Maximal lipidic power in high competitive level triathletes and cyclists.

OBJECTIVE: To describe the fat-oxidation rate in triathlon and different modalities of endurance cycling. METHODS: 34 endurance athletes (15 male triathletes, 4 female triathletes, 11 road cyclists and 4 male mountain bikers) underwent a progressive cycloergometer test until exhaustion. Relative work intensity (VO(2max)), minimal lactate concentration (La(-)(min)), lactic threshold, individual lactic threshold (ILT), maximal fat-oxidation rate (Fat(max), Fat(max) zone) and minimal fat-oxidation rate (Fat(min)) were determined in each of the groups and were compared by means of one-way analysis of variance. RESULTS: No significant differences were found for Fat(max), Fat(min) or for the Fat(max) zone expressed as fat oxidation rate (g/min). Intensities -20%, -10% and -5% Fat(max) were significantly lower for mountain bikers with respect to road cyclists and female triathletes, expressed as % VO(2max). Intensities 20%, 10% and 5% Fat(max) were significantly lower for mountain bikers with respect to male triathletes and female triathletes, and for male triathletes in comparison with female triathletes, expressed as % VO(2max). Lactic threshold and La(-)(min) did not show significant differences with respect to Fat(max). Lactic threshold was found at the same VO(2max) with respect to the higher part of the Fat(max) zone, and La(-)(min) at the same VO(2max) with respect to the lower part of the Fat(max) zone. CONCLUSIONS: The VO(2max) of Fat(max) and the Fat(max) zone may explain the different endurance adaptations of the athletes according to their sporting discipline. Lactic threshold and La(-)(min) were found at different relative work intensities with respect to those of Fat(max) even though they belonged to the Fat(max) zone.

Reduced muscle redox capacity after endurance training in patients with chronic obstructive pulmonary disease.

The present study was undertaken to test whether endurance training in patients with COPD, along with enhancement of muscle bioenergetics, decreases muscle redox capacity as a result of recurrent episodes of cell hypoxia induced by high intensity exercise sessions. Seventeen patients with COPD (FEV(1), 38 +/- 4% pred; PaO2), 69 +/- 2.7 mm Hg; PaCO2, 42 +/- 1.7 mm Hg) and five age-matched control subjects (C) were studied pretraining and post-training. Reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and gamma-glutamyl cysteine synthase heavy subunit chain mRNA expression (gammaGCS-HS mRNA) were measured in the vastus lateralis. Pretraining redox status at rest and after moderate (40% Wpeak) constant-work rate exercise were similar between groups. After training (DeltaWpeak, 27 +/- 7% and 37 +/- 18%, COPD and C, respectively) (p < 0.05 each), GSSG levels increased only in patients with COPD (from 0.7 +/- 0.08 to 1.0 +/- 0.15 nmol/ mg protein, p < 0.05) with maintenance of GSH levels, whereas GSH markedly increased in C (from 4.6 +/- 1.03 to 8.7 +/- 0.41 nmol/ mg protein, p < 0.01). Post-training gammaGCS-HS mRNA levels increased after submaximal exercise in patients with COPD. No evidence of lipid peroxidation was observed. We conclude that although endurance training increased muscle redox potential in healthy subjects, patients with COPD showed a reduced ability to adapt to endurance training reflected in lower capacity to synthesize GSH.

Effects of endurance training on skeletal muscle bioenergetics in chronic obstructive pulmonary disease.

Physiologic adaptations after an 8-wk endurance training program were examined in 13 patients with chronic obstructive pulmonary disease (COPD) (age, 64 +/- 4 [SD] yr; FEV1, 43 +/- 9% pred; PaO2, 72 +/- 8 mm Hg; and PaCO2, 36 +/- 2 mm Hg) and in eight healthy sedentary control subjects (61 +/- 4 yr). Both pre- and post-training studies included: (1) whole-body oxygen consumption (V O2) and one-leg O2 uptake (V O2leg) during exercise; and (2) intracellular pH (pHi) and inorganic phosphate to phosphocreatine ratio ([Pi]/[PCr]) during exercise; and half-time of [PCr] recovery. After training, the two groups increased peak V O2 (p < 0.05 each) and showed a similar fall in submaximal femoral venous lactate levels (p < 0.05 each). However, control subjects increased peak V E (p < 0.01) and raised peak O2 delivery (p = 0.05), not shown in patients with COPD. Both groups increased post-training O2 extraction ratio (p < 0.05). The most consistent finding, however, was in patients with COPD, who had a substantial improvement in cellular bioenergetics: (1) half-time of [PCr] recovery fell from 50 +/- 8 to 34 +/- 7 s (p = 0.02); and (2) at a given submaximal work rate, [Pi]/[PCr] ratio decreased and pHi increased (p < 0.05 each). We conclude that beneficial effects of training in patients with COPD essentially occurred at muscle level during submaximal exercise.

Cellular bioenergetics after erythropoietin therapy in chronic renal failure.

After erythropoietin (rHuEPO) therapy, patients with chronic renal failure (CRF) do not improve peak O2 uptake (VO2 peak) as much as expected from the rise in hemoglobin concentration ([Hb]). In a companion study, we explain this phenomenon by the concurrent effects of fall in muscle blood flow after rHuEPO and abnormal capillary O2 conductance observed in CRF patients. The latter is likely associated with a poor muscle microcirculatory network and capillary-myofiber dissociation due to uremic myopathy. Herein, cellular bioenergetics and its relationships with muscle O2 transport, before and after rHuEPO therapy, were examined in eight CRF patients (27 +/- 7.3 [SD] yr) studied pre- and post-rHuEPO ([Hb] = 7.8 +/- 0.7 vs. 11.7 +/- 0.7 g x dl-1) during an incremental cycling exercise protocol. Eight healthy sedentary subjects (26 +/- 3.1 yr) served as controls. We hypothesize that uremic myopathy provokes a cytosolic dysfunction but mitochondrial oxidative capacity is not abnormal. 31P-nuclear magnetic resonance spectra (31P-MRS) from the vastus medialis were obtained throughout the exercise protocol consisting of periods of 2 min exercise (at 1.67 Hz) at increasing work-loads interspersed by resting periods of 2.5 min. On a different day, after an identical exercise protocol, arterial and femoral venous blood gas data were obtained together with simultaneous measurements of femoral venous blood flow (Qleg) to calculate O2 delivery (QO2leg) and O2 uptake (VO2leg). Baseline resting [phosphocreatine] to [inorganic phosphate] ratio ([PCr]/[Pi]) did not change after rHuEPO (8.9 +/- 1.2 vs. 8.8 +/- 1.2, respectively), but it was significantly lower than in controls (10.9 +/- 1.5) (P = 0.01 each). At a given submaximal or peak VO2leg, no effects of rHuEPO were seen on cellular bioenergetics ([PCr]/[Pi] ratio, %[PCr] consumption halftime of [PCr] recovery after exercise), nor in intracellular pH (pHi). The post-rHuEPO bioenergetic status and pHi, at a given VO2leg, were below those observed in the control group. However, at a given pHi, no differences in 31P-MRS data were detected between post-rHuEPO and controls. After rHuEPO, at peak VO2, Qleg fell 20% (P < 0.04), limiting the change in QO2leg to 17%, a value that did not reach statistical significance. The corresponding O2 extraction ratio decreased from 73 +/- 4% to 68 +/- 8.2% (P < 0.03). These changes indicate that maximal O2 flow from microcirculation to mitochondria did not increase despite the 50% increase in [Hb] and explain how peak VO2leg and cellular bioenergetics (31P-MRS) did not change after rHuEPO. Differences in pHi, possibly due to lactate differences, between post-rHeEPO and controls appear to be a key factor in the abnormal muscle cell bioenergetics during exercise observed in CRF patients.

Development and characterization of an ergometer to study the bioenergetics of the human quadriceps muscle by 31P NMR spectroscopy inside a standard MR scanner.

A description is given of an ergometer made of nonmagnetic materials which fits into a standard whole body MR magnet. T2-weighted images show that exercise is highly specific for quadriceps muscles. The ergometer permits the noninvasive study of T2-related changes in the proton images of the leg as well as changes occurring in muscle bioenergetics during exercise and recovery.

31P-MRS of quadriceps reveals quantitative differences between sprinters and long-distance runners.

Phosphorus-31 nuclear magnetic resonance spectroscopy (31P-MRS) has been used to characterize the spectral pattern of quadriceps muscle at rest for sedentaries (N = 10), sprinters (N = 12), and long-distance runners (N = 10). Intracellular pH (pHi), phosphocreatine (PCr), inorganic phosphate (Pi), phosphodiesters (PDE), adenosine triphosphate (ATP) and total phosphate (Pt), defined as the sum of the areas of PCr, PDE, Pi, and 3 times the beta-ATP resonances, were obtained from all spectra. The pHi and ATP/Pt ratio were the same in the three groups of people studied. The PCr/Pi and PCr/Pt ratios were significantly lower and the Pi/Pt ratio was significantly higher for long-distance runners than for sprinters and sedentaries, while the PDE/Pt ratio was significantly lower for sprinters than for sedentaries and long-distance runners. Furthermore, the PCr concentration for sprinters and sedentaries was significantly higher and the Pi was significantly lower than for long-distance runners. The results obtained in this study can be explained by the accepted differences in fiber type composition between sprint and endurance athletes. We suggest that 31P-MRS at rest could be used to monitor noninvasively the individual adaptive response to training in the metabolic characteristics of the athlete muscle fiber.

Effect of training on the calf muscle energy metabolism. A 31P-NMR study on four elite downhill skiers challenged with a standardized exercise protocol.

This study evaluates the effects of a 6 months' training period on the bioenergetics of the calf muscle of elite athletes by means of phosphorus-31 Nuclear Magnetic Resonance Spectroscopy (31P-NMR). Four downhill skiers, belonging to the Spanish National Team, performed a standardized exercise protocol using their right leg inside a wide-bore 2.35 Tesla magnet. The inorganic phosphate/phosphocreatine (Pi/PC) ratio and intracellular pH (pHi) were measured at steady-state during an exercise protocol composed of 5 work levels between 20% and 80% of the maximum voluntary contraction (MVC), before and after the training period. The measured values, which were markedly scattered at the beginning, regrouped after training. This was caused by a shift towards lower Pi/PC ratios and by a lower pHi acidification in three of the four subjects. This result suggests that 31P-NMR is a good tool to evaluate changes in the muscle aerobic capacity of athletes induced by training.

[Increase of energy expenditure in Parkinson's disease]. / Augmentation de la dépense énergétique au cours de la maladie de Parkinson.

Energy expenditure was determined in 18 patients with Parkinson's disease, 6 healthy volunteers and 6 patients with essential tremor, age-matched, using the indirect calorimetric method which measures the gas exchange rate. The results showed a significant increase in the relative energy expenditure, i.e. the difference between absolute and predictable values from the Harris and Benedict equation, among the parkinsonian patients (+21 +/- 4.1 p. 100; mean +/- S.E.M.) as compared to the 2 control groups (-8.6 +/- 7 p. 100 and -2.1 +/- 4.1 p. 100 respectively; p less than 0.001). There was no correlation between the rate of energy expenditure and the duration or degree of severity of the disease, and particularly the occurrence and magnitude of weight loss, which is frequently observed during the course of the disease. The relative energy expenditure was not significantly different between untreated and treated parkinsonian patients (18.8 +/- 3 p. 100 and 24.5 +/- 6.2 p. 100 respectively). Further investigations were designed to determine whether the increased energy expenditure could reflect a functional impairment of the automatic nervous system. The integrity of the vagus nerve was tested by plotting vs time the plasma Pancreatic Polypeptide levels in response to insulin-induced hypoglycaemia. A physiological stimulation was obtained in the 8 parkinsonian patients studied. This is not the case in chronic autonomic failure. On the contrary, the relative energy expenditure was significantly decreased in the 6 patients that were given a beta-blocking drug, pindolol, 15 mg daily for 3 weeks (+30.7 +/- 4.3 p. 100 before and +21 +/- 4.2 p. 100 after treatment; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)