Incorporation and washout of n-3 PUFA after high dose intravenous and oral supplementation in healthy volunteers.

BACKGROUND & AIMS: Although the physiological effects of n-3 polyunsaturated fatty acids (n-3PUFA) are generally thought to require several weeks of exposure to allow their incorporation into plasma membranes, intravenous (IV) n-3PUFA attenuate the cardiovascular and neuroendocrine response to stress within 3 h. Whether oral n-3 PUFA exert similar early effects remains unknown. OBJECTIVE: To assess whether acute IV or short term oral n-3PUFA administration reproduces the metabolic effects of long term oral supplements during exercise, and how it relates to their incorporation into platelets and red blood cells (RBC) membranes. DESIGN: Prospective single center open label study in 8 healthy subjects receiving a 3-h infusion of 0.6 g/kg body weight n-3PUFA emulsion, followed one week later by an oral administration of 0.6 g/kg over 3 consecutive days. Maximal power output (cycling exercise), maximal heart rate (HR), blood lactate at exhaustion, and platelet function were measured at baseline and after IV or 3-day oral supplementation; platelet and RBC membrane composition were assessed until 15 days after n-3PUFA administration. RESULTS: Both IV and oral n-3PUFA significantly decreased maximal HR (-6% and -5%), maximal power output (-10%) and peak blood lactate (-47% and -52%) Platelet function tests were unchanged. The EPA and DHA membrane contents of RBC and platelets increased significantly, but only to 1.7-1.9% of fatty acid content. CONCLUSION: The cardiovascular and metabolic effects of n-3 PUFA during exercise occur already within 1-3 days of exposure, and may be unrelated to changes in membranes composition. Effects occur within hours of administration and are unrelated to lipid membrane composition. Trial registered at clinicaltrials.gov as NCT00516178.

Effect of a small dose of alcohol on the endurance performance of trained cyclists.

AIM: The aim of this study was to investigate the effect of an acute small ethanol (EtOH) dose (0.5 ml EtOH/kg fat-free mass, combined with carbohydrate) in a drink on endurance performance of trained cyclists. METHODS: Thirteen well-trained male cyclists took part in this study. A 60-min cycling endurance performance test (time trial) was performed in a calorimetric chamber after drinking an EtOH (30 +/- 1.8 ml) or a non-EtOH control (C) drink. RESULTS: Overall, EtOH induced a significant decrease in the average cycling power output (PO) (EtOH: 233 +/- 23 W versus C: 243 +/- 24 W, P < 0.01). The time course of mechanical PO showed an early decrease during the EtOH trial as compared to C (P < 0.01). Due to the lower PO, oxygen consumption, carbon dioxide production and glucose oxidation were significantly lower (P < 0.05) as compared to C. Relative to PO, heart rate response and ratings of perceived exertion (RPE) were increased by EtOH as compared to C (P < 0.05). In contrast, EtOH did not influence gross work efficiency, glycaemia and blood lactate concentration. CONCLUSIONS: These results show that the acute low dose of EtOH decreased endurance performance. An increase of cardio-vascular strain and psychobiological mechanisms may explain this decrease of endurance performance.

Tissue oxygenation and hemodynamic response to NO synthase inhibition in septic shock.

The objective of the study was to evaluate the tissue oxygenation and hemodynamic effects of NOS inhibition in clinical severe septic shock. Eight patients with septic shock refractory to volume loading and high level of adrenergic support were prospectively enrolled in the study. Increasing doses of NOS inhibitors [N(G)-nitro-L-arginine-methyl ester (L-NAME) or N(G)-monomethyl-L-arginine (L-NMMA)] were administered as i.v. bolus until a peak effect = 10 mmHg on mean blood pressure was obtained or until side effects occurred. If deemed clinically appropriate, a continuous infusion of L-NAME was instituted and adrenergic support weaning attempted. The bolus administration of NOS inhibitors transiently increased mean blood pressure by 10 mm Hg in all patients. Seven out of eight patients received an L-NAME infusion, associated over 24 h with a progressive decline in cardiac index (P < 0.001) and an increase in systemic vascular resistance (P < 0.01). Partial or total adrenergic support weaning was rapidly possible in 6/8 patients. Oxygen transport decreased (P < 0.001), but oxygen consumption remained unchanged in those patients in whom it could be measured by indirect calorimetry (5/8). Blood lactate and the difference between tonometric gastric and arterial PCO2 remained unchanged. There were 4/8 ICU survivors. We conclude that nitric oxide synthase inhibition in severe septic shock was followed with a progressive correction of the vasoplegic hemodynamic disturbances with finally normalization of cardiac output and systemic vascular resistances without any demonstrable deterioration in tissue oxygenation.

Inter-limb coordination and energy cost in swimming.

OBJECTIVES: This study investigated the relationship between inter-arm coordination and the energy cost of locomotion in front crawl and breaststroke and explored swimmers' flexibility in adapting their motor organization away from their preferred movement pattern. DESIGN: Nine front-crawlers performed three 300-m in front crawl and 8 breaststrokers performed three 200-m in breaststroke at constant submaximal intensity and with 5-min rests. Each trial was performed randomly in a different coordination pattern: freely chosen, 'maximal glide' and 'minimal glide'. Two underwater cameras videotaped frontal and side views to analyze speed, stroke rate, stroke length and inter-limb coordination. METHODS: In front crawl, inter-arm coordination was quantified by the index of coordination (IdC) and the leg beat kicks were counted. In breaststroke, four time gaps quantified the arm to leg coordination (i.e., time between leg and arm propulsions; time between beginning, 90° flexion and end of arm and leg recoveries). The energy cost of locomotion was calculated from gas exchanges and blood lactate concentration. RESULTS: In both front crawl and breaststroke, the freely chosen coordination corresponded to glide pattern and showed the lowest energy cost (12.8 and 17.1Jkg(-1)m(-1), respectively). Both front-crawlers and breaststrokers were able to reach 'maximal glide' condition (respectively, +35% and +28%) but not 'minimal glide' condition for front crawl. CONCLUSIONS: The freely chosen pattern appeared more economic because more trained. When coordination was constrained, the swimmers had higher coordination flexibility in breaststroke than in front crawl, suggesting that breaststroke coordination was easier to regulate by changing glide time.

Coordination pattern adaptability: energy cost of degenerate behaviors.

This study investigated behavioral adaptability, which could be defined as a blend between stability and flexibility of the limbs movement and their inter-limb coordination, when individuals received informational constraints. Seven expert breaststroke swimmers performed three 200-m in breaststroke at constant submaximal intensity. Each trial was performed randomly in a different coordination pattern: 'freely-chosen', 'maximal glide' and 'minimal glide'. Two underwater and four aerial cameras enabled 3D movement analysis in order to assess elbow and knee angles, elbow-knee pair coordination, intra-cyclic velocity variations of the center of mass, stroke rate and stroke length and inter-limb coordination. The energy cost of locomotion was calculated from gas exchanges and blood lactate concentration. The results showed significantly higher glide, intra-cyclic velocity variations and energy cost under 'maximal glide' compared to 'freely-chosen' instructional conditions, as well as higher reorganization of limb movement and inter-limb coordination (p<0.05). In the 'minimal glide' condition, the swimmers did not show significantly shorter glide and lower energy cost, but they exhibited significantly lower deceleration of the center of mass, as well as modified limb movement and inter-limb coordination (p<0.05). These results highlight that a variety of structural adaptations can functionally satisfy the task-goal.

Blockade of the action of nitric oxide in human septic shock increases systemic vascular resistance and has detrimental effects on pulmonary function after a short infusion of methylene blue

To investigate the role of nitric oxide in human sepsis, ten patients with severe septic shock requiring vasoactive drug therapy and mechanical ventilation were enrolled in a prospective, open, non-randomized clinical trial to study the acute effects of methylene blue, an inhibitor of guanylate cyclase. Hemodynamic and metabolic variables were measured before and 20, 40, 60, and 120 min after the start of a 1-h intravenous infusion of 4 mg/kg of methylene blue. Methylene blue administration caused a progressive increase in mean arterial pressure (60 [55-70] to 70 [65-100] mmHg, median [25-75th percentiles]; P<0.05), systemic vascular resistance index (649 [479-1084] to 1066 [585-1356] dyne s-1 cm-5 m-2; P<0.05) and the left ventricular stroke work index (35 [27-47] to 38 [32-56] g m-1 m-2; P<0.05) from baseline to 60 min. The pulmonary vascular resistance index increased from 150 [83-207] to 186 [121-367] dyne s-1 cm-5 m-2 after 20 min (P<0.05). Mixed venous saturation decreased from 65 [56-76] to 63 [55-69]% (P<0.05) after 60 min. The PaO2/FiO2 ratio decreased from 168 [131-215] to 132 [109-156] mmHg (P<0.05) after 40 min. Arterial lactate concentration decreased from 5.1 ± 2.9 to 4.5 ± 2.1 mmol/l, mean ± SD (P<0.05) after 60 min. Heart rate, cardiac filling pressures, cardiac output, oxygen delivery and consumption did not change. Methylene blue administration was safe and no adverse effect was observed. In severe human septic shock, a short infusion of methylene blue increases systemic vascular resistance and may improve myocardial function. Although there was a reduction in blood lactate concentration, this was not explained by an improvement in tissue oxygenation, since overall oxygen availability did not change. However, there was a significant increase in pulmonary vascular tone and a deterioration in gas exchange. Further studies are needed to demonstrate if nitric oxide blockade with methylene blue can be safe for patients with septic shock and, particularly, if it has an effect on pulmonary function.

Short-lasting systemic and regional benefits of early crystalloid infusion after intravenous inoculation of dogs with live Escherichia coli

We investigated the systemic and regional hemodynamic effects of early crystalloid infusion in an experimental model of septic shock induced by intravenous inoculation with live Escherichia coli. Anesthetized dogs received an intravenous infusion of 1.2 x 10(10) cfu/kg live E. coli in 30 min. After 30 min of observation, they were randomized to controls (no fluids; N = 7), or fluid resuscitation with lactated Ringer's solution, 16 ml/kg (N = 7) or 32 ml/kg (N = 7) over 30 min and followed for 120 min. Cardiac index, portal blood flow, mean arterial pressure, systemic and regional oxygen-derived variables, blood lactate, and gastric PCO2 were assessed. Rapid and progressive cardiovascular deterioration with reduction in cardiac output, mean arterial pressure and portal blood flow (~50, ~25 and ~70%, respectively) was induced by the live bacteria challenge. Systemic and regional territories showed significant increases in oxygen extraction and in lactate levels. Significant increases in venous-arterial (~9.6 mmHg), portal-arterial (~12.1 mmHg) and gastric mucosal-arterial (~18.4 mmHg) PCO2 gradients were also observed. Early fluid replacement, especially with 32 ml/kg volumes of crystalloids, promoted only partial and transient benefits such as increases of ~76% in cardiac index, of ~50% in portal vein blood flow and decreases in venous-arterial, portal-arterial, gastric mucosal-arterial PCO2 gradients (7.2 ± 1.0, 7.2 ± 1.3 and 9.7 ± 2.5 mmHg, respectively). The fluid infusion promoted only modest and transient benefits, unable to restore the systemic and regional perfusional and metabolic changes in this hypodynamic septic shock model.

L-carnitine as an ergogenic aid for patients with chronic obstructive pulmonary disease submitted to whole-body and respiratory muscle training programs

The effects of adding L-carnitine to a whole-body and respiratory training program were determined in moderate-to-severe chronic obstructive pulmonary disease (COPD) patients. Sixteen COPD patients (66 ± 7 years) were randomly assigned to L-carnitine (CG) or placebo group (PG) that received either L-carnitine or saline solution (2 g/day, orally) for 6 weeks (forced expiratory volume on first second was 38 ± 16 and 36 ± 12%, respectively). Both groups participated in three weekly 30-min treadmill and threshold inspiratory muscle training sessions, with 3 sets of 10 loaded inspirations (40%) at maximal inspiratory pressure. Nutritional status, exercise tolerance on a treadmill and six-minute walking test, blood lactate, heart rate, blood pressure, and respiratory muscle strength were determined as baseline and on day 42. Maximal capacity in the incremental exercise test was significantly improved in both groups (P < 0.05). Blood lactate, blood pressure, oxygen saturation, and heart rate at identical exercise levels were lower in CG after training (P < 0.05). Inspiratory muscle strength and walking test tolerance were significantly improved in both groups, but the gains of CG were significantly higher than those of PG (40 ± 14 vs 14 ± 5 cmH2O, and 87 ± 30 vs 34 ± 29 m, respectively; P < 0.05). Blood lactate concentration was significantly lower in CG than in PG (1.6 ± 0.7 vs 2.3 ± 0.7 mM, P < 0.05). The present data suggest that carnitine can improve exercise tolerance and inspiratory muscle strength in COPD patients, as well as reduce lactate production.

Early remodeling of rat cardiac muscle induced by swimming training

The aim of the present investigation was to study the effect of acute swimming training with an anaerobic component on matrix metallopeptidase (MMP) activity and myosin heavy chain gene expression in the rat myocardium. Animals (male Wistar rats, weighing approximately 180 g) were trained for 6 h/day in 3 sessions of 2 h each for 1 to 5 consecutive days (N = 5 rats per group). Rats swam in basins 47 cm in diameter and 60 cm deep filled with water at 33 to 35ºC. After the training period a significant increase (P < 0.05) was observed in the heart weight normalized to body weight by about 22 and 35% in the groups that trained for 96 and 120 h, respectively. Blood lactate levels were significantly increased (P < 0.05) in all groups after all training sessions, confirming an anaerobic component. However, lactate levels decreased (P < 0.05) with days of training, suggesting that the animals became adapted to this protocol. Myosin heavy chain-ß gene expression, analyzed by real time PCR and normalized with GAPDH gene expression, showed a significant two-fold increase (P < 0.01) after 5 days of training. Zymography analysis of myocardium extracts indicated a single ~60-kDa activity band that was significantly increased (P < 0.05) after 72, 96, and 120 h, indicating an increased expression of MMP-2 and suggesting precocious remodeling. Furthermore, the presence of MMP-2 was confirmed by Western blot analysis, but not the presence of MMP-1 and MMP-3. Taken together, our results indicate that in these training conditions, the rat heart undergoes early biochemical and functional changes required for the adaptation to the new physiological condition by tissue remodeling.

Effect of carbohydrate availability on time to exhaustion in exercise performed at two different intensities

This study examined the effects of pre-exercise carbohydrate availability on the time to exhaustion for moderate and heavy exercise. Seven men participated in a randomized order in two diet and exercise regimens each lasting 3 days with a 1-week interval for washout. The tests were performed at 50% of the difference between the first (LT1) and second (LT2) lactate breakpoint for moderate exercise (below LT2) and at 25% of the difference between the maximal load and LT2 for heavy exercise (above LT2) until exhaustion. Forty-eight hours before each experimental session, subjects performed a 90-min cycling exercise followed by 5-min rest periods and a subsequent 1-min cycling bout at 125% VO2max/1-min rest periods until exhaustion to deplete muscle glycogen. A diet providing 10% (CHOlow) or 65% (CHOmod) energy as carbohydrates was consumed for 2 days until the day of the experimental test. In the exercise below LT2, time to exhaustion did not differ between the CHOmod and the CHOlow diets (57.22 ± 24.24 vs 57.16 ± 25.24 min). In the exercise above LT2, time to exhaustion decreased significantly from 23.16 ± 8.76 min on the CHOmod diet to 18.30 ± 5.86 min on the CHOlow diet (P < 0.05). The rate of carbohydrate oxidation, respiratory exchange ratio and blood lactate concentration were reduced for CHOlow only during exercise above LT2. These results suggest that muscle glycogen depletion followed by a period of a low carbohydrate diet impairs high-intensity exercise performance.

Acute exercise performed close to the anaerobic threshold improves cognitive performance in elderly females

The objective of the present study was to compare the effect of acute exercise performed at different intensities in relation to the anaerobic threshold (AT) on abilities requiring control of executive functions or alertness in physically active elderly females. Forty-eight physically active elderly females (63.8 ± 4.6 years old) were assigned to one of four groups by drawing lots: control group without exercise or trial groups with exercise performed at 60, 90, or 110% of AT (watts) and submitted to 5 cognitive tests before and after exercise. Following cognitive pretesting, an incremental cycle ergometer test was conducted to determine AT using a fixed blood lactate concentration of 3.5 mmol/L as cutoff. Acute exercise executed at 90% of AT resulted in significant (P < 0.05, ANOVA) improvement in the performance of executive functions when compared to control in 3 of 5 tests (verbal fluency, Tower of Hanoi test (number of movements), and Trail Making test B). Exercising at 60% of AT did not improve results of any tests for executive functions, whereas exercise executed at 110% of AT only improved the performance in one of these tests (verbal fluency) compared to control. Women from all trial groups exhibited a remarkable reduction in the Simple Response Time (alertness) test (P = 0.001). Thus, physical exercise performed close to AT is more effective to improve cognitive processing of older women even if conducted acutely, and using a customized exercise prescription based on the anaerobic threshold should optimize the beneficial effects.

Association between anaerobic components of the maximal accumulated oxygen deficit and 30-second Wingate test

The purpose of this study was to analyze the relationship between the anaerobic components of the maximal accumulated oxygen deficit (MAOD) and of the 30-second Wingate anaerobic test (30-WAnT). Nine male physical education students performed: a) a maximal incremental exercise test; b) a supramaximal constant workload test to determine the anaerobic components of the MAOD; and c) a 30-WAnT to measure the peak power (PP) and mean power (MP). The fast component of the excess post-exercise oxygen consumption and blood lactate accumulation were measured after the supramaximal constant workload test in order to determine the contributions made by alactic (ALMET) and lactic (LAMET) metabolism. Significant correlations were found between PP and ALMET (r=0.71; P=0.033) and between MP and LAMET(r=0.72; P=0.030). The study results suggested that the anaerobic components of the MAOD and of the 30-WAnT are similarly applicable in the assessment of ALMET and LAMET during high-intensity exercise.

Energy system contribution in a maximal incremental test: correlations with pacing and overall performance in a 10-km running trial

This study aimed to verify the association between the contribution of energy systems during an incremental exercise test (IET), pacing, and performance during a 10-km running time trial. Thirteen male recreational runners completed an incremental exercise test on a treadmill to determine the respiratory compensation point (RCP), maximal oxygen uptake (V˙O2max), peak treadmill speed (PTS), and energy systems contribution; and a 10-km running time trial (T10-km) to determine endurance performance. The fractions of the aerobic (WAER) and glycolytic (WGLYCOL) contributions were calculated for each stage based on the oxygen uptake and the oxygen energy equivalents derived by blood lactate accumulation, respectively. Total metabolic demand (WTOTAL) was the sum of these two energy systems. Endurance performance during the T10-km was moderately correlated with RCP, V˙O2maxand PTS (P<@0.05), and moderate-to-highly correlated with WAER, WGLYCOL, and WTOTAL (P<0.05). In addition, WAER, WGLYCOL, and WTOTAL were also significantly correlated with running speed in the middle (P<0.01) and final (P<0.01) sections of the T10-km. These findings suggest that the assessment of energy contribution during IET is potentially useful as an alternative variable in the evaluation of endurance runners, especially because of its relationship with specific parts of a long-distance race.

The effects of altered heat stress on voluntary pacing strategies during prolonged cycling

Central Governor Model (CGM) suggests that perturbations in the rate of heat storage (AS) are centrally integrated to regulate exercise intensity in a feed-forward fashion to prevent excessive thermal strain. We directly tested the CGM by manipulating ambient temperature (Tam) at 20-minute intervals from 20°C to 35°C, and returning to 20°C, while cycling at a set rate of perceived exertion (RPE). The synchronicity of power output (PO) with changes in HS and Tam were quantified using Auto-Regressive Integrated Moving Averages analysis. PO fluctuated irregularly but was not significantly correlated to changes in thermo physiological status. Repeated measures indicated no changes in lactate accumulation. In conclusion, real time dynamic sensation of Tam and integration of HS does not directly influence voluntary pacing strategies during sub-maximal cycling at a constant RPE while non-significant changes in blood lactate suggest an absence of peripheral fatigue.

Chronic versus acute ingestion of sodium citrate: a randomized placebo controlled cross-over trial for swimming 200 metres in well-trained swimmers age 13-17

A double-blinded, placebo controlled, cross-over design was used to investigate sodium citrate dihydrate (Na-CIT) supplementation improve 200m swimming performance. Ten well-trained, male swimmers (14.9 ± 0.4y; 63.5 ± 4kg) performed four 200m time trials: acute (ACU) supplementation (0.5g/kg), acute placebo (PLC-A), chronic (CHR) (0.1g/kg for 3 days and 0.3g/kg on the 4th day pre-trial), and chronic placebo (PLC-C). Na-CIT was administered 120min pre-trial in solution with 500mL of flavored water; placebo was flavored water. Blood lactate, base excess (BE), bicarbonate, pH, and PCO2 were analyzed at basal, 100min post-ingestion, and 3min post-trial via finger prick. Time, lactate, and rate of perceived exertion were not different between trials. BE and bicarbonate were significantly higher for the ACU and CHR trials compared to placebo. “Responders” improved by 1.03% (P=0.043) and attained significantly higher post-trial lactate concentrations in the ACU versus PLC-A trials and compared to non-responders in the ACU and CHR trials.