Caffeine Before Exercise Could be Risky for Some

A 2006 study suggests that drinking coffee just before a workout might not be the best idea. The Journal of the American College of Cardiology reports that the amount of caffeine in just two cups of coffee limits the body's ability to increase blood flow to the heart during exercise. This is problematic since blood flow to the heart must increase during exercise in order to meet the body's higher demand for oxygen and nutrients.

Study participants were regular coffee drinkers. After abstaining from coffee for 36 hours, their blood flow was measured before and after exercise. Then they ingested caffeine tablets (equal to 2 cups of coffee) and repeated the same test to measure blood floor prior to and after exercise. The caffeine did not affect heart blood flow when the participants were at rest. However, measurements taken immediately after exercise showed a 22% reduction in heart blood flow after they'd taken the caffeine tablets, compared to their previous results. Participants who exercised in a chamber simulating high altitude (15,000 feet) experienced an even greater reduction in blood flow—39% lower.

While caffeine is a stimulant, and previous studies suggest that it may enhance athletic performance, this study suggests the opposite. Caffeine does stimulate the brain, increasing awareness and concentration. Athletes who ingest caffeine before performing may feel that they are enhancing performance, but these researchers suggest that the athletes are simply more alert, awake and focused.

Action Sparked: These study results are especially important for exercisers in high altitudes and cardiac patients who already experience diminished blood flow. When blood flow to the heart is lower than the demands of the body, you won't be able to deliver enough oxygen to the muscles, brain and to the heart itself. This can result in lightheadedness, dizziness or fainting, and these effects can be much worse if a person already has high blood pressure or another heart condition. However, all exercisers should consider abstaining from coffee—and caffeine in general, whether from soda, chocolate, or pills—before working out to decrease their risk.

Instead of hitting the coffee shop on your way to the gym, try filling up your water bottle before you head out the door. Check out the article Drinking Water During Workouts to learn why water is so important before, during and after exercise.
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Member Comments

Good article. Report
This was a very interesting article! Report
Since I got serious with SP back in Oct, I seldom drink coffee in the morning and my BP has dropped considerably. It is not the weight loss because, a few years ago when I lost about 25lbs my BP stayed hi. I was working out seriously at the gym everyday and I asked my doc why my bp was still hi with all the exercise and wgt loss, she told me it was just my family hx, Now I know it was those 3-4 cups of coffee in the am and a few more during day all the way up to after dinner coffee. Report
Funny as I was just about to take few sips of my chilled caramel low fat coffee. I decided not to, just because I was running late to my work out anyway. Then I come across this article, funny. Report
"Then they ingested caffeine tablets (equal to 2 cups of coffee) and repeated the same test to measure blood floor prior to and after exercise."

This is a flawed experiment, with little practical application to the daily lives of Sparkers. The 2006 study was about drinking coffee. This new study is about caffeine tablets. Who takes caffeine tablets...ever? Caffeine is processed differently when consumed slowly and with fat or sugar.

Can Spark People please get a scientist on staff to vet these articles before they are posted? Report
Good article. I don't drink coffee like I use to. I might have a cup on the weekend. Probably twice out the month. Report
There's merit to this idea, but I have low blood pressure, and I think it's partly due to coffee that I don't have to medicate it - I tried meds for low blood pressure once, it wasn't a good trip (and my only trip, fortunately, never done any recreational drugs).

I don't drink soda, only tea and coffee, I'm much fitter than I was, and I don't actually drink it right before any fairly high intensity activity. Most of my exercise comes from walking and yoga, so I'll stick to my coffee. Report
Ugh. Another study that contradicts other studies. I also saw a different study the other day that said that there's no link between caffeine and high blood pressure. Whatever. Report
This is an article that needs dating--the study needs to be cited/dated, and the article itself, too, should be. As a pp has pointed out, it seems the study is several years old.

Not only that, but caffeine tablets aren't the same as drinking coffee--the mechanism for internal absorption, rate of absorption, and accompanying ingredients are all different. As a coffee drinker who has, on occasion, used more direct caffeine supplementation, I know there is a significant difference, not accounted for here. Report
I always drink my coffee AFTER my morning runs. This has nothing to do with my ability to breathe or bloodflow, however...The one time I did drink a cup of coffee before running (at least an hour before my run), my stomach was NOT happy. (I had also eaten breakfast with it.) So from now on, I run first, and coffee is my reward!!!! Report
I checked the link to the other study, and it does appear to be the same one. Thing is, that study was from January of 2006. It may not seem like that long ago, but a lot changes in 6 years when it comes to nutrition and fitness research. I would like to see more recent studies, with more controlled variables, a wider range of subjects (maybe non-caffeine drinkers as well), and more subjects. While this info is intriguing, there should be follow-up studies done, imo. Report
I have heart arrhythmia when I drink caffeine. This article totally makes sense to me. If the caffeine is decreasing blood flow, the heart beats would get erratic. It's a hard sell in this day and age, though. Seems everyone is addicted to caffeine and PROUD of it. Report
Whoa, this is scary--I've been holding on to a bag of guarana seed powder to add to my pre-workout smoothies once I hit a fat-burning plateau. Glad I came across this first. o_O Report
This makes total sense. I'm a 35-year old who regularly drank Coca-Cola, coffee, etc. Recent heart palpitations and tests that revealed high blood pressure among other things caused me to rethink my caffeine addiction. I still drink black tea on occasion, but gave up the other stuff. I do notice a difference in blood flow...I have difficulty in the uptake of blood in one of my arteries. This has been a wakeup call to treat my body better, and I love not having the tension and headaches all the time. I still eat chocolate on occasion, usually dark chocolate, but so far black tea and chocolate seem to be OK. Thanks for the informative article. Report
This is a very good article. My husband who had a quadruple bypass last year walks on a daily basis - lately he consumes two (16) oz cups of coffee prior to his walks. Although one of his bypassed vein failed in the right bottom of the heart , his heart muscle is strong. My point is that he has noticed the difference if he consumes coffee prior to a workout, he tends to be out of breathe. On the days that we juice prior to his walks his ability is swifter. Hmmmm Report


About The Author

Jen Mueller
Jen Mueller
Jen received her master's degree in health promotion and education from the University of Cincinnati. A mom and avid runner, she is an ACE-certified personal trainer, health coach and medical exercise specialist, with additional certifications in behavior change, functional training and senior fitness. She is also a RRCA-certified running coach. See all of Jen's articles.