Heavy exercise prior to a liver enzyme blood test can elevate the ALT or AST, but just how much exercise are we talking here?

“AST and ALT elevation after exercise is related to inflammation of the muscles, or muscle cell damage, says Hwan Yoo, MD, a board certified gastroenterologist with Mercy Medical Center in Baltimore, MD.

“AST or ALT are called transaminases,” continues Dr. Yoo. “These are present mainly in liver cells, but as well as in any muscle cells.

“Therefore, any level of exercise or physical activity causing muscle cell damage could cause elevation of these enzymes by being released from the inflamed or dead muscle cells.”

This phenomenon has gained some attention as a result of the CrossFit craze. In fact, it even has a mascot: Dr. Rhabdo.

“Rhabdo” is short for rhabdomyolysis, a condition of lethally injured muscle fibers that leak their contents into the athlete’s or gym enthusiast’s bloodstream.

This condition is very serious, and a classic symptom is tea or cola colored urine.

James Heilman, MD

Dr. Yoo continues, “One of the well-known pathological conditions related to high AST elevation is heart attack or acute myocardial infarction.

“This phenomenon is known to happen in weightlifters, marathon runners or soldiers who perform heavy duty labors.

“This is relative for each individual depending on the tolerance of the individual to exercise.

“This type of AST and ALT elevation are not considered to be a type of liver disease.”

Are CrossFit competitors the most physically fit athletes on the planet?

Some say so, while others insist that the following other kinds of athletes are the most physically fit: surfers, MMA fighters, marathon runners, sprinters, gymnasts, extreme mountaineers, triathletes and bodybuilders.

Must a person perform CrossFit workouts to be super fantastic fit? No.

When’s the next time you’ll need to do 100 pull-ups in a row followed by 100 switch-jumps, 50 burpees and then loads of barbell cleans, all in 20 minutes?

Though CrossFit athletes are in phenomenal shape, they’re putting their joints at high risk of permanent injury down the road.

As for Dr. Rhabdo, death from this is rare, but possible. Very prompt treatment is key to full recovery.

Just how much exercise, or how intense the exercise needs to be, to merely elevate the liver’s ALT and AST, without accompanying symtoms, is not specifically known.

For example, will a 45 minute bodybuilding routine do it for next-day’s liver enzyme blood draw?

Will a 30 minute, medium intensity jog on a treadmill do it?

To avoid an exercise-induced elevation of ALT and AST for a scheduled blood draw, try to avoid structured exercise the day before. This way, you’ll more likely have a more “true” enzyme result.

However, the enzymes may still turn out to be elevated.

In fact, one study showed that in healthy men, the ALT and AST remained elevated seven days after exercise—which consisted of an hour-long weightlifting session.

The report by Pettersson, et al, concluded: Intensive muscular exercise, e.g. weightlifting, should also be considered as a cause of asymptomatic elevations of liver function tests in daily clinical practice.

Dr. Yoo is an experienced liver specialist at The Center for Liver and Hepatobiliary Diseases. He works with his patients to best manage their liver disease through innovative pill therapy.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  
Source: ncbi.nlm.nih.gov/pmc/articles/PMC2291230/