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  • Exercise metabolism  (2)
  • Alveolar-arterialPO2 difference  (1)
  • Blood lactate  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Fluid replacement drinks during high intensity exercise effects on minimizing exercise-induced disturbances in homeostasis (1990)
    Springer
    European journal of applied physiology 60 (1990), S. 54-60 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Electrolytes ; Fluid balance ; Glucose ; Exercise metabolism ; Blood pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The purpose of these experiments was to examine the influence of various fluid replacement drinks on exercise-induced disturbances in homeostasis during heavy exercise. Nine trained cyclists performed constant load exercise on a cycle ergometer to fatigue on three occasions with 1-week separating experiments. The work rate was set initially at ∼ 85% of $$\dot V_{o_{2{\text{ }}max} } $$ (range 82–88%) with fatigue being defined as a 10% decline in power output below the initial value. During each experiment subjects consumed one of the following three beverages prior to and every 15 min during exercise: (1) non-electrolyte placebo (NEP; 31 mosmol · kg−1); (2) glucose polymer drink containing electrolytes (GP; 7% CHO, 231 mosmol · kg−1), and (3) electrolyte placebo drink without carbohydrate (EP; 48 mosmol · kg−1). Both the GP and EP beverage contained sodium citrate/citric acid (C) as a flavoring agent while C was not contained in the NEP drink. Although seven of nine subjects worked longer during the GP and EP treatment when compared with the NEP trial, the difference was not significant (P〉0.05). No differences (P〉0.05) existed between the GP and EP treatments in performance time. Exercise changes in rectal temperature, heart rate, Δ % plasma volume and plasma concentrations of total protein, free fatty acids, glucose, lactate, potassium, chloride, calcium, and sodium did not differ (P〉0.05) between trials. In contrast, blood hydrogen ion concentration [H+] was significantly lower (P〈0.05) at 30 min of exercise during the GP and EP treatment when compared with the NEP run. These data provide evidence that electrolyte drinks do not minimize exercise-induced disturbances in blood-electrolyte concentrations during heavy execrcise when compared with nonelectrolyte drinks; however, these results suggest that fluid replacement beverages containing buffers (i.e. C) and/or electrolytes may minimize blood alterations in [H+] during intense exercise. Additional research is required to determine if the buffering influence of these beverages has an ergogenic benefit during heavy exercise.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00572186
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  • 2
    Digitale Medien
    Digitale Medien
    Exercise-induced hypoxemia in athletes: Role of inadequate hyperventilation (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 37-42 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Alveolar-arterialPO2 difference ; Pulmonary gas exchange ; VO2max ; Hypoxia ; Hyperoxia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary These experiments examined the exercise-induced changes in pulmonary gas exchange in elite endurance athletes and tested the hypothesis that an inadequate hyperventilatory response might explain the large intersubject variability in arterial partial pressure of oxygen (P a02) during heavy exercise in this population. Twelve highly trained endurance cyclists [maximum oxygen consumption (VO2max) range = 65-77 ml·kg−1·min−1] performed a normoxic graded exercise test on a cycle ergometer toVO2max at sea level. During incremental exercise atVO2max 5 of the 12 subjects had ideal alveolar to arterial P02 gradients (P A-aO2) of above 5 kPa (range 5-5.7) and a decline from restingP aO2 (ΔP aO2) 2.4 kPa or above (range 2.4-2.7). In contrast, 4 subjects had a maximal exercise (P A-aO2) of 4.0-4.3 kPa with ΔP aO2 of 0.4-1.3 kPa while the remaining 3 subjects hadP A-aO2 of 4.3-5 kPa with ΔP aO2 between 1.7 and 2.0 kPa. The correlation between PAO2 andP aO2 atVO2max was 0.17. Further, the correlation between the ratio of ventilation to oxygen consumption VSP aO2 and arterial partial pressure of carbon dioxide VSP aO2 atVO2max was 0.17 and 0.34, respectively. These experiments demonstrate that heavy exercise results in significantly compromised pulmonary gas exchange in approximately 40% of the elite endurance athletes studied. These data do not support the hypothesis that the principal mechanism to explain this gas exchange failure is an inadequate hyperventilatory response.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01466272
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  • 3
    Digitale Medien
    Digitale Medien
    Oxygen uptake kinetics in trained athletes differing in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (1985)
    Springer
    European journal of applied physiology 54 (1985), S. 306-308 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Oxygen uptake kinetics ; $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ; Exercise metabolism ; Trained athletes ; Gas exchange
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Previous work has shown that when $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics are compared for endurance trained athletes and untrained subjects, the highly trained athletes have a faster response time. However, it remains to be determined whether the more rapid adjustment of $$\dot V_{{\text{O}}_{\text{2}} }$$ toward steady state in athletes is due to $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ differences or training adaptation alone. One approach to this problem is to study the time course of $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics at the onset of work in athletes who differ in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ but have similar training habits. Therefore, the purpose of these experiments was to compare the time course of $$\dot V_{{\text{O}}_{\text{2}} }$$ kinetics at the onset of exercise in athletes with similar training routines but who differ in $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . Ten subjects ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ range 50–70 ml · kg−1 · min−1) performed 6-minutes of cycle ergometer exercise at ∼50% $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ . Ventilation and gas exchange were monitored by open circuit techniques. The data were modeled with a single component exponential function incorporating a time delay, (T D ); $$\Delta \dot V_{{\text{O}}_{{\text{2}}f} } = \Delta \dot V_{{\text{O}}_{2ss} } {\text{ (1}} - e^{ - t - T_D /_{\tau )} }$$ , where Τ is the time constant $$\Delta \dot V_{{\text{O}}_{{\text{2}}f} }$$ is the increase in $$\dot V_{{\text{O}}_{\text{2}} }$$ at time t and $$\Delta \dot V_{{\text{O}}_{{\text{2ss}}} }$$ is the steady-rate increment above resting $$\dot V_{{\text{O}}_{\text{2}} }$$ . Kinetic analysis revealed a range of $$\dot V_{{\text{O}}_{\text{2}} }$$ half times from 21.6 to 36.0 s across subjects with a correlation coefficient of r=−0.80 (p〈0.05) between $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ and $$\dot V_{{\text{O}}_{\text{2}} }$$ half time. These data suggest that in highly trained indicivuals with similar training habits, those with a higher $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ achieve a more rapid $$\dot V_{{\text{O}}_{\text{2}} }$$ adjustment at the onset of work.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00426150
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  • 4
    Digitale Medien
    Digitale Medien
    Precision of ventilatory and gas exchange alterations as a predictor of the anaerobic threshold (1984)
    Springer
    European journal of applied physiology 52 (1984), S. 173-177 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Anaerobic threshold ; Ventilatory threshold ; Exercise ventilation ; Gas exchange ; Blood lactate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Anaerobic threshold has been defined as the oxygen uptake ( $$\dot V_{{\text{O}}_{\text{2}} }$$ ) at which blood lactate (La) begins to rise systematically during graded exercise (Davis et al. 1982). It has become common practice in the literature to estimate the anaerobic threshold by using ventilatory and/or gas exchange alterations. However, confusion exists as to the validity of this practice. The purpose of this study was to examine the precision with which ventilatory and gas exchange techniques for determining anaerobic threshold predicted the anaerobic threshold resolved by La criteria. The anaerobic threshold was chosen using three criteria: (1) systematic increase in blood La (ATLa), (2) systematic increase in ventilatory equivalent for O2 with no change in the ventilatory equivalent for CO2 ( $${\text{AT}}_{\dot V_{\text{E}} } /\dot V_{{\text{O}}_{\text{2}} }$$ ), and (3) non-linear increase in expired ventilation graphed as a function of $$\dot V_{{\text{O}}_{\text{2}} }$$ ( $${\text{AT}}_{\dot V_{\text{E}} }$$ ). Thirteen trained male subjects performed an incremental cycle ergometer test to exhaustion in which the load was increased by 30 W every 3 minutes. Ventilation, gas exchange measures, and blood samples for La analysis were obtained every 3rd min throughout the test. In five of the thirteen subjects tested the anaerobic threshold determined by ventilatory and gas exchange alterations did not occur at the same $$\dot V_{{\text{O}}_{\text{2}} }$$ as the ATLa. The highest correlation between a gas exchange anaerobic threshold and ATLa was found for $${\text{AT}}_{\dot V_{\text{E}} } /\dot V_{{\text{O}}_{\text{2}} }$$ and was r=0.63 (P〈0.05). These data provide evidence that the ATLa and $${\text{AT}}_{\dot V_{\text{E}} }$$ do not always occur simultaneously and suggest limitations in using ventilatory or gas exchange measures to estimate the ATla.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00433388
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