Pre-Workout Supplements – The Science And Side Effects Explained

Everybody wants the best from their workout, and taking the right pre-workout supplement will help you be the best and get the best results.

There’s a wide range available and knowing what the best pre workout supplement is can be difficult.  However, generally they all work by increasing the body’s ability to produce energy quickly: allowing you to train harder and more frequently and achieving results quicker.

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The science

Blends of creatine, Branched Chain Amino Acids (BCAAs), protein, taurine, B vitamins and caffeine; shakes, bars, tablets, we all have our favourite, but what’s the science? How do they work? Let’s look at the main ingredients:

Creatine is proven to help increase the speed and force at which muscles work. It helps muscles repair and delays muscle fatigue, allowing a stronger, more rewarding workout and greater muscle mass, faster. It’s only stored by the body for a short time, so for those of us training hard, taking a supplement is very beneficial. The body converts creatine into creatine phosphate which is stored in the muscles, ready to be used as energy. It’s obvious then, that the more stores we have, the more its available to be used as energy. (But there is a saturation point, so it’s recommended to load with 15-25g a day for five days then maintain that level with 3-5g per day thereafter.) It’s especially useful in heavy weight lifting and HIIT training as these exercises use ‘short twitch’ muscle fibres which draw on the creatine phosphate reserves for short bursts of energy.

BCAAs are amino acids that are metabolised by the muscles rather than the stomach, preventing catabolism, or the breakdown of muscle tissue, and protein breakdown and instead helps the muscles repair and build up.  Serotonin, released by the brain, increases during exercise and causes fatigue, BCAAs lower serotonin production leading to less fatigue and more power for your workout.

Caffeine keeps us going, keeps us alert and allows us to really push all we can into our workouts. Caffeine increases thermogenesis (the production of heat) which helps burn fat by increasing the amount of energy (calories) our body can burn. Caffeine also helps improve resistance training by increasing anaerobic capacity. Most pre-workout supplements also contain B vitamins, which help manufacture red blood cells which carry oxygen around the body, increasing energy and aerobic capacity.

But what about side effects?

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Many supplements contain high levels of caffeine which can cause heart palpitations, nausea, vomiting, headaches, anxiety and even make an underlying heart problem worse. Taken at the same time as coffee or cola and these symptoms could be exacerbated.

Other side effects can include insomnia, high blood pressure, kidney damage, itchy, red skin, diarrhoea, dizziness and cramps, all associated with high levels of caffeine and other stimulants such as taurine and can be greatly reduced by drinking plenty of water.


Pre-workout supplements, taken at the recommended dosage can be a great way to supercharge and get the most from your workout. If you notice any side effects that hinder your progress, stop taking your supplements and have a chat with your doctor if they don’t get any better.


Kelly Crawford is passionate about health, well being, running and minimalist. As a competitive runner, she has insight into the struggles of balancing work-outs with good nutrition and injury prevention. She is a contributing writer for – a site dedicated to health, nutrition and fitness advice.

Written by Valentin Bosioc

Valentin Bosioc - wellness specialist, certified personal trainer, certified fitness instructor, celebrity trainer, Musclemania Champion, Ninja Warrior Semifinalist, world wide motivator!

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