Systematic review: pre- and post-operative prognostic value of cardiopulmonary exercise testing in liver transplant candidates.

BACKGROUND: Cardiopulmonary exercise testing (CPET) is the gold standard for the objective assessment of functional status. In many conditions, CPET outperforms the traditional variables in predicting mortality. AIM: In patients with cirrhosis listed for liver transplantation, our primary aim was to determine the prognostic value of CPET for pre-and post-transplant mortality and, in particular, whether CPET remained predictive after adjustment for liver disease severity. METHODS: A systematic literature review was conducted in databases Medline, Scopus, Embase and PubMed. Where possible, data were pooled for meta-analyses using a DerSimonian and Laird random effects model. RESULTS: A total of seven studies were retrieved, including 1107 patients with a mean MELD of 14.2 (standard deviation 1.6) and peak baseline VO2 of 17.4 mL/kg/min. In all of the studies in which multivariable analysis was performed, CPET variables were independent predictors of pre-transplant mortality (three studies) and post-transplant mortality (four studies). In the three studies where we could aggregate post-transplant mortality data, post-transplant mortality was predicted by AT with a mean difference of 2.0 (95% confidence interval, CI: 0.42-3.59; Z = 2.48, P = 0.01) between survivors and nonsurvivors. The peak VO2 was not significant (0.77 95% CI: -1.36 to 2.90; Z = 0.71, P = 0.48). CONCLUSIONS: Patient's listed for liver transplant have significant functional limitations, with a weighted mean VO2 below the threshold level required for independent living. Although heterogeneity in study designs with respect to timing, CPET variables, and cut-off values precluded the determination of CPET mortality thresholds, the studies support CPET as an objective and independent predictor of pre- and post-transplant mortality.

Cardiovascular MRI predicts 5-year adverse clinical outcome in heart transplant recipients.

Imaging recommendations for the follow-up of heart transplant recipients (HTRs) lack evidence justifying their prognostic value. Cardiovascular magnetic resonance imaging (CMRI) can characterize heart structure and function and has prognostic value in many myocardial diseases. We hypothesized that CMRI evaluation of cardiac allografts would predict adverse events. We performed CMRI on 60 HTRs evaluating biventricular size, function and myocardial scar. We performed survival analysis to identify independent predictors of cardiovascular (CV) death or hospitalization. Participants had a mean age of 51 ± 14 years, mean graft age of 3.5 years (±4) and 75% are male. Median follow-up time was 4.9 years with 22 CV hospitalizations and 7 CV deaths. A multivariable survival analysis of imaging and clinical variables identified myocardial scar (hazard ratio [HR] of 10.7, p = 0.005), right ventricular end- diastolic volume index (RVEDVI; 1.1/mL/m(2) , p = 0.001), graft age (HR = 1.2/year, p = 0.004) and previous allograft rejection (HR = 4.4, p = 0.006) as predictive of time to CV death or hospitalization. CMRI-derived myocardial scar and RVEDVI are independently associated with CV outcomes in HTRs.

Meeting report: consensus recommendations for a research agenda in exercise in solid organ transplantation.

With improved survival rates in solid organ transplantation there has been an increased focus on long-term outcomes following transplant, including physical function, health-related quality-of-life and cardiovascular mortality. Exercise training has the potential to affect these outcomes, however, research on the optimal timing, type, dose of exercise, mode of delivery and relevant outcomes is limited. This article provides a summary of a 2-day meeting held in April 2013 (Toronto, Canada) in which a multi-disciplinary group of clinicians, researchers, administrators and patient representatives engaged in knowledge exchange and discussion of key issues in exercise in solid organ transplant (SOT). The outcomes from the meeting were the development of top research priorities and a research agenda for exercise in SOT, which included the need for larger scale, multi-center intervention studies, development of standardized outcomes for physical function and surrogate measures for clinical trials, examining novel modes of exercise delivery and novel outcomes from exercise training studies such as immunity, infection, cognition and economic outcomes. The development and dissemination of "expert consensus guidelines," synthesizing both the best available evidence and expert opinion was prioritized as a key step toward improving program delivery.

Aging blunts hyperventilation-induced hypocapnia and reduction in cerebral blood flow velocity during maximal exercise.

Cerebral blood flow (CBF) increases from rest to ∼60% of peak oxygen uptake (VO(2peak)) and thereafter decreases towards baseline due to hyperventilation-induced hypocapnia and subsequent cerebral vasoconstriction. It is unknown what happens to CBF in older adults (OA), who experience a decline in CBF at rest coupled with a blunted ventilatory response during VO(2peak). In 14 OA (71 ± 10 year) and 21 young controls (YA; 23 ± 4 years), we hypothesized that OA would experience less hyperventilation-induced cerebral vasoconstriction and therefore an attenuated reduction in CBF at VO(2peak). Incremental exercise was performed on a cycle ergometer, whilst bilateral middle cerebral artery blood flow velocity (MCA V (mean); transcranial Doppler ultrasound), heart rate (HR; ECG) and end-tidal PCO(2) (P(ET)CO(2)) were monitored continuously. Blood pressure (BP) was monitored intermittently. From rest to 50% of VO(2peak), despite greater elevations in BP in OA, the change in MCA V(mean) was greater in YA compared to OA (28% vs. 15%, respectively; P < 0.0005). In the YA, at intensities >70% of VO(2peak), the hyperventilation-induced declines in both P(ET)CO(2) (14 mmHg (YA) vs. 4 mmHg (OA); P < 0.05) and MCA V(mean) (-21% (YA) vs. -7% (OA); P < 0.0005) were greater in YA compared to OA. Our findings show (1), from rest-to-mild intensity exercise (50% VO(2peak)), elevations in CBF are reduced in OA and (2) age-related declines in hyperventilation during maximal exercise result in less hypocapnic-induced cerebral vasoconstriction.

Utility of transcranial Doppler ultrasound for the integrative assessment of cerebrovascular function.

There is considerable utility in the use of transcranial Doppler ultrasound (TCD) to assess cerebrovascular function. The brain is unique in its high energy and oxygen demand but limited capacity for energy storage that necessitates an effective means of regional blood delivery. The relative low cost, ease-of-use, non-invasiveness, and excellent temporal resolution of TCD make it an ideal tool for the examination of cerebrovascular function in both research and clinical settings. TCD is an efficient tool to access blood velocities within the cerebral vessels, cerebral autoregulation, cerebrovascular reactivity to CO(2), and neurovascular coupling, in both physiological states and in pathological conditions such as stroke and head trauma. In this review, we provide: (1) an overview of TCD methodology with respect to other techniques; (2) a methodological synopsis of the cerebrovascular exam using TCD; (3) an overview of the physiological mechanisms involved in regulation of the cerebral blood flow; (4) the utility of TCD for assessment of cerebrovascular pathology; and (5) recommendations for the assessment of four critical and complimentary aspects of cerebrovascular function: intra-cranial blood flow velocity, cerebral autoregulation, cerebral reactivity, and neurovascular coupling. The integration of these regulatory mechanisms from an integrated systems perspective is discussed, and future research directions are explored.

Exercise training improves aerobic capacity and skeletal muscle function in heart transplant recipients.

The aim of this study was to examine the effects of 12 weeks of supervised aerobic and strength training (SET) versus no-training (NT) on peak aerobic power (VO2peak), submaximal exercise left ventricular (LV) systolic function, peripheral vascular function, lean tissue mass and maximal strength in clinically stable heart transplant recipients (HTR). Forty-three HTR were randomly assigned to 12 weeks of SET (n = 22; age: 57 +/- 10 years; time posttransplant: 5.4 +/- 4.9 years) or NT (n = 21; age: 59 +/- 11 years; time posttransplant: 4.4 +/- 3.3 years). The change in VO2peak (3.11 mL/kg/min, 95% CI: 1.2-5.0 mL/kg/min), leg and total lean tissue mass (0.78 kg, 95% CI: 0.31-1.3 kg and 1.34 kg, 95% CI: 0.34-2.3 kg, respectively), chest-press (10.4 kg, 95% CI: 5.2-15.5 kg) and leg-press strength (34.7 kg, 95% CI: 3.7-65.6 kg) were significantly higher after SET versus NT. No significant change was found for submaximal exercise LV systolic function or brachial artery endothelial-dependent or -independent vasodilation. Supervised exercise training is an effective intervention to improve VO2peak, lean tissue mass and muscle strength in HTR. This training regimen did not improve exercise LV systolic function or brachial artery endothelial function.

A prediction model for estimating pulmonary oxygen uptake during the 6-minute walk test in organ transplant recipients.

We developed a multivariate prediction equation for estimating the highest obtainable pulmonary oxygen uptake (VO2p) during the 6-minute walk test (6-MWT) in 54 organ transplant recipients: heart/heart-double-lung (n=14), kidney/kidney-pancreas (n=16), liver (n=14), double lung (n=8), bone marrow (n=2). They were of age, 48+/-12 years. Participants performed a 6-MWT during which expired gases were collected and analyzed with a portable metabolic system interfaced with a wireless heart rate monitor. The following variables significantly contributed to the model for predicting the highest obtainable 6-MWT VO2p: 6-MWT distance (m), age (years), gender (male=0, female=1), resting heart rate, peak heart rate, weight (kg), and transplant type (kidney/kidney-pancreas=1, other=0), where: VO2p=1.253+0.022 (6-MWT distance)+0.112 (age) -3.192 (gender) -0.104 (resting heart rate)+0.127 (peak 6-MWT heart rate)-0.084 (weight)+2.116 (transplant type). The explanatory variables in our final model accounted for 78% of the variance in 6-MWT VO2p. In conclusion, the addition of an easily estimated 6-MWT VO2p will provide added clinical information of functional capacity following an exercise rehabilitation intervention or during routine follow-up for organ transplant recipients.

The effect of high-intensity rowing and combined strength and endurance training on left ventricular systolic function and morphology.

Combined strength and endurance training may result in alterations in left ventricular (LV) systolic function and morphology, however, the acute effect of high-intensity rowing exercise and concurrent training-induced adaptations on LV systolic function are not well known. The purpose of this investigation was to assess LV systolic function before and after a simulated 2000-m rowing race on a Concept II rowing ergometer and evaluate these adaptations following 10 weeks of concurrent strength and endurance training. Furthermore, resting LV morphology was assessed prior to and following the 10-week training program. Ten male subjects underwent two-dimensional echocardiograms at rest, immediately following (95 +/- 27 s), as well as 5 and 45 minutes after, a simulated 2000-m rowing race. These measurements were also made before and after 10 weeks of training. Irrespective of testing time, performance of a 2000-m rowing race resulted in an increase in fractional area change (0.51 +/- 0.06 vs. 0.63 +/- 0.09; p < 0.05) due to an increase in LV contractility. Concurrent strength and endurance training resulted in an increase in the resting LV diastolic cavity area (20.64 +/- 2.59 vs. 22.82 +/- 2.17 cm (2); p < 0.05), end systolic myocardial area (23.27 +/- 4.86 vs. 24.56 +/- 4.00 cm (2); p < 0.05) and LV mass (179.07 +/- 46.91 g vs. 210.46 +/- 51.13 g; p < 0.05). These findings suggest that the acute increase in LV systolic function following a simulated 2000-m rowing race was due to heightened LV contractile reserve. Further, 10 weeks of combined strength and endurance training resulted in an increase in resting LV diastolic cavity size, wall thickness and mass.

Therapeutic exercise for individuals with heart failure: special attention to older women with heart failure.

BACKGROUND: A cardinal feature of heart failure (HF) is the reduced peak aerobic power (VO(2peak)) secondary to alterations in cardiovascular and musculoskeletal function. Methods and results During the last decade, a number of randomized trials have examined the role that exercise training plays in attenuating the HF-mediated decline in VO(2peak) and muscle strength. The major finding of these investigations was that aerobic or strength training was an effective intervention to increase VO(2peak), muscular strength, distance walked in 6 minutes, and quality of life without negatively altering left ventricular systolic function. Despite these benefits, a limitation of these investigations was the primary focus on males <60 years with impaired left ventricular systolic function. Thus the role that exercise training may play in attenuating the HF-mediated decline in VO(2peak) in women > or =65 years of age remains unknown. CONCLUSION: Older women with HF have a VO(2peak) that is below the minimal threshold level required for independent living. Moreover, older women with HF have greater disability then men and are less likely to be referred to an exercise rehabilitation program. Accordingly, future exercise intervention trials are required to examine the role that exercise training may play in attenuating the HF-mediated decline in cardiorespiratory and musculoskeletal fitness and disability in older women with HF.

Biochemical changes as a result of prolonged strenuous exercise.

OBJECTIVE: To briefly review biochemical changes that may result from prolonged strenuous exercise and to relate these changes to health risk. METHODS: Medline and Sports Discus databases were searched for relevant articles. Additional articles were found using cross referencing and the authors' knowledge of the subject area. RESULTS: Prolonged strenuous exercise may result in a series of biochemical changes that are of concern from a health point of view. Generally, these changes are benign, but some, especially hyponatraemia, are potentially life threatening occurrences. CONCLUSION: Doctors and athletes should be aware of the potentially adverse biochemical changes, especially hyponatraemia, that may result from prolonged strenuous exercise.

Impaired left ventricular systolic function after a half-ironman race.

OBJECTIVE: To assess the effects of prolonged strenuous exercise in the form of a half-ironman (HI) race (2 km swim, 90 km bike ride and a 21 km run) on left ventricular systolic function. METHODS AND RESULTS: The study participants consisted of nine male triathletes (mean age +/- SD 32+/-5 years) who competed in the Great White North HI race. Two-dimensional transthoracic echocardiograms were obtained two to three days before the HI (prerace), immediately after completion of the HI (postrace) and 24 h after cessation of exercise. Compared with before the race, performing an HI was associated with a decline in systolic blood pressure (prerace 127.2+/-15.0 mmHg compared with after the race 116.1+/-10.2 mmHg, P<0.05), the systolic blood pressure to end-systolic cavity area ratio (a surrogate for left ventricular contractility - prerace 14.3+/-3.0 mmHg/cm(2) compared with postrace 11.0+/-2.2 mmHg/cm(2), P<0.05) and the fractional area change (prerace 54.1+/-3.8% compared with postrace 47.4+/-5.5%, P<0.05). There was also a concomitant increase in heart rate (prerace 56.3+/-9.4 beats/min compared with postrace 74.1+/-10.7 beats/min, P<0.05), the end-systolic cavity area (prerace 9.2+/-2.2 cm(2) compared with postrace 10.8+/-1.9 cm(2), P<0.05) and the end-systolic cavity area to end-systolic myocardial area ratio (prerace 0.39+/-0.08 compared with postrace 0.51+/-0.1, P<0.05), which returned toward baseline values 24 h after cessation of the HI. CONCLUSIONS: Performing an HI appears to be associated with a transient impairment in left ventricular contractility and a subsequent decline in left ventricular systolic function that tends to return toward normal values within 24 h after cessation of exercise.

Left ventricular wall stress during leg-press exercise performed with a brief Valsalva maneuver.

STUDY OBJECTIVES: To assess the effects of leg-press (LP) exercise performed with a brief (2 to 3 s) Valsalva maneuver on left ventricular (LV) systolic function and LV wall stress in five healthy men (mean +/- SD age, 27.6 +/- 2.9 years). METHODS AND MEASUREMENTS: Subjects performed submaximal (80% one repetition maximum [1RM], 337.9 +/- 109.1 kg; 95% 1RM, 400.6 +/- 129.8 kg) and maximal LP exercise (420 +/- 118.6 kg) during which central arterial pressure, intrathoracic pressure, and two-dimensional echocardiographic analysis of LV systolic function and LV wall stress were measured. RESULTS: Compared with baseline, LP exercise resulted in an increase in intrathoracic pressure (baseline, 1.7 +/- 2.9 mm Hg; 80% 1RM, 111.7 +/- 20.2 mm Hg; 95% 1RM, 112.2 +/- 21.1 mm Hg; 100% 1RM, 111.0 +/- 21.3 mm Hg; p < 0.05) and LV end-systolic pressure (baseline, 120.0 +/- 13.2 mm Hg; 80% 1RM, 251.6 +/- 15.3 mm Hg; 95% 1RM, 255.3 +/- 12.2 mm Hg; 100% 1RM, 242.8 +/- 16.5 mm Hg; p < 0.05) with no changes in LV end-systolic transmural pressure (baseline, 118.3 +/- 12.6 mm Hg; 80% 1RM, 140.0 +/- 6.1 mm Hg; 95% 1RM, 143.1 +/- 16.1 mm Hg; 100% 1RM, 131.8 +/- 29.7 mm Hg; p > 0.05), LV end-systolic wall stress (baseline, 91.7 +/- 20.2 kilodyne/cm(2); 80% 1RM, 78.0 +/- 24.4 kilodyne/cm(2); 95% 1RM, 81.4 +/- 25.3 kilodyne/cm(2); 100% 1RM, 85.9 +/- 20.1 kilodyne/cm(2); p > 0.05), or LV fractional area change (baseline, 0.48 +/- 0.03; 80% 1RM, 0.52 +/- 0.11; 95% 1RM, 0.53 +/- 0.06; 100% 1RM, 0.52 +/- 0.05; p > 0.05). CONCLUSION: LP exercise performed with a brief Valsalva maneuver is not associated with an alteration in LV wall stress or LV systolic function in healthy young men.

Effects of half ironman competition on the development of late potentials.

OBJECTIVES: The primary purpose was to evaluate the prevalence of late potentials (LPs) in triathletes before and after a half ironman triathlon. The secondary purpose was to examine whether LPs are the electrocardiographic expression of a greater myocardial mass. METHODS: Nine asymptomatic male triathletes (mean age +/- SD, 32 +/- 5 yr) were examined using signal-averaged ECG (SAECG) 48-72 h before (PRE), immediately after (POST), and 24-48 h after the completion (RECOVERY) of a half ironman triathlon. Late potentials were considered to be present if two of the following SAECG anomalies were observed: 1) a prolonged filtered QRS (/QRS) complex (> or = 114 ms), 2) a lengthened low amplitude signal (LAS) duration (>38 ms), and/or 3) a low root mean square (RMS) voltage of the last 40 ms of the fQRS (<20 microV). Left ventricular dimensions were determined at PRE using M-mode echocardiography. RESULTS: There were no significant differences between PRE, POST, and RECOVERY in the fQRS duration, the LAS duration, or the RMS voltage. Two athletes displayed a single SAECG abnormality during PRE and two SAECG anomalies (i.e., LPs) during POST. Late potentials remained in one of the two athletes during RECOVERY. A moderate relationship existed between fQRS and left ventricular mass (r = 0.67, P < 0.05). CONCLUSIONS: Ultra-endurance training and/or events do not lead to LPs in the majority of triathletes who do not possess ventricular arrhythmias. However, a small subset of triathletes do display SAECG anomalies, which are augmented by an ultra-endurance event and may persist even after recovery from the event. Left ventricular mass does not affect overall SAECG parameters.

Effects of 16 weeks of resistance training on left ventricular morphology and systolic function in healthy men >60 years of age.

Resistance training (RT) has gained popularity as an effective form of exercise for older adults. However, the effects of RT on left ventricular (LV) morphology and systolic function in older persons is not well known. The purpose of this study was to assess the effects of 16 weeks of RT on LV morphology and systolic function in healthy older men. Subjects were randomly assigned into a RT group (n = 10; mean+/- SD age, 68 +/- 3 years) or a nonexercise control group (n = 10; age 68 +/- 4 years). RT was performed 3 times per week for 16 weeks at a mean intensity between 60% and 80% of 1 repetition maximum. Leg and bench press 1 repetition maximum and 2-dimensional echocardiography were performed at baseline and after 4, 8, 12, and 16 weeks of training in the RT group. Sixteen weeks of RT was associated with an increase in leg press maximal strength (baseline, 285 +/- 48 kg; after 16 weeks, 367 +/- 47 kg; p <0.05) and bench press maximal strength (baseline, 59 +/- 11 kg; after 16 weeks, 69 +/- 11 kg; p <0.05). No change in leg press maximal strength (baseline, 291 +/- 59 kg; after 16 weeks, 290 +/- 53 kg; p >0.05) or bench press maximal strength (baseline, 60 +/- 9 kg; after 16 weeks, 61 +/- 13 kg; p > .05) was found in control subjects during the same time. RT was not associated with changes in LV cavity size, wall thickness, mass, or systolic function after 4, 8, 12, and 16 weeks of exercise. Thus, 16 weeks of RT was sufficient to increase leg press and bench press maximal strength but did not alter the size or systolic function of the senescent left ventricle.

Effects of long term resistance training on left ventricular morphology.

OBJECTIVES: To assess the effects of long term (mean +/- SD 10+/-5 years, range three to 25 years) resistance training on left ventricular (LV) dimensions and mass. METHODS AND RESULTS: The study participants were 21 elite male power-lifters (age 33.4+/-5.9 years) and 10 sedentary male control subjects (age 30.9+/-4.2 years). Two-dimensionally guided transthoracic M-mode echocardiograms were obtained at rest to quantify LV diastolic cavity dimension, posterior wall thickness, ventricular septal wall thickness and LV mass. Long term resistance training was not associated with an alteration in LV diastolic cavity dimension (resistance trained 54. 4+/-4.3 mm versus control 51.8+/-5.6 mm), ventricular septal wall thickness (resistance trained 9.7+/-1.0 mm versus control 10.1+/-0.7 mm), posterior wall thickness (resistance trained 9.6+/-1.5 mm versus control 9.3+/-1.4 mm) or LV mass (resistance trained 200. 3+/-32.5 g versus control 186.5+/-39.6 g). In addition, no resistance-trained athlete was found to have an LV mean wall thickness above clinical normal limits (12 mm or less). CONCLUSION: Contrary to common beliefs, long term resistance training as performed by elite male power-lifters does not alter LV morphology.

Left ventricular morphology in junior and master resistance trained athletes.

PURPOSE: The objective of this cross-sectional investigation was to assess the effects of short (< 5 yr) versus long-term (> or = 18 yr) resistance training (RT) on left ventricular (LV) dimensions and mass. METHODS: The subjects for this study were 20 elite male powerlifters (8 junior athletes [JA], mean +/- SD, age: 21.1 +/- 1.2 yr and 12 master athletes [MA], age: 46.0 +/- 5.5 yr) and 19 age-matched male controls (8 young controls [YC], age: 21.8 +/- 2.8 yr and 11 middle-aged controls [MAC], age: 46.8 +/- 4.4 yr). Two-dimensionally guided transthoracic M-mode echocardiograms were performed at rest to quantify LV systolic and diastolic cavity dimension (LVIDs and LVIDd, respectively), ventricular septal wall thickness (VST), posterior wall thickness (PWT), LV mass (LVM), and LV systolic function as measured as fractional shortening (FS). RESULTS: Short- or long-term RT was not associated with a significant alteration in LVIDd (JA: 53.2 +/- 4.5 mm, YC: 52.1 +/- 3.7 mm, MA: 53.0 +/- 5.1 mm, MAC: 51.8 +/- 4.4 mm), LVIDs (JA: 33.5 +/- 4.8 mm, YC: 32.9 +/- 3.4 mm, MA: 33.0 +/- 4.4 mm, MAC: 31.4 +/- 3.7 mm), VST (JA: 9.4 +/- 0.9 mm, YC: 9.4 +/- 0.9 mm, MA: 9.4 +/- 1.6 mm, MAC: 9.7 +/- 0.9 mm), PWT (JA: 9.2 +/- 0.9 mm, YC: 9.4 +/- 0.9 mm, MA: 9.0 +/- 1.1 mm, MAC: 9.5 +/- 1.0 mm), LVM (JA: 184.6 +/- 36.1 g, YC: 179.0 +/- 26.5 g, MA, 183.3 +/- 58.1 g, MAC: 184.1 +/- 38.1 g), or FS (JA: 0.37 +/- 0.1%, YC: 0.37 +/- 0.05%, MA: 0.38 +/- 0.1%, MAC: 0.40 +/- 0.04%). CONCLUSIONS: These findings suggest that short or long-term RT as performed by elite junior and master powerlifters does not alter LV morphology or systolic function.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part II: Novel techniques and new advances.

For exercise physiologists and sport cardiologists, one of the greatest challenges is to develop a valid, reliable, noninvasive and affordable measure of cardiac output (Q). There are several techniques available to measure Q during exercise conditions. These procedures generally provide accurate and reliable determinations of Q during submaximal exercise, but may be limited during maximal exercise conditions. The most commonly used noninvasive measures are the acetylene (C2H2) and carbon dioxide (CO2) rebreathe methods as reviewed in part I of this article. Only the foreign gas rebreathe method, using C2H2, meets all of the criteria of being noninvasive, easy to use, reliable and valid for use during maximal exercise. New methodologies have recently been developed to measure Q during exercise conditions. Although not as popular as the C2H2 and CO2 rebreathe methods, these methods have increasingly gained favour in exercise physiology and sport cardiology settings. The majority of these measures (if performed meticulously), with the exception of impedance cardiography, provide reasonably accurate and reliable determinations of Q. However, the cost of usage and technological limitations during maximal exercise have prevented these techniques from replacing the conventional measures of Q during exercise conditions. Doppler echocardiography and the modified C2H2 methods hold promise for the assessment of Q during maximal exercise. With further advances in these technologies their use in exercise physiology and sport cardiology setting may become more common.

Reliability and validity of measures of cardiac output during incremental to maximal aerobic exercise. Part I: Conventional techniques.

The assessment of cardiac function, particularly cardiac output (Q) during heavy exercise is essential for the evaluation of cardiovascular factors that might limit oxygen transport. A series of invasive and noninvasive techniques has been developed for the assessment and monitoring of Q during resting and submaximal exercise conditions. However, very few techniques have been found to give accurate and reliable determinations of Q during vigorous to maximum exercise. For exercise physiologists and sport cardiologists, maximal exercise data are of primary importance. The 'gold standard' measures of cardiac function are considered to be the direct Fick and dye-dilution methods. These have been widely shown to give accurate and reliable determinations of Q during resting and submaximal exercise conditions; however, their use during maximal exercise conditions is debatable due to the inherent risks involved with each and their increasing inaccuracy during the later stages of vigorous exercise. Thermodilution has also been considered to be a relatively good method for the determination of Q during rest and exercise conditions, but recent authors have questioned its use due to the nature of the measure and its inaccuracy during strenuous exercise. Various noninvasive measures of cardiac function have been developed to overcome the problems associated with the 'gold standard' measures. The first part of this article discusses conventional techniques used in exercise physiology settings. The majority of these provide accurate and reliable determinations of Q during rest and submaximal exercise. However, very few techniques are suitable for maximal exercise conditions. Perhaps only the foreign gas rebreathe using acetylene (C2H2) meets all the criteria of being noninvasive, simple to use, reliable over repeated measurements, accurate and useful during maximal exercise.

Left ventricular morphology in elite female resistance-trained athletes.

Long-term resistance training as performed by elite female resistance-trained athletes appears to be an insufficient stimulus to alter left ventricular cavity size, wall thickness, or estimated mass.

Effects of short-term altitude training and tapering on left ventricular morphology in elite swimmers.

Short or long-term athletic training has been associated with left ventricular (LV) morphological adaptations, including increases in wall thickness, cavity dimension and estimated LV mass. A limitation of previous studies assessing the 'athlete heart' was that exercise training was performed at sea level. Since the 1968 Olympic summer games a popular method of maximizing athletic performance has been to use altitude training (AT) as a means of improving sea level performance. However, the effects of short term AT and taper training on LV morphology have not been well studied. Based on this limitation, the effects of three weeks of intense AT (1848 m) or low level control training (CT) (1050 m) followed by two weeks of taper training were investigated in 15 elite swimmers between 16 and 21 years of age. Short term AT or CT training followed by two weeks of taper training was not associated with alterations in LV diastolic cavity dimension (AT pre 53.3 +/- 2.8 mm versus post 52.6 +/- 4.3 mm; CT pre 52.9 +/- 3.7 mm versus post 51.2 +/- 4.0 mm), ventricular septal wall thickness (AT pre 9.6 +/- 1.0 mm versus post 9.4 +/- 1.1 mm; CT pre 8.4 +/- 1.2 mm versus post 8.6 +/- 1.1 mm), estimated LV mass (AT pre 186.4 +/- 45.8 g versus post 190.0 +/- 48.2 g; CT pre 159.1 +/- 35.8 g versus post 160.1 +/- 40.8 g) or fractional shortening (AT pre 36.8 +/- 3.5% versus post 34.8 +/- 2.7%; CT pre 32.6 +/- 5.0% versus post 32.8 +/- 4.7%). However, a main time effect, independent of training intervention, was observed for posterior wall thickness (pre 8.7 +/- 1.4 mm versus post 9.3 +/- 1.1 mm, P < 0.05). Therefore, with the exception of posterior wall thickness, short term AT followed by two weeks of taper training appears not to be associated with alterations in LV morphology or systolic function.