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  • 1
    Electronic Resource
    Electronic Resource
    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
    Keywords: Oxygen uptake kinetics ; $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ; Exercise metabolism ; Trained athletes ; Gas exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426150
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Clenbuterol-induced fiber type transition in the soleus of adult rats (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 391-396 
    Details
    ISSN: 1439-6327
    Keywords: Key words β(2)-Adrenoceptor agonist ; Skeletal muscle ; Fiber type ; Myosin heavy chain isoforms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study examined the effects of 6 weeks of treatment with the β(2)-adrenoceptor agonist, clenbuterol, on the soleus muscle of adult female Sprague-Dawley rats. Animals (4 months old) were divided into two groups: clenbuterol treated (CL, n=7) (2 mg·kg–1 body mass injected subcutaneously every other day), and control (CON, n=7) (injected with isotonic saline). Post-treatment body weights were ≈5% greater in the CL group compared to CON (P〈0.05). Polyacrylamide gel electrophoresis (SDS-PAGE) of soleus myofibrillar protein indicated a clenbuterol-induced decrease (P〈0.05) in the relative percentage of type I myosin heavy chain (MHC) with a concomitant increase (P〈0.05) in type IIdx MHC, while the proportion of type IIa MHC was unaffected. ATPase fiber typing revealed increases (P〈0.05) in the proportion of type II fibers expressed both as a percentage of total fiber number and total cross-sectional area (CSA). Finally, mean type II fiber CSA was ≈25% greater (P〈0.05) in the CL groups as compared to the CON group. These data indicate that clenbuterol treatment results in alterations in the MHC phenotype and an increased proportion of type II fiber CSA in the soleus of adult rats. These observations were due to an increase in the total number of type II fibers, as well as hypertrophy of these fibers. Thus, the relative increase in the number of histochemically determined type II fibers and the emergence of the normally unexpressed type IIdx MHC isoform in the soleus suggest a clenbuterol-induced transition of muscle fiber phenotype as well as selective hypertrophy of the type II fibers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050091
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Clenbuterol-induced fiber type transition in the soleus of adult rats (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 391-396 
    Details
    ISSN: 1439-6327
    Keywords: β(2)-Adrenoceptor agonist ; Skeletal muscle ; Fiber type ; Myosin heavy chain isoforms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined the effects of 6 weeks of treatment with theβ (2)-adrenoceptor agonist, clenbuterol, on the soleus muscle of adult female Sprague-Dawley rats. Animals (4 months old) were divided into two groups: clenbuterol treated (CL,n=7) (2 mg kg−1 body mass injected subcutaneously every other day), and control (CON,n=7) (injected with isotonic saline). Post-treatment body weights were ≈ 5% greater in the CL group compared to CON (P〈0.05). Polyacrylamide gel electrophoresis (SDS-PAGE) of soleus myofibrillar protein indicated a clenbuterol-induced decrease (P〈0.05) in the relative percentage of type I myosin heavy chain (MHC) with a concomitant increase (P〈0.05) in type IIdx MHC, while the proportion of type IIa MHC was unaffected. ATPase fiber typing revealed increases (P〈0.05) in the proportion of type II fibers expressed both as a percentage of total fiber number and total cross-sectional area (CSA). Finally, mean type II fiber CSA was ≈25% greater (P〈0.05) in the CL groups as compared to the CON group. These data indicate that clenbuterol treatment results in alterations in the MHC phenotype and an increased proportion of type II fiber CSA in the soleus of adult rats. These observations were due to an increase in the total number of type II fibers, as well as hypertrophy of these fibers. Thus, the relative increase in the number of histochemically determined type II fibers and the emergence of the normally unexpressed type IIdx MHC isoform in the soleus suggest a clenbuterol-induced transition of muscle fiber phenotype as well as selective hypertrophy of the type 11 fibers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02337718
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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