoids have decreased adrenomedullary reserve and impaired exercise-induced changes in glucose but normal short-term high-intensity exercise performance. Whether the combination of epinephrine and cortisol deficiency poses a risk for hypoglycemia and/or decreased endurance during long-term physical stress has to be determined.

Limiar de lactato em exercicio resistido

Lactate thresholds (LT) during activities such as running, cycling, rowing, and swimming have been the subject of many studies for the past several decades. However, little is known about the LT parameter during endurance exercises. The purpose of this study was to assess and compare relative and absolute values of LT relative to individual maximal workload during leg-press (LP) and elbow flexion (EF) exercises for both trained (T) and untrained (U) male participants. There was no difference between the relative LT for the four groups (LP-T = 32.22 ± 4.40%; LP-U = 28.0 ± 6.32%; EF-T = 32.22 ± 6.66%; RD-U = 28.88 ± 3.33%). On the other hand, the absolute values for both trained groups (LP-T = 173.0 ± 51.97 kg and EF-T = 18.73 ± 4.13 kg) were significantly different (p< .05) compared to the untrained groups (LP-U = 84.10 ± 18.78 kg; EF-U = 10.81 ± 1.27 kg). The results suggest that the LT for LP and EF exercises are similar only when relative workload is considered.

GENDER DIFFERENCES IN CENTRAL AND PERIPHERAL FACTORS OF SKELETAL MUSCLE FATIGUE

Women generally exhibit greater fatigue resistance than men, due in part to differences in muscle mass. Less muscle mass in women results in decreased oxygen demand and increased oxygen delivery at the same relative workload compared to men and yields greater endurance. The purpose of this study was to examine sex differences in muscle fatigue between male and female athletes matched for muscle mass. Twenty four males and females were tested and yielded eight male-female pairs matched for age, training history and thigh muscle volume. Thigh muscle volume was estimated via circumference and skinfold measurements using the truncated cone method. Mean difference in thigh muscle volume between subjects within each pair was 2.13 ml (SD = 2.25). Strength was measured as maximum voluntary contraction (MVC), determined by superimposing an electrical stimulus at 3x threshold (26-pulse, 100-Hz, 250-ms train) while subjects performed a 5-second maximum isometric contraction on a Cybex® dynamometer. Central activation ratio (CAR = MVC / MVC + electrical stimulation) was calculated to insure maximum motor unit recruitment. Subjects then completed a fatigue protocol of intermittent, 5-second sustained isometric leg extension at 50% of initial MVC with alternating 5-second rest periods until exhaustion. At termination, a final 5-second MVC was performed with superimposed electrical stimulation and CAR was calculated to quantify the contribution of central factors to fatigue. Sex differences in time to fatigue, rate of fatigue, percent of initial strength at fatigue, and CAR were assessed with paired ttests. There were no significant differences within matched pairs for time to fatigue, rate of fatigue, or percent of initial strength. There was no significant difference in CAR. The

THE EFFECTS OF A MONITORED AEROBIC EXERCISE PROGRAM ON CHRONIC FATIGUE SYNDROME (CFS)

CFS is a serious disabling illness, characterized by severe and chronic fatigue, with rheumatological, infectious, and neuropsychiatric symptoms. In the absence of any specific organ or system to treat, therapy for CFS is experimental and often includes mild physical exercise. However, many patients complain that exercise exacerbates their symptoms. PURPOSE To determine the effects of a monitored aerobic exercise program on CFS symptoms. METHODS Twenty-three CFS patients (CFS-TR) and 18 healthy, sedentary subjects (CON-TR) participated in a three day per week treadmill walking program for 10 weeks. Training intensity progressed to 50% peak oxygen uptake during the last six weeks. Twelve CFS and seven CON were used for nontraining groups. All subjects performed a graded cardiopulmonary treadmill exercise test (CPX) pre and post 10 weeks. On each training day feelings of well-being and ratings of muscle soreness were ascertained. Pre and post 10 weeks, symptoms of CFS were assessed utilizing a packet of questionnaires that included the following: Multi-Fatigue Index, Medical Outcomes Study SF36, Profile of Mood States, and Beck Depression Inventory (BDI). RESULTS Two CFS-TR patients withdrew for reasons not attributed to symptom exacerbation. None of the metabolic variables measured during the CPX significantly changed for any group (all p > .05). Total CPX exercise time increased for the training groups (p < .04). The ratings of perceived exertion at absolute and relative workloads decreased for the CFS-TR (p < .05). Feelings of well-being and ratings of muscle soreness did not change for the CFS-TR (all p > .05). BDI scores for all CFS patients decreased over time (p < .05) but no significant changes were seen for any of the additional variables measured with the symptom questionnaires (all p > .05). CONCLUSION CFS patients can tolerate mild to moderate aerobic exercise; training improved exercise tolerance but did not improve or exacerbate CFS symptoms. Supported by NIH Center Grant U01 AI-32247.

Exercise induces transient transcriptional activation of the PGC-1alpha gene in human skeletal muscle.

Endurance exercise training induces mitochondrial biogenesis in skeletal muscle. The peroxisome proliferator activated receptor co-activator 1alpha (PGC-1alpha) has recently been identified as a nuclear factor critical for coordinating the activation of genes required for mitochondrial biogenesis in cell culture and rodent skeletal muscle. To determine whether PGC-1alpha transcription is regulated by acute exercise and exercise training in human skeletal muscle, seven male subjects performed 4 weeks of one-legged knee extensor exercise training. At the end of training, subjects completed 3 h of two-legged knee extensor exercise. Biopsies were obtained from the vastus lateralis muscle of both the untrained and trained legs before exercise and after 0, 2, 6 and 24 h of recovery. Time to exhaustion (2 min maximum resistance), as well as hexokinase II (HKII), citrate synthase and 3-hydroxyacyl-CoA dehydrogenase mRNA, were higher in the trained than the untrained leg prior to exercise. Exercise induced a marked transient increase (P < 0.05) in PGC-1alpha transcription (10- to > 40-fold) and mRNA content (7- to 10-fold), peaking within 2 h after exercise. Activation of PGC-1alpha was greater in the trained leg despite the lower relative workload. Interestingly, exercise did not affect nuclear respiratory factor 1 (NRF-1) mRNA, a gene induced by PGC-1alpha in cell culture. HKII, mitochondrial transcription factor A, peroxisome proliferator activated receptor alpha, and calcineurin Aalpha and Abeta mRNA were elevated (approximately 2- to 6-fold; P < 0.05) at 6 h of recovery in the untrained leg but did not change in the trained leg. The present data demonstrate that exercise induces a dramatic transient increase in PGC-1alpha transcription and mRNA content in human skeletal muscle. Consistent with its role as a transcriptional coactivator, these findings suggest that PGC-1alpha may coordinate the activation of metabolic genes in human muscle in response to exercise.

Pulse rate criteria for determining the energy cost of exercise

From the pulse rate curve taken during exercise and recovery from highly qualified sportsmen performing a bicycle exercise test at a maximum workload, the work pulse sum, pulse debt, and pulse cost were calculated. Plots of these indices versus the time to exhaustion and versus the relative exercise workload were identical to the respective plots of oxygen consumption during exercise, oxygen debt, and oxygen requirement. The exercise pulse cost can serve as a criterion for quantifying physical workloads.

Training-induced alterations in glucose metabolism during moderate-intensity exercise.

In several species, physical conditioning (training) provokes a large shift in substrate utilisation during submaximal exercise. Few studies in horses have quantitatively examined these effects. Therefore, the effects of exercise training on plasma glucose kinetics during submaximal exercise were examined in 7 horses (5 Thoroughbred, 2 Standardbred; age 3-9 years) that had been paddock-rested for at least 6 months. Two days after determination of maximum aerobic capacity (VO2max), horses ran on a treadmill (4 degree incline) at 55% of VO2max (UT) for 60 min or until fatigue and then completed 6 weeks of moderate-intensity training on a treadmill (5 days/week). Following training and a second VO2max test, the horses completed exercise trials at the same absolute (ABS) and relative (REL) workload in random order, with at least 3 days between tests. After training, VO2max had increased (P<0.05) by 14.9% (mean +/- s.e. pretraining 118.4 +/- 7.4 ml/kg bwt/min; post-training 136.1 +/- 7.8 ml/kg bwt/min). Mean exercise duration was longer (P<0.05) in the ABS trial (57 +/- 1.9 min) than in the UT (46 +/- 3.9 min) and REL (49 +/- 4.6 min) trials. Plasma glucose concentration increased during exercise, and was lower (P<0.05) in ABS than in UT and REL at the end of exercise. Mean glucose rate of appearance (Ra) and disappearance (Rd) were 22 and 21% lower (P<0.05), respectively, in ABS than in UT, but mean glucose Ra and Rd did not differ between the UT and REL trials. Exercise-induced changes in glucagon, epinephrine and norepinephrine were blunted (P<0.05) in ABS, but not REL, when compared to UT. It is concluded that 6 weeks of moderate-intensity training results in a decrease in glucose flux during submaximal exercise at the same absolute, but not relative, workload. The training-induced decrease in glucose flux may, in part, be due to altered plasma concentrations of the major glucoregulatory hormones.

Relationships between HR and (.)VO(2) in the obese.

To enable more targeted exercise prescription for the obese, the purpose of this study was to consider relationships between relative indices of (.)VO(2peak), (.)VO(2)R, HR(peak), and HRR in a sample of obese adults. In particular, the study aimed to determine whether %HRR was equivalent to %(.)VO(2peak) or %(.)VO(2)R. A further aim was to evaluate whether the %(.)VO(2peak)-%HR(peak) relationship defined by the ACSM holds in the obese population, or whether there is a deviation in this relationship as is noted in individuals with low functional capacity. Finally, the study aimed to determine the degree of variability in relative workload relating to lactate threshold (LT). Thirty-two sedentary obese adults, 17 women and 15 men (42.1 +/- 9.6 yr; 37.4 +/- 5.7 kg.m) attended a testing session each week for 3 wk. The three sessions involved 1) familiarization with testing protocols; 2) graded treadmill tests to evaluate submaximal and peak cardiorespiratory capacity; and 3) assessment of body composition via deuterium dilution, and resting HR (HR(rest)) and oxygen consumption ((.)VO(2rest)) collected during assessment of resting metabolic rate (RMR) via a ventilated hood system. The primary findings were that in the obese: 1) the %HR(peak)-%(.)VO(2peak) relationship was significantly greater than the ACSM recommendations, 2) the %HRR was equivalent with (.)VO(2)R not %(.)VO(2peak), and 3) exercise prescription at fixed percentages of (.)VO(2peak) or HR(peak) corresponded with wide ranges of exercise intensities in relation to LT. The relationships between cardiorespiratory parameters defined in normal weight populations differ to some degree in the obese, and this has implications both for optimizing exercise intensity for weight loss and exercise adherence in obese adults.