Air to muscle O2 delivery during exercise at altitude

[EN] Hypoxia-induced hyperventilation is critical to improve blood oxygenation, particularly when the arterial Po2 lies in the steep region of the O2 dissociation curve of the hemoglobin (ODC). Hyperventilation increases alveolar Po2 and, by increasing pH, left shifts the ODC, increasing arterial saturation (Sao2) 6 to 12 percentage units. Pulmonary gas exchange (PGE) is efficient at rest and, hence, the alveolar-arterial Po2 difference (Pao2-Pao2) remains close to 0 to 5mm Hg. The (Pao2-Pao2) increases with exercise duration and intensity and the level of hypoxia. During exercise in hypoxia, diffusion limitation explains most of the additional Pao2-Pao2. With altitude, acclimatization exercise (Pao2-Pao2) is reduced, but does not reach the low values observed in high altitude natives, who possess an exceptionally high DLo2. Convective O2 transport depends on arterial O2 content (Cao2), cardiac output (Q), and muscle blood flow (LBF). During whole-body exercise in severe acute hypoxia and in chronic hypoxia, peak Q and LBF are blunted, contributing to the limitation of maximal oxygen uptake (Vo2max). During small-muscle exercise in hypoxia, PGE is less perturbed, Cao2 is higher, and peak Q and LBF achieve values similar to normoxia. Although the Po2 gradient driving O2 diffusion into the muscles is reduced in hypoxia, similar levels of muscle O2 diffusion are observed during small-mass exercise in chronic hypoxia and in normoxia, indicating that humans have a functional reserve in muscle O2 diffusing capacity, which is likely utilized during exercise in hypoxia. In summary, hypoxia reduces Vo2max because it limits O2 diffusion in the lung.

Effects of recovery mode on performance, O2 uptake, and O2 deficit during high-intensity intermittent exercise

[EN] The aim of this study was to determine the influence of activity performed during the recovery period on the aerobic and anaerobic energy yield, as well as on performance, during high-intensity intermittent exercise (HIT). Ten physical education students participated in the study. First they underwent an incremental exercise test to assess their maximal power output (Wmax) and VO2max. On subsequent days they performed three different HITs. Each HIT consisted of four cycling bouts until exhaustion at 110% Wmax. Recovery periods of 5 min were allowed between bouts. HITs differed in the kind of activity performed during the recovery periods: pedaling at 20% VO2max (HITA), stretching exercises, or lying supine. Performance was 3-4% and aerobic energy yield was 6-8% (both p < 0.05) higher during the HITA than during the other two kinds of HIT. The greater contribution of aerobic metabolism to the energy yield during the high-intensity exercise bouts with active recovery was due to faster VO2 kinetics (p< 0.01) and a higher VO2peak during the exercise bouts preceded by active recovery (p < 0.05). In contrast, the anaerobic energy yield (oxygen deficit and peak blood lactate concentrations) was similar in all HITs. Therefore, this study shows that active recovery facilitates performance by increasing aerobic contribution to the whole energy yield turnover during high-intensity intermittent exercise.

Reductions in systemic and skeletal muscle blood flow and oxygen delivery limit maximal aerobic capacity in humans

[EN] BACKGROUND: A classic, unresolved physiological question is whether central cardiorespiratory and/or local skeletal muscle circulatory factors limit maximal aerobic capacity (VO2max) in humans. Severe heat stress drastically reduces VO2max, but the mechanisms have never been studied. METHODS AND RESULTS: To determine the main contributing factor that limits VO2max with and without heat stress, we measured hemodynamics in 8 healthy males performing intense upright cycling exercise until exhaustion starting with either high or normal skin and core temperatures (+10 degrees C and +1 degrees C). Heat stress reduced VO2max, 2-legged VO2, and time to fatigue by 0.4+/-0.1 L/min (8%), 0.5+/-0.2 L/min (11%), and 2.2+/-0.4 minutes (28%), respectively (all P<0.05), despite heart rate and core temperature reaching similar peak values. However, before exhaustion in both heat stress and normal conditions, cardiac output, leg blood flow, mean arterial pressure, and systemic and leg O2 delivery declined significantly (all 5% to 11%, P<0.05), yet arterial O2 content and leg vascular conductance remained unchanged. Despite increasing leg O2 extraction, leg VO2 declined 5% to 6% before exhaustion in both heat stress and normal conditions, accompanied by enhanced muscle lactate accumulation and ATP and creatine phosphate hydrolysis. CONCLUSIONS: These results demonstrate that in trained humans, severe heat stress reduces VO2max by accelerating the declines in cardiac output and mean arterial pressure that lead to decrements in exercising muscle blood flow, O2 delivery, and O2 uptake. Furthermore, the impaired systemic and skeletal muscle aerobic capacity that precedes fatigue with or without heat stress is largely related to the failure of the heart to maintain cardiac output and O2 delivery to locomotive muscle.

Validez del déficit máximo de oxigeno acumulado como índice de capacidad anaeróbica

[ES] Para determinar la validez del déficit acumulado de oxígeno (DMOA) como índice de capacidad anaeróbica, en 29 varones, estudiantes de Educación Física, se determinó el DMOA, la concentración de lactato en sangre capilar al finalizar un test supramáximo al 120 % VO2max, la potencia media y máxima desarrolladas en el test de Wingate y la masa muscular de las extremidades inferiores mediante absorciometría fotónica dual de rayos X. El DMOA correlacionó con la concentracción de lactato en sangre alcanzada al final del test de capacidad anaeróbica (r=0.43, p<0.05, n=28), con el trabajo realizado y con el VO2 acumulado en el test de capacidad anaeróbica (r=0.59, p<0.001, n=28 y r=0.56, p<0.01, n=29, respectivamente). La lactatemia al final del test de capacidad anaeróbica correlacionó con trabajo realizado en el test de capacidad anaeróbica en valores absolutos (r=0.49, p<0.01, n=27) y con el trabajo divido entre la masa muscular de las extremidades inferiores (r=0.65, p<0.001, n=26). No se observaron correlaciones significativas entre el DMOA y la potencia máxima, ni tampoco entre el DMOA y la potencia media desarrolladas en el test Wingate, ya sea expresadas en valores absolutos o referidos a la masa muscular de las piernas. Tampocó correlacionó la lactatemia alcanzada al final del test de capacidad anaeróbica con la potencia máxima ni con la potencia media desarrollada en el test de Wingate. Aunque conceptualmente el DMOA es el mejor no invasivo procedimiento para medir la capacidad anaeróbica, la ausencia de correlaciones con otras variables que se han mostrado útiles en la evaluación de las cualidades anaeróbicas limita su interés desde el punto de vista práctico.

Outcome respiratorio a lungo termine nei soggetti affetti da cardiopatia congenita sottoposti ad intervento cardiochirurgico

Introduction: In the last years cardiac surgery for congenital heart disease (CHD) reduced dramatically mortality modifying prognosis, but, at the same time, increased morbidity in this patient population. Respiratory and cardiovascular systems are strictly anatomically and functionally connected, so that alterations of pulmonary hemodynamic conditions modify respiratory function. While very short-term alterations of respiratory mechanics after surgery were investigated by many authors, not as much works focused on long-term changes. In these subjects rest respiratory function may be limited by several factor: CHD itself (fetal pulmonary perfusion influences vascular and alveolar development), extracorporeal circulation (CEC), thoracotomy and/or sternotomy, rib and sternal contusions, pleural adhesions and pleural fibrosis, secondary to surgical injury. Moreover inflammatory cascade, triggered by CEC, can cause endothelial damage and compromise gas exchange. Aims: The project was conceived to 1) determine severity of respiratory functional impairement in different CHD undergone to surgical correction/palliation; 2) identify the most and the least CHD involved by pulmonary impairement; 3) find a correlation between a specific hemodynamic condition and functional anomaly, and 4) between rest respiratory function and cardiopulmonary exercise test. Materials and methods: We studied 113 subjects with CHD undergone to surgery, and distinguished by group in accord to pulmonary blood flow (group 0: 28 pts with normal pulmonary flow; group 1: 22 pts with increased flow; group 2: 43 pts with decreased flow; group 3: 20 pts with total cavo-pulmonary anastomosis-TCPC) followed by the Pediatric Cardiology and Cardiac Surgery Unit, and we compare them to 37 age- and sex-matched healthy subjects. In Pediatric Pulmonology Unit all pts performed respiratory function tests (static and dynamic volumes, flow/volume curve, airway resistances-raw- and conductance-gaw-, lung diffusion of CO-DLCO- and DLCO/alveolar volume), and CHD pts the same day had cardiopulmonary test. They all were examined and had allergological tests, and respiratory medical history. Results: restrictive pattern (measured on total lung capacity-TLC- and vital capacity-VC) was in all CHD groups, and up to 45% in group 2 and 3. Comparing all groups, we found a significant difference in TLC between healthy and group 2 (p=0.001) and 3 (p=0.004), and in VC between group 2 and healthy (p=0.001) and group 1(p=0.034). Inspiratory capacity (IC) was decreased in group 2 related to healthy (p<0.001) and group 1 (p=0.037). We showed a direct correlation between TLC and VC with age at surgery (p=0.01) and inverse with number of surgical interventions (p=0.03). Reduced FEV1/FVC ratio, Gaw and increased Raw were mostly present in group 3. DLCO was impaired in all groups, but up to 80% in group 3 and 50% in group 2; when corrected for alveolar volume (DLCO/VA) reduction persisted in group 3 (20%), 2 (6.2%) and 0 (7.1%). Exercise test was impaired in all groups: VO2max and VE markedly reduced in all but especially in group 3, and VE/VCO2 slope, marker of ventilatory response to exercise, is increased (<36) in 62.5% of group 3, where other pts had anyway value>32. Comparing group 3 and 2, the most involved categories, we found difference in VO2max and VE/VCO2 slope (respectively p=0.02 and p<0.0001). We evidenced correlation between rest and exercise tests, especially in group 0 (between VO2max and FVC, FEV1, VC, IC; inverse relation between VE/VCO2slope and FVC, FEV1 and VC), but also in group 1 (VO2max and IC), group 2 (VO2max and FVC and FEV1); never in group 3. Discussion: According with literature, we found a frequent impairment of rest pulmonary function in all groups, but especially in group 2 and 3. Restrictive pattern was the most frequent alteration probably due to compromised pulmonary (vascular and alveolar) development secondary to hypoperfusion in fetal and pre-surgery (and pre-TCPC)life. Parenchymal fibrosis, pleural adhesions and thoracic deformities can add further limitation, as showed by the correlation between group 3 and number of surgical intervention. Exercise tests were limited, particularly in group 3 (complex anatomy and lost of chronotropic response), and we found correlations between rest and exercise tests in all but group 3. We speculate that in this patients hemodynamic exceeds respiratory contribution, though markedly decreased.

Caratterizzazione tecnica e fisiologica della Muay Thai

La Muay Thai, comunemente detta “Boxe Thailandese” è un'arte marziale che rientra nella classificazione delle attività intermittenti con entrambi i sistemi energetici reclutati, aerobico e anaerobico, è inoltre caratterizzata dal fatto che il combattimento alla distanza si alterna alla lotta, denominata “clinch”. Nonostante la popolarità della Muay Thai, in ambito mondiale, stia progressivamente aumentando così come è in aumento il numero di atleti che la praticano, le ricerche incentrate su questa arte marziale e gli studi relativi agli aggiustamenti cardiometabolici nonché alle modalità temporali con cui gli specifici gesti atletici si possono succedere nel tempo durante un match, sono ancora estremamente esigui. L’oggetto del nostro studio è stato l’analisi della struttura temporale del combattimento, tramite la Match Analysis off line (analisi visiva del combattimento), con comparazione dei dati ottenuti tra il vincitore (winner) e il perdente (loser) e la valutazione dell’andamento di alcuni importanti parametri metabolici attraverso la misurazione del lattato e della HR, durante un incontro reale di Boxe Thailandese. La sperimentazione è stata condotta su un gruppo di dieci soggetti di sesso maschile, praticanti la disciplina ad un alto livello nazionale, la cui media ± deviazione standard (DS), di età, peso e altezza è di 24,6 ±4,01 anni, 69,4 ±7 kg e 174,1 ±4,3 cm. Gli atleti sono stati sottoposti, in due diverse giornate separate da almeno tre giorni, a due test; durante una prima seduta sperimentale preliminare abbiamo determinato il massimo consumo di ossigeno (VO2max) nel corso di un test sul nastro trasportare, con concomitante stima della Soglia anaerobica (SA) e misura della massima frequenza cardiaca (HR max). In una seconda seduta sperimentale abbiamo effettuato i test di combattimento in palestra e infine abbiamo analizzato i video degli incontri attraverso la Match Analysis. Dai risultati della Match - Analysis è scaturito che i vincitori hanno eseguito un numero più elevato di azioni efficaci (p < 0,05) rispetto ai non-vincitori, grazie ad un numero maggiore di combinazioni (C ) e di attacchi singoli (A) e un numero minore di difese (D) e di tecniche inefficaci. È così emerso come il livello delle realizzazioni sia quasi esclusivamente dovuto all’efficacia della tecnica e alla tattica delle azioni. Abbiamo quindi focalizzato la nostra attenzione sul clinch e sulle azioni di attacco perché si ipotizzava che potessero essere attività dispendiose e probabilmente responsabili dell’incremento di lattato durante il combattimento, dall’ analisi dei dati però non è stata riscontrata nessuna significativa correlazione tra l’andamento dei dati metabolici e le fasi di attacco e di lotta. Dai nostri risultati emerge in maniera interessante come durante le fasi attive del combattimento si siano raggiunti alti valori di lattato ematico e di frequenza cardiaca, rispettivamente di 12,55 mmol/L e di 182,68 b/min, ben oltre la SA rilevata nel test incrementale dove la HR si posizionava a 168,2 b/min. In conclusione si evidenzia come la Boxe Thailandese sia una disciplina caratterizzata da un considerevole impegno energetico-metabolico, sia aerobico che anaerobico. La predominanza del metabolismo lattacido è dimostrata dagli elevati valori di lattato osservati nel presente studio e dalla frequenza degli attacchi (8,6 ± 3,5 sec.). Questo studio potrà essere utilizzato dagli allenatori per la predisposizione di allenamenti specifici che inducano gli adattamenti propri della Muay Thai.

The Influence of Baseline Metabolic Rate and Exercise Training on Cardio-Respiratory Dynamics

Speeding the VO2 kinetics results in a reduction of the O2 deficit. Two factors might determine VO2 kinetics: oxygen delivery to muscle (Tschakovsky and Hughson 1999) and a muscle 'metabolic inertia' (Grassi et al. 1996). Therefore, in study 1 we investigated VO2 kinetics and cardiovascular system adaptations during step exercise transitions in different regions of the moderate domain. In study 2 we investigated muscle oxygenation and cardio-pulmonary adaptations during step exercise tests before, after and over a period of training. Study 1 methods: Seven subjects (26 ± 8 yr; 176 ± 5 cm; 69 ± 6 kg) performed 4 types of step transition from rest (0-50W; 0-100W) or elevate baseline (25-75W; 25-125W). GET and VO2max were assessed before testing. O2 uptake and were measured during testing. Study 2 methods: 10 subjects (25 ± 4 yr; 175 ± 9 cm; 71 ± 12 kg) performed a step transition test (0 to 100 W) before, after and during 4 weeks of endurance training (ET). VO2max and GET were assessed before and after of ET (40 minutes, 3 times a week, 60% O2max). VO2 uptake, Q and deoxyheamoglobin were measured during testing. Study 1 results: VO2 τ and the functional gain were slower in the upper regions of the moderate domain. Q increased more abruptly during rest to work condition. Q τ was faster than VO2 τ for each exercise step. Study 2 results: VO2 τ became faster after ET (25%) and particularly after 1 training session (4%). Q kinetics changed after 4 training sessions nevertheless it was always faster than VO2 τ. An attenuation in ∆[HHb] /∆VO2 was detectible. Conclusion: these investigations suggest that muscle fibres recruitment exerts a influence on the VO2 response within the moderate domain either during different forms of step transition or following ET.

Ruolo del test da sforzo cardiopolmonare nei pazienti affetti da cardiomiopatia ipertrofica in età pediatrica

Background Decreased exercise capacity, and reduction in peak oxygen uptake are present in most patients affected by hypertrophic cardiomyopathy (HCM) . In addition an abnormal blood pressure response during a maximal exercise test was seen to be associated with high risk for sudden cardiac death in adult patients affected by HCM. Therefore exercise test (CPET) has become an important part of the evaluation of the HCM patients, but data on its role in patients with HCM in the pediatric age are quite limited. Methods and results Between 2004 and 2010, using CPET and echocardiography, we studied 68 children (mean age 13.9 ± 2 years) with HCM. The exercise test was completed by all the patients without adverse complications. The mean value of achieved VO2 max was 31.4 ± 8.3 mL/Kg/min which corresponded to 77.5 ± 16.9 % of predicted range. 51 patients (75%) reached a subnormal value of VO2max. On univariate analysis the achieved VO2 as percentage of predicted and the peak exercise systolic blood pressure (BP) Z score were inversely associated with max left ventricle (LV) wall thickness, with E/Ea ratio, and directly related with Ea and Sa wave velocities No association was found with the LV outflow tract gradient. During a mean follow up of 2.16 ± 1.7 years 9 patients reached the defined clinical end point of death, transplantation, implanted cardioverter defibrillator (ICD) shock, ICD implantation for secondary prevention or myectomy. Patients with peak VO2 < 52% or with peak systolic BP Z score < -5.8 had lower event free survival at follow up. Conclusions Exercise capacity is decreased in patients with HCM in pediatric age and global ventricular function seems being the most important determinant of exercise capacity in these patients. CPET seems to play an important role in prognostic stratification of children affected by HCM.

Valutazione dell'efficacia di iniezioni peritendinee di acido ialuronico nel tendine rotuleo di ratto disallenato

Introduzione L’attività fisica moderata seguita da improvvisa interruzione può influenzare le caratteristiche biologiche del tendine. Lo scopo del lavoro è stato quello di valutare l’attività cellulare, le caratteristiche istologiche, istomorfometriche e microstrutturali del tendine patellare e della sua entesi in condizioni di non allenamento (sedentarietà), allenamento ed improvviso arresto dell’attività fisica. E’ stato ipotizzato che un’iniezione peri-tendinea di acido ialuronico nelle settimane successive all’improvviso arresto dell’attività fisica potesse mantenere l’integrità strutturale e biologica del tendine patellare. Materiali e Metodi 24 ratti Sprague Dawley maschi di 8 settimane sono stati suddivisi in tre gruppi, allenati per 10 settimane, fino a 60-80% VO2max. I ratti sono stati suddivisi in tre gruppi: Non Allenati (6), Allenati (6), Disallenati (12). A 6 dei 12 ratti del gruppo Detrained, è stata praticata un’infiltrazione peri-tendinea a nel tendine patellare destro di 300 μl di acido ialuronico, mentre nei rimanenti 6, è stata praticata l’infiltrazione con soluzione fisiologica. I tendini rotulei espiantati sono stati valutati con coltura cellulare, valutazione biologica molecolare, valutazioni morfologiche microstrutturali, proliferazione, conta ed attività cellulare. Risultati I risultati in vitro hanno evidenziato vitalità e conta cellulare simili fra i Gruppi Trained e Detrained-HA con un incremento significativo del metabolismo cellulare rispetto agli altri Gruppi. La cellularità ha mostrato valori maggiori nei Gruppi Non Allenati e Detrained-NaCl ove si è osservata una biosintesi del collagene III superiore ai Gruppi Trained e Detrained-HA. Contrariamente, la produzione di collagene I e II presentava valori maggiori nei Gruppi Trained e Detrained-HA suggerendo una superiore efficienza tessutale e metabolica di questi ultimi. Conclusioni Questi risultati confermano che l’allenamento ed il suo improvviso arresto hanno effetti sulla struttura tendinea patellare di ratto e che l’iniezione peritendinea di acido ialuronico nel periodo di inattività ha effetti significativi su metabolismo cellulare e sul tendine rispetto al trattamento con soluzione fisiologica.

Acclimatization improves submaximal exercise economy at 5533m

We tested whether the better subjective exercise tolerance perceived by mountaineers after altitude acclimatization relates to enhanced exercise economy. Thirty-two mountaineers performed progressive bicycle exercise to exhaustion at 490 m and twice at 5533 m (days 6–7 and day 11), respectively, during an expedition to Mt. Muztagh Ata. Maximal work rate (Wmax) decreased from mean ± SD 356 ± 73 watts at 490 m to 191 ± 49 watts and 193 ± 45 watts at 5533 m, days 6–7 and day 11, respectively; corresponding maximal oxygen uptakes (VO2max) were 50.7 ± 9.5, 26.3 ± 5.6, 24.7 ± 7.0 mL/min/kg (P = 0.0001 5533 m vs 490 m). On days 6–7 (5533 m), VO2 at 75% Wmax (152 ± 37 watts) was 1.75 ± 0.45 L/min, oxygen saturation 68 ± 8%. On day 11 (5533 m), at the same submaximal work rate, VO2 was lower (1.61 ± 0.47 L/min, P < 0.027) indicating improved net efficiency; oxygen saturation was higher (74 ± 7%, P < 0.0004) but ratios of VO2 to work rate increments remained unchanged. On day 11, mountaineers climbed faster from 4497 m to 5533 m than on days 5–6 but perceived less effort (visual analog scale 50 ± 15 vs 57 ± 20, P = 0.006) and reduced symptoms of acute mountain sickness. We conclude that the better performance and subjective exercise tolerance after acclimatization were related to regression of acute mountain sickness and improved submaximal exercise economy because of lower metabolic demands for non-external work-performing functions.

Effect of acute hypoxia on maximal oxygen uptake and maximal performance during leg and upper-body exercise in Nordic combined skiers

We examined the effect of normobaric hypoxia (3200 m) on maximal oxygen uptake (VO2max) and maximal power output (Pmax) during leg and upper-body exercise to identify functional and structural correlates of the variability in the decrement of VO2max (DeltaVO2max) and of maximal power output (DeltaPmax). Seven well trained male Nordic combined skiers performed incremental exercise tests to exhaustion on a cycle ergometer (leg exercise) and on a custom built doublepoling ergometer for cross-country skiing (upper-body exercise). Tests were carried out in normoxia (560 m) and normobaric hypoxia (3200 m); biopsies were taken from m. deltoideus. DeltaVO2max was not significantly different between leg (-9.1+/-4.9%) and upper-body exercise (-7.9+/-5.8%). By contrast, Pmax was significantly more reduced during leg exercise (-17.3+/-3.3%) than during upper-body exercise (-9.6+/-6.4%, p<0.05). Correlation analysis did not reveal any significant relationship between leg and upper-body exercise neither for DeltaVO2max nor for DeltaPmax. Furthermore, no relationship was observed between individual DeltaVO2max and DeltaPmax. Analysis of structural data of m. deltoideus revealed a significant correlation between capillary density and DeltaPmax (R=-0.80, p=0.03), as well as between volume density of mitochondria and DeltaPmax (R=-0.75, p=0.05). In conclusion, it seems that VO2max and Pmax are differently affected by hypoxia. The ability to tolerate hypoxia is a characteristic of the individual depending in part on the exercise mode. We present evidence that athletes with a high capillarity and a high muscular oxidative capacity are more sensitive to hypoxia.

Prostaglandin E1 testing in heart failure-associated pulmonary hypertension enables transplantation: the PROPHET study

BACKGROUND: Elevated pulmonary vascular resistance (PVR) is relevant to prognosis of congestive heart failure and heart transplantation. Proof of reversibility by pharmacologic testing in potential transplantation candidates is important because it indicates a reduced probability of right ventricular failure or death in the early post-transplant period. This study aimed to clarify the possible extent of acute reversibility of elevated PVR in a large, consecutive cohort of heart transplant candidates. METHODS: This study included 208 consecutive patients (age 52 +/- 10 years, 89% men and 11% women, ejection fraction 21 +/- 9%, Vo2max 12.6 +/- 4.2 ml/kg/min) being evaluated for heart transplantation in 7 transplant centers in Germany and Switzerland. Testing was performed with increasing intravenous doses of prostaglandin E1 (PGE1; average maximum dose 173 +/- 115 ng/kg/min for at least 10 minutes) in 92 patients exhibiting a baseline PVR of > 2.5 Wood units (WU) and/or a transpulmonary gradient (TPG) of > 12 mm Hg. RESULTS: PGE1 testing lowered PVR from 4.1 +/- 2.0 to 2.1 +/- 1.1 WU (p < 0.01), increased cardiac output from 3.8 +/- 1.0 to 5.0 +/- 1.5 liters/min (p < 0.01), and decreased TPG from 14 +/- 4 to 10 +/- 3 mm Hg (p < 0.01), mean pulmonary artery pressure (PAM) from 39 +/- 9 to 29 +/- 9 mm Hg (p < 0.01) and mean pulmonary capillary wedge pressure (PCWP) from 24 +/- 7 to 19 +/- 9 mm Hg (p < 0.01). Mean aortic pressure (MAP) decreased to 85% and systemic vascular resistance (SVR) to 65% of baseline values (p < 0.01). Symptomatic systemic hypotension was not observed. For the whole population the percentage of patients with PVR > 2.5 WU was reduced from 44.2% to 10.5% with PGE1. PVR decreased in each patient; only 2 patients (1%) remained ineligible for listing because of a final PVR of > 4.0 WU. TPG, ejection fraction and male gender were independent predictors of reversibility of PVR. CONCLUSIONS: Elevated PVR in heart transplant candidates is highly reversible and can be normalized during acute pharmacologic testing with PGE1.

Coronary collateral flow in response to endurance exercise training

BACKGROUND: In humans, it is not known whether physical endurance exercise training promotes coronary collateral growth. The following hypotheses were tested: the expected collateral flow reduction after percutaneous coronary intervention of a stenotic lesion is prevented by endurance exercise training; collateral flow supplied to an angiographically normal coronary artery improves in response to exercise training; there is a direct relationship between the change of fitness after training and the coronary collateral flow change. METHODS AND RESULTS: Forty patients (age 61+/-8 years) underwent a 3-month endurance exercise training program with baseline and follow-up assessments of coronary collateral flow. Patients were divided into an exercise training group (n=24) and a sedentary group (n=16) according to the fact whether they adhered or not to the prescribed exercise program, and whether or not they showed increased endurance (VO2max in ml/min per kg) and performance (W/kg) during follow-up versus baseline bicycle spiroergometry. Collateral flow index (no unit) was obtained using pressure sensor guidewires positioned in the coronary artery undergoing percutaneous coronary intervention and in a normal vessel. In the vessel initially undergoing percutaneous coronary intervention, there was an increase in collateral flow index among exercising but not sedentary patients from 0.155+/-0.081 to 0.204+/-0.056 (P=0.03) and from 0.189+/-0.084 to 0.212+/-0.077 (NS), respectively. In the normal vessel, collateral flow index changes were from 0.176+/-0.075 to 0.227+/-0.070 in the exercise group (P=0.0002), and from 0.219+/-0.103 to 0.238+/-0.086 in the sedentary group (NS). A direct correlation existed between the change in collateral flow index from baseline to follow-up and the respective alteration of VO2max (P=0.007) and Watt (P=0.03). CONCLUSION: A 3-month endurance exercise training program augments coronary collateral supply to normal vessels, and even to previously stenotic arteries having undergone percutaneous coronary intervention before initiating the program. There appears to be a dose-response relation between coronary collateral flow augmentation and exercise capacity gained.

Training in hypoxia and its effects on skeletal muscle tissue

It is well established that local muscle tissue hypoxia is an important consequence and possibly a relevant adaptive signal of endurance exercise training in humans. It has been reasoned that it might be advantageous to increase this exercise stimulus by working in hypoxia. However, as long-term exposure to severe hypoxia has been shown to be detrimental to muscle tissue, experimental protocols were developed that expose subjects to hypoxia only for the duration of the exercise session and allow recovery in normoxia (live low-train high or hypoxic training). This overview reports data from 27 controlled studies using some implementation of hypoxic training paradigms. Hypoxia exposure varied between 2300 and 5700 m and training duration ranged from 10 days to 8 weeks. A similar number of studies was carried out on untrained and on trained subjects. Muscle structural, biochemical and molecular findings point to a specific role of hypoxia in endurance training. However, based on the available data on global estimates of performance capacity such as maximal oxygen uptake (VO2max) and maximal power output (Pmax), hypoxia as a supplement to training is not consistently found to be of advantage for performance at sea level. There is some evidence mainly from studies on untrained subjects for an advantage of hypoxic training for performance at altitude. Live low-train high may be considered when altitude acclimatization is not an option.

The effect of aerobic exercise on intrahepatocellular and intramyocellular lipids in healthy subjects

BACKGROUND Intrahepatocellular (IHCL) and intramyocellular (IMCL) lipids are ectopic lipid stores. Aerobic exercise results in IMCL utilization in subjects over a broad range of exercise capacity. IMCL and IHCL have been related to impaired insulin action at the skeletal muscle and hepatic level, respectively. The acute effect of aerobic exercise on IHCL is unknown. Possible regulatory factors include exercise capacity, insulin sensitivity and fat availability subcutaneous and visceral fat mass). AIM To concomitantly investigate the effect of aerobic exercise on IHCL and IMCL in healthy subjects, using Magnetic Resonance spectroscopy. METHODS Normal weight, healthy subjects were included. Visit 1 consisted of a determination of VO2max on a treadmill. Visit 2 comprised the assessment of hepatic and peripheral insulin sensitivity by a two-step hyperinsulinaemic euglycaemic clamp. At Visit 3, subcutaneous and visceral fat mass were assessed by whole body MRI, IHCL and IMCL before and after a 2-hours aerobic exercise (50% of VO(2max)) using ¹H-MR-spectroscopy. RESULTS Eighteen volunteers (12M, 6F) were enrolled in the study (age, 37.6±3.2 years, mean±SEM; VO(2max), 53.4±2.9 mL/kg/min). Two hours aerobic exercise resulted in a significant decrease in IMCL (-22.6±3.3, % from baseline) and increase in IHCL (+34.9±7.6, % from baseline). There was no significant correlation between the exercise-induced changes in IMCL and IHCL and exercise capacity, subcutaneous and visceral fat mass and hepatic or peripheral insulin sensitivity. CONCLUSIONS IMCL and IHCL are flexible ectopic lipid stores that are acutely influenced by physical exercise, albeit in different directions. TRIAL REGISTRATION ClinicalTrial.gov NCT00491582.