Caffeine attenuates the exercise-induced increase in plasma [K+] in humans

Lindinger, Michael I.; Graham, T. E.; Spriet, Lawrence L.

doi:10.1152/jappl.1993.74.3.1149

Cited by 107 publications

(85 citation statements)

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“…Adenosine receptors are found in most tissues, including lipocytes and skeletal muscles (11), and activation of A 1 receptors leads to inhibition of lipolysis, activation of potassium channels, reduction in the atrioventricular node conduction, and inhibition of the basal and provoked neuronal activity (29). As caffeine acts as an adenosine-receptor antagonist, caffeine ingestion can thereby lead to elevation of free fatty acids before and during exercise (5,15), decrease the extracellular potassium concentration and by this promote action potential in muscle cells (4,26,29), and provoke release of the neurotransmitter serotonin that has a possible effect in mediating the feeling of fatigue (28,32). Caffeine is also associated with elevated plasma epinephrine, and glycogen sparing does occur in the active muscle, at least in the first few minutes (13).…”

Section: Discussionmentioning

confidence: 99%

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

Nørager

Jensen

Madsen³

et al. 2005

Journal of Applied Physiology

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Norager, C. B., M. B. Jensen, M. R. Madsen, and S. Laurberg. Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study. J Appl Physiol 99: 2302-2306, 2005. First published August 4, 2005 doi:10.1152/japplphysiol.00309.2005.-This study investigated the effect of caffeine on physical performance in healthy citizens aged Ն70 yr. The randomized, double-blind, placebo-controlled, crossover study was conducted in 15 men and 15 women recruited by their general practitioner. Participants abstained from caffeine for 48 h and were randomized to receive one capsule of placebo and then caffeine (6 mg/kg) or caffeine and then placebo with 1 wk in between. One hour after intervention, we measured reaction and movement times, postural stability, walking speed, cycling at 65% of expected maximal heart rate, perceived effort during cycling, maximal isometric arm flexion strength, and endurance. Analysis was by intention to treat, and P Ͻ 0.05 was regarded as significant. Caffeine increased cycling endurance by 25% [95% confidence interval (CI): 13-38; P ϭ 0.0001] and isometric arm flexion endurance by 54% (95% CI: 29 -83; P ϭ 0.0001). Caffeine also reduced the rating of perceived exertion after 5 min of cycling by 11% (95% CI: 5-17; P ϭ 0.002) and postural stability with eyes open by 25% (95% CI: 2-53; P ϭ 0.03). Caffeine ingestion did not affect muscle strength, walking speed, reaction, and movement times. At the end of the study, 46% of participants correctly identified when they received caffeine and placebo. Caffeine increased exercise endurance in healthy citizens aged Ն70 yr, but the participants' reasons for stopping the test may have varied between subjects, as the cycling test was done at ϳ55% of maximal oxygen consumption. Further studies are required to investigate whether caffeine can be utilized to improve the physical performance of elderly citizens. fatigue; perceived exertion; postural stability; elderly CAFFEINE INGESTION INCREASES the endurance of young people exercising at 60 -85% of their maximal oxygen uptake (12,13,38). It also seems to improve endurance as measured by repeated submaximal isometric contraction (34) and decreases the rate of perceived exertion during exercise (6, 9, 37). Typically, doses of ϳ6 mg/kg caffeine (equivalent to 4 cups of coffee) were used in these studies.With a growing number of elderly with a physically active lifestyle and many elderly participating in rehabilitation programs, the endurance-enhancing effect of caffeine is of increasing interest in this age group. However, the enduranceenhancing effect of caffeine found in young subjects has not previously been examined in the elderly.The aim of this study was to investigate whether 6 mg/kg caffeine improves physical performance and reduces the perceived effort during work in healthy citizens aged Ն70 yr. The main hypothesis was that caffeine would improve cycling endurance at 65% of expected maximal heart rate, and the secondary hypothesis was that caffeine would improv...

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Section: Discussionmentioning

confidence: 99%

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

Nørager

Jensen

Madsen³

et al. 2005

Journal of Applied Physiology

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“…Thirty-three peer-reviewed research articles met the inclusion criteria (Alves et al, 1995;Bell, Jacobs, & Zamecnik, 1998;Berglund & Hemmingsson, 1982;Bridge & Jones, 2006;Butts & Crowell, 1985;Cadarette, Levine, Berube, Posner, & Evans, 1983;Cha et al, 2001;Cohen et al, 1996;Collomp et al, 2002;Conway, Orr, & Stannard, 2003;Costill et al, 1978;Denadai & Denadai, 1998;French et al, 1991;Fulco et al, 1994;Graham, Hibbert, & Sathasivam, 1998;Graham & Spriet, 1991;Greer, Hudson, Ross, & Graham, 2001;Ivy et al, 1979;Jenkins, Trilk, Singhal, O'Conner, & Cureton, 2008;Lindinger, Graham, & Spriet, 1993;MacIntosh & Wright, 1995;McLellan, Bell, & Kamimori, 2004;McNaughton et al, 2008;Norager, Jensen, Madsen, & Laurberg, 2005;Pasman et al, 1995;Powers, Byrd, Tulley, & Callendar, 1983;Sasaki et al, 1987;Slivka et al, 2008;Spriet et al, 1992;Trice & Haymes, 1995;Van Soeren & Graham, 1998; Table 3). Three research articles Berglund & Hemmingsson, 1982;Butts & Crowell, 1985) reported Note.…”

Section: Study Characteristics For Caf Versus Placebo Analysismentioning

confidence: 99%

Does Caffeine Added to Carbohydrate Provide Additional Ergogenic Benefit for Endurance?

Conger¹,

Warren²,

Hardy³

et al. 2011

International Journal of Sport Nutrition and Exercise Metabolism

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Context: Carbohydrate (CHO) and caffeine (CAF) both improve endurance performance. Purpose: To determine by systematic literature review coupled with meta-analysis whether CAF ingested with CHO (CHO+CAF) improves endurance performance more than CHO alone. Methods: Databases were searched using the keywords caffeine, endurance, exercise, carbohydrate, and performance. Criteria for inclusion were studies that used human subjects performing an endurance-exercise performance task and included both a CHO and CHO+CAF condition. Effect sizes (ESs) were calculated as the standardized mean difference. Results: Twenty-one studies met the criteria for analysis. ESs for individual studies ranged from -0.08 (trivial effect favoring CHO) to 1.01 (large effect favoring CHO+CAF). The overall ES equaled 0.26 (95% CI 0.15-0.38, p < .001), indicating that CHO+CAF provides a small but significant performance benefit over CHO. ES was not significantly (p > .05) related to CAF dose, exercise duration, or performance-assessment method. To determine whether ES of CHO+CAF vs. CHO was different than CAF compared with water (placebo), a subgroup meta-analysis compared 36 CAF vs. placebo studies against the 21 CHO+CAF vs. CHO studies. The overall ES for the former group of studies (ES = 0.51, 95% CI 0.40-0.61) was nearly 2-fold greater than in CHO+CAF vs. CHO studies (p = .006). Conclusions: CHO+CAF ingestion provides a significant but small effect to improve endurance performance compared with CHO alone. However, the magnitude of the performance benefit that CAF provides is less when added to CHO than when added to placebo.

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“…Caffeine can also prolong the endurance time and at the same time reduce the perception of fatigue during resistive breathing [24]. This last event is confirmed by lower levels of plasma K+ concentration with a subsequent potential increase of force generation in skeletal muscles and a possible delay of fatigue both at respiratory level and at that of skeletal muscles [25][26]. The net result could be an artificial improvement of physical performances.…”

Section: Stimulantsmentioning

confidence: 88%

Doping and Respiratory System

Casali

Pinchi

Puxeddu

2016

Monaldi Arch Chest Dis

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Historically many different drugs have been used to enhance sporting performances. The magic elixir is still elusive and the drugs are still used despite the heavy adverse effects. The respiratory system is regularly involved in this research probably because of its central location in the body with several connections to the cardiovascular system. Moreover people are aware that O2 consumption and its delivery to mitochondria firstly depend on ventilation and on the respiratory exchanges. The second step consists in the tendency to increase V’O2 max and to prolong its availability with the aim of improving the endurance time and to relieve the fatigue. Many methods and substances had been used in order to gain an artificial success. Additional oxygen, autologous and homologous transfusion and erithropoietin, mainly the synthetic type, have been administered with the aim of increasing the amount of oxygen being delivered to the tissues. Some compounds like stimulants and caffeine are endowed of excitatory activity on the CNS and stimulate pulmonary ventilation. They did not prove to have any real activity in supporting the athletic performances. Beta-adrenergic drugs, particularly clenbuterol, when administered orally or parentherally develop a clear illicit activity on the myosin fibres and on the muscles as a whole. Salbutamol, terbutaline, salmeterol and formoterol are legally admitted when administrated by MDI in the treatment of asthma. The prevalence of asthma and bronchial hyperactivity is higher in athletes than amongst the general population. This implies that clear rules must be provided to set a correct diagnosis of asthma in the athletes and a correct therapy to align with the actual guidelines according to the same rights of the “other” asthmatic patients.

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Caffeine attenuates the exercise-induced increase in plasma [K+] in humans

Cited by 107 publications

References 0 publications

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

Caffeine improves endurance in 75-yr-old citizens: a randomized, double-blind, placebo-controlled, crossover study

Does Caffeine Added to Carbohydrate Provide Additional Ergogenic Benefit for Endurance?

Doping and Respiratory System

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