Exercise-induced increases in NT-proBNP are not related to the exercise-induced immune response.

OBJECTIVE: To investigate if the exercise-induced immune response contributes to the exercise-induced increase in brain natriuretic peptide (BNP) in healthy athletes. This has previously been speculated, as elevated concentrations of BNP or N-terminal pro brain natriuretic peptide (NT-proBNP) in cardiovascular patients were found to be related to immune reactions and elevations in inflammatory cytokines such as interleukin 6 (IL-6). METHODS: Stored serum samples were analysed for NT-proBNP concentrations of 14 healthy endurance athletes (mean age: 25 (SD 5) years; VO(2peak) 67 (SD 6) ml/min/kg), who had been examined previously for exercise-induced immune reactions and their dependence on carbohydrate supplementation (6 or 12% carbohydrate vs placebo beverages) after three bouts of 4 h cycling at a given workload of 70% of the individual anaerobic threshold. Venous blood samples were taken before, immediately after, and 1 h and 1 day after exercise. Leucocyte subpopulations were determined immediately after blood sampling by flow cytometry. Serum samples for posterior analysis of C-reactive protein (CRP), IL-6, cortisol and NT-proBNP were stored at -80 degrees C. RESULTS: The exercise-induced increases in NT-proBNP (p<0.001) were not related to the exercise-induced immune response, although exercise induced marked (CHOS-dependent) increases in IL-6, CRP, cortisol, leucocytes, neutrophils, monocytes and natural killer cells. CONCLUSION: It is unlikely that the exercise-induced increases in NT-proBNP or BNP in healthy athletes are caused by the exercise-induced immune response. Therefore, exercise-induced increases in NT-proBNP or BNP in healthy athletes have to be differentiated from increases in cardiovascular patients with systemic inflammation.

Effectiveness of low-intensity endurance training.

Recent studies point to the preventive efficacy of low-intensity endurance training in terms of cardiovascular risk factor modification and mortality reduction. In addition, it is frequently recommended as a means of stimulating fat metabolism. It was the intention of this study to clarify if endurance training effectiveness remains unimpaired when exercise intensity is reduced by a certain amount from "moderate" to "low", but total energy expenditure held constant. For this purpose, 39 healthy untrained subjects (44 +/- 7 yrs, 82 +/- 19 kg; 173 +/- 9 cm) were stratified for endurance capacity and sex and randomly assigned to 3 groups: "moderate intensity" (MOD, n = 13, 5 sessions per week, 30 min each, intensity 90 % of the anaerobic threshold [baseline lactate + 1.5 mmol/l]), "low intensity" (LOW, n = 13, 5 sessions per week, intensity 15 bpm below MOD, duration proportionally longer to arrive at the same total energy output as MOD), and control (CO, n = 13, no training). Training was conducted over 12 weeks and each session monitored by means of portable heart rate (HR) recorders. Identical treadmill protocols prior to and after the training program served for exercise prescription and documentation of endurance effects. VO (2max) improved similarly in both training groups (MOD + 1.5 ml x min (-1) x kg (-1); LOW + 1.7 ml x min (-1) x kg (-1); p = 0.97 between groups). Compared with CO (- 1.0 ml x min (-1) x kg (-1)) this effect was significant for LOW (p < 0.01) whereas there was only a tendency for MOD (p = 0.07). However, objective criteria (HR (max), maximal blood lactate) indicated that a different degree of effort was responsible for this finding. In comparison with CO (mean decrease of 3 bpm), average HR during incremental exercise decreased significantly by 9 bpm (MOD, p < 0.05 vs. CO) and 6 bpm (LOW, p = 0.26), respectively. However, there was no significant difference between MOD and LOW (p = 0.60), but for changes in oxygen uptake at the anaerobic threshold (VO (2AT)) it was observed that MOD was significantly more effective than CO (p = 0.048) and LOW (p = 0.04). It is concluded that within a middle-aged population of healthy untrained subjects, endurance training effectiveness might be slightly impaired when the training heart rate is chosen 15 bpm lower as compared to moderate intensity, but the total energy output held equal.

Metabolic profile of 4 h cycling in the field with varying amounts of carbohydrate supply.

Several laboratory studies have demonstrated a performance-enhancing effect of carbohydrate (CHO) supplementations during endurance sessions of long duration. However, the transferability of these results to real training and competition circumstances has not been conclusively shown. Therefore, we tried to test the influence of graded CHO substitution on substrate utilization and selected physiological parameters under standardized but practically orientated field conditions. Fourteen endurance-trained male subjects [mean (SD): 25 (5) years, 72 (9) kg, .VO(2max) 67 (6) ml.min(-1).kg(-1), individual anaerobic threshold (IAT) 269 (30) W] after a stepwise increasing pre-test had to perform three 4-h endurance rides on their own bicycles with simultaneous spiroergometry: constant workload 70% IAT (monitoring by SRM-System). Before and during exercise, solutions without (0%), with 6% or 12% CHO were administered double-blindly and in randomized order (total volume: 50 ml.kg(-1)). After cessation of exercise, significant differences between 0% and both CHO concentrations were detected for blood glucose (GLU; 75 mg dl(-1) for 0% vs 101 mg dl(-1) for 6% vs 115 mg dl(-1) for 12%; P<0.001) and respiratory exchange ratio (0.84 vs 0.88 vs 0.90; P<0.01; correlation to GLU: r=0.46, P<0.05). Free fatty acids (0.19 vs 0.16 vs 0.10 mmol l(-1)) and glycerol (0.41 vs 0.22 vs 0.12 mmol l(-1)) were significantly different between the endurance trials in a dose-dependent manner (both P<0.001). Lactate concentration ( P=0.42) and heart rate ( P=0.12) had no significant influence from CHO substitution. We conclude that CHO substitution during 4-h endurance training inhibits lipolysis in a dose-dependent manner and enhances aerobic glycolysis. This proves that earlier laboratory findings can be replicated under field conditions using modern portable equipment.

Mobilization and oxidative burst of neutrophils are influenced by carbohydrate supplementation during prolonged cycling in humans.

Prolonged, strenuous exercise may lead to suppressive effects on the immune system, which might be responsible for a greater susceptibility to opportunistic infections. The aim of this study was to examine the influence of carbohydrate substitution (CHS) during prolonged, strenuous exercise on neutrophil granulocytes and their oxidative burst (intracellular oxidation of dihydrorhodamine(123) to rhodamine(123) after induction by formylized 1-methionyl-1-leucyl-1-phenylalanin) using flow cytometry. In three trials different concentrations of CHS (placebo compared to 6% and 12% CHS; 50 ml.kg(-1)) were given randomly to 14 endurance trained cyclists [mean (SD) age 25 (5) years, maximal oxygen uptake 67 (6) ml.min(-1).kg(-1)] cycling for 4 h in a steady state at 70% of their individual anaerobic threshold. Blood samples were taken before, immediately after cessation, 1 h and 19 h after exercise. A significant rise in neutrophil counts was observed immediately after cessation and 1 h after exercise with a return to normal rest values 19 h after exercise for all three conditions ( P<0.001). The relative proportions of rhodamine(123)+ neutrophils were significantly diminished in all three conditions 1 h after exercise ( P<0.01), while the mean fluorescence intensity was lowest in the placebo trial and differed significantly to the 12% CHS trial ( P=0.024) and almost significantly to the 6% CHS trial ( P=0.052). In conclusion, these data suggest a beneficial effect of CHS on the neutrophil oxidative burst and a possible attenuation of the susceptibility to infections, presumably due to the reduction of metabolic stress in prolonged, strenuous exercise.