European journal of applied physiology
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Eur. J. Appl. Physiol. · Sep 2003
Clinical TrialThe effects of a single bout of downhill running and ensuing delayed onset of muscle soreness on running economy performed 48 h later.
Delayed onset of muscle soreness (DOMS) is a common response to exercise involving significant eccentric loading. Symptoms of DOMS vary widely and may include reduced force generating capacity, significant alterations in biochemical indices of muscle and connective tissue health, alteration of neuromuscular function, and changes in mechanical performance. The purpose of the investigation was to examine the effects of downhill running and ensuing DOMS on running economy and stride mechanics. ⋯ The change in VO(2) was inversely correlated with the change in stride length ( r= -0.535). Lactate was significantly elevated at RE2 for each run intensity, with a mean increase of 0.61 mmol l(-1). Based on these findings, it is suggested that muscle damage led to changes in stride mechanics and a greater reliance on anaerobic methods of energy production, contributing to the change in running economy during DOMS.
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Eur. J. Appl. Physiol. · Sep 2003
Clinical TrialBeat-to-beat noninvasive stroke volume from arterial pressure and Doppler ultrasound.
The proper understanding of the cardiovascular mechanisms involved in complaints of short-lasting dizziness and the evaluation of unexplained recurrent syncope requires continuous monitoring of cardiac stroke volume (SV) in addition to blood pressure and heart rate. The primary aim of the present study was to evaluate a pulse wave analysis method that calculates beat-to-beat flow from non-invasive arterial pressure by simulating a non-linear, time-varying model of human aortic input impedance (Modelflow; MF), by comparing MF stroke volume (SV(MF)) to Doppler ultrasound (US) flow velocity SV (SV(US)). A second purpose was to compare the two methods under two different conditions: the supine and head-up tilt (30 degrees ) position. ⋯ Beat-to-beat changes in SV in the supine resting condition were equally well assessed by both methods. Systematic differences appear during HUT30 and show opposite signs. The difference between the two methods upon a change in body position may be attributed to limitations in each method.
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Eur. J. Appl. Physiol. · Aug 2003
Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men.
Hormonal and neuromuscular adaptations to strength training were studied in eight male strength athletes (SA) and eight non-strength athletes (NA). The experimental design comprised a 21-week strength-training period. Basal hormonal concentrations of serum total testosterone (T), free testosterone (FT) and cortisol (C) and maximal isometric strength, right leg 1 repetition maximum (RM) of the leg extensors were measured at weeks 0, 7, 14 and 21. ⋯ Basal T concentrations (mean of 0, 7, 14 and 21 weeks) and changes in isometric force after the 21-week period correlated with each other (r=0.84, P<0.01) in SA. The individual changes in the acute T responses between weeks 0 and 21 and the changes in muscle CSA during the 21-week training correlated with each other (r=0.76, P<0.05) in NA. The correlations between T and the changes in isometric strength and in muscle CSA suggest that both serum basal testosterone concentrations and training-induced changes in acute testosterone responses may be important factors for strength development and muscle hypertrophy.
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Eur. J. Appl. Physiol. · Feb 2003
Clinical Trial Controlled Clinical TrialLong-term exposure to intermittent hypoxia results in increased hemoglobin mass, reduced plasma volume, and elevated erythropoietin plasma levels in man.
While it is well established that highlanders have optimized their oxygen transport system, little is known about the acclimatization of those who move between different altitudes. The purpose of this study was to establish whether the acclimatization to long-term intermittent hypoxic exposure in members of the Chilean Army who frequently move from sea level to 3,550 m altitude is correlated with acute acclimatization or chronic adaptation to hypoxia. A group of officers was exposed intermittently to hypoxia for about 22 years (OI, officers at intermittent hypoxia) and a group of soldiers for 6 months (SI, soldiers at intermittent hypoxia). ⋯ Moreover, intermittent hypoxic exposure of OI and SI resulted in increased plasma erythropoietin (Epo) levels, which peaked on day 2 at high altitude followed by decreasing levels during the successive days, and reaching pre-altitude values in SI even when staying at altitude. In conclusion, with regard to tHb and RCV, the acclimatization to long-term intermittent hypoxia resembles the adaptation to chronic hypoxia, while PV and BV regulation mimicked acclimatization to acute hypoxia. Remarkably, finely controlled regulation of Epo expression still occurs after up to 22 years of weekly exposure to altitude.