Caffeine is a stimulant and a powerful antioxidant – 2 things we are told are great for taking before a workout, be it cardio or weight training, but caffeine also elevates cortisol, which is almost a curse word in exercising circles, so is caffeine pre-workout good or bad?


Caffeine overview

Caffeine is a naturally occurring compound which is most known for its ability to increase alertness a wake you up. Many a modern man will say that they can’t start their day until they have had their first coffee of the day to wake them up. Caffeine is also a pretty powerful antioxidant, so is able to protect the body from oxidative stress which is great.

cup-of-coffeeA cup of instant coffee will contain approximately 100mg of caffeine, and this is the primary dietary source of caffeine, although a cup of tea contains about 75mg and similar amounts can be found in energy drinks or in the form of tablets. Once ingested, caffeine will start to be present in the blood stream within 15 minuets, and will be competently absorbed within 45mins. You can read more about how caffeine interacts in your body here.


Caffeine in your brain

Caffeine inhibits the uptake of a neuro-transmitter called adenosine in the brain, which is responsible for making us feel tired. This inhibition makes you feel alert, improves mood, concentration and reaction time. Concentration is a clear benefit for all sports, whether you are lifting weights or running distances – you need focus. I can also see mood being of great benefit for all types of workouts too, certainly for me, when I am in a good mood I am much more motivated to exercise. For most types of exercise such as running or weight training improved reaction time is of no real benefit, but if you are involved in a reaction sport such as football it does have this additional benefit. These benefits are clear, well researched and well understood.

Caffeine has also been shown to stimulate the pituitary gland to increase the release of fight and flight hormones such as cortisol into the body. Cortisol has been shown to improve training performance in both body-builders1 and in endurance sports1. However, cortisol is a hormone which is strongly associated with stress and causes catabolism in skeletal muscles3. So although it seems to be useful in the short term for performance, it may have negative long term effects on muscle development and growth.



Caffeine in your body

Caffeine and cortisol are both known to act as a vaso-constrictors4, which means it causes blood vessels to constrict, which restricts blood flow throughout the body. This will have the biggest impact on skeletal muscles, and will restrict delivery of nutrients such as oxygen, glucose, and amino acids as well as increase blood pressure5.

This vasco-constriction doesn’t seem to effect performance, but may impact the rate of recovery of muscle tissues. This vaso-constriction might be counteracted by the vaso-dilatiory effect which are caused by exercising muscles, so may be less important when it comes to exercising.

Caffeine is a known diuretic, which means you will lose a lot of water. Caffeine causes more water to be filtered out of the kidneys into the bladder, and this can cause you to become dehydrated if you aren’t careful. There is also nothing worse when you are trying to squeeze out that last rep, and all you can think about is how full your bladder is – so off-putting! This dehydration can have a negative effect on physical performance too6, so make sure you are drinking plenty of water whilst exercising.

Caffeine is a good antioxidant, and as exercising produces more radicals in the body, it’s a good idea to increase your antioxidants. Some argue that your muscles require the radical damage to stimulate growth and recovery, and I agree with this to some extent. After all, those radicals are a very natural part of exercise, and taking 1000’s of mg of vitamin C to neutralise them isn’t. A few mgs of caffeine isn’t going to mop up all these radicals though, and will only offer a little more radical protection, which may be good.



Is caffeine good or bad pre-workout?

It really is down to you, your lifestyle, and how you like to workout. If you have quite a stressful and busy life, your cortisol levels might already be a bit high, so taking caffeine before exercising might not be a great idea as it could have negative effects. If you tend not to drink water during working out, again, you might want to give caffeine a miss as you could easily get dehydrated. However, if you enjoy the stimulating effects of caffeine and have a stress-free life then caffeine can help improve your performance. I personally wouldn’t regularly take caffeine pre-workout though, simply because you will start to build a tolerance and need more and more to get the same stimulation. Rather only take caffeine when you feel like you could do with a little stimulation, or are planning a heavy session.




1. K. Häkkinen. (1987). Relationships Between Training Volume, Physical Performance Capacity, and Serum Hormone Concentrations During Prolonged Training in Elite Weight Lifters. International Journal of Sports Medicine. – (61), 65

2. Atti Mero, Laura Jaakkola, Paavo V. Komi. (1990). Serum hormones and physical performance capacity in young boy athletes during a 1-year training period. European Journal of Applied Physiology and Occupational Physiology. 60 (1), 32-37.

3.ARNY A. FERRANDO, CHARLES A. STUART, MELINDA SHEFFIELD-MOORE, and ROBERT R. WOLFE. (1999). Inactivity Amplifies the Catabolic Response of Skeletal Muscle to Cortisol . Endocrine Society. 84 (10), 1945-7197.

4.Paul Smits MD, Jacques W M Lenders MD and Theo Thien MD. (1990). Caffeine and theophylline attenuate adenosine-induced vasodilation in humans. Clinical Pharmacology and Therapeutics. 48, 410-418

5. Robert Fraser, Mary C. Ingram, Niall H. Anderson, Caroline Morrison, Eleanor Davies, John M. C. Connell. (1999). Cortisol Effects on Body Mass, Blood Pressure, and Cholesterol in the General Population.Hypertension. 33, 1364-1368.

6. Bob Murray PhD. (2007). Hydration and Physical Performance. Journal of the American College of Nutrition. 26 (7), 29-30.

Images courtesy of eyeore2710, redheadebtyfn and navcent

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