European journal of applied physiology
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Eur. J. Appl. Physiol. · Jun 2011
Randomized Controlled TrialHyperoxia-induced alterations in cardiovascular function and autonomic control during return to normoxic breathing.
Hyperoxia causes hemodynamic alterations. We hypothesized that cardiovascular and autonomic control changes last beyond the end of hyperoxic period into normoxia. Ten healthy volunteers were randomized to breathe either medical air or 100% oxygen for 45 min in a double-blind study design. ⋯ After the end of hyperoxic exposure, the shift of the power spectral distribution of heart rate variability toward a pattern of increased cardiac sympathetic activity lasted for 30 min (p < 0.05), reflecting a resuming of baseline autonomic balance. Cardiac output and stroke volume were significantly decreased during hyperoxia and returned to baseline values (10 min) later than heart rate. In conclusion, hyperoxia effects continue during return to normoxic breathing, but cardiac and vascular parameters followed different time courses of recovery.
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Eur. J. Appl. Physiol. · Apr 2011
Clinical TrialPerformance and physiological responses to repeated-sprint exercise: a novel multiple-set approach.
We investigated the acute and chronic responses to multiple sets of repeated-sprint exercise (RSE), focusing on changes in acceleration, intermittent running capacity and physiological responses. Ten healthy young adults (7 males, 3 females) performed an incremental test, a Yo-Yo intermittent recovery test level1 (Yo-Yo IR1), and one session of RSE. RSE comprised three sets of 5 × 4-s maximal sprints on a non-motorised treadmill, with 20 s of passive recovery between repetitions and 4.5 min of passive recovery between sets. ⋯ Repeated-sprint training, comprising only 10 min of exercise overall, effectively improved performance during multiple-set RSE. This exercise model better reflects team-sport activities than single-set RSE. The rapid training-induced improvement in acceleration, quantified here for the first time, has wide applications for professional and recreational sport activities.
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Eur. J. Appl. Physiol. · Apr 2011
Clinical TrialUltrasound lung "comets" increase after breath-hold diving.
The purpose of the study was to analyze the ultrasound lung comets (ULCs) variation, which are a sign of extra-vascular lung water. Forty-two healthy individuals performed breath-hold diving in different conditions: dynamic surface apnea; deep variable-weight apnea and shallow, face immersed without effort (static maximal and non-maximal). The number of ULCs was evaluated by means of an ultrasound scan of the chest, before and after breath-hold diving sessions. ⋯ Second, the blood pooling effect found during the diving response Redistributes blood to the pulmonary vascular bed. Third, it is possible that the intense involuntary diaphragmatic contractions occurring during the "struggle phase" of the breath-hold can also produce a blood shift from the pulmonary capillaries to the pulmonary alveoli. A combination of these factors may explain the observed increase in ULC scores in deep, shallow maximal and shallow dynamic apneas, whereas shallow non-maximal apneas seem to be not "ULC provoking".
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Eur. J. Appl. Physiol. · Mar 2011
Clinical TrialSyncope is unrelated to supine and postural hypotension following prolonged exercise.
Syncope is widely reported following prolonged exercise. It is often assumed that the magnitude of exercise-induced hypotension (post-exercise hypotension; PEH), and the hypotensive response to postural change (initial orthostatic hypotension; IOH) are predictors of syncope post-exercise. The aim of this study was to determine the relationship between PEH, IOH, the residual IOH and syncope following prolonged exercise. ⋯ Although the magnitude of IOH was similar to post-exercise [-28 ± 12 vs. -20 ± 14% (pre-exercise); P > 0.05], the BP recovery following IOH was incomplete [-9 ± 9 vs. -1 ± 11 (pre-exercise); P < 0.05]; however, neither showed a relation to HUT-time completed (r(2) = 0.18, r (2) = 0.01; P > 0.05, respectively). Although an inability to maintain BP is a common feature of syncope post-exercise, the magnitude of PEH, IOH and residual IOH do not predict time to syncope. Practically, endurance athletes who present with greater hypotension are not necessarily at a greater risk of syncope than those who present with lesser reductions in BP.
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Eur. J. Appl. Physiol. · Feb 2011
Randomized Controlled TrialEffect of endurance training on performance and muscle reoxygenation rate during repeated-sprint running.
The aim of the present study was to examine the effect of an 8-week endurance training program on repeated-sprint (RS) performance and post-sprints muscle reoxygenation rate in 18 moderately trained males (34 ± 5 years). Maximal aerobic speed (MAS), 10 km running and RS (2 × 15-s shuttle-sprints, interspersed with 15 s of passive recovery) performance were assessed before and after the training intervention. Total distance covered (TD) and the percentage of distance decrement (%Dec) were calculated for RS. ⋯ The improvement of Reoxy rate was largely correlated with improvements in MAS [r = 0.63 (90% CL, 0.31;-0.82)] and %Dec [r = -0.52 (-0.15;-0.76)]. Present findings confirm the beneficial effect of endurance training on post-sprint muscle reoxygenation rate, which is likely to participate in the improvement of repeated-sprint ability after training. These data also confirm the importance of aerobic conditioning in sports, where repeating high-intensity/maximal efforts within a short time-period are required.