Caffeine: Everything you need to know

Caffeine is one of the most popular supplements for enhancing performance, after being removed from the World Anti-Doping Agency banned list in January 2004. It improves endurance in men and women (Shen et al., 2019), team sport performance (Salinero et al., 2019; Stuart et al., 2005), increases time to fatigue (Bowtell et al., 2018) and 1RM strength exercise capacity (Del Coso et al., 2011; Grgic et al., 2019). So how does caffeine operate in the body?

According to Martins et al. (2020) there are three key mechanisms by which caffeine operates to improve performance and delay fatigue. Firstly, it affects the central nervous system. During fatigue adenosine binds to A1 and A2 receptors inhibiting the release of neurotransmitters noradrenaline and dopamine (Fredholm et al., 2005). Caffeine, however, displaces adenosine from those receptors which provides a stimulant response (Elmenhorst et al., 2012), blunting the fatigue effects. This decreases perceived exertion during exercise (McLellan et al., 2016; Daly et al., 1983). Secondly, caffeine increases lipolysis. Caffeine activates the sympathetic nervous system (Graham et al., 2000) and increases the breakdown of triglyceride stored within the adipose tissue. This improves the supply of free fatty acids available for the muscle which inhibits carbohydrate metabolism, increasing exercise capacity (Graham et al., 1995). Thirdly, caffeine provides neuromuscular benefits. During contractions calcium binds to troponin exposing a binding site for cross-bridge cycling and when the rate of calcium reuptake cannot sustain the demand, fatigue is induced. Caffeine, however, improves the re-uptake of calcium in the sarcoplasmic reticulum (SR) (Klein et al., 1990), causing more rapid and forceful contractions - where most gym enthusiasts see an increase in strength with supplementation. The optimum dosage of caffeine to improve performance is 3-6mg/kg/BW (Goldstein et al., 2010; Maughan et al., 2018; Skinner et al., 2019), 60minutes before exercise as this is the time taken to reach peak concentrations in the blood. Doses greater than 6mg/kg/BW do not show any further enhancement of performance (Graham et al., 1992), and over 12mg/kg/BW is toxic to the body (Ali et al., 2015).

However, a major issue in supplementing with caffeine is the obvious negative effect on sleep (Ali et al., 2015). This would have a negative effects on your gains in the gym because adaptions to your training occur whilst your body is getting as good nights rest, more specifically during REM periods of your sleep. It takes 5 hours for caffeine concentrations to fall by half, with it lasting longer in females (Skinner et al., 2019). Meaning it would probably be a good idea to leave at least a 5 hour gap between your caffeine supplemented workout and when you nod off to sleep. Caffeine also has a negative habituation effect (Lara et al., 2019) seen by a reduction in performance enhancement with consistent supplementation. You might have seen this evident in your own workouts or mates who seem to keep adding in more scoops of Pre-Workout every week as their body has become accustomed to the dose. Coming out of this cycle can be very difficult.

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Thank you for taking the time to read this blog, I hope you enjoyed. Please see my website if you're interested in more blogs like this, where I am also selling my own training plans. You can find me on instagram @hb.fitt_

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Abbreviations:

mg/kg/BW - Milligrams per Kilogram per BodyWeight

REM - Rapid Eye Movement

References:

Bowtell, J.L., Mohr, M., Fulford, J., Jackman, S.R., Ermidis, G., Krustrup, P. and Mileva, K.N., 2018. Improved exercise tolerance with caffeine is associated with modulation of both peripheral and central neural processes in human participants. Frontiers in Nutrition, 5, p.6.

Daly, J.W., Butts-Lamb, P. and Padgett, W., 1983. Subclasses of adenosine receptors in the central nervous system: interaction with caffeine and related methylxanthines. Cellular and molecular neurobiology, 3(1), pp.69-80.

Del Coso, J., Muñoz, G. and Muñoz-Guerra, J., 2011. Prevalence of caffeine use in elite athletes following its removal from the World Anti-Doping Agency list of banned substances. Applied physiology, nutrition, and metabolism, 36(4), pp.555-561.

Elmenhorst, D., Meyer, P.T., Matusch, A., Winz, O.H. and Bauer, A., 2012. Caffeine occupancy of human cerebral A1 adenosine receptors: in vivo quantification with 18F-CPFPX and PET. Journal of Nuclear Medicine, 53(11), pp.1723-1729.

Fredholm, B.B., Chen, J.F., Masino, S.A. and Vaugeois, J.M., 2005. Actions of adenosine at its receptors in the CNS: insights from knockouts and drugs. Annu. Rev. Pharmacol. Toxicol., 45, pp.385-412.

Goldstein, E. R., Ziegenfuss, T., Kalman, D., Kreider, R., Campbell, B., Wilborn, C., ... & Antonio, J. (2010). International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition, 7(1), 1-15.

Graham, T.E. and Spriet, L.L., 1991. Performance and metabolic responses to a high caffeine dose during prolonged exercise. Journal of applied physiology, 71(6), pp.2292-2298.

Graham, T.E. and Spriet, L.L., 1995. Metabolic, catecholamine, and exercise performance responses to various doses of caffeine. Journal of applied physiology, 78(3), pp.867-874.

Graham, T.E., Helge, J.W., MacLean, D.A., Kiens, B. and Richter, E.A., 2000. Caffeine ingestion does not alter carbohydrate or fat metabolism in human skeletal muscle during exercise. The Journal of physiology, 529(Pt 3), p.837.

Grgic, J., Sabol, F., Venier, S., Tallis, J., Schoenfeld, B.J., Del Coso, J. and Mikulic, P., 2019. Caffeine supplementation for powerlifting competitions: An evidence-based approach. Journal of human kinetics, 68(1), pp.37-48

Klein, M.G., Simon, B.J. and Schneider, M.F., 1990. Effects of caffeine on calcium release from the sarcoplasmic reticulum in frog skeletal muscle fibres. The Journal of physiology, 425(1), pp.599-626.

Lara, B., Ruiz-Moreno, C., Salinero, J. J., & Del Coso, J. (2019). Time course of tolerance to the performance benefits of caffeine. PLoS One, 14(1), e0210275.

Martins, G.L., Guilherme, J.P.L.F., Ferreira, L.H.B., de Souza-Junior, T.P. and Lancha Jr, A.H., 2020. Caffeine and exercise performance: Possible directions for definitive findings. Frontiers in Sports and Active Living, p.202.

Maughan, R.J., Burke, L.M., Dvorak, J., Larson-Meyer, D.E., Peeling, P., Phillips, S.M., Rawson, E.S., Walsh, N.P., Garthe, I., Geyer, H. and Meeusen, R., 2018. IOC consensus statement: dietary supplements and the high-performance athlete. International journal of sport nutrition and exercise metabolism, 28(2), pp.104-125.

McLellan, T.M., Caldwell, J.A. and Lieberman, H.R., 2016. A review of caffeine’s effects on cognitive, physical and occupational performance. Neuroscience & Biobehavioral Reviews, 71, pp.294-312.

Salinero, J.J., Lara, B. and Del Coso, J., 2019. Effects of acute ingestion of caffeine on team sports performance: a systematic review and meta-analysis. Research in sports Medicine, 27(2), pp.238-256.

Shen, J.G., Brooks, M.B., Cincotta, J. and Manjourides, J.D., 2019. Establishing a relationship between the effect of caffeine and duration of endurance athletic time trial events: A systematic review and meta-analysis. Journal of science and medicine in sport, 22(2), pp.232-238.

Skinner, T. L., Desbrow, B., Arapova, J., Schaumberg, M. A., Osborne, J., Grant, G. D., ... & Leveritt, M. D. (2019). Women experience the same ergogenic response to caffeine as men. Medicine and Science in Sports and Exercise, 51(6), 1195-1202.

Stuart, G.R., Hopkins, W.G., Cook, C. and Cairns, S.P., 2005. Multiple effects of caffeine on simulated high-intensity team-sport performance. Medicine and science in sports and exercise, 37(11), pp.1998-2005.