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  • 1
    ISSN: 1439-6327
    Keywords: Key words Energy cost of running ; Fatigue ; Carbohydrate feeding ; Triathlon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to examine whether the increase in the energy cost of running (Cr), previously reported to occur at the end of a prolonged run, could be influenced by the ingestion of either an artificially sweetened placebo (Pl) or a 5.5% carbohydrate (CHO) solution. Ten well-trained triathletes completed three testing sessions within a 3-week period. The aim of the first session was to determine maximal oxygen uptake (V˙O2 max) and the velocity associated with ventilatory threshold (νVT). The second and the third sessions were composed of two submaximal treadmill runs (20 min long, 0% grade, performed at νVT), before and after an 80-min overground run, also conducted at νVT. During these submaximal tests, the subjects ingested (in a random order) either a Pl or CHO solution prior to the first submaximal run and every 20 min after that. During the first session, ventilatory threshold (VT) occurred at [mean (SD)] 81.2 (2.5)% V˙O2 max and 16.5 (0.6) km · h−1. A significant effect of exercise duration was found on Cr (ΔCr) at the end of the run, whatever the solution ingested (ΔCr= 5.7% and 7.01% for CHO and Pl, respectively). A reduction in the respiratory exchange ratio (from 0.98 to 0.90) was observed only at the end of the Pl trial. In this study, Cr seems to be affected only to a minor extent by substrate turnover. Moreover, the increase in the demand for oxygen, estimated from the increase in ventilation, accounted for only a minor proportion of the increase in Cr (11% and 17% for CHO and Pl, respectively). No correlation was found between the changes in Cr and the changes in the other physiological parameters recorded. These results suggest, indirectly, that Cr increases during a 2-h run at 80% V˙O2 max in well-trained subjects can be explained mainly by alterations in neuromuscular performance, which lead to a decrease in muscle efficiency.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1439-6327
    Keywords: Triathlon ; Oxygen uptake ; ventilation ; Biochemical variables ; Plasma volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the present study was to verify the increase in energy cost of running at the end of a triathlon. A group 11 trained male subjects performed a triathlon (15-km swimming, 40-km cycling, 10-km running). At least 1 week later the subjects ran 10-km as a control at the same pace as the triathlon. Oxygen uptake ( $$\dot V$$ O2), ventilation ( $$\dot V$$ E) and heart rate (HR) were measured during both 10-km runs with a portable telemetry system. Blood samples were taken prior to the start of the triathlon and control run, after swimming, cycling, triathlon run and control run. Compared to the control values the results demonstrated that triathlon running elicited a significantly higher (P 〈 0.005) mean $$\dot V$$ O2 [51.2 (SEM 0.4) vs 47.8 (SEM 0.4) ml·min−1·kg−] $$\dot V$$ E [86 (SEM 4.2) vs 74 (SEM 5.3) l·min−1], and HR [162 (SEM 2) vs 156 (SEM 1.9) beats·min−1)]. The triathlon run induced a greater loss in body mass than the control run [2 (SEM 0.2) vs 0.6 (SEM 0.2) kg], and a greater decrease in plasma volume [14.4% (SEM 1.5) vs 6.7% (SEM 0.9)]. The lactate concentrations observed at the end of both 10-km runs did not differ [2.9 (SEM 0.2) vs 2.5 (SEM 0.2) m·mol·l−1]. Plasma free fatty acids concentrations were higher (P 〈 0.01) after the triathlon than after the control run [1.53 (SEM 0.2) to 0.51 (SEM 0.07) mmol·l−1]. Plasma creatine kinase concentrations rose under both conditions from 58 (SEM 12) to 112 (SEM 14) UI·l−1 after the triathlon, and from 61 (SEM 7) to 80 (SEM 6) UI·l−1 after the control run. This outdoor study of running economy at the end of an Olympic distance triathlon demonstrated a decrease in running efficiency.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1439-6327
    Keywords: Altitude ; Hypobaric chamber ; Physical training ; Aerobic metabolism ; Erythropoiesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of training in a hypobaric chamber on aerobic metabolism were studied in five high performance triathletes. During 3 weeks, the subjects modified their usual training schedule (approximately 30 h a week), replacing three sessions of bicycling exercise by three sessions on a cycle ergometer in a hypobaric chamber simulating an altitude of 4,000 m (462 mm Hg). Prior to and after training in the hypobaric chamber the triathletes performed maximal and submaximal exercise in normoxia and hypoxia (462 mm Hg). Respiratory and cardiac parameters were recorded during exercise. Lactacidaemia was measured during maximal exercise. Blood samples were drawn once a week to monitor blood cell parameters and erythropoetin concentrations. Training in the hypobaric chamber had no effect on erythropoiesis, the concentrations of erythropoetin always remaining unchanged, and no effect on the maximal oxygen uptake ( $$\dot V$$ O2max) and maximal aerobic capacity measured in normoxia or hypoxia. Submaximal performance increased by 34% during a submaximal exhausting exercise performed at a simulated altitude of 2,000 m. During a submaximal nonexhausting test, ventilation values tended to decrease for similar exercise intensities after training in hypoxia. The changes in these parameters and the improved performance found for submaximal exercise may have been the result of changes taking place in muscle tissue or the result of training the respiratory muscles.
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  • 4
    ISSN: 1439-6327
    Keywords: Key words Ergometry ; Human quadriceps ; Knee extensor exercise ; Muscle performance testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four incremental protocols of knee extension exercise of different stage durations were compared to study the effect of the protocol upon power output at the last stage (P peak). Previous studies of knee extension have found very different power outputs with similar ergometers and these large differences have been interpreted as being the result of the fatigue due to the durations of the protocols. The knee extension device used in previous studies was modified to avoid the action of the knee and hip flexors: the subjects pushing on a lever instead of pulling a rod. In the present study five subjects performed four incremental knee extension exercises which differed with regard to stage duration (60, 90, 180 or 360 s) on this ergometer. The P peak, peak oxygen uptake (V˙O2peak) and peak heart rate (HRpeak) were measured at the end of each of these four incremental protocols. In eight subjects, the reliability of the protocols with the two shortest increments (60 and 90-s stages) was verified by measuring P peak at 60 s and 90 s (P peak60, P peak90) twice. The knee ergometer proposed in the present paper was easy to use without any special training and should improve the measurement of P peak. The P peak60 [49.4 (SD 5.6) W] was higher than at 180 s [P peak180, 43.6 (SD 5.8) W, P 〈 0.05] and at 360 s [P peak360, 43.4 (SD 5.3) W, P 〈 0.05]. All the other differences in P peak, V˙O2 peak and HRpeak were not significant. All correlations between P peak60, P peak90, P peak180 and P peak360 were significant, except those between P peak360 and P peak90 or P peak180. The effect of the stage duration on power output and oxygen uptake at the end of the knee extension exercises was not great. Consequently, the large differences in power output and oxygen uptake observed in previous studies cannot be explained by the protocol only. The significant difference between P peak 60 and P peak90 was of the order of 10% in agreement with findings in the literature using cycle ergometry. The reliability of P peak60 and P peak90 was high and the use of these protocols can be recommended if further studies show that the measurement of P peak, is useful in the evaluation of local endurance.
    Type of Medium: Electronic Resource
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