PTEN inhibition enhances angiogenesis in an in vitro model of ischemic injury by promoting Akt phosphorylation and subsequent hypoxia inducible factor-1α upregulation

Angiogenesis is an important pathophysiological response to cerebral ischemia. PTEN is a lipid phosphatase whose loss activates PI3K/Akt signaling, which is related to HIF-1α upregulation and enhanced angiogenesis in human cancer cells. However, the specific roles of PTEN in endothelial cell functions and angiogenesis after cerebral ischemia remain unknown. Therefore, we sought to examine the potential effects of PTEN inhibition on post-ischemic angiogenesis in human blood vessel cells and to determine the underlying mechanism. In this present study, human umbilical vein endothelial cells (HUVECs) were exposed to oxygen-glucose deprivation (OGD), cell proliferation, migration and apoptosis, in vitro tube formation and expression of PTEN/Akt pathway and angiogenic factors were examined in HUVECs after treatment with PTEN inhibitor bisperoxovanadium (bpV) at different doses. The results showed that bpV significantly increased the cell proliferation and reduced cell apoptosis indicating that the drug exerts a cytoprotective effect on HUVECs with OGD exposure. bpV also enhanced cell migration and tube formation in HUVECs following OGD, and upregulated HIF-1α and VEGF expressions, but attenuated endostatin expression. Additionally, western blotting analysis demonstrated that Akt phosphorylation in HUVECs was significantly increased after bpV treatment. These findings suggest that PTEN inhibition promotes post-ischemic angiogenesis in HUVECs after exposure to OGD and this enhancing effect might be achieved through activation of the Akt signal cascade.

Routine pre- and post-neoadjuvant chemotherapy fitness testing is not indicated for oesophagogastric cancer surgery

Introduction There is a known correlation between anaerobic threshold (AT) during cardiopulmonary exercise testing and development of cardiopulmonary complications in high-risk patients undergoing oesophagogastric cancer surgery. This study aimed to assess the value of routine retesting following neoadjuvant chemotherapy. Methods Patients undergoing neoadjuvant chemotherapy with subsequent oesophagogastric cancer surgery with pre- and post-neoadjuvant chemotherapy cardiopulmonary exercise data were identified from a prospectively maintained database. Measured cardiopulmonary exercise variables included AT and maximum oxygen uptake at peak exercise (VO2 peak). Anaerobic threshold values within 1 ml/kg/minute were considered static. Patients were grouped into AT ranges of less than 9 ml/kg/minute, 9-11 ml/kg/minute and greater than 11 ml/kg/minute. Outcome measures were unplanned intensive care stay, postoperative cardiovascular morbidity and mortality. Results Between May 2008 and August 2017, 42 patients from 675 total resections were identified, with a mean age of 65 years (range 49-84 years). Mean pre-neoadjuvant chemotherapy AT was 11.07 ml/kg/minute (standard deviation, SD, 3.24 ml/kg/minute, range 4.6-19.3 ml/kg/minute) while post-neoadjuvant chemotherapy AT was 11.19 ml/kg/minute (SD 3.05 ml/kg/minute, range 5.2-18.1 ml/kg/minute). Mean pre-neoadjuvant chemotherapy VO2 peak was 17.13 ml/kg/minute, while post-chemotherapy this mean fell to 16.59 ml/kg/minute. Some 44.4% of patients with a pre-chemotherapy AT less than 9 ml/kg/minute developed cardiorespiratory complications compared with 42.2% of those whose AT was greater than 9 ml/kg/minute (P = 0.914); 63.6% of patients in the post-neoadjuvant chemotherapy group with an AT less than 9 ml/kg/minute developed cardiorespiratory complications. There was no correlation between direction of change in AT and outcome. Conclusion In our patient population, neoadjuvant chemotherapy does not appear to result in a significant mean reduction in cardiorespiratory fitness. Routine pre- and post-neoadjuvant chemotherapy cardiopulmonary exercise testing is currently not indicated; however, larger studies are required to demonstrate this conclusively.

Effect of sodium bicarbonate on prolonged running performance: A randomized, double-blind, cross-over study

BACKGROUND

The ability to sustain intense exercise seems to be partially limited by the body's capability to counteract decreases in both intra- and extracellular pH. While the influence of an enhanced buffering capacity via sodium bicarbonate (BICA) on short-term, high-intensity exercise performance has been repeatedly investigated, studies on prolonged endurance performances are comparatively rare, especially for running. The aim of the following study was to assess the ergogenic effects of an oral BICA substitution upon exhaustive intensive endurance running performance.

METHOD

In a double-blind randomized cross-over study, 18 trained runners (VO2peak: 61.2 ± 6.4 ml•min-1•kg-1) performed two exhaustive graded exercise tests and two constant load tests (30 main at 95% individual anaerobic threshold (IAT) followed by 110% IAT until exhaustion) after ingestion of either sodium bicarbonate (BICA) (0.3 g/kg) or placebo (4 g NaCl) diluted in 700 ml of water. Time to exhaustion (TTE) in the constant load test was defined as the main outcome measure. Throughout each test respiratory gas exchange measurements were conducted as well as determinations of heart rate, blood gases and blood lactate concentration.

RESULTS

TTE in the constant load test did not differ significantly between BICA and placebo conditions (BICA: 39.6 ± 5.6 min, placebo: 39.3 ± 5.6 min; p = 0.78). While pH in the placebo test dropped to a slightly acidotic value two minutes after cessation of exercise (7.34 ± 0.05) the value in the BICA trial remained within the normal range (7.41 ± 0.06) (p < 0.001). In contrast, maximum running speed (Vmax) in the exhaustive graded exercise test was significantly higher with BICA (17.4 ± 1.0 km/h) compared to placebo (17.1 ± 1.0 km/h) (p = 0.009). The numerical difference in maximum oxygen consumption (VO2peak) failed to reach statistical significance (BICA: 61.2 ± 6.4 ml•min-1•kg-1, placebo: 59.8 ± 6.4 ml•min-1•kg-1; p = 0.31). Maximum blood lactate was significantly higher with BICA compared to the corresponding placebo test (BICA: 11.1 ± 2.3 mmol/l, placebo: 8.9 ± 3.0 mmol/l; p < 0.001). At the end of exercise, an acidotic pH value was found in both exhaustive graded exercise tests (p = 0.002). BICA caused gastrointestinal side effects in 15 patients.

CONCLUSION

Maximal performance was enhanced significantly after BICA administration. The ergogenic effect of BICA in the exhaustive graded exercise test can most likely be attributed to an increased anaerobic glycolysis that is reflected by an accumulation of lactate. However, TTE in prolonged high-intensity running was not improved. Even at the end of exercise no severe metabolic acidosis was found. Metabolic acidification as one of the dominant factors causing muscular fatigue should therefore be reconsidered.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS) DRKS00011284.

Effect of caffeine ingestion on anaerobic capacity quantified by different methods

We investigated whether caffeine ingestion before submaximal exercise bouts would affect supramaximal oxygen demand and maximal accumulated oxygen deficit (MAOD), and if caffeine-induced improvement on the anaerobic capacity (AC) could be detected by different methods. Nine men took part in several submaximal and supramaximal exercise bouts one hour after ingesting caffeine (5 mg·kg-1) or placebo. The AC was estimated by MAOD, alternative MAOD, critical power, and gross efficiency methods. Caffeine had no effect on exercise endurance during the supramaximal bout (caffeine: 131.3 ± 21.9 and placebo: 130.8 ± 20.8 s, P = 0.80). Caffeine ingestion before submaximal trials did not affect supramaximal oxygen demand and MAOD compared to placebo (7.88 ± 1.56 L and 65.80 ± 16.06 kJ vs. 7.89 ± 1.30 L and 62.85 ± 13.67 kJ, P = 0.99). Additionally, MAOD was similar between caffeine and placebo when supramaximal oxygen demand was estimated without caffeine effects during submaximal bouts (67.02 ± 16.36 and 62.85 ± 13.67 kJ, P = 0.41) or when estimated by alternative MAOD (56.61 ± 8.49 and 56.87 ± 9.76 kJ, P = 0.91). The AC estimated by gross efficiency was also similar between caffeine and placebo (21.80 ± 3.09 and 20.94 ± 2.67 kJ, P = 0.15), but was lower in caffeine when estimated by critical power method (16.2 ± 2.6 vs. 19.3 ± 3.5 kJ, P = 0.03). In conclusion, caffeine ingestion before submaximal bouts did not affect supramaximal oxygen demand and consequently MAOD. Otherwise, caffeine seems to have no clear positive effect on AC.

Influence of Acetaminophen Consumption on Perceived Exertion at the Lactate Concentration Threshold

The purpose of this investigation was to study effects of acetaminophen consumption on ratings of perceived exertion and estimated time limit responses at the lactate threshold. 98 young regional to national level athletes performed a graded exhausting exercise on an outdoor running track to estimate their maximal aerobic velocity and the velocity associated with their lactate concentration threshold. Urine (30 mL) was collected during this test and analysed for numerous substances. During urinary screening for doping substances, 9 acetaminophen consumers (9.2%) among the 98 included athletes were detected. These acetaminophen consumers have significantly lower perceived exertion at velocity corresponding to the lactate concentration threshold than nonconsumers (11.9 ± 2.1 vs 13.6 ± 2.1, respectively) although they were at the same relative exercise intensity. This result shows that acetaminophen consumption may have mediated the perceived exertion response at the lactate concentration threshold. This may then suggest that the pain induced by training load could be a factor in use of self-prescribed pain relievers. Such consumption must be taken into account by medical staff, trainers, or educators who have to give information on the use and adverse effects of this substance and to propose palliative methods to their athletes.

The effects of beta alanine plus creatine administration on performance during repeated bouts of supramaximal exercise in sedentary men

AIM

The aim of this study was to investigate the effects of beta alanine and/or creatine supplementation on performance during repeated bouts of supramaximal exercise in sedentary men.

METHODS

Forty-four untrained healthy men (aged 20-22 years, weight: 68-72 kg, height: 174-178 cm) participated in the present study. After performing the Wingate Test (WAnT) for three times in the baseline exercise session, the subjects were assigned to one of four treatment groups randomly: 1) placebo (P; 10 g maltodextrose); 2) creatine (Cr; 5 g creatine plus 5 g maltodextrose); 3) beta-alanine (β-ALA; 1,6 g beta alanine plus 8,4 g maltodextrose); and 4) beta-alanine plus creatine (β-ALA+Cr; 1,6 g beta alanine plus 5 g creatine plus 3,4 g maltodextrose). Participants were given the supplements orally twice a day for 22 consecutive days, then four times a day for the following 6 days. After 28 days, the second exercise session was applied during which peak power (PP) and mean power (MP) were measured and fatigue index (FI) was calculated.

RESULTS

PP and MP decreased and FI increased in all groups during exercise before and after the treatment. During the postsupplementation session PP2 and PP3 increased in creatine supplemented group (from 642.7±148.6 to 825.1±205.2 in PP2 and from 522.9±117.5 to 683.0±148.0 in PP3, respectively). However, MP increased in β-ALA+Cr during the postsupplementation compared to presupplementation in all exercise sessions (from 586.2±55.4 to 620.6±49.6 in MP1, from 418.1±37.2 to 478.3±30.3 in MP2 and from 362.0±41.3 to 399.1±3 in MP3, respectively). FI did not change with beta alanine and beta alanine plus creatine supplementation during the postsupplementation exercise session.

CONCLUSION

Beta-alanine and beta alanine plus creatine supplementations have strong performance enhancing effect by increasing mean power and delaying fatigue Index during the repeated WAnT.

From rest to stressed: endothelin-1 levels in young healthy smokers and non-smokers

INTRODUCTION

Endothelin-1 (ET-1) is a potent vasoconstrictor produced by vascular endothelial cells, and a known marker of endothelial dysfunction. However, the acute and chronic effects of smoking and nicotine gum on the ET-1 response to acute physical stress in young healthy smokers have not been investigated.

METHODS

Healthy smokers (n=35) and non-smokers (n=35) underwent an exercise test to exhaustion (maximal oxygen consumption) on a treadmill. Smokers were assessed a) after 12h smoking abstinence (termed chronic smoking), b) immediately after smoking one cigarette (termed acute smoking), and c) immediately after chewing nicotine gum. Blood was drawn immediately pre-exercise, and 3 minutes post-exercise. During exercise, cardiorespiratory parameters were obtained breath-by-breath using an automated metabolic cart. Plasma ET-1 levels were quantified using enzyme-linked immunosorbent-assay. The above protocol was designed to incorporate exercise as a vascular stressor to reveal changes that would not be detected at rest.

RESULTS

Mean age was 28.6±7.2 years and body mass index (BMI) was 23.6±3.2 kg/m(2). Post-exercise ET-1 levels were significantly lower than pre-exercise levels in non-smokers (P<0.001) and smokers under all three conditions (P=0.005, P<0.001, P=0.001, respectively). There were no differences in post-exercise ET-1 levels between non-smokers and smokers under all three conditions, however the absolute and relative decrease in ET-1 levels was significantly smaller in chronic smokers compared with non-smokers (P=0.007 and P=0.004). Chronic smokers had a significantly lower exercise-induced change in tidal volume (P=0.050), fraction of expired CO2 (P=0.021), oxygen consumption (P=0.005), carbon dioxide elimination (P=0.004) and peak expiratory flow (P=0.003) compared with non-smokers. Furthermore, the decrease in ET-1 observed in non-smokers in response to exercise was significantly associated with exercise induced-changes in inspiratory time, time for a tidal volume cycle, respiratory frequency, inspired minute ventilation and peak inspiratory flow.

CONCLUSIONS

An acute decrease of circulating ET-1 in response to acute maximal exercise in young healthy individuals was noted. Chronic smokers had a significantly diminished decrease in ET-1 compared with non-smokers, however there were no significant differences in the ET-1 response between smokers under the three smoking conditions. Smokers were not able to achieve the same exercise-induced changes in cardiorespiratory parameters as non-smokers. By incorporating exercise as a vascular stressor in our study, we have taken a novel approach to provide evidence of an altered ET-1 and cardiorespiratory response that would not otherwise be observed at rest in young active healthy smokers.

Creatine supplementation prevents acute strength loss induced by concurrent exercise

PURPOSE

To investigate the effect of creatine (CR) supplementation on the acute interference induced by aerobic exercise on subsequent maximum dynamic strength (1RM) and strength endurance (SE, total number of repetitions) performance.

METHODS

Thirty-two recreationally strength-trained men were submitted to a graded exercise test to determine maximal oxygen consumption (VO2max: 41.56 ± 5.24 ml kg(-1) min(-1)), anaerobic threshold velocity (ATv: 8.3 ± 1.18 km h(-1)), and baseline performance (control) on the 1RM and SE (4 × 80 % 1RM to failure) tests. After the control tests, participants were randomly assigned to either a CR (20 g day(-1) for 7 days followed by 5 g day(-1) throughout the study) or a placebo (PL-dextrose) group, and then completed 4 experimental sessions, consisting of a 5-km run on a treadmill either continuously (90 % ATv) or intermittently (1:1 min at vVO2max) followed by either a leg- or bench-press SE/1RM test.

RESULTS

CR was able to maintain the leg-press SE performance after the intermittent aerobic exercise when compared with C (p > 0.05). On the other hand, the PL group showed a significant decrease in leg-press SE (p ≤ 0.05). CR supplementation significantly increased bench-press SE after both aerobic exercise modes, while the bench-press SE was not affected by either mode of aerobic exercise in the PL group. Although small increases in 1RM were observed after either continuous (bench press and leg press) or intermittent (bench press) aerobic exercise in the CR group, they were within the range of variability of the measurement. The PL group only maintained their 1RM.

CONCLUSIONS

In conclusion, the acute interference effect on strength performance observed in concurrent exercise may be counteracted by CR supplementation.

Caffeine alters anaerobic distribution and pacing during a 4000-m cycling time trial

The purpose of the present study was to investigate the effects of caffeine ingestion on pacing strategy and energy expenditure during a 4000-m cycling time-trial (TT). Eight recreationally-trained male cyclists volunteered and performed a maximal incremental test and a familiarization test on their first and second visits, respectively. On the third and fourth visits, the participants performed a 4000-m cycling TT after ingesting capsules containing either caffeine (5 mg.kg⁻¹ of body weight, CAF) or cellulose (PLA). The tests were applied in a double-blind, randomized, repeated-measures, cross-over design. When compared to PLA, CAF ingestion increased mean power output [219.1±18.6 vs. 232.8±21.4 W; effect size (ES)  = 0.60 (95% CI = 0.05 to 1.16), p = 0.034] and reduced the total time [419±13 vs. 409±12 s; ES = −0.71 (95% CI = −0.09 to −1.13), p = 0.026]. Furthermore, anaerobic contribution during the 2200-, 2400-, and 2600-m intervals was significantly greater in CAF than in PLA (p<0.05). However, the mean anaerobic [64.9±20.1 vs. 57.3±17.5 W] and aerobic [167.9±4.3 vs. 161.8±11.2 W] contributions were similar between conditions (p>0.05). Similarly, there were no significant differences between CAF and PLA for anaerobic work (26363±7361 vs. 23888±6795 J), aerobic work (68709±2118 vs. 67739±3912 J), or total work (95245±8593 vs. 91789±7709 J), respectively. There was no difference for integrated electromyography, blood lactate concentration, heart rate, and ratings of perceived exertion between the conditions. These results suggest that caffeine increases the anaerobic contribution in the middle of the time trial, resulting in enhanced overall performance.

Effect of antioxidant supplementation on insulin sensitivity in response to endurance exercise training

While production of reactive oxygen and nitrogen species (RONS) is associated with some of the beneficial adaptations to regular physical exercise, it is not established whether RONS play a role in the improved insulin-stimulated glucose uptake in skeletal muscle obtained by endurance training. To assess the effect of antioxidant supplementation during endurance training on insulin-stimulated glucose uptake, 21 young healthy (age 29 ± 1 y, BMI 25 ± 3 kg/m(2)) men were randomly assigned to either an antioxidant [AO; 500 mg vitamin C and 400 IU vitamin E (α-tocopherol) daily] or a placebo (PL) group that both underwent a supervised intense endurance-training program 5 times/wk for 12 wk. A 3-h euglycemic-hyperinsulinemic clamp, a maximal oxygen consumption (Vo(2max)) and maximal power output (P(max)) test, and body composition measurements (fat mass, fat-free mass) were performed before and after the training. Muscle biopsies were obtained for determination of the concentration and activity of proteins regulating glucose metabolism. Although plasma levels of vitamin C (P < 0.05) and α-tocopherol (P < 0.05) increased markedly in the AO group, insulin-stimulated glucose uptake increased similarly in both the AO (17.2%, P < 0.05) and the PL (18.9%, P < 0.05) group in response to training. Vo(2max) and P(max) also increased similarly in both groups (time effect, P < 0.0001 for both) as well as protein content of GLUT4, hexokinase II, and total Akt (time effect, P ≤ 0.05 for all). Our results indicate that administration of antioxidants during strenuous endurance training has no effect on the training-induced increase in insulin sensitivity in healthy individuals.

Hawthorn Extract Randomized Blinded Chronic Heart Failure (HERB CHF) trial

AIMS

Hawthorn's efficacy when added to contemporary evidence-based heart failure therapy is unknown. We aimed to determine whether hawthorn increases submaximal exercise capacity when added to standard medical therapy.

METHODS AND RESULTS

We performed a randomized, double-blind, placebo-controlled trial in 120 ambulatory patients aged > or = 18 years with New York Heart Association (NYHA) class II-III chronic heart failure. All patients received conventional medical therapy, as tolerated, and were randomized to either hawthorn 450 mg twice daily or placebo for 6 months. The primary outcome was change in 6 min walk distance at 6 months. Secondary outcomes included quality of life (QOL) measures, peak oxygen consumption, and anaerobic threshold during maximal treadmill exercise testing, NYHA classification, left ventricular ejection fraction (LVEF), neurohormones, and measures of oxidative stress and inflammation. There were no significant differences between groups in the change in 6 min walk distance (P = 0.61), or on measures of QOL, functional capacity, neurohormones, oxidative stress, or inflammation. A modest difference in LVEF favoured hawthorn (P = 0.04). There were significantly more adverse events reported in the hawthorn group (P = 0.02), although most were non-cardiac.

CONCLUSION

Hawthorn provides no symptomatic or functional benefit when given with standard medical therapy to patients with heart failure. This trial is registered in ClinicalTrials.gov ID: NCT00343902.

Role of alpha-tocopherol in cardiopulmonary fitness in endurance athletes, cyclists

Exercise increases oxygen consumption and causes a disturbance of intracellular pro-oxidant-antioxidant homeostasis. Athletes are exposed to acute and chronic stress that may lead to increased generation of oxidative species. Hence oxidative stress increases in athletes. Administration of antioxidant like alpha-tocopherol as supplementation may reduce the cell damage caused due to oxidative stress. In the present study, our aim was to study the effects of alpha-tocopherol supplementation on the cardiopulmonary fitness in endurance athletes (cyclists) and non-athletes. Our study included 40 cyclists who were trained under District Youth Service & Sports Office. 40 controls were randomly selected from student group of B.L.D.E.A's Medical College. Alpha-tocopherol (Vitamin E) 200 mg/day for 21 days wasgiven to study group and placebo was given to placebo group. Various physiological parameters like heart rate, blood pressure, respiratory rate were recorded, for assessing cardiopulmonary fitness: Physical Fitness Index (PFI) and VO2 max ml/min/kg were recorded before and after supplementation of vitamin E in athletes, and were compared with placebo group before and after supplementation of placebo and also with non-athletes. The results obtained from present study indicate that antioxidant like alpha-tocopherol supplementation did not contribute significantly to improve the cardiopulmonary fitness of endurance athletes.

Effects of acute L-carnitine intake on metabolic and blood lactate levels of elite badminton players

OBJECTIVES

Purpose of this study is to research the effects of acute L-Carnitine intake on badminton players' metabolic and blood lactate values.

DESIGN

A total of 16 Turkish national badminton players (8 male, 8 female) were voluntarily participated into study. MaxVO2, MET, energy consumption, HR (heart rate), VE (minute ventilation), R (respiratory exchange ratio), AT (anaerobic threshold), oxygen pulse and blood lactate (LA) of subjects were measured by Sensormedics VmaxST and Accutrend Lactate Analyzer. The participants were subjected to the test protocol twice before and after 2g of L-Carnitine intake. The data were evaluated by the use of SPSS 13.0 for Windows.

RESULTS

No significant differences were found between 1st. (without L-Carnitine intake) and 2nd. (with L-Carnitine intake) measurements of female participants as regards to all measured parameters. There was a significant difference in EMHR (exercise maximum heart rate) of males between two measurements (p<0.05). However the differences in other parameters were not significant. AT values of female subjects were not significant difference (p>0.05). Respiratory exchange ratio of males was significantly different at anaerobic threshold (p<0.05).

CONCLUSION

Results of this study show that L-carnitine intake one hour prior to the exercise has no effect on the metabolic and blood lactate values of badminton players.

The Long-Acting Phosphodiesterase Inhibitor Tadalafil does not Influence Athletes' V·O2max, Aerobic, and Anaerobic Thresholds in Normoxia

Whereas experimental studies showed that in healthy trained subjects, the phosphodiesterase-5 inhibitor (PDE-5i) sildenafil improves exercise capacity in hypoxia and not in normoxia, no studies on the effects of the long half-life PDE-5i tadalafil exist. In order to evaluate whether tadalafil influences functional parameters and performance during a maximal exercise test in normoxia, we studied 14 healthy male athletes in a double-blind cross-over protocol. Each athlete performed two tests on a cycle ergometer, both after placebo or tadalafil (at therapeutic dose: 20 mg) administration. Oxygen consumption (VO2), blood lactate, respiratory exchange ratio, rate of perceived exertion, arterial blood pressure (BP), heart frequency (HR) and oxygen pulse (VO2/HR) were evaluated before exercise, at individual ventilatory and anaerobic thresholds (IVT and IAT), at VO2max and during recovery. Compared to placebo, a single tadalafil administration significantly reduced systolic BP before and after exercise (p < 0.05), decreased VO2/HR at IVT (13.3 +/- 1.8 vs. 14.5 +/- 2.1 mL . beat (-1); p = 0.03), but did not modify individual VO2max, IVT, or IAT. In healthy athletes, 20 mg of tadalafil does not substantially influence physical fitness-related parameters, exercise tolerance, and cardiopulmonary responses to maximal exercise in normoxia; it remains to be verified if higher doses/prolonged use influence health and/or sport performance in field conditions.

Effects of short-term prednisolone intake during submaximal exercise

PURPOSE

To examine the prednisolone's ergogenic and metabolic effects during submaximal exercise.

METHODS

Ten recreational male athletes completed two cycling trials at 70-75% peak O2 consumption until exhaustion after either placebo (Pla, lactose) or oral prednisolone (Pred, 60 mg.d(-1) for 1 wk) treatment, according to a double-blind and randomized protocol. Blood samples were collected at rest and during exercise and recovery to determine ACTH, growth hormone (GH), prolactin (PRL), DHEA, insulin, blood glucose, and blood lactate values.

RESULTS

Time of cycling was significantly increased after chronic Pred treatment (Pred: 74.5+/-9.5 min; Pla: 46.1+/-3.3 min, P<0.01). Pred intake significantly lowered basal, exercise, and recovery ACTH, DHEA, and PRL concentrations, whereas GH concentrations were significantly lowered by Pred after 30 min of exercise. Blood glucose and insulin were significantly (P<0.05) increased by Pred during the whole experiment and until 30 min of exercise. Blood lactate concentrations were higher after Pred versus Pla at 10 min of exercise until 10 min of recovery (P<0.05).

CONCLUSION

From these data, short-term Pred intake did seem to significantly improve performance during submaximal exercise, with concomitant alterations in hormonal and metabolic responses. Further studies will be necessary to elucidate the mechanisms of these hormonal and metabolic changes, and to determine whether the changes may be associated with the marked performance improvement obtained.

Effects of growth hormone on exercise capacity and cardiopulmonary performance in patients with chronic heart failure

BACKGROUND

Because GH exerted beneficial effects in various experimental models of heart failure, we investigated the effects of GH on physical exercise capacity and cardiopulmonary performance in patients with dilated cardiomyopathy and chronic heart failure (CHF).

METHODS

Twenty-two patients with CHF (New York Heart Association functional class II-III) underwent spirometry and a symptom-limited, cardiopulmonary exercise testing before and after 3 months of GH (n = 11; seven males; seven idiopathic; 57 +/- 11 yr; 4 IU sc every other day) or placebo (n = 11; eight males; six idiopathic; 54 +/- 10 yr) administration, in a randomized, double-blind trial. Background CHF therapy remained unchanged.

RESULTS

GH, but not placebo, increased IGF-I serum concentration (from 144 +/- 35 to 293 +/- 58 ng/ml; P < 0.005) and improved New York Heart Association functional class (from 2.4 +/- 0.5 to 1.8 +/- 0.4; P < 0.005), exercise duration (from 831 +/- 273 to 925 +/- 266 sec; P < 0.005), peak power output (from 245 +/- 127 to 280 +/- 132 W; P < 0.05), peak minute ventilation (from 52.5 +/- 16.1 to 61.3 +/- 17.3 liters/min; P < 0.05), peak oxygen consumption (from 19.8 +/- 5.6 to 25.1 +/- 5.6 ml/kg.min; P < 0.005), and anaerobic threshold (from 14.9 +/- 4.8 to 20.0 +/- 4.5 ml/kg.min; P < 0.005) without affecting lung function parameters. Furthermore, the slope of the relationship between minute ventilation and pulmonary carbon dioxide production (ventilatory efficiency) decreased from 34.7 +/- 5.1 to 31.7 +/- 5.3 (P < 0.005), whereas the slope of the relation between percent predicted heart rate reserve used and percent observed metabolic reserve used (chronotropic index) rose from 0.57 +/- 0.20 to 0.69 +/- 0.18 (P < 0.005).

CONCLUSION

Given the predictive value of physical exercise capacity and cardiopulmonary performance in CHF progression, these data provide additional insights into the mechanisms by which GH may potentially benefit CHF patients.

Prolonged administration of recombinant human erythropoietin increases submaximal performance more than maximal aerobic capacity

The effects of recombinant human erythropoietin (rHuEpo) treatment on aerobic power (VO2max) are well documented, but little is known about the effects of rHuEpo on submaximal exercise performance. The present study investigated the effect on performance (ergometer cycling, 20-30 min at 80% of maximal attainable workload), and for this purpose eight subjects received either 5,000 IU rHuEpo or placebo every second day for 14 days, and subsequently a single dose of 5,000 IU/placebo weekly/10 weeks. Exercise performance was evaluated before treatment and after 4 and 11 weeks of treatment. With rHuEpo treatment VO2max increased (P<0.05) by 12.6 and 11.6% in week 4 and 11, respectively, and time-to-exhaustion (80% VO2max) was increased by 54.0 and 54.3% (P<0.05) after 4 and 11 weeks of treatment, respectively. However, when normalizing the workload to the same relative intensity (only done at time point week 11), TTE was decreased by 26.8% as compared to pre rHuEpo administration. In conclusion, in healthy non-athlete subjects rHuEpo administration prolongs submaximal exercise performance by about 54% independently of the approximately 12% increase in VO2max.

Effect of nutritionally enriched coffee consumption on aerobic and anaerobic exercise performance

The purpose of this study was to compare nutritionally enriched JavaFit coffee (JF) to commercially available decaffeinated coffee (P) with regard to impact on endurance and anaerobic power performance in a physically active, college-aged population. Ten subjects (8 men, 2 women) performed two 30-second Wingate anaerobic power tests and 2 cycle ergometer tests (75% VO2 max) to exhaustion. Mean VO2 was measured during each endurance exercise protocol. Excess postexercise oxygen consumption (EPOC) and respiratory exchange ratio (RER) were recorded for 30 minutes following all exercise sessions. Area under the curve analysis was used to compare EPOC between JF and P for all exercise sessions. No differences were seen between JF and P in any of the power performance measures. However, time to exhaustion was significantly (p = 0.05) higher in JF (35.3 +/- 15.2 minutes) compared with P (27.3 +/- 10.7 minutes). No difference between JF and P were seen in EPOC in either the aerobic or anaerobic exercise sessions. A significant (p < 0.05) difference in average 30-minute postanaerobic power exercise RER was seen between JF (0.87 +/- 0.04) and P (0.83 +/- 0.03), but not following endurance exercise. A nutritionally-enriched coffee beverage appears to enhance time to exhaustion during aerobic exercise, but does not provide an ergogenic benefit during anaerobic exercise.

Glucose supplements increase human muscle in vitro Na+-K+-ATPase activity during prolonged exercise

Regulation of maximal Na+-K+-ATPase activity in vastus lateralis muscle was investigated in response to prolonged exercise with (G) and without (NG) oral glucose supplements. Fifteen untrained volunteers (14 males and 1 female) with a peak aerobic power (V̇o2peak) of 44.8 ± 1.9 ml·kg−1·min−1; mean ± SE cycled at ∼57% V̇o2peak to fatigue during both NG (artificial sweeteners) and G (6.13 ± 0.09% glucose) in randomized order. Consumption of beverage began at 30 min and continued every 15 min until fatigue. Time to fatigue was increased ( P < 0.05) in G compared with NG (137 ± 7 vs. 115 ± 6 min). Maximal Na+-K+-ATPase activity (Vmax) as measured by the 3- O-methylfluorescein phosphatase assay (nmol·mg−1·h−1) was not different between conditions prior to exercise (85.2 ± 3.3 or 86.0 ± 3.9), at 30 min (91.4 ± 4.7 vs. 91.9 ± 4.1) and at fatigue (92.8 ± 4.3 vs. 100 ± 5.0) but was higher ( P < 0.05) in G at 90 min (86.7 ± 4.2 vs. 109 ± 4.1). Na+-K+-ATPase content (βmax) measured by the vanadate facilitated [3H]ouabain-binding technique (pmol/g wet wt) although elevated ( P < 0.05) by exercise (0<30, 90, and fatigue) was not different between NG and G. At 60 and 90 min of exercise, blood glucose was higher ( P < 0.05) in G compared with NG. The G condition also resulted in higher ( P < 0.05) serum insulin at similar time points to glucose and lower ( P < 0.05) plasma epinephrine and norepinephrine at 90 min of exercise and at fatigue. These results suggest that G results in an increase in Vmax by mechanisms that are unclear.

Effect of atorvastatin on energy expenditure and skeletal muscle oxidative metabolism at rest and during exercise

Statins are associated with adverse effects in skeletal muscle. This study tested the hypothesis that atorvastatin would increase the respiratory exchange ratio (RER) at rest and during exercise. Twenty-eight healthy subjects (mean age 52 years) were enrolled in a double-blind, placebo-controlled, randomized study of the effects of atorvastatin (40 mg/day) on whole body energetics over 8 weeks. Ventilatory gas exchange measurements, at rest and during bicycle ergometry, were used to assess muscle oxidative metabolism. Thirteen subjects from each treatment arm completed the study. Eight weeks of atorvastatin lowered plasma low-density lipoprotein cholesterol concentration but had no effect on resting or submaximal energy expenditure, RER, or calculated fatty acid oxidation rates. Atorvastatin did not affect maximal exercise oxygen consumption or the anaerobic threshold. Eight weeks of atorvastatin therapy was not associated with alterations in substrate oxidation, or muscle oxidative function at rest, or during exercise in healthy adults.

Effect of tadalafil on anaerobic performance indices in healthy athletes

OBJECTIVE

Given the therapeutic and non-therapeutic use of the tadalafil, (phosphodiesterase-5 inhibitor, PDE-5i), we examined its effects on anaerobic performance indices.

METHODS

In total, 12 well-trained subjects reported to the laboratory on two occasions 1 week apart to perform a 30 s Wingate anaerobic power test (WAnT) on a bicycle ergometer. The day before the WAnT, the subjects were double-blinded to receive an oral dose of tadalafil (20 mg) or placebo. Blood lactate value at rest and 1, 3, 6 and 10 minutes of recovery phase, mean power, peak power, time to peak power and fatigue index were assessed for each WAnT.

RESULTS

Blood lactate values at the 3-min recovery WAnT increased significantly in the tadalafil condition (mean (SD) 13.9 (1.7) v 12.8 (1.3) mmol/l; p<0.05) and time to peak power decreased significantly (6.3 (1.3) v 5.7 (1.5) s; p = 0.05). No differences were observed in any other parameters between the two conditions.

CONCLUSION

The primary finding of this investigation was that the administration of a single dose of a long-term PDE-5i does not substantially influence anaerobic performance indices. However, results demonstrated both an increase in lactate values at the 3-min point of the recovery phase and a decrease in time to peak power.

Effects of eight weeks of caffeine supplementation and endurance training on aerobic fitness and body composition

The purpose of this study was to examine the effects of daily administration of a supplement that contained caffeine in conjunction with 8 weeks of aerobic training on VO(2)peak, time to running exhaustion at 90% VO(2)peak, body weight, and body composition. Thirty-six college students (14 men and 22 women; mean +/- SD, age 22.4 +/- 2.9 years) volunteered for this investigation and were randomized into either a placebo (n = 18) or supplement group (n = 18). The subjects ingested 1 dose (3 pills = 201 mg of caffeine) of the placebo or supplement per day during the study period. In addition, the subjects performed treadmill running for 45 minutes at 75% of the heart rate at VO(2)peak, three times per week for 8 weeks. All subjects were tested pretraining and posttraining for VO(2)peak, time to running exhaustion (TRE) at 90% VO(2)peak, body weight (BW), percentage body fat (%FAT), fat weight (FW), and fat-free weight (FFW). The results indicated that there were equivalent training-induced increases (p < 0.05) in VO(2)peak and TRE for the supplement and placebo groups, but no changes (p > 0.05) in BW, %FAT, FW, or FFW for either group. These findings indicated that chronic use of the caffeine-containing supplement in the present study, in conjunction with aerobic training, provided no ergogenic effects as measured by VO(2)peak and TRE, and the supplement was of no benefit for altering body weight or body composition.

The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities

The purpose of this study was to examine the acute effects of a caffeine-containing supplement on upper- and lower-body strength and muscular endurance as well as anaerobic capabilities. Thirty-seven resistance-trained men (mean +/- SD, age: 21 +/- 2 years) volunteered to participate in this study. On the first laboratory visit, the subjects performed 2 Wingate Anaerobic Tests (WAnTs) to determine peak power (PP) and mean power (MP), as well as tests for 1 repetition maximum (1RM), dynamic constant external resistance strength, and muscular endurance (TOTV; total volume of weight lifted during an endurance test with 80% of the 1RM) on the bilateral leg extension (LE) and free-weight bench press (BP) exercises. Following a minimum of 48 hours of rest, the subjects returned to the laboratory for the second testing session and were randomly assigned to 1 of 2 groups: a supplement group (SUPP; n = 17), which ingested a caffeine-containing supplement, or a placebo group (PLAC; n = 20), which ingested a cellulose placebo. One hour after ingesting either the caffeine-containing supplement or the placebo, the subjects performed 2 WAnTs and were tested for 1RM strength and muscular endurance on the LE and BP exercises. The results indicated that there was a significant (p < 0.05) increase in BP 1RM for the SUPP group, but not for the PLAC group. The caffeine-containing supplement had no effect, however, on LE 1RM, LE TOTV, BP TOTV, PP, and MP. Thus, the caffeine-containing supplement may be an effective supplement for increasing upper-body strength and, therefore, could be useful for competitive and recreational athletes who perform resistance training.

Effect of chronic supplementation with branched-chain amino acids on the performance and hepatic and muscle glycogen content in trained rats

The objective of this study was to evaluate the effects of a diet supplemented with branched-chain amino acids (BCAA; 3.57% and 4.76%) on the performance and glycogen metabolism of trained rats. Thirty-six adult male Wistar rats received the control diet (AIN-93M) (n=12) and two diets supplemented with BCAA (S1: AIN-93M+3.57% BCAA, n=12, and S2: AIN-93M+4.76% BCAA, n=12) for 6 weeks. The training protocol consisted of bouts of swimming exercise (60 min day(-1)) for 6 weeks at intensities close to the lactate threshold. On the last day of the experiment, all groups were trained for 1 h (1H) or were submitted to the exhaustion test (EX). The time to exhaustion did not differ between groups. The groups submitted to the exhaustion test presented a reduction in plasma glucose and an increase in plasma ammonia and blood lactate concentrations compared to the 1H condition. In the 1H condition, hepatic glycogen concentration was significantly higher in group S2 compared to the control diet and S1 groups (132% and 44%, respectively). Group S2 in the 1H condition presented a higher muscle glycogen concentration (45%) compared to the control diet group. In the EX condition, a significantly higher hepatic glycogen concentration was observed for group S2 compared to the control diet and S1 groups (262% and 222%, respectively). Chronic supplementation with BCAA promoted a higher hepatic and muscle glycogen concentration in trained animals, with this effect being dose dependent.

L-citrulline reduces time to exhaustion and insulin response to a graded exercise test

PURPOSE

Oral L-arginine supplementation has been shown to improve treadmill time to exhaustion and resting insulin sensitivity in individuals with peripheral vascular disease and type 2 diabetes, respectively. Furthermore, L-citrulline supplementation increases plasma L-arginine concentration to a level higher than that achieved by oral L-arginine supplementation. The purpose of this investigation was therefore to determine whether time to exhaustion during a graded treadmill test, as well as plasma insulin and glucose profiles, could be improved with oral L-citrulline supplementation in healthy individuals.

METHODS

Seventeen young (18-34 yr), healthy male and female volunteers performed incremental treadmill tests to exhaustion following either placebo or citrulline ingestion (3 g 3 h before test, or 9 g over 24 h prior to testing).

RESULTS

Steady-state submaximal respiratory exchange ratio and VO2max were not significantly different between placebo and citrulline trials. Treadmill time to exhaustion was lower following citrulline ingestion than during placebo trials (888.2 +/- 17.7 vs 895.4 +/- 17.9 s; P < 0.05; N = 17), which was accompanied by a higher rating of perceived exertion during exercise in the L-citrulline compared with the placebo condition. There was also an increase in plasma insulin in response to this high-intensity exercise in the placebo, but not in the L-citrulline, condition (P < 0.05).

CONCLUSIONS

It can be concluded that, contrary to the hypothesized improvement in treadmill time following L-citrulline ingestion, there is a reduction in treadmill time following L-citrulline ingestion over the 24 h prior to testing. The normal response of increased plasma insulin following high-intensity exercise is also not present in the L-citrulline condition, indicating that L-citrulline ingestion may reduce nitric oxide-mediated pancreatic insulin secretion or increased insulin clearance.

Short term salbutamol ingestion and supramaximal exercise in healthy women

OBJECTIVE

To test the hypothesis that chronic salbutamol intake improves performance during supramaximal exercise and to estimate the effects of this treatment on body composition, bone mass, and metabolic indices in healthy women.

METHODS

Fourteen female volunteers (seven sedentary and seven recreationally trained) performed a 30 second Wingate test with and without salbutamol ingestion (12 mg/day for four weeks) in a random, double blind, crossover design. Blood samples were collected at rest, at the end of the test, and during passive recovery for lactate measurement. Body composition and bone mass were determined by dual energy x ray absorptiometry.

RESULTS

Peak power appeared significantly earlier and was significantly (p<0.05) increased after salbutamol intake in all subjects. There was no difference in total work performed and fatigue indices with salbutamol compared with placebo. No significant alterations in lean or fat body mass and bone variables were observed with salbutamol treatment in either trained or untrained subjects during the trial. In contrast, blood lactate was significantly (p<0.05) increased during the recovery period after salbutamol ingestion compared with placebo.

CONCLUSION

As in men, chronic administration of therapeutic concentrations of salbutamol did not induce an anabolic effect in women but increased maximal anaerobic power. Further studies are necessary to clarify the mechanisms involved.

Effects of chronic NaHCO3 ingestion during interval training on changes to muscle buffer capacity, metabolism, and short-term endurance performance

This study determined the effects of altering the H(+) concentration during interval training, by ingesting NaHCO(3) (Alk-T) or a placebo (Pla-T), on changes in muscle buffer capacity (beta m), endurance performance, and muscle metabolites. Pre- and posttraining peak O(2) uptake (V(O2 peak)), lactate threshold (LT), and time to fatigue at 100% pretraining V(O2 peak) intensity were assessed in 16 recreationally active women. Subjects were matched on the LT, were randomly placed into the Alk-T (n = 8) or Pla-T (n = 8) groups, and performed 8 wk (3 days/wk) of six to twelve 2-min cycle intervals at 140-170% of their LT, ingesting NaHCO(3) or a placebo before each training session (work matched between groups). Both groups had improvements in beta m (19 vs. 9%; P < 0.05) and V(O2 peak) (22 vs. 17%; P < 0.05) after the training period, with no differences between groups. There was a significant correlation between pretraining beta m and percent change in beta m (r = -0.70, P < 0.05). There were greater improvements in both the LT (26 vs. 15%; P = 0.05) and time to fatigue (164 vs. 123%; P = 0.05) after Alk-T, compared with Pla-T. There were no changes to pre- or postexercise ATP, phosphocreatine, creatine, and intracellular lactate concentrations, or pH(i) after training. Our findings suggest that training intensity, rather than the accumulation of H(+) during training, may be more important to improvements in beta m. The group ingesting NaHCO(3) before each training session had larger improvements in the LT and endurance performance, possibly because of a reduced metabolic acidosis during training and a greater improvement in muscle oxidative capacity.

Evaluation of enalapril+losartan treatment with cardiopulmonary exercise test in patients with left ventricular dysfunction

The aim of this study was to evaluate the effects of the combination of enalapril and losartan in patients with left ventricular systolic dysfunction by means of cardiopulmonary exercise test (CPET). Patients with left-ventricular systolic dysfunction and ejection fractions of 40% or less were included to the study. All patients were under the treatment of enalapril 20 mg once daily. The study group consisted of 20 patients (18 men, 2 women; mean age +/- standard deviation: 62.4 +/-6.5 years) and the comparison group consisted of 10 (8 men, 2 women; mean age 59.3 +/-11.9 years). The dose of 50 mg of losartan once daily was given additionally to the study patients. Breath-by-breath CPET was performed before administration of losartan and then 6-8 weeks later in the study group and 2 times with an interval of 6-8 weeks in the control group without any change in the treatment protocol. In the study group the average exercise times were 361 +/-192 and 454 +/-205 seconds (p = 0.001) before and after the study. Peak oxygen consumption ( VO2) values were 1,209 +/-366 and 1,284 +/-398 mL/minute before and after the study (p = 0.01). Anaerobic threshold VO2 values were 785 +/-187 and 855 +/-217 mL/minute before and after the study, respectively (p = 0.01). Peak heart rates (HR) were 141 +/-28 and 143 +/-22/minute (p = 0.35); peak VO2/HR values were 9.02 +/-3.1 and 9.3 +/-3 mL/minute (p = 0.4) before and after the study, respectively. On the other hand, in the control group, average exercise times were 556 +/-250 and 528 +/-251 seconds (p = 0.8); peak VO2 values were 1,502 +/-537 and 1,450 +/-501 mL/minute (p = 0.2); and anaerobic threshold VO2 values were 1,005 +/-338 and 975 +/-319 mL/min (p = 0.7), before and after the study respectively. At the highest comparable exercise stage for both tests in the study group the expired volume/oxygen consumption ( VE/ VO2) ratio declined from 35.1 +/-6.2 to 32.4 +/-5.6 (p = 0.007). VE values declined from 37.5 +/-10.9 to 33.9 +/-10.1 L (p = 0.02); heart rate declined from 140 +/-27 to 132 +/-21/minute (p = 0.02). No significant change was observed in the mentioned values for the control group. Addition of losartan to the standard therapy in patients with left ventricular systolic dysfunction improved exercise capacity and caused lower heart rate and ventilation requirements for the same exercise level.

The effects of creatine supplementation on performance during the repeated bouts of supramaximal exercise

AIM

The aim of this study was to investigate the effects of creatine supplementation on performance during the repeated bouts of supramaximal exercise.

METHODS

Twenty-three untrained young males participated in the study. A double blind design was used to create the creatine and placebo groups. Wingate test was performed 5 times with 90 g x kg(-1) body weight load with 2-min intervals. Peak power, mean power (MP), fatigue index (FI) were calculated. Capillary blood samples for lactate analysis were taken during the initial rest period and soon after the fifth Wingate test. For 6 days the creatine group (n=12) ingested 5 g creatine monohydrate, the placebo group (n=11) a flavored drink without creatine monohydrate 4 times daily. On the 7th day, the Wingate tests were repeated, as was the 1st day.

RESULTS

In the creatine group, MP in the 3rd and 4th Wingate test, in the placebo group FI in the 1st and 2nd Wingate test significantly increased. While the total power output obtained from the five Wingate tests increased 7.6% from 366.3+/-65 W to 394+/-67.1 W, there was no change in the placebo group.

CONCLUSIONS

It is concluded that creatine supplementation enhances total power output during the repeated bouts of supramaximal exercise separated by short resting intervals.

Effects of Acute Salbutamol Intake During a Wingate Test

To investigate the impact of acute salbutamol intake on performance and selected hormonal and metabolic variables during supramaximal exercise, 13 recreational male athletes performed two 30-second Wingate tests after either placebo (PLA, lactose) or salbutamol (SAL, 4 mg) oral administration, according to a double-blind and randomized protocol. Blood samples collected at rest, end of the Wingate test, recovery (5, 10, 15 min) were tested for growth hormone (GH), insulin (INS), blood glucose (GLU), and lactate determination. We found the peak and mean power performed significantly increased after SAL vs. PLA (PPSAL: 896 +/- 46; PPPLA: 819 +/- 57 W; MPSAL: 585 +/- 27; MPPLA: 534 +/- 35 W, p < 0.05), whereas no change was observed in the fatigue index. Blood glucose and INS were significantly increased by SAL at rest, at the end of the Wingate test, and during the 5 first minutes of recovery (p < 0.05). Plasma GH was significantly decreased by SAL (p < 0.05) during the recovery whereas end-exercise and recovery blood lactate tended but were not significantly increased after SAL vs. PLA. From these data, acute salbutamol intake at therapeutical dosage did appear to improve peak power and mean power during a supramaximal exercise, but the mechanisms involved need further investigation.

Effect of low-dose, short-duration creatine supplementation on anaerobic exercise performance

To examine the efficacy of a low-dose, short-duration creatine monohydrate supplement, 40 physically active men were randomly assigned to either a placebo or creatine supplementation group (6 g of creatine monohydrate per day). Testing occurred before and at the end of 6 days of supplementation. During each testing session, subjects performed three 15-second Wingate anaerobic power tests. No significant (p > 0.05) group or time differences were observed in body mass, peak power, mean power, or total work. In addition, no significant (p > 0.05) differences were observed in peak power, mean power, or total work. However, the change in the rate of fatigue of total work was significantly (p < 0.05) lower in the creatine supplementation group than in the placebo group, indicating a reduced fatigue rate in subjects supplementing with creatine compared with the placebo. Although the results of this study demonstrated reduced fatigue rates in patients during high-intensity sprint intervals, further research is necessary in examining the efficacy of low-dose, short-term creatine supplementation.

L-carnitine and exercise tolerance in medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency: a pilot study

Skeletal muscle function may be impaired in patients with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, but the value of L-carnitine in their long-term management is not clear. This study was designed as a pilot to examine the effects of L-carnitine on exercise tolerance in patients with MCAD deficiency. Four clinically asymoptomatic MCAD-deficient patients, aged 8 to 20 years, were studied. Incremental ramp exercise tests were carried out before and after 4 weeks' treatment with oral L-carnitine (100 mg/kg per day). During exercise without L-carnitine supplementation, plasma carnitine concentrations fell, associated with an increased excretion of urinary acylcarnitines, notably acetylcarnitine, hexanoylcarnitine and octanoylcarnitine. L-carnitine treatment prevented this fall in plasma carnitine and resulted in greater increases in excretion of acylcarnitines. All four patients showed biologically significant improvement in peak oxygen uptake (peak VO2, 18-32% improvement), VO2 at a heart rate of 170 beats/min (15-23% improvement), VO2 at anaerobic threshold (27-42% improvement), and/or oxygen pulse (10-32% improvement). Exercise tolerance in MCAD-deficient patients may be improved by short-term L-carnitine supplementation. This may be the direct result of improved intramitochondrial homeostasis induced by L-carnitine in removing accumulating acyl moieties.

Cordyceps Sinensis (CordyMax Cs-4) supplementation does not improve endurance exercise performance

It is purported that supplementation with Cordyceps Sinensis (CordyMax Cs-4) will improve oxidative capacity and endurance performance. The intent of this investigation was to examine the effects of CordyMax Cs-4 supplementation on VO<(2peak,) ventilatory threshold, and endurance performance in endurance-trained cyclists. Twenty-two male cyclists participated in 5 weeks of supplementation with CordyMax Cs-4 tablets (3 g/d). Training intensity was maintained by weekly documentation and reporting throughout the 5-week period. Subjects completed a VO(2peak) test and work-based time trial prior to and following the supplementation period. VO(2peak) was similar within and between placebo (PLA) and treatment (CS) groups prior to (59.9 +/- 5.9 vs. 59.1 +/- 5.4 ml/kg/min, respectively) and following (60.1 +/- 5.5 vs. 57.1 +/- 5.8 ml/kg/min, respectively) the supplementation period. Ventilatory threshold (VT) was measured at 72 +/- 10% of VO(2peak) in P and T prior to supplementation and did not change in either group following the supplementation. PLA completed the time trial in 61.4+/- 2.4 min compared to 62.1+/- 4.0 min in T. Time trial measurements did not differ between groups, nor did they change in response to supplementation. It is concluded that 5 weeks of CordyMax Cs-4 supplementation has no effect on aerobic capacity or endurance exercise performance in endurance-trained male cyclists.

[Structural modification and bioactivity of cyclovirobuxine D]

AIM

To search for new compounds for the treatment of cardiovascular diseases by structural modification of cyclovirobuxine D.

METHODS

According to rational drug design principle, a series of cyclovirobuxine D analogues were prepared, and their bioactivities were tested.

RESULTS

Ten new compounds were syntheized and confirmed by spectra.

CONCLUSION

Endurance lacking oxygen activity and antiarrhythmia effects of some analogues of cyclovirobuxine D were tested. Some compounds showed better activity than cyclovirobuxine D.

Effects of high dose oral creatine supplementation on anaerobic capacity of elite wrestlers

AIM

The purpose of this study was to investigate the effect of high dose oral creatine supplementation on anaerobic capacity of elite wrestlers.

METHODS

EXPERIMENTAL DESIGN

comparative randomized design.

SETTING

Wingate anaerobic tests of the participants were taken at the Human Performance Laboratory of the Department of Physical Education and Sports in The Middle East Technical University, Ankara, Turkey.

PARTICIPANT

20 active international level wrestlers participated (22 to 27 years old).

INTERVENTIONS

the daily dosage of creatine or placebo was divided into 4 equal amounts (5 gx4 = 20 g). Every 5 g of supplement was dissolved in 250 ml water and it was given to participants 1 hour before breakfast, lunch, dinner, and workout session.

MEASURES

subjects underwent a 30-s Wingate Anaerobic tests until exhaustion in pre- and post-tests. After the pretest measurements were completed, participants were classified as creatine (Cr., n=10) and placebo (Pl., n=10) groups with regard to their average anaerobic power scores obtained during the test.

RESULTS

Results of paired "t"-test revealed that there was no significant change in placebo group between pre- and post-test in average and peak anaerobic power. However, average and peak power mean scores obtained from post-test (8.123+/-0.448 W/kg and 10.523 +/-1.004 W/kg) were significantly (p<0.01) higher than pretest (7.233+/-0.483 W/kg and 8.992+/- 0.665 W/kg) for creatine group. Results of the independent "t"-test also indicated that the mean gained scores of creatine group in average and peak power were significantly higher than placebo group (p<0.01).

CONCLUSION

This study demonstrates that short-term high dose oral creatine supplementation has an ergogenic effect on anaerobic capacity of elite wrestlers.

Gender differences in the regulation of amino acid metabolism

Exercising men, compared with women, have a greater increase in leucine oxidation but not lysine rate of appearance. The cause for this sexual dimorphism is unknown; however, an inhibition of beta-adrenoreceptor activity has previously been shown to mediate amino acid metabolism (Lamont LS, McCullough AJ, and Kalhan SC. Am J Physiol Endocrinol Metab 268: E910-E916, 1995; Lamont LS, Patel DG, and Kalhan SC. J Appl Physiol 67: 221-225, 1989). This study was a gender comparison of leucine and lysine kinetics during a beta-adrenoreceptor blockade (beta1,beta2-blockade) and a placebo control by using a double-blind crossover protocol. Subjects exercised at 50% of their trial-specific maximal O2 consumption (1 h) after 7 days of dietary control. During exercise with beta-blockade, men had an increased nonprotein respiratory exchange ratio (P < 0.001), whereas women had an increased circulation of free fatty acids (P < 0.001). The genders also displayed distinct differences in exercise amino acid kinetics. The men, but not the women, increased leucine oxidation (P < 0.005) and lysine rate of appearance (P < 0.009) when exercising during beta-adrenergic blockade. This study indicates that during beta-blockade, exercising men increase their need for amino acids (and carbohydrate) to fuel energy needs, whereas women increase their mobilization of fat, thereby requiring less alternative fuels such as carbohydrate and amino acids. Gender-specific fuel preferences during exercise are regulated by beta-adrenergic-receptor activity. Substrate availability during exercise appears to modulate the amino acid oxidation differences between genders.

Effect of bovine colostrum on anaerobic exercise performance and plasma insulin-like growth factor I

In this study, we examined the effects of bovine colostrum on peak vertical jump power (VJpeak), peak cycle power (CPpeak), alactic anaerobic work capacity, resistance exercise one-repetition maxima (1-RM) and plasma insulin-like growth factor I (IGF-I) concentrations. Using a randomized, double-blind, placebo-controlled, parallel design, 51 males completed 8 weeks of resistance and plyometric training while consuming 60 g x day(-1) of bovine colostrum (n = 26) or concentrated whey protein powder (n = 25). Peak vertical jump power, peak cycle power, alactic anaerobic work capacity, 1-RM and plasma IGF-I were not different between groups at baseline (P > 0.33). Peak vertical jump power and peak cycle power were still not significantly different between groups by week 4 (VJpeak: bovine colostrum, 7231 +/- 488 W; whey protein, 7214 +/- 530 W; P = 0.99; CPpeak: bovine colostrum, 1272 +/- 202 W; whey protein, 1232 +/- 208 W; P = 0.99). By week 8, however, peak vertical jump power (bovine colostrum, 7370 +/- 503 W; whey powder, 7237 +/- 481 W; 95% confidence intervals, 54 to 170 W; P < 0.01) and peak cycle power (bovine colostrum, 1400 +/- 215 W; whey protein, 1311 +/- 192 W; 95% confidence intervals, 20 to 61 W; P < 0.01) were significantly higher in the bovine colostrum condition. Alactic anaerobic work capacity and 1-RM increased (P < 0.001), but the increases were not different between groups (P > 0.08). Plasma IGF-I did not change in either group (P = 0.55). We conclude that bovine colostrum supplementation during training significantly increased peak anaerobic power, but had no effect on alactic anaerobic work capacity, 1-RM or plasma IGF-I.

Impairment of metabolic capacities in copper and calcium contaminated wild yellow perch (Perca flavescens)

This study examined variations in resting oxygen consumption rate (ROCR), post-exercise oxygen consumption rate, relative scope for activity (RSA), liver and muscle aerobic and anaerobic capacities (using citrate synthase (CS) and lactate dehydrogenase, respectively, as indicators), and tissue biosynthetic capacities (using nucleoside diphosphate kinase (NDPK) as an indicator), in wild yellow perch from four lakes varying in copper (Cu) and cadmium (Cd) contamination. Liver Cu and Cd concentrations largely reflected environmental contamination and were positively correlated with liver protein concentrations and NDPK activities. Our results suggest that metal contamination leads to an upregulation of liver protein metabolism, presumably at least in part for the purpose of metal detoxification. In contrast, muscle NDPK activities decreased with increasing liver Cd concentrations and NDPK activities. There was a 25% decrease in ROCR for a doubling of liver Cu concentrations and a 42% decrease in RSA for a doubling of liver Cd concentrations in the range studied. Cu contamination was also associated with lower muscle CS activities. Our results support previous findings of impaired aerobic capacities in the muscle of metal-contaminated fish, and demonstrate that this impairment is also reflected in aerobic capacities of whole fish. The evidence presented suggests that mitochondria may be primary targets for inhibition by Cu, and that Cd may reduce gill respiratory capacity. Muscle aerobic and anaerobic capacities were inversely related. This work indicates that metal exposure of wild yellow perch leads to a wide range of disturbances in metabolic capacities.

Effect of creatine supplementation on aerobic performance and anaerobic capacity in elite rowers in the course of endurance training

The effect of oral creatine supplementation on aerobic and anaerobic performance was investigated in 16 elite male rowers during 7-day endurance training. Before and after the daily ingestion of 20 g creatine monohydrate for 5 days (Cr-Group, n=8) or placebo (Pl-Group, n=8), subjects performed two exercise tests on a rowing ergometer: (a) incremental exercise consisting of 3-min stage durations and increased by 50 W until volitional exhaustion; (b) an all-out anaerobic exercise performed against a constant load of 7 W/kg. Heart rate and blood lactate concentrations were determined during exercise and recovery. Maximal power output did not significantly differ after the treatment in either group. The mean individual lactate threshold rose significantly after Cr treatment from 314.3 +/- 5.0 W to 335.6 +/- 7.1 W (p<.01), as compared with 305.0 +/- 6.9 W and 308.9 +/- 5.9 W (ns), before and after placebo ingestion, respectively. During the anaerobic test, the athletes supplemented with creatine were able to continue rowing longer (mean increase, 12.1 +/- 4.5 s; p<.01) than Pl-Group (2.4 +/- 8.2 s; ns). No significant differences were found between groups in blood LA after the all-out exercise. The results indicate that in elite rowers, creatine supplementation improves endurance (expressed by the individual lactate threshold) and anaerobic performance, independent of the effect of intensive endurance training.

Effects of sildenafil on cardiopulmonary responses during stress

PURPOSE

To investigate possible effects of sildenafil on the cardiopulmonary responses during sexual intercourse we evaluated cardiopulmonary responses during exercise in a group of impotent patients.

MATERIALS AND METHODS

The study sample included patients with erectile dysfunction who underwent a cardiopulmonary exercise test before and after the administration of 100 mg. sildenafil citrate. Cardiopulmonary exercise test parameters at rest, at the anaerobic threshold, at peak exercise and at 1-minute recovery were recorded, including systolic and diastolic blood pressure, the heart rate, O2 consumption, CO2 production, ventilation and the respiratory rate. Furthermore, O2 consumption per kg. body weight, the ventilatory equivalent for O2 consumption (ventilation/O2 consumption) and CO2 production (ventilation/CO2 production), the respiratory quotient, metabolic equivalents metabolic equivalents, oxygen pulse (O2 consumption/heart rate) and the change in O2 consumption/change in heart rate were calculated.

RESULTS

In 2 of the 43 patients enrolled in the study myocardial ischemia and high blood pressure were detected at rest in 2, respectively, who were excluded from analysis. In the remaining 41 patients with a mean age +/- SD of 52.3 +/- 8.6 years a statistically significant decrease in systolic and diastolic blood pressure was noted after sildenafil use at all stages tested (p <0.002 to 0.001). The heart rate mildly increased after sildenafil use at rest and at peak exercise (p = 0.018). The O2 pulse decreased at the anaerobic threshold (p = 0.003), peak exercise (p = 0.001) and recovery (p = 0.047). In the 11 patients with a mean age of 40.8 +/- 10.12 years who had psychogenic erectile dysfunction the only 2 parameters affected were an increased heart rate and decreased systolic blood pressure at rest, while O2 consumption/heart rate decreased at the anaerobic threshold. In the 18 patients with a mean age of 61.1 +/- 8.9 years who had organic erectile dysfunction and an unremarkable medical history a decrease was noted in systolic and diastolic blood pressure at rest and at peak exercise, and diastolic blood pressure also at recovery, while the heart rate increased at recovery. In the 12 patients with a mean age of 60.16 +/- 9.12 years who had treated cardiovascular disease systolic and diastolic blood pressure decreased at all states and O2 consumption/heart rate at the anaerobic threshold and at peak exercise, while increased values were noted for the respiratory rate at the anaerobic threshold and ventilation/CO2 production at recovery.

CONCLUSIONS

Hemodynamic changes after sildenafil administration should be considered minimal in concert with patient health status. Younger patients without signs of systemic atherosclerosis compensate the vasodilatory effect of sildenafil during exercise, while in older patients with vasculogenic erectile dysfunction moderate changes may be noted regardless of cardiovascular disease in the medical history.

Comparison of linezolid activities under aerobic and anaerobic conditions against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium were exposed to linezolid (MIC of 2 mg/liter) under aerobic or anaerobic conditions in an in vitro pharmacodynamic model. Drug concentration and half-life were adjusted to simulate clinical dosing (600 mg twice daily) of linezolid. Linezolid produced a 2-log(10) killing at 24 h, and rates of killing against each of these facultative organisms as measured by mean survival time appeared similar under aerobic and anaerobic conditions.

Preischemic administration of ribose to delay the onset of irreversible ischemic injury and improve function: studies in normal and hypertrophied hearts

Compared with normal hearts, those with pathology (hypertrophy) are less tolerant of metabolic stresses such as ischemia. Pharmacologic intervention administered prior to such stress could provide significant protection. This study determined, firstly, whether the pentose sugar ribose, previously shown to improve postischemic recovery of energy stores and function, protects against ischemia when administered as a pretreatment. Secondly, the efficacy of this same pretreatment protocol was determined in hearts with pathology (hypertrophy). For study 1, Sprague-Dawley rats received equal volumes of either vehicle (bolus i.v. saline) or ribose (100 mg/kg) before global myocardial ischemia. In study 2, spontaneously hypertensive rats (SHR; blood pressure approximately 200/130) with myocardial hypertrophy underwent the same treatment protocol and assessments. In vivo left ventricular function was measured and myocardial metabolites and tolerance to ischemia were assessed. In normal hearts, ribose pretreatment significantly elevated the heart's energy stores (glycogen), and delayed the onset of irreversible ischemic injury by 25%. However, in vivo ventricular relaxation was reduced by 41% in the ribose group. In SHR, ribose pretreatment did not produce significant elevations in the heart's energy or improvements in tolerance to global ischemia, but significantly improved ventricular function (maximal rate of pressure rise (+dP/dt(max)), 25%; normalized contractility ((+dP/dt)/P), 13%) despite no change in hemodynamics. Thus, administration of ribose in advance of global myocardial ischemia does provide metabolic benefit in normal hearts. However, in hypertrophied hearts, ribose did not affect ischemic tolerance but improved ventricular function.

Caffeine is ergogenic after supplementation of oral creatine monohydrate

PURPOSE

The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence.

METHODS

Fourteen trained male subjects performed treadmill running to volitional exhaustion (T(lim)) at an exercise intensity equivalent to 125% VO(2max). Three trials were performed, one before 6 d of creatine loading (0.3 g x kg x d(-1) baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg x kg(-1)) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise.

RESULTS

Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total VO(2) was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 +/- 3.89 L vs 11.67 +/- 3.61 L). In addition, caffeine T(lim) (222.1 +/- 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 +/- 33.4 s) and placebo (198.3 +/- 45.4 s) T(lim). RPE was also lower at 90 s in the caffeine treatment (13.8 +/- 1.8 RPE points) in comparison with baseline (14.6 +/- 1.9 RPE points).

CONCLUSION

As indicated by a greater T(lim), acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.

Influence of caffeine ingestion on autonomic nervous activity during endurance exercise in humans

The effects of caffeine ingestion on the activities of the autonomic nervous system (ANS) during endurance exercise at low intensity were investigated using a power spectrum analysis of heart rate variability. Placebo or caffeine (300 mg) capsules were randomly administered to the subjects. Each subject ingested the samples 2 h before cycling on an ergometer for 30 min at an intensity corresponding to 40%-50% of his ventilatory threshold. The electrocardiogram, blood pressure (BP) and gas exchange parameters were monitored during rest and exercise. The results indicated that there were no significant differences in heart rate and systolic blood pressure between the trials. The spectrum integrated values of the low frequency power and total power components in the caffeine trial were significantly greater than in the placebo trial during exercise, which implied that activities of the ANS were augmented by caffeine. Caffeine also induced enhanced lipid oxidation as shown by the significantly lower respiratory gas exchange ratio and increases in diastolic blood pressure during exercise. The results shed some light upon the relationship between the activity of the ANS, energy metabolism and BP. In conclusion, the results suggest that caffeinated beverages have a potential to be useful supplements to the prescription of exercise for individuals who experience a depressed activity of the ANS. The results also suggest that the experiment protocol used in this study is a sensitive and noninvasive method for evaluating the effects of various foods and nutrients on the activity of the ANS.

The effect of sodium citrate intake on anaerobic performance in normoxia and after sudden ascent to a moderate altitude

BACKGROUND

The effect of sodium citrate intake on anaerobic performance in normoxia and acute hypoxia was tested in 17 healthy male subjects.

METHODS

The subjects underwent a high-intensity exercise protocol in conditions of normoxia (N) and at 2320 m above the sea level (H). Each condition was combined with the intake of a placebo (Pl) or sodium citrate (C).

RESULTS

The results obtained showed a drop in the maximum HR (p<0.001), due to the effect of the altitude (185+/-8 vs 176+/-8 bpm for N and H under Pl conditions and 189+/-9 vs 178+/-8 bpm for N and H under C conditions). C caused an increase in the RER (p<0.05) and the maximum Lac (p<0.01). The action of this same factor brought about a drop in the maximum VE (p<0.01) (182.60+/-21.58 vs 177.38+/-20.29 l x min(-1) in N and 185.71+/-22.98 vs 179.06+/-22.91 l x min(-1) in H). The interaction of both C and H affected the maximum concentration of lactate obtained (p<0.01), which fell as regards that expected by the corresponding action of both factors separately (14.33+/-2.94 vs 17.8+/-2.74 mMol x l(-1) with Pl and C in N and 15.29+/-2.15 vs 15.54+/-2.59 mMol x l(-1) in H). There were no significant differences in the length of work time in each of the conditions established.

CONCLUSIONS

It would, therefore, seem that in the conditions described, the intake of sodium citrate does not cause appreciable changes in anaerobic performance.

Effect of beta(1)-selective adrenergic blockade on maximal blood lactate steady state in healthy men

The aim of this study was to compare the effect of taking bisoprolol (B), a highly beta(1)-selective adrenoceptor antagonist to that of a placebo (P) on maximal lactate steady state (MLSS), which reflects the transition from oxidative to partially anaerobic metabolism. Ten healthy male subjects [mean (SD) age 23 (3) years, height 181 (6) cm, body mass 76 (6) kg] randomly received oral P or B (5 mg x day(-1)) for 2 weeks using a double-blind crossover design. In the 2nd week, the subjects performed an incremental cycle ergometer test until exhaustion to determine the second blood lactate turn point (LTP(2)). At regular intervals of 24-48 h, the subjects performed 2-3 steady-state tests to determine the MLSS. During the incremental exercise, heart rate (HR) was significantly lower at rest (15 beats x min(-1)), at LTP(2) (23 beats x min(-1)) and at maximal power output (19 beats x min(-1)) when taking B compared to P. Oxygen pulse was significantly higher taking B and no significant differences were observed for any of the respiratory gas exchange measurements (RGEM) (oxygen consumption, carbon dioxide production, minute ventilation, respiratory exchange ratio), exercise intensity or blood lactate concentration (LA) at baseline, at LTP(2) and at maximal power output. During exercise at constant intensity, significant differences between B and P were found for HR [148 (12) compared to 176 (11) beats x min(-1)] and oxygen pulse [21.8 (1.9) compared to 19.2 (1.6) ml] at MLSS. No difference was found for exercise intensity [216 (18) compared to 218 (18) W], for RGEM, LA [5.3 (1.1) compared to 4.8 (1.5) mmol x l(-1)] and ratings of perceived exertion [18.1 (1.6) compared to 17.4 (1.7)] for B and P at MLSS. In both, the power output at LTP(2) was slightly higher than power output at MLSS (within an intensity step). Commonly measured cardiorespiratory and subjective variables determined during treatment with 5 mg bisoprolol can be used for testing cardiorespiratory fitness and for prescription of training intensity.

Long-term administration of L-carnitine to humans: effect on skeletal muscle carnitine content and physical performance

BACKGROUND

Long-term administration of high oral doses of L-carnitine on the skeletal muscle composition and the physical performance has not been studied in humans.

METHODS

Eight healthy male adults were treated with 2 x 2 g of L-carnitine per day for 3 months. Muscle biopsies and exercise tests were performed before, immediately after, and 2 months after the treatment. Exercise tests were performed using a bicycle ergometer for 10 min at 20%, 40%, and 60% of the individual maximal workload (P(max)), respectively, until exhaustion.

RESULTS

There were no significant differences between V(O(2)max), RER(max), and P(max) between the three time points investigated. At submaximal intensities, the only difference to the pretreatment values was a 5% increase in V(O(2)) at 20% and 40% of P(max) 2 months after the cessation of the treatment. The total carnitine content in the skeletal muscle was 4.10 +/- 0.82 micromol/g before, 4.79 +/- 1.19 micromol/g immediately after, and 4.19 +/- 0.61 micromol/g wet weight 2 months after the treatment (no significant difference). Activities of the two mitochondrial enzymes citrate synthase and cytochrome oxidase, as well as the skeletal muscle fiber composition also remained unaffected by the administration of L-carnitine.

CONCLUSIONS

Long-term oral treatment of healthy adults with L-carnitine is not associated with a significant increase in the muscle carnitine content, mitochondrial proliferation, or physical performance. Beneficial effects of the long-term treatment with L-carnitine on the physical performance of healthy adults cannot be explained by an increase in the carnitine muscle stores.

Myocardial protection of the pressure overload hypertrophied heart in human cardiac surgery by acceleration of anaerobic glycolysis

BACKGROUND

Because of the decreased tolerance to ischemia and increased reperfusion injury in hypertrophied myocardium, myocardial hypertrophy is a well known risk factor for cardiac surgery. We have previously demonstrated in a left ventricular hypertrophy (LVH) model that a highly buffered cardioplegic solution (HBS) that provided glucose as a substrate and promoted anaerobic glycolysis during ischemia afforded superior myocardial protection when compared to standard formulations. And we reported the superiority of this cardioplegia in human cardiac surgery.

METHODS

In this study, 16 patients with aortic stenosis (AS) and LVH receiving HBS were reviewed and compared to another patient group with AS and LVH who received either cold blood cardioplegia (CBC; n=5) or glucose insulin potassium (GIK; n=6).

RESULTS

Postoperative cardiac index was better in the HBS group than the other two groups with similar or lower catecholamine. CK-MB was lower in HBS group than GIK group, but this was not significant. Only one DC cardioversion was required in the HBS group, whereas 2 DC in the CBC group and total 7 DC in the GIK group.

CONCLUSIONS

We found that histidine buffered cardioplegic solution provided comparable or better pump performance after surgery with relatively lower inotropic requirement, less DC cardioversion and homologous blood requirements for left ventricular hypertrophied heart associated with aortic stenosis.

Is there a physiologic basis for creatine use in children and adolescents?

The purported ergogenic benefits of creatine for the adult population have been well documented. In able-bodied children and adolescents, there is a paucity of data on creatine use and the purported ergogenic effects of creatine. Only 1 study to date has investigated the ergogenic properties of creatine in the adolescent population. The purpose of this review was to try to establish a rationale for creatine use in the child and adolescent population. The limited literature available in this area did not provide a strong enough rationale from either a physiologic or performance perspective for creatine supplementation in these populations. However, significantly more research is required before definitive conclusions can be made.