Coffee 'eases exercise pain'

“Coffee before gym session ‘takes the pain out of exercise,’” The Daily Telegraph has reported. The newspaper says that Professor Motl from the University of Illinois, who has studied the relationship between coffee and exercise for years, has demonstrated in new research that coffee consumption can reduce the pain of high-intensity exercise. It is thought that this is due to its effect on receptors in the body, which normally alert the brain to muscle strain.

In the study involved giving 24 fit young men either caffeine pills or placebo pills before intense cycling. Taking a moderate amount of caffeine prior to exercise reduced the perception of muscle pain. However, there are several limitations to this study, including its small size and its use of subjects that might not represent the average person’s fitness level.

It is potentially harmful to take any substance to reduce pain during exercise because pain can signal when exercise is too intense. Toning things down to a more reasonable level would be more beneficial than trying to block out the pain in the body.

Where did the story come from?

This research was conducted by Rachael Gliottoni, Robert Motl and colleagues of the Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, and the Center for Sport and Health Sciences, Iceland University of Education. No sources of funding were reported for this research.

The study was published in the International Journal of Sport Nutrition and Exercise Metabolism, a  peer-reviewed medical journal.

What kind of scientific study was this?   

This was an experimental study that aimed to investigate the effect of moderate doses of caffeine on the intensity of quadricep muscle pain during high-intensity cycling.

Following on from results of previous studies, which have demonstrated that caffeine reduces muscle pain in normally low-caffeine consumers, the researchers expected caffeine to be associated with a reduction in pain intensity when compared with a placebo, and that the effect would be greatest in those who normally drink minimal amounts of caffeine.

The researchers recruited a group of 24 male college students who were regular exercisers. To be eligible for this study, these men had to be of above-average fitness, be non-smokers, be of an average body weight, and have no self-reported hypersensitivity to caffeine.

Before preliminary testing, the participants completed a seven-day caffeine consumption questionnaire, and their medical history was assessed. They were then divided into two groups, depending on caffeine consumption: 12 who drank ≤100 mg/day and 12 who drank ≥400mg per day.

Testing took place on three occasions: one preliminary test and two experimental tests. Tests were on separate days, conducted in the early morning and one week apart. Prior to the test, participants abstained from caffeine and food for 12 hours, and alcohol for 24 hours. On the two test days, participants ingested either 5mg/kg caffeine capsules (equivalent to consuming approximately two and a half to three 8-oz cups of ground roasted coffee) or placebo capsules. The 30-minute exercise tests were performed one hour after tablet consumption when caffeine levels were believed to be at their peak.

All participants performed an exercise test on a computer-driven cycle that could measure peak oxygen consumption. After inserting a mouthpiece to collect expired gases, participants performed a five-minute warm-up at 25 watts. The initial work rate for the exercise test was 50 watts, and the work rate continuously increased at a rate of 24W/min until the participant said they were exhausted.

Lung respiratory measurements were taken every 25 seconds, and heart rate, perceived exertion and intensity of muscle pain were recorded every five minutes. Intensity of quadriceps muscle pain was assessed using a numbered scale: 0 = no pain at all, 0.5 = very faint pain (just noticeable), 1 = weak pain, 2 = mild pain, 3 = moderate pain, 4 = somewhat strong pain, 5 = strong pain, 7 = very strong pain, and 10 = extremely intense pain (almost unbearable). Work rate was gradually reduced, trying to maintain a constant expired gas concentration.

Results were compared by caffeine use (low vs. high) and by capsule taken (caffeine vs. placebo).

What were the results of the study?  

There was a larger reduction in work rate over time in the low caffeine user group compared to high users, but there was no difference according to the type of capsule taken.

There was no difference in oxygen consumption during exercise between the two groups, nor when the two different capsules were taken.

For quadricep pain intensity rating, there was a statistically significant difference between caffeine and placebo consumption prior to exercise, with caffeine causing a reduction in reported pain intensity. This effect was the same for both those who normally drank low caffeine and those who drank high amounts of caffeine.

What interpretations did the researchers draw from these results?  

The researchers conclude that both low and high habitual caffeine consumers report a significant and moderate reduction in quadricep muscle pain intensity, following ingestion of a moderate dose of caffeine. However, their theory that the effect might be greater among low consumers of caffeine was not supported.

What does the NHS Knowledge Service make of this study? 

Although this study demonstrated that taking a moderate amount of caffeine prior to 30 minutes of intense cycling exercise reduced reported pain levels, there are several important points to consider:

• This was a very small study, with only 24 participants. Although other studies investigating this question have been conducted (but not analysed in this appraisal article), the small sample size of this study means that the differences in results may have occurred only by chance.
• The study involved a very select group of healthy young men with ‘above average fitness’, therefore these participants cannot be considered to be comparable to the general population.
• The self-reported measure of quadricep pain intensity, although a validated scale, is a subjective response. This means similar levels of pain could be rated quite differently between participants.
• The study only examined the effects during two, 30-minute intense cycling bouts. This study cannot assess the longer-term benefits or adverse effects of such intense exercise on a regular basis, nor the effects of a longer cycling bout in a single session. Also, whether the pain-reducing effect of caffeine would be maintained with long-term regular use is unclear.

Importantly, caution should be taken by individuals thinking of drinking coffee, or taking anything else, to try and ‘take the pain out of exercise’. In people not accustomed to exercising, excessive muscle or joint pain during exercise should be an indication that the exercise level is too intense. Toning things down to a mild-to-moderate level would be more beneficial to the person’s health and fitness than trying to block out pain sensations in the body. The stimulant effects of drinking high quantities of caffeine should also be noted.