Autonomic nervous function at rest in aerobically trained and untrained oldermen

Therelationship between aerobictraining, vagal influence on the heart and ageing was examined by assessing aerobic fitness andresting heart rate variability in trained and untrained older men. Subjects were 11 trained cyclistsand runners (mean age=6±61·6 years) and 11 untrained, age-matchedmen (mean age=66±1·2 years). Heart rate variability testing involvedsubjects lying supine for 25 min during which subjects’ breathing was paced andmonitored (7·5 breaths min^?1). Heart rate variability was assessedthrough time series analysis (HRV_ts) of the interbeat interval. Results indicated thattrained older men (3·55±0·21 l min^?1) hadsignificantly (P<0·05) greater VO _2maxthan that of control subjects (2·35±0·15 l min^?1).Also, trained older men (52±1·8 beats min^?1) hadsignificantly (P<0·05) lower supine resting heart rate than that of controlsubjects (65±4·2 beats min^?1). HRV_ts at highfrequencies was greater for trained men (5·98±0·22) than for untrainedmen (5·23±0·32). These data suggest that regular aerobic exercise inolder men is associated with greater levels of HRV_ts at rest.     

Perfusion heterogeneity does not explain excess muscle oxygen uptake during variable intensity exercise

The association between muscle oxygen uptake (VO₂) and perfusion or perfusion heterogeneity (relative dispersion, RD) was studied in eight healthy male subjects during intermittent isometric (1 s on, 2 s off) one‐legged knee‐extension exercise at variable intensities using positron emission tomography and a‐v blood sampling. Resistance during the first 6 min of exercise was 50% of maximal isometric voluntary contraction force (MVC) (HI‐1), followed by 6 min at 10% MVC (LOW) and finishing with 6 min at 50% MVC (HI‐2). Muscle perfusion and O₂ delivery during HI‐1 (26 ± 5 and 5·4 ± 1·0 ml 100 g^?1 min^?1) and HI‐2 (28 ± 4 and 5·8 ± 0·7 ml 100 g^?1 min^?1) were similar, but both were higher (P<0·01) than during LOW (15 ± 3 and 3·0 ± 0·6 ml 100 g^?1 min^?1). Muscle VO₂ was also higher during both HI workloads (HI‐1 3·3 ± 0·4 and HI‐2 4·1 ± 0·6 ml 100 g^?1 min^?1) than LOW (1·4 ± 0·4 ml 100 g^?1 min^?1; P<0·01) and 25% higher during HI‐2 than HI‐1 (P<0·05). O₂ extraction was higher during HI workloads (HI‐1 62 ± 7 and HI‐2 70 ± 7%) than LOW (45 ± 8%; P<0·01). O₂ extraction tended to be higher (P = 0·08) during HI‐2 when compared to HI‐1. Perfusion was less heterogeneous (P<0·05) during HI workloads when compared to LOW with no difference between HI workloads. Thus, during one‐legged knee‐extension exercise at variable intensities, skeletal muscle perfusion and O₂ delivery are unchanged between high‐intensity workloads, whereas muscle VO₂ is increased during the second high‐intensity workload. Perfusion heterogeneity cannot explain this discrepancy between O₂ delivery and uptake. We propose that the excess muscle VO₂ during the second high‐intensity workload is derived from working muscle cells.     

Body composition,maximal aerobic performance and inflammatory biomarkers in endurance-trained athletes

This study was designed to examine the relationships between body composition, cardiorespiratory fitness and simultaneously measured inflammatory parameters in endurance-trained athletes. In 20 well-trained rowers (19·0 ± 2·9 years; 185·6 ± 4·8 cm; 85·7 ± 10·8 kg; 17·1 ± 5·1% body fat; maximal oxygen consumption [VO₂max]: 63·9 ± 8·5 ml min⁻¹ kg⁻¹), body composition was measured by dual-energy X-ray absorptiometry and cardiorespiratory fitness by direct VO₂max test. Twelve inflammatory factors [interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, vascular endothelial growth factor, interferon-gamma (IFN-γ), tumour necrosis factor-alpha, IL-1α, IL-1β, monocyte chemoattractant protein-1 (MCP-1), epidermal growth factor (EGF)] were analysed from serum samples. Serum IFN-γ was related (P<0·05) to fat-free mass (FFM) (r = −0·56) and muscle mass (r = −0·50). The stepwise regression analysis showed that IFN-γ explained 27·5%, and IFN-γ and IL-6 together explained 39·8% of the variability of FFM, while IFN-γ explained 21·1%, and IFN-γ together with EGF explained 36·6% of the variability of muscle mass in male rowers. Serum IL-8 (r = −0·65) and VEGF (r = −0·48) correlated (P<0·05) with VO₂max kg⁻¹. Serum IL-8 explained 38·5% of the variability of VO₂max kg⁻¹. Significant correlations were also found among several inflammatory parameters, indicating that various inflammatory cytokines act on the body as an ensemble. In conclusion, this cross-sectional study in endurance-trained male rowers showed that FFM and muscle mass were negatively correlated with serum IFN-γ level, whereas cardiorespiratory fitness was negatively related to serum IL-8 level.     

The associations between peak O2 consumption and leptin in 10‐ to 12‐year‐old boys

The aim of this study was to assess the associations of circulating levels of leptin with the peak O₂ consumption (VO_2peak) in 10 ‐ to 12‐year‐old boys of different BMI selected by Cole et al. (BMJ, 320,2000,1–6): total group (n = 248), normal (n = 190), overweight (n = 34) and obese (n = 24). We hypothesized that there is a close relationship in overweight and obese subgroups of boys with relative VO_{2peak kg}^?1(ml min^?1 kg^?1) and leptin. Most of the subjects were Tanner stage 2. Peak O₂ consumption was measured directly using an increasing incremental protocol until volitional exhaustion on an electronically braked cycle ergometer. The expired gas was sampled continuously breadth‐by‐breadth mode for the measurement of oxygen consumption (MetaMax, Germany). Blood samples were obtained after an overnight fast from an antecubital vein for leptin measurements. Peak O₂ consumption (l min^?1) was higher or lower (ml min^?1 kg^?1) in overweight and obese groups, compared with normal BMI group. Leptin was higher in overweight and obese groups, compared with normal BMI group. Peak O₂ consumption (l min^?1) correlated significantly with leptin only in total group (n = 248, r   =   0·196). Contrary, relative VO_2peak kg^?1 correlated significantly and negatively with leptin. The relationship was highest on the total group (r   =  ?0·674). We can conclude that leptin first of all correlated negatively with relative peak O₂ consumption. Absolute VO_2peak correlated with leptin only in total group.     

The effect of different exercise‐testing protocols on atrial natriuretic peptide

The aim of this study was to examine and to compare alterations in the secretion of atrial natriuretic peptide (ANP) during different exercise‐testing protocols in moderately trained men. Fifteen healthy male physical education students were studied (mean age 22·3 ± 2·5 years, training experience 12·3 ± 2·5 years, height 1·80 ± 0·06 m, weight 77·4 ± 8·2 kg). Participants performed an initial graded maximal exercise testing on a treadmill for the determination of VO_2max (duration 7·45–9·3 min and VO_2max 55·05 ± 3·13 ml kg^?1 min^?1) and were examined with active recovery (AR), passive recovery (PR) and continuous running (CR) in random order. Blood samples for plasma ANP concentration were taken at rest (baseline measurement), immediately after the end of exercise as well as after 30 min in passive recovery time (PRT). The plasma ANP concentration was determined by radioimmunoassay (RIA). The results showed that ANP plasma values increased significantly from the rest period to maximal values. In the short‐term graded maximal exercise testing the ANP plasma values increased by 56·2% (44·8 ± 10·4 pg ml^?1 versus 102·3 ± 31·3 pg ml^?1, P<0.001) and in the CR testing the ANP levels increased by 29·2% (44·8 ± 10·4 pg ml^?1 versus 63·3 ± 19·8 pg ml^?1, P<0.001) compared to the baseline measurement. Moreover, the values of ANP decreased significantly (range 46·4–51·2%, P<0.001) in PRT after the end of the four different exercise modes. However, no significant difference was evident when ANP values at rest and after AR and PR were compared. It is concluded that the exercise testing protocol may affect the plasma ANP concentrations. Particularly, short‐term maximal exercise significantly increases ANP values, while the intermittent exercise form of active and passive recovery decreases ANP concentrations.     

The influence of a fast ramp rate on peak cardiopulmonary parameters during arm crank ergometry

The influence of a very fast ramp rate on cardiopulmonary variables at ventilatory threshold and peak exercise during a maximal arm crank exercise test has not been extensively studied. Considering that short arm crank tests could be sufficient to achieve maximal oxygen consumption (VO₂), it would be of practical interest to explore this possibility. Thus, this study aimed to analyse the influence of a fast ramp rate (20 W min^?1) on the cardiopulmonary responses of healthy individuals during a maximal arm crank ergometry test. Seventeen healthy individuals performed maximal cardiopulmonary exercise tests (Ultima CardiO2; Medical Graphics Corporation, St Louis, USA) in arm ergometer (Angio, LODE, Groningen, The Netherlands) following two protocols in random order: fast protocol (increment: 2 w/6 s) and slow protocol (increment: 1 w/6 s). The fast protocol was repeated 60–90 days after the 1st test to evaluate protocol reproducibility. Both protocols elicited the same peak VO₂ (fast: 23·51 ± 6·00 versus slow: 23·28 ± 7·77 ml kg^?1 min^?1; P = 0·12) but peak power load in the fast ramp protocol was higher than the one in the slow ramp protocol (119 ± 43 versus. 102 ± 39 W, P < 0·001). There was no other difference in ventilatory threshold and peak exercise variables when 1st and 2nd fast protocols were compared. Fast protocol seems to be useful when healthy young individuals perform arm cardiopulmonary exercise test. The usefulness of this protocol in other populations remains to be evaluated.     

Day-to-day variation in oxygen consumption and energy expenditure during submaximal treadmill walking in female adolescents

The day-to-day variation in oxygen consumption (V˙O ₂) and energy expenditure (EE) during horizontal treadmill walking was measured using indirect calorimetry in 20 female adolescents (mean age 17·3 years). Two different walking speeds were used: 5 km h^?1 and an individually convenient speed of 3·0 km h^?1 (mean). The two sets of measurements were performed on 2 consecutive days, and great care was taken to minimize possible disturbing factors. The mean V˙O ₂ was 919 ml min^?1 at 5 km h^?1 and 622 ml min^?1 at the individual speed, and the mean values of EE were 4·5 kcal min^?1 and 3·1 kcal min^?1 respectively. The individual day-to-day variation in V˙O ₂ (at 5 km h^?1) was between ?11·7% and +12·6% of the mean V˙O ₂. The coefficient of variation (CV) was 6·4% when values were calculated in ml min^?1 kg^?1. The energy expenditure varied somewhat less between the 2 days (CV = 5·7%). The corresponding value for EE when walking at the individual speed was 7·2%, and the mean day-to day variation in V˙O ₂ was 7·5% (CV). The rate of perceived exertion according to Borg's scale was lower on day 2 (11·9) compared with day 1 (13·0) when walking at 5 km h^?1. There was no difference in heart rate between the 2 days. It is concluded that EE varies somewhat less than V˙O ₂ on successive days, probably because of an interchangeable relationship between breathing gases, depending on which substrate is used for combustion. When using V˙O ₂ and EE for evaluation of physical capacity, the day-to-day variation in the measurements must be taken into consideration.     

Reproducibility of peak oxygen consumption and the impact of test variability on classification of individual training responses in young recreationally active adults

This study investigated whether VO₂peak is reproducible across repeated tests before (PRE) and after (POST) training, and whether variability across tests impacts how individual responses are classified following 3 weeks of aerobic exercise training (cycle ergometry). Data from 45 young healthy adults (age: 20·1 ± 0·9 years; VO₂peak, 42·0 ± 6·7 ml·min^?1) from two previously published studies were utilized in the current analysis. Non‐responders were classified as individuals who failed to demonstrate an increase or decrease in VO₂peak that was greater than 2·0 times the typical error of measurement (107 ml·min^?1) away from zero, while responders and adverse responders were above and below this cut‐off, respectively. VO₂peak tests at PRE (three total) and POST (three total) were highly reproducible (PRE and POST average and single measures ICCs: range 0·938–0·992), with low coefficients of variation (PRE:4·9 ± 3·1%, POST: 4·8 ± 2·7%). However, a potential learning effect was observed in the VO₂peak tests prior to training, as the initial pretraining test was significantly lower than the third (p = 0·010, PRE 1: 2 946 ± 924 ml·min^?1, PRE 3: 3 042 ± 919 ml·min^?1). This resulted in fewer individuals classified as adverse responders for Test 3 compared to any combination of tests that included Test 1, suggesting that a single ramp test at baseline may not be sufficient to accurately classify the VO₂peak response in young recreationally active individuals. Thus, it is our recommendation that the initial VO₂peak test be used as a familiarization visit and not included for analysis.     

Day‐to‐day variation in oxygen consumption at submaximal loads during ergometer cycling by adolescents

The day‐to‐day variation in oxygen consumption (V˙O₂) during ergometer cycling by 20 healthy adolescents, 10 females and 10 males, was measured using indirect calorimetry. The two sets of measurements were performed on two consecutive days. Great care was taken to minimize possible disturbing factors. Cycling started at 50 and 100 W for female and male adolescents, respectively. The load was increased at a rate of 5 W 30 s^?1. In order to reach steady state, the load was kept constant for 3·5 min twice during the cycling session, at 100 and 130 W for the females and at 130 and 160 W for the males. Cycling continued until exhaustion. The maximal loads were 196 W (mean) and 271 W (mean) for females and males, respectively. At the maximal loads the day‐to‐day variation (±2 SD) in oxygen consumption (V˙O₂) was ±330 ml min^?1 for females and 390 ml min^?1 for males. At the submaximal loads the day‐to‐day variation in heart rate (HR) was 9·3 beats min^?1 (±2 SD) (coefficient of variation, CV=3·4% at 130 W) for both sexes. The day‐to‐day variation in oxygen consumption (V˙O₂) was ±199 ml min^?1 (±2 SD) at the different submaximal loads and did not differ between female and male adolescents (CV=5·7% at 130 W). This natural day‐to‐day variation must be taken into consideration when using a submaximal ergometer cycling test for the evaluation of physical capacity in the two sexes.     

Circulatory response to single circuit weight and walking training sessions of similar energy cost in middle‐aged overweight females

The aim of this study was to compare circulatory responses to circuit weight (CWT) and aerobic walking training sessions of similar energy cost in middle‐aged overweight females. Thirty‐three middle‐aged pre‐menopausal females participated in the experiment. They were divided into overweight (n=18, 36·2 ± 6·3 years, 166·3 ± 8·0 cm, 83·5 ± 9·7 kg, BMI 30·2 ± 3·1 kg m^–2) and non‐overweight control (n=15, 34·1 ± 6·3 years, 165·0 ± 5·6 cm, 61·6 ± 5·0 kg, BMI 22·7 ± 1·5 kg m^–2) groups. Individual physical working capacity (PWC) was measured using the cycle ergometer test (calculated at the level of predicted HR_max (205 – ½ age). A CWT session consisted of leg extension, bench press, sit‐ups and leg press exercises. The subjects performed four circuits at the maximal possible speed, using a work‐to‐rest ratio of 60 s. Blood pressure (BP) was measured during every rest period between the exercises, and the heart rate (HR) was recorded continuously during the whole CWT programme. During the walking training session, the subjects walked as fast as possible on the indoor track. The total energy cost of the walking training session was the same as during the CWT session, approximately 270 kcal, and was controlled by a CALTRAC accelerometer. HR and BP were measured every 5 min during the walking training session. The PWC index was significantly (P<0·05) higher in the overweight group in comparison with the control females (215·4 ± 76·1 and 187·9 ± 42·4 W, respectively). The resting BP was normal in both groups (<140/90 mmHg). HR was between 120 and 140 beats min^–1 during CWT and walking sessions. There were no differences in BP during both training sessions in overweight and control subjects. It was concluded that both CWT and walking training sessions were acceptable forms of physical activity to increase cardiovascular fitness in middle‐aged overweight and normal body weight females.     

The exercise heart rate profile in master athletes compared to healthy controls

Endurance exercise protects the heart via effects on autonomic control of heart rate (HR); however, its effects on HR indices in healthy middle‐aged men are unclear. This study compared HR profiles, including resting HR, increase in HR during exercise and HR recovery after exercise, in middle‐aged athletes and controls. Fifty endurance‐trained athletes and 50 controls (all male; mean age, 48·7 ± 5·8 years) performed an incremental symptom‐limited exercise treadmill test. The electrocardiographic findings and HR profiles were evaluated. Maximal O₂ uptake (52·6 ± 7·0 versus 34·8 ± 4·5 ml kg^?1 min^?1; P<0·001) and the metabolic equivalent of task (15·4 ± 1·6 versus 12·2 ± 1·5; P<0·001) were significantly higher in athletes than in controls. Resting HR was significantly lower in athletes than in controls (62·8 ± 6·7 versus 74·0 ± 10·4 beats per minute (bpm), respectively; P<0·001). Athletes showed a greater increase in HR during exercise than controls (110·1 ± 11·0 versus 88·1 ± 15·4 bpm; P<0·001); however, there was no significant between‐group difference in HR recovery at 1 min after cessation of exercise (22·9 ± 5·6 versus 21·3 ± 6·7 bpm; P = 0·20). Additionally, athletes showed a lower incidence of premature ventricular contractions (PVCs) during exercise (0·0% versus 24·0%; P<0·001). Healthy middle‐aged men participating in regular endurance exercise showed more favourable exercise HR profiles and a lower incidence of PVCs during exercise than sedentary men. These results reflect the beneficial effect of endurance training on autonomic control of the heart.     

Effects of different periods of hypoxic training on glucose metabolism and insulin sensitivity

This study examined the effects of different periods of hypoxic training on glucose metabolism. Sedentary subjects underwent hypoxic training (FiO₂ = 15·0%) for either 2 weeks (2‐week group; n = 11) or 4 weeks (4‐week group; n = 10). The 2‐week group conducted training sessions on 6 days week^?1 for 2 weeks, whereas the 4‐week group conducted training sessions on 3 days week^?1 for 4 weeks. Body fat mass or abdominal fat area did not change after training period in either group. VO_2max increased in both groups after training period (42 ± 2 versus 43 ± 2 ml min^?1 kg^?1 in 2‐week group, 41 ± 1 versus 42 ± 2 ml min^?1 kg^?1 in 4‐week group). Both groups showed a reduction in mean blood pressure after training period (92 ± 3 versus 90 ± 3 mmHg in 2‐week group, 91 ± 2 versus 87 ± 2 mmHg in 4‐week group, P≤0·05). No change was observed in blood glucose response after glucose ingestion after training period. However, area under the curve for serum insulin concentrations after glucose ingestion significantly decreased in only 4‐week group (6910 ± 763 versus 5812 ± 872 μIU ml^?1 120 min, P≤0·05). In conclusion, hypoxic training reduced blood pressure with independent on training duration. However, a longer period of hypoxic training led to greater improvements in insulin sensitivity compared with equivalent training over a shorter period, suggesting that hypoxic training programmes for more than 4 weeks might be more beneficial for improving insulin sensitivity.     

Assessment of anaerobic power to verify VO2max attainment

Across various populations, verification testing is used to confirm VO₂max attainment and has repeatedly shown similar VO₂max values to those obtained from incremental exercise. Yet, many individuals show meaningful differences in VO₂max between protocols, and an explanation for this is unknown. The aim of the study was to elucidate this phenomenon in 30 men and women of similar age, fitness, and physical activity using assessment of anaerobic power. On day 1, they completed the Wingate test, and returned at least 48 h later to complete incremental cycle ergometry followed by a verification protocol. During exercise, ventilation, pulmonary gas exchange data, and heart rate (HR) were continuously measured. Mean VO₂max was similar (P > 0·05) between protocols (42·05 ± 5·88 ml kg^?1 per min versus 42·03 ± 5·75 ml kg^?1 per min, respectively), although seven subjects (23%) revealed a VO₂max that was not ‘verified’ by the supramaximal protocol. Indices of power output and gas exchange data were similar (P > 0·05) between subjects who revealed a ‘true’ VO₂max compared to those who did not, although peak and mean power was consistently higher in persons whose VO₂max was not ‘verified.’ A previously established HRmax criterion for verification testing was not met in 17% of subjects. Additional study is merited to identify alternate determinants of VO₂max, such as muscle activation via assessment of motor unit recruitment, and to investigate utility of verification testing to confirm VO₂max attainment in elite athletes and the elderly.     

Accuracy and responsiveness of the stepwatch activity monitor and ActivPAL in patients with COPD when walking with and without a rollator

Purpose: To evaluate the measurement properties of the StepWatch^? Activity Monitor (SAM) and ActivPAL in COPD. Method: Whilst wearing both monitors, participants performed walking tasks at two self-selected speeds, with and without a rollator. Steps obtained using the monitors were compared with that measured by direct observation. Results: Twenty participants aged 73?±?9 years (FEV₁?=?35?±?13% pred; 8 males) completed the study. Average speeds for the slow and normal walking tasks were 34?±?7 m·min^?1and 46?±?10 m·min^?1, respectively. Agreement between steps recorded by the SAM with steps counted was similar irrespective of speed or rollator use (p?=?0.63) with a mean difference and limit of agreement (LOA) of 2 steps·min^?1 and 6 steps·min^?1, respectively. Agreement for the ActivPAL was worse at slow speeds (mean difference 7 steps·min^?1; LOA 10 steps·min^?1) compared with normal speeds (mean difference 4 steps·min^?1; LOA 5 steps·min^?1) (p?=?0.03), but was unaffected by rollator use. The change in step rate between slow and normal walking via direct observation was 12?±?7 steps·min^?1 which was similar to that detected by the SAM (12?±?6 steps·min^?1) and ActivPAL (14?±?7 steps·min^?1). Conclusions: The SAM can be used to detect steps in people who walk very slowly including those who use a rollator. Both devices were sensitive to small changes.

Implications for Rehabilitation

• The evaluation of physical activity (PA) before and after pulmonary rehabilitation in people with chronic obstructive pulmonary disease (COPD) has evolved to be an important outcome measure.

• Selecting an appropriate device to obtain valid measures of PA remains a challenge, especially for those individuals who walk slowly or use a rollator to assist with ambulation.

• The StepWatchTM Activity Monitor and the ActivPAL have been shown in this study to be sensitive to small changes in step rate, thus these devices can be used to assess changes in physical activity in individuals with COPD such as following pulmonary rehabilitation, including those who walk slowly or use a walking aid such as a rollator.

     

Evaluation of three measures of cardiorespiratory fitness in independently ambulant stroke survivors

Measuring cardiorespiratory fitness (CRF) in the stroke population is challenging. Currently, the recommended method is a graded exercise test (GXT) on an ergometer such as a treadmill or cycle, which may not always be possible. We investigated whether walking tests such as the six-minute walk test (6MWT) and the shuttle walk test (SWT) may be appropriate indicators of CRF in the stroke population. Twenty-three independently ambulant stroke survivors (11 men, age 61.5 ± 18.4 years) within one-year post stroke performed the 6MWT, SWT, and cycle GXT, during which peak oxygen consumption (VO_2peak) and heart rate (HR_peak) were recorded. There were no differences (p > 0.05) in mean VO_2peak among the three tests (min-max: 17.08–18.09 mL kg^?1 min^?1). For individuals, small discrepancies in VO_2peak between the 6MWT and other tests were greater with higher fitness levels. HR_peak was significantly (p = 0.005) lower during the 6MWT. Correlations between VO_2peak and performance measures within each test were high (6MWT VO_2peak and distance: r = 0.78, SWT VO_2peak and shuttles: r = 0.73, cycle GXT VO_2peak and workload: r = 0.77) suggesting the performance measures may be clinically useful as proxy measures of CRF. Common comorbidities, such as lower-limb joint pain and poor balance, and participant’s fastest walking speed, should inform the choice of CRF test.     

Decreased aerobic capacity 4 years after aortic valve replacement in male patients operated upon for chronic aortic regurgitation

Exercise testing is underutilized in patients with valve disease. We have previously found a low physical work capacity in patients with aortic regurgitation 6 months after aortic valve replacement (AVR). The aim of this study was to evaluate aerobic capacity in patients 4 years after AVR, to study how their peak oxygen uptake (peakVO₂) had changed postoperatively over a longer period of time. Twenty‐one patients (all men, 52 ± 13 years) who had previously undergone cardiopulmonary exercise testing (CPET) pre‐ and 6 months postoperatively underwent maximal exercise testing 49 ± 15 months postoperatively using an electrically braked bicycle ergometer. Breathing gases were analysed and the patients’ physical fitness levels categorized according to Åstrand’s and Wasserman’s classifications. Mean peakVO₂ was 22·8 ± 5·1 ml × kg^?1 × min^?1 at the 49‐month follow‐up, which was lower than at the 6‐month follow‐up (25·6 ± 5·8 ml × kg^?1 × min^?1, P = 0·001). All but one patient presented with a physical fitness level below average using Åstrand’s classification, while 13 patients had a low physical capacity according to Wasserman’s classification. A significant decrease in peakVO₂ was observed from six to 49 months postoperatively, and the decrease was larger than expected from the increased age of the patients. CPET could be helpful in timing aortic valve surgery and for the evaluation of need of physical activity as part of a rehabilitation programme.     

Estimation de la consommation pic d��oxyg��ne par la perception de l��effort chez des patients ob��ses et diab��tiques de type 2

Objectives

The main objectives of this study were: 1) to assess the validity of predicting peak oxygen uptake (.VO₂peak) from ratings of perceived exertion (RPE) during a sub-maximal graded exercise test (GXT), in obese patients with diabetes, and 2) to compare the accuracy of predictions obtained from RPE ?? 15 and RPE ?? 17. Materials and methods: Seventeen obese women with type 2 diabetes performed GXT to volitional exhaustion, in which oxygen uptake (.VO₂) and RPE were measured. Individual linear regressions between.VO₂ and RPE, that were collected during the first stages of GXT (RPE ?? 15 and RPE ?? 17), were extrapolated to RPE = 20 in order to predict.VO₂peak. Results: Actual (12.7 ± 3.6 ml.min^?1.kg^?1) and predicted.VO₂peak from RPE ?? 15 and RPE ?? 17 (13.1 ± 3.7 and 13.3 ± 3.8 ml.min^?1.kg^?1, respectively) were not significantly different. The actual.V O₂peak were significantly correlated to the predicted.VO₂peak from RPE ?? 15 and RPE ?? 17 (R = 0.89 and R = 0.92, respectively). The 95% limits of agreement analysis were ?0.4 ± 3.4 and ?0.6 ± 3.0 ml.min^?1.kg^?1 for the predictions from RPE ?? 15 and RPE ?? 17, respectively.

Conclusion

Results suggested that the RPE ?? 15 provide accurate.V O₂peak prediction in obese women with type 2 diabetes. However, the accurate of predictions was improved when the.VO₂peak was predicted from RPE ?? 17. Consequently, RPE may be used to predict.VO₂peak and to decrease the risk of cardio-vascular complications during GXT.     

Decreased leg glucose uptake during exercise contributes to the hyperglycaemic effect of octreotide

Aim: During prolonged infusion of somatostatin, there is an increase in arterial glucose concentration, and this increase persists even during prolonged exercise. The aim of the study was to measure glucose uptake in the leg muscles during infusion of the somatostatin analogue octreotide before and during leg exercise. Material and methods: Eight healthy male subjects were investigated twice in the fasting state: during 3 h infusion of octreotide [30 ng (kg min)^?1] or sodium chloride with exercise at 50% of maximal VO₂ in the last hour. Glucose uptake and oxygen uptake in the leg were measured using Fick’s principle by blood sampling from an artery and a femoral vein. Blood flow in the leg was measured using the indicator (indocyanine green) dilution technique. Results: After an initial decrease during rest, octreotide infusion resulted in a significant increase in arterial glucose concentrations compared to control conditions during exercise (mean ± SEM: 7·6 ± 0·6 versus 5·6 ± 0·1 mmol l^?1, P<0·01). During rest, octreotide did not change the leg glucose uptake (59 ± 10 versus 55 ± 11 μmol min^?1). In contrast, leg glucose uptake was significantly lower during exercise compared to control conditions (208 ± 79 versus 423 ± 87 μmol min^?1, P<0·05). During exercise, leg oxygen uptake was not different in the two experiments (20·4 ± 1·3 versus 19·5 ± 1·1 μmol min^?1). Conclusion: In conclusion, infusion of octreotide reduced leg glucose uptake during exercise, despite the same leg oxygen consumption and blood flow compared to control conditions. The hyperglycaemic effect of octreotide can partly be explained by the reduction in leg glucose uptake. Furthermore, the results suggest that a certain level of circulating insulin is necessary to obtain sufficient stimulation of glucose uptake in the exercising muscles.     

Normovolemia defined according to cardiac stroke volume in healthy supine humans

Background: Both hypovolemia and a fluid overload are detrimental for outcome in surgical patients but the effort to establish normovolemia is hampered by the lack of an operational clinical definition. Manipulating the central blood volume on a tilt table demonstrates that the flat part of the Frank‐Starling curve is reached when subjects are supine and that finding may be applicable for a clinical definition of normovolemia. However, it is unknown whether stroke volume (SV) responds to an increase in preload induced by fluid administration. Methods: In 20 healthy subjects (23 ± 2 years, mean ± SD), SV was measured by esophageal Doppler before and after fluid administration to evaluate whether SV increases in healthy, non‐fasting, supine subjects. Two hundred millilitres of a synthetic colloid (hydroxyethyl starch, HES 130/0·4) was provided and repeated if a ≥10% increment in SV was obtained. Results: None of the subjects increased SV ≥10% following fluid administration but there was a minor increase in mean arterial pressure (92 ± 15 to 93 ± 12 mmHg, P = 0·01), while heart rate (HR) (66 ± 12 beats min^?1; P = 0·32), cardiac output (4·8 ± 1·1 l min^?1; P = 0·25) and the length of the systole corrected to a HR of 60 beats/min (corrected flow time; 344 ± 24 ms; P = 0·31) did not change. Conclusion: Supporting the proposed definition of normovolemia, non‐fasting, supine, healthy subjects are provided with a preload to the heart that does not limit SV suggesting that the upper flat part of the Frank‐Starling relationship is reached.     

Cardiac sympathetic activity is associated with inflammation and neurohumoral activation in patients with idiopathic dilated cardiomyopathy

Background: Idiopathic dilated cardiomyopathy (IDC) is characterized by sympathetic nervous overactivity, inflammation and neurohumoral activation; however, their interrelationships are poorly understood. Methods and results: We studied 99 patients with IDC (age 54 ± 1 years, left ventricular ejection fraction (EF) 40 ± 1%, maximum oxygen uptake (VO₂max) 20 ± 1 ml kg^?1 min^?2, mean ± SEM) by using ¹²³I‐metaiodobenzylguanidine (MIBG) imaging. MIBG washout and MIBG heart/mediastinum (H/M)‐ratio at 4 h postinjection were calculated. In addition, the plasma levels of interleukin (IL)‐6 and N‐terminal B‐type natriuretic peptide (NT‐proBNP) were measured. MIBG washout and MIBG H/M ratio had a significant correlation with IL‐6 (r = 0·42, P<0·001 and r = ?0·31, P<0·01) and NT‐proBNP (r = 0·48, P<0·001 and r = ?0·40, P<0·001). During a median follow‐up of 4·1 years, 20 patients (20%) had an adverse cardiac event (death, heart transplantation or application of biventricular pacemaker or implantable cardioverter–defibrillator). In these patients, MIBG washout was higher (53 ± 4 versus 40 ± 2%, P = 0·01) and H/M ratio lower (1·38 ± 0·04 versus 1·51 ± 0·02, P = 0·01) than in patients without an event. Conclusions: In dilated cardiomyopathy, myocardial sympathetic innervation and activity are related to inflammation and neurohumoral activation. These relationships are at least partly independent of left ventricular function and exercise capacity.