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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 55 (1986), S. 405-409 
    ISSN: 1439-6327
    Keywords: Cortisol ; Iron ; Maximal oxygen consumption ; Performance ; Endurance exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary As very few of the competitors in a triathlon are truly specialist in more than one of the three disciplines, high levels of physical (and mental) stress may result during the course of the event. We investigated some of the physiological responses occurring in runners participating in an “Iron Man” triathlon consisting of canoeing (20 km), cycling (90 km) and running (42 km), in that sequence. Twenty-one male entrants volunteered as subjects for the study. Prior to the competition, maximal oxygen consumption ( $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ ) was determined. Basal venous blood samples were collected on the day prior to the competition and post-exercise venous blood samples were collected within 5 minutes of completion of the race. Serum iron was significantly reduced from a mean basal value of 20.6 Μmol · l−1 to a mean value of 8.4 Μmol · l−1 after the race. Cortisol levels showed a 3 fold increase after the race. Gross $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (l · min−1) and mass standardised $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (ml · min−1 · kg−1) were both negatively correlated to cortisol levels after the race (p〈0.05). Total performance time was not related to gross $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (l · min−1) but was well correlated to mass corrected $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (ml · min−1 · kg−1). The marked fall in serum iron may have been related to heavy sweating or prelatent iron deficiency. Chronic iron deficiency (without frank anaemia) can impair physical performance, although we were unable to show any significant correlation between serum iron level after the race and time taken to complete the event. The subjects with a lower $$\dot V_{{\text{O}}_{{\text{2max}}} }$$ (ml · min−1 · kg−1) had a higher cortisol concentration. In spite of a longer performance time, these subjects were apparently still exposed to greater physiological strain.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 54 (1985), S. 436-441 
    ISSN: 1439-6327
    Keywords: Swimming ; Biochemical changes ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We set out to demonstrate whether changes in plasma volume, haematocrit and some important blood constituents occurred after swimming 100 m and 800 m, as well as monitoring the duration of these changes. We measured exercise-induced changes in concentration of plasma constituents in eight subjects, and determined the expected effects of haemoconcentration on these constituents. We also investigated the different biochemical responses occurring after maximal exercise (100 m), as compared to submaximal exercise (800 m). The haematocrit increased significantly after the 100 m swim and to a lesser extent after the 800-m swim, returning to basal levels within 30 min. The plasma volume decreased by 16% on completion of the 100 m and by 8% on completion of the 800 m. The blood lactate concentration increased 15-fold and 10-fold after the 100-m and 800-m swims respectively. The plasma potassium concentration increased significantly immediately on completion of the 100-m swim, then decreased significantly at 2 1/2 and 5 min post-exercise, returning to near-basal values at 30 min. The potassium concentration measured after the 800-m event did not differ significantly from basal levels, however the measured concentrations were significantly lower than the concentrations expected on the basis of haemoconcentration. The plasma sodium concentrations measured after both 100-m and 800-m swims were significantly increased. However, calculations correcting for haemoconcentration showed significant losses in toal circulating sodium. Our study demonstrates marked changes in plasma volume and certain blood constituents after maximal intensity swimming, and less marked changes after submaximal exercise. We also demonstrated the importance of taking the effects of haemoconcentration into account when evaluating changes in concentration of plasma constituents.
    Type of Medium: Electronic Resource
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