J Bangsbo

..The latter finding may be explained by low glycogen levels in individual muscle fibers. Blood lactate is a poor indicator of muscle lactate during soccer match play...

..Instead, accumulation of potassium in muscle interstitium may be an important factor in the development of fatigue...

..Thus mechanical efficiency declines as intense exercise is continued. Furthermore, when intense exercise is repeated, there is a shift toward greater aerobic energy contribution, but the total ATP turnover is not significantly altered...

..The present findings demonstrate that increasing PDH(a) does not alter muscle O2 uptake and anaerobic ATP provision during the initial phase of intense dynamic knee-extensor exercise in humans...

..The limited oxygen utilization in the initial phase of intense exercise is not caused by insufficient oxygen availability...

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..The Yo-Yo IR tests provide a simple and valid way to obtain important information of an individual's capacity to perform repeated intense exercise and to examine changes in performance...

..These differences should be taken into account when planning the training and nutritional strategies of top-class players, who require a significant energy intake during a week...

..Am J Physiol 282:R273-R280, 2002), the present data suggest that muscle TCAI accumulate during the initial seconds of exercise; however, this increase is not essential for the contraction-induced increase in mitochondrial respiration...

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..2) vs. 527.1 mmol/kg (SD 117.6); C and HT, respectively]. In conclusion, within the range of temperatures studied, passively increasing muscle temperature before exercise has no effect on muscle energy turnover during dynamic exercise...

..Moreover, when an exhaustive exercise bout is repeated with lowered glycogen levels, the level of oxidative stress is not different than that of the first bout...

..The present study demonstrates that when intense exercise is repeated muscle heat production is not changed, but muscle aerobic energy turnover is elevated and anaerobic energy production is reduced during the first minutes of exercise...

..In conclusion, regular recreational football training has significant favorable effects on the cardiovascular risk profile in untrained premenopausal women and is at the least as efficient as continuous running...

..Increased mVO2 probably makes a small contribution to during the first 15-20 s of exercise...

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..Thus the ethanol outflow-to-inflow ratio does not represent skeletal muscle BF but rather contraction-induced changes in molecular transport in the interstitium or over the microdialysis membrane...

..Furthermore, formation and release of purines occurs mainly after intense exercise and leads to a considerable loss of nucleotides...

..Thus, football can be used as an activity to elevate the physical capacity of untrained women...

..7 +/- 0.6 kg), whereas no change was observed for DAG. In conclusion, football training is an attractive non-pharmacological supplement to the treatment of mild-to-moderate arterial hypertension in untrained middle-aged men...

..Thus, small-sided football games appear to have the potential to create physiological adaptations and improve performance with regular training for a variety of study groups...

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..Some effects may have been reversed during isolation of the mitochondria and the changes in mitochondrial function in situ upon exhaustion may have been more extensive than observed...

..The present data support a potential role for interstitial K(+) in regulation of blood flow and development of fatigue...

..The magnitude of increase was similar for active exercise. The results demonstrate that a period of passive movement promotes endothelial cell proliferation and angiogenic factors and initiates capillarization in skeletal muscle...

..This might be due to systematic errors or to loose coupling of the mitochondrial respiration under intense exercise...

..In conclusion, athletes from disciplines involving periods of intense exercise can benefit from the inclusion of speed endurance sessions in their training programs...

..However, the fundamental questions of to what extent adenosine is formed in skeletal muscle tissue of humans, whether it is present in the interstitium, and where it exerts its vasodilatory effect remain unanswered...

..Thus, muscle glycogen availability and low muscle pH do not per se control but appear to affect the rate of glycogenolysis/glycolysis and fatigue development during a repeated high-intensity exercise lasting 1/2-2 min...

..Taken together, recreational football appears to effectively stimulate musculoskeletal, metabolic and cardiovascular adaptations of importance for health and thereby reduces the risk of developing life-style diseases...

..Thus, the data strongly suggest that NO is not essential for the regulation of blood flow or oxygen uptake in contracting human skeletal muscle...

..The results demonstrate that intense intermittent endurance training induces capillary growth and a transient proliferation of endothelial cells within 4 weeks, with a similar growth occurring around type I versus type II muscle fibres...

..Thigh OCC caused an altered recruitment of fibres and muscle portions, suggesting a significant afferent response affecting the activation of fibres in the contracting muscles...

..Furthermore, the reduction in muscle ATP observed after intense training does not appear to be limiting for high-intensity exercise performance...

..Moreover, football training induced consistent cardiac adaptations, which may have implications for long-term cardiovascular health...

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..The lack of effect of training on basal muscle VEGF protein levels and VEGF secretion during exercise suggests that increased VEGF levels are not a prerequisite for exercise-induced capillary growth in healthy muscle...

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..The present data indicate that testosterone is important for development of strength in young boys and that, independent of serum testosterone concentration, E players have developed greater muscle strength compared with NE players...

..05), and 40 +/- 14% (P = 0.06), respectively. It is concluded that translocation of subunits is an important mechanism involved in the short time upregulation of the Na(+)-K(+) pumps in association with human muscle activity...

..e., ?30 s. Muscle capillaries and the Na(+)-K(+) pump ?(1)-subunit seem to be important determinants for performance during exhaustive high-intensity exercises lasting between 30 s and 4 min...

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..6 min and amounted to 0.24 l min(-1). The present study demonstrates that additional type I and II fibres are recruited with time during intense sub-maximal exercise in temporal association with a significant slow component of VO2...

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..In conclusion, cellular adaptations to high-intensity exercise training may, in part, be induced by transcriptional regulation. After training, the transcriptional response to an exercise bout at a given workload is diminished...

..To examine the physiological response, reliability, and validity of the Yo-Yo intermittent recovery level 2 test (Yo-Yo IR2)...

..Additionally, the study suggests that fatigue during intense intermittent short-term exercise was unrelated to muscle CP, lactate, pH, and glycogen...

..The high [K+]i levels reached at exhaustion can be expected to cause fatigue, which is supported by the finding that a faster accumulation of interstitial K+, induced by prior arm exercise, was associated with a reduced time to fatigue...

..Alternatively, mitochondrial efficiency is lowered as exercise progresses, since ATP turnover was unaltered during the ischaemic exercise bout...

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..In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+...

..To examine the activity profile and physical loading of elite female soccer players during match play and to study the relationship between training status and physical match performance...

..9 +/- 6.6, 354 +/- 39, and 25.3 +/- 5.9 mmol kg(-1) d.w., respectively. In summary, the PT-test can be used to evaluate a soccer player's technical skills under conditions similar to intense periods of a soccer game...

..In conclusion, fatigue or impaired performance in soccer occurs during various phases in a game, and different physiological mechanisms appear to operate in different periods of a game...

..The present study demonstrated a link between interstitial H+ and K+ accumulation, which may be through the ATP-sensitive K+ channels (KATP channels), which are sensitive to changes in H+...

..In conclusion, activation of additional muscle mass does not result in a higher exercise-induced increase in Na(+)-K(+)-ATPase subunit-specific mRNA...

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..Adaptations with training do have an effect on the metabolic response to exercise and specific improvement in work capacity...

..The data show that ROS are formed within skeletal muscle during exercise and that oral intake of antioxidants can enhance the exercise-induced adaptive mRNA responses of eNOS and UCP3...

..However, during intense contraction some Na(+)-K(+) pumps are inactivated and together with further ionic disturbances, likely precipitate muscle fatigue...

..The present data demonstrate that intense interval training elevates muscle oxygen uptake, blood flow and vascular conductance in the initial phase of exercise at high, but not at low, intensities...

..We propose that enhanced blood flow and passive stretch are positive physiological stimulators of factors associated with capillary growth in human muscle...

..Furthermore, performance during intense exercise can be improved and endurance performance maintained even with a reduction in training volume if the intensity of training is very high...

..The results indicate that an increased Na(+),K(+) pump expression per se is of importance for thigh K(+) reuptake at the onset of low and moderate intensity exercise, but less important during high intensity exercise...

..These findings suggest that FT fiber recruitment elevates energy requirement of dynamic exercise in humans and support an important role of active FT fibers in producing the slow component of VO2..

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..The difference in high-intensity running between the 2 levels demonstrates the importance of intense intermittent exercise for match performance in women soccer. Thus, these aspects should be trained intensively in women soccer...