Supplement Highlight: Caffeine

Pre-Workout supplements are incredibly popular and many make claims that only their special blend will increase your strength, allow you to get more reps in before failure, bust through plateaus, and basically become the Incredible Hulk for an hour each day you are in the gym. When it comes to ergogenic or performance enhancing supplements, there are only a handful that can reliably back up the claims they make, and no one company has an exclusive right to these ingredients. The most commonly consumed in a pre-workout supplement is caffeine. But do you know what caffeine actually does for you during a workout?

Caffeine reliably decreases perceptions of effort and aids in fatigue resistance to strenuous activities. It also improves mental alertness and focus which can be helpful if you have a demanding work schedule and find it difficult to give your workouts the attention they need to be effective.

In multiple studies, caffeine has shown to increase power output and allow for individuals to perform more repetitions before failure. The effects have shown to be greater on lower body strength, though the exact reason for why is unclear. It could be that lower body exercises are generally harder, so caffeine’s effect on reducing perceived effort is more noticeable.

In most research showing positive effects of caffeine, a dose of 3-6mg of caffeine per kilogram of bodyweight were used. For a 175lb (or 79kg) person, he/she would consume somewhere between 225-475mg of caffeine about 45 minutes prior to working out. That may sound high, but the truth is we build a tolerance to caffeine pretty quickly and with that tolerance, the performance enhancing effects decrease. So, starting with somewhere between 80-100mg of caffeine before your workout and slowly increasing over time will allow you to get the most benefit from this supplement during your workouts! However, if you read that recommendation and said, “Ha! I take 3 scoops of pre-workout every day.” You may want to consider reducing your intake and allowing your tolerance to return to that range.

To get the most out of caffeine during your training, you should reserve it for your hardest workouts 1-2 times per week and reduce your intake during other times of those days.

If you’re curious about how much caffeine is in regularly consumed beverages, here is a quick guide:

  • 8 oz Coffee: 80-150mg
  • 1 shot Espresso: 50-65mg
  • Black Tea: 25-50mg
  • Green Tea: 25-30mg
  • 8 oz Cola: 25-50mg
  • Typical energy drinks: 80-160mg
  • C4 Pre-Workout: 130-150mg per scoop

And if you’re looking to improve your performance in the gym, try partnering caffeine a pre-workout snack! To learn more about pre- and post-workout supplementation as well as how to eat to perform and recover from exercise, reach out to our Registered Dietitian Eddie Fitzgerald at


By Eddie Fitzgerald, RD, LDN, Performance Dietitian