"Feeling the burn" after a workout is really your body recovering from the stress and strain of exercise. It's a process that might get a boost from a new supplement.

WebMD Feature

Reviewed By Brunilda Nazario

If your fitness routines have ever run a bit too long, or you've worked out a little too hard, you know the misery of post-workout pain. Anywhere from several hours to several days later you still might feel the fitness "burn", not to mention fatigue.

Now researchers say they have a clue as to why - and a new natural supplement promises to make a difference.

Indeed, the latest buzz in the fitness universe is "heat shock proteins" (HSP) - a biochemical reaction that some say figures heavily into your body's ability to recover from stress and strain.

Our Body Knows Best

"Our body is our own best defense against illness because it does have the power to cure itself -and there is some evidence to show that heat shock proteins might be one way the body counteracts the structural breakdown of protein," says Robert Gotlin, DO, director of Orthopedics and Sports Rehabilitation at Beth Israel Medical Center in New York.

As he explains, HSP reside in the body at a low but constant level - almost dormant, until something stirs their release. That something, says Gotlin, is stress - particularly a heavy workout.

"As your body endures the stress it sends out biochemical signals that activate the heat stress proteins, which are then mobilized - so blood levels rise," Gotlin tells WebMD. It is that elevation, he says, that some researchers believe might play a role in the fitness recovery process, and in helping to keep muscles strong.

Indeed, in studies on 11 male athletes presented earlier this year at the annual meeting of the American College of Sports Medicine (ACSM), researchers from Yokohama City University in Japan revealed that increasing muscle temperature to 40-42 degrees Celsius up to 24 hours before strenuous exercise helps sustain muscle strength, even after that temperature returns to normal. They concluded that the mechanism behind the protective effect of the heat was the subsequent rise in heat shock proteins.

Moreover, in research published in the journal Medicine and Science in Sports and Exercise in 2000, doctors from the University of Tuebingen, in Germany, compared the HSP levels of 12 well-trained athletes before and after a run, to 12 athletes who rested. The result: The athletes had much higher levels of HSP after the race - a finding researchers believe helped them maintain their fitness and strength even after the run was over.

Rising To The Challenge

While it's clear that exercise causes HSP to rise, studies show the natural activation process can take three hours or more after the stress begins. Now, however, a new fitness supplement called PrePair claims to give HSP a gentle nudge, causing levels to rise as soon as 15 minutes after a workout starts. And it does so using an extract made from the skin of the prickly pear cactus fruit.

"The extract mobilizes your natural supply of heat shock proteins almost immediately after the body experiences stress - which in turn helps the repair process to begin right away," says Marilyn Booker, the clinical director of Perfect Equation, the company that distributes PrePair in the U.S.

It is because of that ultra quick HSP response that Booker says athletes are less likely to feel fatigue, and have a greater ability to workout harder and longer with less risk of muscle damage or post workout pain.

The key ingredient in PrePair is called Tex-OE, extracted from the skin of the cactus fruit. According Booker, what makes PrePair different from other prickly pear cactus sources is the patented process that separates the extract from the fibrous skin - intrinsic, she says, to obtaining results.

"Fiber prevents the extract from being absorbed by the body - so in order to gain the benefits we had to develop a patented process that separates the extract from the fibrous skin, " Booker tells WebMD.

It also allows the supplement to last in the body up to three days - but, says Booker, "If your muscles aren't under stress, the heat shock proteins won't rise."

And the company offers some human, cell culture, and animal studies to back up their claims. Human studies conducted by the company on divers, cyclists, and runners found those who took PrePair claimed to have roughly twice the strength, distance or stamina they did before.

Supplemental Information

But while results are impressive, it's important to note that PrePair's studies were small, and not published in any medical journal, which means they were not subject to review by experts who could verify either the results, or the conditions under which the testing was carried out.

Moreover, even if PrePair can elevate heat shock proteins after fitness activities, as it claims, some experts question whether that elevation is really key to the repair process - or just something that occurs simultaneously.

"The big question now is will the elevation of heat shock proteins following stressors - using this supplement or any other means - really reduce muscle damage or increase the recovery process," says Malachy McHugh, PhD, director of research, Nicholas Institute of Sports Medicine and Athletic Trauma in New York City.

While McHugh remains intrigued with the link between heat shock proteins and exercise, he cautions that right now there is no science to show that they make a difference in recovery, or if they do, if speeding up production with a supplement has any real value.

"Ultimately, you need some measure of damage or disruption of the cells to see if those who take the supplement fare better than those who don't," McHugh tells WebMD.

Nutrition expert and author Shawn Talbott, PhD, agrees. "The question that needs to be answered is whether or not impacting heat shock proteins is going to impact the rate of injury or fatigue, or make fitness workouts safer - and right now we have no well controlled peer reviewed studies to tell us that," says Talbott, a professor at The University of Utah and the author of "The Cortisol Connection."

And, in fact, there is already one animal study that shows that, on it's own, elevated HSP may not make much of a difference at all. In preliminary research presented at the ACSM conference in May, doctors from Georgia State University in Atlanta used heat to increase production of HSP in mice. While they clearly documented elevations in HSP, it did not appear to protect the mice against exercise induced injury - or speed their recovery afterwards.

Although the company who makes PrePair provided WebMD with toxicity studies on mice showing the supplement was proven safe, and says thousands of products sold have yielded no reports of adverse effects, Gotlin believes this is not enough proof to offer a blanket guarantee of safety to all fitness buffs who use it.

"I would need large-scale human trials before I would take this supplement, or recommend it," says Gotlin.

Talbott is more certain of the safety aspect and says he would recommend the product. However, he tells WebMD, "I'm just not sure if raising heat shock proteins has been proven to make a significant difference in our fitness activities."

Published June 30, 2003

Sources: Robert Gotlin, MD, director of Orthopedics and Sports Rehabilitation at Beth Israel Medical Center in New York City; Marilyn Booker, RN, clinical director, Perfect Equation; Malachy McHugh, PhD, director of research, Nicholas Institute of Sports Medicine and Athletic Trauma, Lenox Hill Hospital, New York City; Shawn Talbott, PhD, professor, University of Utah, fellow, American College of Sports Medicine; "Attenuation of Muscle Damage by Muscle Hyperthermia One Day Prior to Eccentric Exercise",annual meeting, American College of Sports Medicine, San Francisco, May, 2003; Medicine and Science in Sports and Exercise, 2000, 32:592-600; White Paper: Tex-OE?, A Natural Cactus Extract With The Ability to Accelerate The Synthesis of Protective Heat Shock Proteins (HSPs); "Effects of Prophylactic Heating On Eccentric Contraction-Induced Injury in Mouse Skeletal Muscle", annual meeting, American College of Sports Medicine, May, 2003, San Francisco.

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