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.     

Left ventricular diastolic function is enhanced after peak exercise in endurance‐trained adolescents as well as in their non‐trained controls

The aims of the study were to explore the temporal change of cardiac function after peak exercise in adolescents, and to investigate how these functional changes relate to maximal oxygen uptake (VO_2max). The cohort consisted of 27 endurance‐trained adolescents aged 13–19 years, and 27 controls individually matched by age and gender. Standard echocardiography and colour tissue Doppler were performed at rest, and immediately after as well as 15 min after a maximal cardio pulmonary exercise test (CPET) on a treadmill. The changes in systolic and diastolic parameters after exercise compared to baseline were similar in both groups. The septal E/e′‐ratio increased immediately after exercise in both the active and the control groups (from 9·2 to 11·0; P<0·001, and from 8·7 to 10·2; P = 0·008, respectively). In a comparison between the two groups after CPET, the septal E/e′‐ratio was higher in the active group both immediately after exercise and 15 min later compared to the control group (P = 0·007 and P = 0·006, respectively). We demonstrated a positive correlation between VO_2max and cardiac function including LVEF and E/e′ immediately after CPET, but the strongest correlation was found between VO_2max and LVEDV (r = 0·67, P<0·001) as well as septal E/e′ (r = 0·34, P = 0·013). Enhanced diastolic function was found in both groups, but this was more pronounced in active adolescents. The cardiac functional response to exercise, in terms of LVEF and E/e′, correlates with the increase in VO₂ uptake. These findings in trained as well as un‐trained teenagers have practical implications when assessing cardiac function.     

Assessment of the influence of age on the rate of heart rate decline after maximal exercise in non‐athletic adult males

This study investigated the influence of age on heart rate (HR) decline after exercise in non‐athletic adult males. One hundred and fourteen adult males (66 young, 25 ± 6·26 years; 48 old, 53 ± 8·54 years) participated in the study. Subjects performed maximum‐effort ergometer exercise in incremental stages. HR was measured at rest and continuously monitored during and after exercise. Maximum oxygen uptake (VO_2max) was measured during the exercise using respiratory gas analyser. Body mass index (BMI) was computed from weight and height measurements, while rating of perceived exertion (RPE) was obtained immediately after the exercise. Results indicated age differences in the rate of HR decline with the young presenting significantly higher %HR decline (P<0·001) than old adults at both levels of recovery. When linearly correlated with age, the rate of HR decline in 1 and 3 min indicated variances of (52%,56%) in young adults, and (54%,49%) in the old adults. After controlling for VO_2max, resting HR, BMI and RPE, the influence of age on rate of HR decline in the two phases of recovery disappeared in young. In the older adult group, it reduced greatly in the 1‐min recovery (r² = 25%; P = 0·001) and disappeared in the 3‐min recovery. Pattern of HR recovery did not differ between the two age groups while age threshold was observed in HR recovery in 1 min. In summary, the influence that age appeared to have on the rate of HR decline could not hold when factors affecting HR recovery were taken into account.     

Automated ultrasound edge‐tracking software comparable to established semi‐automated reference software for carotid intima‐media thickness analysis

Many commercial ultrasound systems are now including automated analysis packages for the determination of carotid intima‐media thickness (cIMT); however, details regarding their algorithms and methodology are not published. Few studies have compared their accuracy and reliability with previously established automated software, and those that have were in asymptomatic adults. Therefore, this study compared cIMT measures from a fully automated ultrasound edge‐tracking software (EchoPAC PC, Version 110.0.2; GE Medical Systems, Horten, Norway) to an established semi‐automated reference software (Artery Measurement System (AMS) II, Version 1.141; Gothenburg, Sweden) in 30 healthy preschool children (ages 3–5 years) and 27 adults with coronary artery disease (CAD; ages 48–81 years). For both groups, Bland–Altman plots revealed good agreement with a negligible mean cIMT difference of ?0·03 mm. Software differences were statistically, but not clinically, significant for preschool images (P = 0·001) and were not significant for CAD images (P = 0·09). Intra‐ and interoperator repeatability was high and comparable between software for preschool images (ICC, 0·90–0·96; CV, 1·3–2·5%), but slightly higher with the automated ultrasound than the semi‐automated reference software for CAD images (ICC, 0·98–0·99; CV, 1·4–2·0% versus ICC, 0·84–0·89; CV, 5·6–6·8%). These findings suggest that the automated ultrasound software produces valid cIMT values in healthy preschool children and adults with CAD. Automated ultrasound software may be useful for ensuring consistency among multisite research initiatives or large cohort studies involving repeated cIMT measures, particularly in adults with documented CAD.     

Functional near‐infrared spectroscopy to probe sensorimotor region activation during electrical stimulation‐evoked movement

This study used non‐invasive functional near‐infrared spectroscopy (fNIRS) neuroimaging to monitor bilateral sensorimotor region activation during unilateral voluntary (VOL) and neuromuscular electrical stimulation (NMES)‐evoked movements. Methods. In eight healthy male volunteers, fNIRS was used to measure relative changes in oxyhaemoglobin (O₂Hb) and deoxyhaemoglobin (HHb) concentrations from a cortical sensorimotor region of interest in the left (LH) and right (RH) hemispheres during NMES‐evoked and VOL wrist extension movements of the right arm. Results. NMES‐evoked movements induced significantly greater activation (increase in O₂Hb and concomitant decrease in HHb) in the contralateral LH than in the ipsilateral RH (O₂Hb: 0·44 ± 0·16 μM and 0·25 ± 0·22 μM, P = 0·017; HHb: ?0·19 ± 0·10 μM and ?0·12 ± 0·09 μM, P = 0·036, respectively) as did VOL movements (0·51 ± 0·24 μΜ and 0·34 ± 0·21 μM, P = 0·031; HHb: ?0·18 ± 0·07 μΜ and ?0·12 ± 0·04 μΜ, P = 0·05, respectively). There was no significant difference between conditions for O₂Hb (P = 0·144) and HHb (P = 0·958). Conclusion. fNIRS neuroimaging enables quantification of bilateral sensorimotor regional activation profiles during voluntary and NMES‐evoked wrist extension movements.     

Influence of exercise intensity on systemic oxidative stress and antioxidant capacity

The aim of the current study was to examine the influence of exercise intensity on systemic oxidative stress (OS) and endogenous antioxidant capacity. Non‐smoking, sedentary healthy adult males (n = 14) participated in two exercise sessions using an electronically braked cycle ergometer. The first session consisted of a graded exercise test to determine maximal power output and oxygen consumption (VO_2max). One week later, participants undertook 5‐min cycling bouts at 40%, 55%, 70%, 85% and 100% of VO_2max, with passive 12‐min rest between stages. Measures of systemic OS reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), heart rate (HR), VO₂, blood lactate and rating of perceived exertion were assessed at rest and immediately following each exercise stage. Significant (P<0·05) differences between exercise bouts were examined via repeated measures ANOVA and post hoc pairwise comparisons with Bonferroni correction. Increasing exercise intensity significantly augmented HR (P<0·001), VO₂ (P<0·001), blood lactate (P<0·001) and perceived exertion (P<0·001) with no significant effect on dROM levels compared with resting values. In contrast, increasing exercise intensity resulted in significantly (P<0·01) greater BAP at 70% (2427 ± 106), 85% (2625 ± 121) and 100% (2651 ± 92) of VO_2max compared with resting levels (2105 ± 57 μmol Fe²⁺/L). The current results indicate that brief, moderate‐to‐high‐intensity exercise significantly elevates endogenous antioxidant defences, possibly to counteract increased levels of exercise‐induced reactive oxygen species. Regular moderate‐to‐high‐intensity exercise may protect against chronic OS associated diseases via activation, and subsequent upregulation of the endogenous antioxidant defence system.     

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.     

Commonly used reference values underestimate oxygen uptake in healthy, 50‐year‐old Swedish women

Cardiopulmonary exercise testing (CPET) is the gold standard among clinical exercise tests. It combines a conventional stress test with measurement of oxygen uptake (V_O2) and CO₂ production. No validated Swedish reference values exist, and reference values in women are generally understudied. Moreover, the importance of achieved respiratory exchange ratio (RER) and the significance of breathing reserve (BR) at peak exercise in healthy individuals are poorly understood. We compared V_O2 at maximal load (peakV_O2) and anaerobic threshold (V_O2@AT) in healthy Swedish individuals with commonly used reference values, taking gender into account. Further, we analysed maximal workload and peakV_O2 with regard to peak RER and BR. In all, 181 healthy, 50‐year‐old individuals (91 women) performed CPET. PeakV_O2 was best predicted using Jones et al. (100·5%). Furthermore, underestimation of peakV_O2 in women was found for all studied reference values (P<0·001) and was largest for Hansen‐Wasserman: women had 115% of predicted peakV_O2, while men had 103%. PeakV_O2 was similar in subjects with peak RER of 1–1·1 and RER > 1·1 (2 328·7 versus 2 176·7 ml min^?1, P = 0·11). Lower BR (≤30%) related to significantly higher peakV_O2 (P<0·001). In conclusion, peakV_O2 was best predicted by Jones. All studied reference values underestimated oxygen uptake in women. No evidence for demanding RER > 1·1 in healthy individuals was found. A lowered BR is probably a normal response to higher workloads in healthy individuals.     

Forearm–finger skin temperature gradient as an index of cutaneous perfusion during steady‐state exercise

The purpose of this study was to examine whether the forearm–finger skin temperature gradient (T_{forearm–finger}), an index of vasomotor tone during resting conditions, can also be used during steady‐state exercise. Twelve healthy men performed three cycling trials at an intensity of ~60% of their maximal oxygen uptake for 75 min separated by at least 48 h. During exercise, forearm skin blood flow (BF_F) was measured with a laser‐Doppler flowmeter, and finger skin blood flow (PPG) was recorded from the left index fingertip using a pulse plethysmogram. T_{forearm–finger} of the left arm was calculated from the values derived by two thermistors placed on the radial side of the forearm and on the tip of the middle finger. During exercise, PPG and BF_F increased (P<0·001), and T_{forearm–finger} decreased (P<0·001) from their resting values, indicating a peripheral vasodilatation. There was a significant correlation between T_{forearm–finger} and both PPG (r = ?0·68; P<0·001) and BF_F (r = ?0·50; P<0·001). It is concluded that T_{forearm–finger} is a valid qualitative index of cutaneous vasomotor tone during steady‐state exercise.     

The effects of beta‐alanine supplementation on physical working capacity at heart rate threshold

Beta‐alanine (BA) supplementation has been shown to delay neuromuscular fatigue as a result of increased muscle carnosine concentrations. Carnosine has also been found in brain and cardiac tissue. The physical working capacity test at heart rate threshold (PWC_HRT) is a global estimate of the onset of fatigue during exercise, influenced by central and peripheral factors. The purpose of this study was to determine the effects of 28 days of BA supplementation on the PWC_HRT. Thirty subjects (mean ± SD; age: 21·0 ± 2·1 years; body mass: 72·7 ± 14·5 kg; height: 170·1 ± 7·9 cm) were randomly assigned to BA (n = 15) or placebo (PL, n = 15) groups. Testing included eight to nine total visits: an enrolment day, physical screening, peak oxygen consumption (V^·O_2peak) and two PWC_HRT assessments over 4 days. Significant differences existed between BA and PL for PWC_HRT (P = 0·001; mean?: BA? = +24·2 watts, PL? = +11·2 watts), but not for V^·O_2peak (P = 0·222), time to exhaustion (TTE; P = 0·562) or ventilatory threshold (VT; P = 0·134). Results suggest that BA may increase heart rate training threshold. These results, in combination with one previous study reporting a potential effect of BA on HR, suggest that future studies should evaluate both central and peripheral aspects of fatigue with BA intake.     

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.     

Calculation algorithms alter the breath‐by‐breath gas exchange values when abrupt changes in ventilation occur

The automatic metabolic units calculate breath‐by‐breath gas exchange from the expiratory data only, applying an algorithm (‘expiration‐only’ algorithm) that neglects the changes in the lung gas stores. These last are theoretically taken into account by a recently proposed algorithm, based on an alternative view of the respiratory cycle (‘alternative respiratory cycle’ algorithm). The performance of the two algorithms was investigated where changes in the lung gas stores were induced by abrupt increases in ventilation above the physiological demand. Oxygen, carbon dioxide fractions and ventilatory flow were recorded at the mouth in 15 healthy subjects during quiet breathing and during 20‐s hyperventilation manoeuvres performed at 5‐min intervals in resting conditions. Oxygen uptakes and carbon dioxide exhalations were calculated throughout the acquisition periods by the two algorithms. Average ventilation amounted to 6·1 ± 1·4 l min^?1 during quiet breathing and increased to 41·8 ± 27·2 l min^?1 during the manoeuvres (P<0·01). During quiet breathing, the two algorithms provided overlapping gas exchange data and noise. Conversely, during hyperventilation, the ‘alternative respiratory cycle’ algorithm provided significantly lower gas exchange data as compared to the values yielded by the ‘expiration‐only’ algorithm. For the first breath of hyperventilation, the average values provided by the two algorithms amounted to 0·37 ± 0·34 l min^?1 versus 0·96 ± 0·73 l min^?1 for O₂ uptake and 0·45 ± 0·36 l min^?1 versus 0·80 ± 0·58 l min^?1 for exhaled CO₂ (P<0·001 for both). When abrupt increases in ventilation occurred, such as those arising from a deep breath, the ‘alternative respiratory cycle’ algorithm was able to halve the artefactual gas exchange values as compared to the ‘expiration‐only’ approach.     

Pharmacokinetics of single‐dose rosiglitazone in chronic ambulatory peritoneal dialysis patients

Background: End‐stage renal disease (ESRD) is associated with marked alterations in the pharmacokinetics of many drugs, not only from reduction in renal clearance but also from changes in metabolic activity, bioavailability, volume of distribution and plasma protein binding. Objective: To study the pharmacokinetics of a single 8‐mg oral dose of rosiglitazone in patients with ESRD and requiring long‐term chronic ambulatory peritoneal dialysis (CAPD). Method: The medication was administered just before the first exchange of peritoneal dialysis fluid on the day that blood and peritoneal dialysate collection was performed. Results: In our CAPD patients the mean (±SD) T_max and T_1/2 of rosiglitazone were 1·20 ± 0·26 and 21·38 ± 21·96 h respectively. These values were different to those reported for healthy volunteers reported in previous studies. The mean area under the concentration–time curve (AUC_(0–∞)) and an average maximum observed plasma concentration (C_max) of rosiglitazone in our CAPD patients were 4203·56 ± 2916·97 ng h/mL and 409·67 ± 148·89 ng/mL respectively. These appear no different from those reported in healthy volunteers . Conclusion: The apparently significant difference in T_1/2 of rosiglitazone in CAPD patients compared with healthy volunteers suggest that dose adjustment may be necessary in order to avoid toxicity.     

Hamstrings‐to‐quadriceps strength and size ratios of male professional soccer players with muscle imbalance

The aim of this study was to determine the correlation between the concentric hamstrings/quadriceps muscle strength (H_con:Q_con) and cross‐sectional area ratios (H_csa:Q_csa) in professional soccer players with H_con:Q_con imbalance. Nine male professional soccer players (25·3 ± 4·1 years) performed five maximal concentric contractions of the knee extensors (KE) and flexors (KF) at 60 s^?1 to assess H_con:Q_con. The test was performed using the dominant (preferred kicking), and non‐dominant limb with a 5‐min recovery period was allowed between them. Only players with H_con:Q_con < 0·60 (range: 0·45–0·59) in both limbs were included in this study. The muscle cross‐sectional area (CSA) of KE and KF was determined by magnetic resonance imaging. The correlations between H_con:Q_con and H_csa:Q_csa in the dominant leg (r = ?0·33), non‐dominant leg (r = 0·19) and in the both legs combined (r = 0·28) were not statistically significant (P>0·05). Thus, the H_con:Q_con seems not to be determined by H_csa:Q_csa in professional soccer players with H_con:Q_con imbalance.     

Measurement of maximal isometric torque and muscle quality of the knee extensors and flexors in healthy 50‐ to 70‐year‐old women

Muscle quality is defined as strength per unit muscle mass. The aim of this study was to measure the maximal voluntary isometric torque of the knee extensor and flexor muscle groups in healthy older women and to develop an index of muscle quality based on the combined knee extensor and flexor torque per unit lean tissue mass (LTM) of the upper leg. One hundred and thirty‐six healthy 50‐ to 70‐year‐old women completed an initial measurement of isometric peak torque of the knee extensors and flexors (Con‐Trex MJ; CMV AG, Dubendorf, Switzerland) that was repeated 7 days later. Subsequently, 131 women returned for whole‐ and regional‐body composition analysis (iDXA^?; GE Healthcare, Chalfont St Giles, Buckinghamshire, UK). Isometric peak torque demonstrated excellent within‐assessment reliability for both the knee extensors and flexors (ICC range: 0·991–1·000). Test–retest reliability was lower (ICC range: 0·777–0·828) with an observed mean increase of 5% in peak torque [6·2 (17·2) N m] on the second day of assessment (P<0·001). The relative mean decrease in combined isometric peak torque (?12·2%; P = 0·001) was double that of the relative, non‐significant, median difference in upper leg LTM (?5·3%; P = 0·102) between those in the 5th and 6th decade. The majority of difference in peak isometric torque came from the knee extensors (15·1 N m, P<0·001 versus 2·4 N m, P = 0·234). Isometric peak torque normalized for upper leg LTM (muscle quality) was 8% lower between decades (P = 0·029). These findings suggest strength per unit tissue may provide a better indication of age‐related differences in muscle quality prior to change in LTM.     

Metabolic cost of locomotion during treadmill walking with blood flow restriction

We explored whether interval walking with blood flow restriction (BFR) increases net metabolic cost of locomotion in healthy young men at their optimal walking speed. We also determined whether decreased walking economy resulting from BFR might be accompanied by an increase in ventilation relative to VO₂ and VCO₂. Finally, we examined possible relationships between the changes in ratings of perceived exertion (RPE) and those obtained in minute ventilation (V_E) during walking with BFR. Eighteen healthy men (age: 22·5 ± 3·4 years) performed graded treadmill exercise to assess VO_2max. In a randomized fashion, participants also performed five bouts of 3‐min treadmill exercise with and without BFR at their optimal walking speed. Walking with BFR elicited an overall increase in net VO₂ (10·4%) compared with that seen in the non‐BFR condition (P<0·05). The participants also demonstrated greater V_E and V_E/VO₂ values while walking with BFR (P<0·05). Conversely, V_E/VCO₂ was similar between conditions at each walking bout. We found no significant correlation between the changes in V_E and RPE induced by walking with BFR (r = 0·38, P>0·05). Our results indicate that (i) BFR decreases net walking economy in healthy young men, even at their optimal walking speed; (ii) heightened ventilatory drive may explain a small proportion of BFR effects on walking economy; and (iii) the ventilatory responses to BFR walking may be largely independent of changes in perceived exertion and are likely matched to the flux of CO₂ between muscles and respiratory centres.     

Relationship between peak cardiac pumping capability and indices of cardio-respiratory fitness in healthy individuals

Cardiac power output (CPO) is a unique and direct measure of overall cardiac function (i.e. cardiac pumping capability) that integrates both flow‐ and pressure‐generating capacities of the heart. The present study assessed the relationship between peak exercise CPO and selected indices of cardio‐respiratory fitness. Thirty‐seven healthy adults (23 men and 14 women) performed an incremental exercise test to volitional fatigue using the Bruce protocol with gas exchange and ventilatory measurements. Following a 40‐min recovery, the subjects performed a constant maximum workload exercise test at or above 95% of maximal oxygen consumption. Cardiac output was measured using the exponential CO₂ rebreathing method. The CPO, expressed in W, was calculated as the product of the mean arterial blood pressure and cardiac output. At peak exercise, CPO was well correlated with cardiac output (r = 0·92, P<0·01), stroke volume (r = 0·90, P<0·01) and peak oxygen consumption (r = 0·77, P<0·01). The coefficient of correlation was moderate between CPO and anaerobic threshold (r = 0·47, P<0·01), oxygen pulse (r = 0·57, P<0·01), minute ventilation (r = 0·53, P<0·01) and carbon dioxide production (r = 0·56, P<0·01). Small but significant relationship was found between peak CPO and peak heart rate (r = 0·23, P<0·05). These findings suggest that only peak cardiac output and stroke volume truly reflect CPO. Other indices of cardio‐respiratory fitness such as oxygen consumption, anaerobic threshold, oxygen pulse, minute ventilation, carbon dioxide production and heart rate should not be used as surrogates for overall cardiac function and pumping capability of the heart.     

Variability of automated carotid intima‐media thickness measurements by novice operators

Carotid intima‐media thickness (C‐IMT) measurements provide a non‐invasive assessment of subclinical atherosclerosis. The aim of the study was to assess the inter‐ and intra‐observer variability of automated C‐IMT measurements undertaken by two novice operators using the Panasonic CardioHealth Station. Participants were free from cardio‐metabolic disease, and each underwent serial bilateral C‐IMT ultrasound measurements. Immediate interoperator measurement variability was calculated by comparing initial measurements taken by two operators. Immediate retest variability was calculated from two consecutive measurements and longer term variability was assessed by conducting a further scan 1 week later. Fifty apparently healthy participants (n = 20 females), aged 26·2 ± 5·0 years, were recruited. Operator 1 recorded a median (interquartile range) right and left‐sided C‐IMT of 0·471 mm (0·072 mm) and 0·462 mm (0·047 mm). Female's right and left C‐IMT were 0·442 mm (0·049 mm) and 0·451 mm (0·063 mm), respectively. The limits of agreement (LoA) for immediate interoperator variability were ?0·063 to 0·056 mm (mean bias ?0·003 mm). Operator 1's immediate retest intra‐operator LoA were ?0·057 to 0·046 mm (mean bias was ?0·005 mm). One‐week LoA were ?0·057 to 0·050 mm (mean bias ?0·003 mm). Operator 2 recorded median right and left‐sided C‐IMT of 0·467 mm (0·089 mm) and 0·458 mm (0·046 mm) for males, respectively, whilst female measurements were 0·441 mm (0·052 mm) and 0·444 mm (0·054 mm), respectively. Operator 2's intra‐operator immediate retest LoA were ?0·056 to 0·056 (mean bias 相似文献   

Gamma‐variate plasma clearance versus urinary plasma clearance of 51Cr‐EDTA in patients with cirrhosis with and without fluid retention

In patients with fluid retention, the plasma clearance of ⁵¹Cr‐EDTA (Cl_exp obtained by multiexponential fit) may overestimate the glomerular filtration rate (GFR). The present study was undertaken to compare a gamma‐variate plasma clearance (Cl_gv) with the urinary plasma clearance of ⁵¹Cr‐EDTA (Cl_u) in patients with cirrhosis with and without fluid retention. A total of 81 patients with cirrhosis (22 without fluid retention, 59 with ascites) received a quantitative intravenous injection of ⁵¹Cr‐EDTA followed by plasma and quantitative urinary samples for 5 h. Cl_gv was determined from the injected dose relative to the plasma concentration‐time area, obtained by a gamma‐variate iterative fit. Cl_exp and Cl_u were determined by standard technique. In patients without fluid retention, Cl_gv, Cl_exp and Cl_u were closely similar. The difference between Cl_gv and Cl_u (Cl_gv – Cl_u = ΔCl) was mean ?0·6 ml min^?1 1·73 m^?2. In patients with ascites, ΔCl was significantly higher (11·8 ml min^?1 1·73 m^?2, P<0·0001), but this value was lower than Cl_exp – Cl_u (17·5 mL min^?1 1·73 m^?2, P<0·01). ΔCl increased with lower values of GFR (P<0·001). In conclusion, in patients with fluid retention and ascites Cl_gv and Cl_exp overestimates GFR substantially, but the overestimation is smaller with Cl_gv. Although Cl_u may underestimate GFR slightly, patients with ascites should collect urine quantitatively to obtain a reliable measurement of GFR.