June 30, 2010
Jeremy Craig, 404-413-1357
ATLANTA — Your morning jolt of coffee is more than a way to start your day — coffee’s caffeine also has a positive effect on your endurance and strength, according to an analysis by a Georgia State professor.
Gordon Warren, professor of physical therapy, took a look at numerous studies dating back to 1939 that have examined the effects of caffeine on muscular strength and endurance. Warren’s analysis appears in the July edition of the American College of Sports Medicine’s flagship journal, Medicine and Science in Sports and Exercise.
Put together, they indicate overall that caffeine appears to improve muscular strength and endurance, but the effect on strength is primarily in the knee extensor muscles and not other muscle groups. The knee extensor muscles are also known as the quadriceps or thigh muscles, which act together to extend the knee.
“In humans, caffeine is thought to affect the central nervous system to improve the ability to activate muscle,” said Warren, of the School of Health Professions in the College of Health and Human Sciences. “However, there are some indications that it could have direct effects on the muscle tissue itself.”
Most people cannot use their quadriceps to their fullest extent. On average, a person can activate 80 to 90 percent of the muscle mass, but for others, the amount of activation can be as low as 50 percent, Warren said.
“For someone who can maximally activate their quads, caffeine is not going to help, but for those who cannot, it will have an effect,” he said.
About 300 to 400 milligrams of caffeine — the amount in three to four cups of coffee — can improve muscular performance. While the overall improvement in muscular strength and endurance is only about 7 to 18 percent, this can make a difference for endurance athletes, Warren said.
“To the average person, it doesn’t sound like a lot,” he said. “But when you’re talking about elite athletes, who win and lose events in the order of seconds, 7 percent is quite a bit.”
Warren said further research is needed to determine why caffeine appears to improve strength in the quadriceps and not other muscle groups. Further investigation should also look at the mechanisms of improvement.
The article, “Effect of Caffeine Ingestion on Muscular Strength and Endurance: A Meta-Analysis,” is available online at http://journals.lww.com/acsm-msse/pages/default.aspx.