Lactate, ATP, and CP in working muscles during exhaustive exercise in man
TL;DR: The dynamics of lactate accumulation in working muscle was studied in three subjects performing maximal bicycle exercise of 2, 6, and 16 min duration.
Abstract: The dynamics of lactate accumulation in working muscle was studied in three subjects performing maximal bicycle exercise of 2, 6, and 16 min duration. In separate experiments, the two longer maxima...
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TL;DR: This review deals with the biochemical adaptations induced in skeletal muscle by the endurance type of exercise and with the physiological consequences of these adaptations.
Abstract: Two quite distinct adaptive responses can be induced in skeletal muscle by regularly performed, strenuous exercise. The nature of the exercise stimulus determines the type of adaptation. One type of adaptation involves hypertrophy of the muscle cells with an increase in strength; it is exemplified in its most extreme form by the muscles of weight lifters and body builders. The second type of adaptation involves an increase in the capacity of muscle for aerobic metabolism with an increase in endurance and is found in its most highly developed form in the muscles of competi tive middleand long-distance runners, long-distance cross-country skiers, bicy clists, and swimmers. Although many types of physical activity can bring about varying degrees of both types of adaptation in the same muscle, it does appear that these adaptations can occur quite independently of each other in their most extreme forms. For example, the hypertrophied muscles of weight lifters do not appear to have an increased respiratory capacity (45), whereas the muscles of rodents trained by prolonged daily running, which have a large increase in respiratory capacity, are not hypertrophied (56, 92) and show no increase in strength (12). This review deals with the biochemical adaptations induced in skeletal muscle by the endurance type of exercise and with the physiological consequences of these adaptations.
1,047 citations
TL;DR: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity as mentioned in this paper, and it is a mental disorder that can affect cognitive and skilled performance of individuals.
Abstract: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. Although the impact of mental fatigue on cognitive and skilled performance is well known, its...
900 citations
01 Jan 2008
TL;DR: Experimental evidence is provided that mental fatigue limits exercise tolerance in humans through higher perception of effort rather than cardiorespiratory and musculoenergetic mechanisms.
Abstract: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. Although the impact of mental fatigue on cognitive and skilled performance is well known, its effect on physical performance has not been thoroughly investigated. In this randomized crossover study, 16 subjects cycled to exhaustion at 80% of their peak power output after 90 min of a demanding cognitive task (mental fatigue) or 90 min of watching emotionally neutral documentaries (control). After experimental treatment, a mood questionnaire revealed a state of mental fatigue (P = 0.005) that significantly reduced time to exhaustion (640 +/- 316 s) compared with the control condition (754 +/- 339 s) (P = 0.003). This negative effect was not mediated by cardiorespiratory and musculoenergetic factors as physiological responses to intense exercise remained largely unaffected. Self-reported success and intrinsic motivation related to the physical task were also unaffected by prior cognitive activity. However, mentally fatigued subjects rated perception of effort during exercise to be significantly higher compared with the control condition (P = 0.007). As ratings of perceived exertion increased similarly over time in both conditions (P < 0.001), mentally fatigued subjects reached their maximal level of perceived exertion and disengaged from the physical task earlier than in the control condition. In conclusion, our study provides experimental evidence that mental fatigue limits exercise tolerance in humans through higher perception of effort rather than cardiorespiratory and musculoenergetic mechanisms. Future research in this area should investigate the common neurocognitive resources shared by physical and mental activity.
736 citations
Cites background from "Lactate, ATP, and CP in working mus..."
...Given the lack of effect on cardiac output, it is not surprising that mental fatigue did not affect V̇O2, minute ventilation, and blood lactate responses with the exception of blood lactate concentration at exhaustion, which was actually higher in the control condition because of longer exercise duration (32)....
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TL;DR: The maximal accumulated O2 deficit, which appears to be a direct quantitative expression of the anaerobic capacity, can be calculated after measuring the O2 uptake during one exhausting bout of exercise lasting 2-3 min.
Abstract: We present a method for quantifying the anaerobic capacity based on determination of the maximal accumulated O2 deficit. The accumulated O2 deficit was determined for 11 subjects during 5 exhausting bouts of treadmill running lasting from 15 s to greater than 4 min. The accumulated O2 deficit increased with the duration for exhausting bouts lasting up to 2 min, but a leveling off was found for bouts lasting 2 min or more. Between-subject variation in the maximal accumulated O2 deficit ranged from 52 to 90 ml/kg. During exhausting exercise while subjects inspired air with reduced O2 content (O2 fraction = 13.5%), the maximal O2 uptake was 22% lower, whereas the accumulated O2 deficit remained unchanged. The precision of the method is 3 ml/kg. The method is based on estimation of the O2 demand by extrapolating the linear relationship between treadmill speed and O2 uptake at submaximal intensities. The slopes, which reflect running economy, varied by 16% between subjects, and the relationships had to be determined individually. This can be done either by measuring the O2 uptake at a minimum of 10 different submaximal intensities or by two measurements close to the maximal O2 uptake and by making use of a common Y-intercept of 5 ml.kg-1.min-1. By using these individual relationships the maximal accumulated O2 deficit, which appears to be a direct quantitative expression of the anaerobic capacity, can be calculated after measuring the O2 uptake during one exhausting bout of exercise lasting 2-3 min.
667 citations
TL;DR: It is concluded that Wb normally incurred during maximal exercise causes vasoconstriction in locomotor muscles and compromises locomotor muscle perfusion and VO2.
Abstract: Harms, Craig A., Mark A. Babcock, Steven R. McClaran, David F. Pegelow, Glenn A. Nickele, William B. Nelson, and Jerome A. Dempsey.Respiratory muscle work compromises leg blood flow during maximal ...
662 citations
Cites background from "Lactate, ATP, and CP in working mus..."
...Fromwhat source is the energy expenditure derived to maintain this work rate? An increased lactate metabolism may account for a small portion of this (10), although this was not reflected in changes in circulating lactate concentrations across the working limb (Table 2)....
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