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  • 1
    Electronic Resource
    Electronic Resource
    Effects of β-adrenergic blockade on training-induced structural adaptations in rat left ventricle (1988)
    Springer
    European journal of applied physiology 57 (1988), S. 671-676 
    Details
    ISSN: 1439-6327
    Keywords: Rat ; Left ventricle ; Training ; Metoprolol ; Propranolol ; Capillary density ; Myocyte ; Atrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The study was designed to evaluate the effects of eight weeks of exercise training or training-β-adrenergic blockade combination on gross and microscopic alterations of rat cardiac muscle and microvascular bed. Rats were randomly assigned to either sedentary control (C), trained (T), metoprolol-trained (MT), or propranolol-trained (pT) groups. The training protocol involved treadmill running for 8 weeks at 0.5 m s−1, 20% grade. Earlier experiments by us showed this training protocol to be effective in producing significant changes in selected skeletal muscle enzyme activities in all trained groups. In the current study an absolute reduction in left ventricular (LV) weight was observed in the PT compared to the C group (0.91±0.02 vs. 1.04±0.04 g,P〈0.05). LV weight in the T and MT groups was no different from C so that LV to BW ratio (mg·g−1) was significantly increased (P〈0.05) due to a similar reduction in body weight (BW) in all three training groups. Morphometric analysis of LV myocardium revealed no significant differences in myocyte mean cross-sectional area (μm2) in any of the groups (289±16-C, 332±20-T, 281±44-MT, and 273±12-PT). Capillary density independently calculated by light and electron microscopy was unchanged by training or trainings-blockade combination. It was concluded that training of sufficient intensity and duration to produce skeletal muscle enzyme adaptations does not necessarily produce myocyte hypertrophy or alter LV capillarity. Additionally functioningβ-adrenergic receptors appear to play a role in both the central and peripheral adaptations to endurance exercise training.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01075987
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of pedaling frequency on glycogen depletion rates in type I and type II quadriceps muscle fibers during submaximal cycling exercise (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 360-364 
    Details
    ISSN: 1439-6327
    Keywords: Fiber type ; Muscle glycogen ; Cycling ; Pedaling frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study was conducted to determine whether the pedaling frequency of cycling at a constant metabolic cost contributes to the pattern of fiber-type glycogen depletion. On 2 separate days, eight men cycled for 30 min at approximately 85% of individual aerobic capacity at pedaling frequencies of either 50 or 100 rev·min−1. Muscle biopsy samples (vastus lateralis) were taken immediately prior to and after exercise. Individual fibers were classified as type I (slow twitch), or type II (fast twitch), using a myosin adenosine triphosphatase stain, and their glycogen content immediately prior to and after exercise quantified via microphotometry of periodic acid-Schiff stain. The 30-min exercise bout resulted in a 46% decrease in the mean optical density (D) of type I fibers during the 50 rev·min−1 condition [0.52 (0.07) to 0.28 (0.04)D units; mean (SEM)] which was not different (P〉0.05) from the 35% decrease during the 100 rev · min−1 condition [0.48 (0.04) to 0.31 (0.05)D units]. In contrast, the meanD in type II fibers decreased 49% during the 50 rev·min−1 condition [0.53 (0.06) to 0.27 (0.04) units]. This decrease was greater (P〈0.05) than the 33% decrease observed in the 100 rev·min −1 condition [0.48 (0.04) to 0.32 (0.06) units). In conclusion, cycling at the same metabolic cost at 50 rather than 100 rev·min−1 results in greater type II fiber glycogen depletion. This is attributed to the increased muscle force required to meet the higher resistance per cycle at the lower pedal frequency. These data are consistent with the view that force development as opposed to velocity of contraction determines the degree of type II fiber recruitment when the metabolic cost of exercise is held constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00868141
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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