Disclaimer: This article is not intended to replace a seeing a doctor or to undermine what a doctor may or may not interpret from lab values. This article is meant to be a resource for productive discussion with a physician about your lab values.
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Intense exercise can create lab abnormalities displayed on common blood tests.
Intense exercise can elevate enzyme levels of Creatine Kinase indicating disease states or muscle damage.
Intense exercise can elevate markers of liver damage AST and ALT.
Intense exercise can also elevate markers of kidney function, BUN.
It is important to know about these lab abnormalities and discuss the with your doctor.
Did I need a needle stuck into my liver?
I was 20 years old, and I was in for a routine check up with some basic labs and a brief exam. There wasn’t much to talk about I was healthy and felt pretty good. At this point in life, I lifted weights 6x a week for around 1-1.5 hours.
I would have assumed everything would look flawless but, I was wrong. I got a call back from the sports medicine GP that I had seen, stating I needed to come back in and discuss some elevated lab values.
He was very concerned about why my liver values (AST and ALT) were elevated. He felt that there was a possibility for liver disease occurring or possibly something even worse. He decided an ultrasound was needed to get a better look at my liver.
I got the ultrasound done and in the meantime, I started to do some reading about the lab aberrations in my results. I found that there were possibilities my doctor overlooked, like hard weight training.
The ultrasound came back completely normal, as I had expected it. The doctor was not convinced and wanted to move onto a liver biopsy to get a look at the liver. That was where I drew the line. For one, I had incurred a lot of medical bills from this work up already, and second I disliked the idea of sticking a 12-inch needle into my liver. I discussed some of the literature I had found and we came to an agreement that was pursuing this without symptoms was not needed.
Doctors Want to Help
As athletes, we are seen differently by general public. But, we are also seen differently by doctors who want to help but, can create issues when we seek any treatment or labs. It’s not that the body is functioning differently than our non-lifting brethren. It comes from the stress placed on the body when someone intensely exercises.
Heavy exercise does not affect all of the labs that are run but it does change some key ones that might be run as general wellness checks by a general practitioner.
Heavy exercise is a trauma and stress on the body. Resistance exercise tears muscle fibers creating damage and releases various enzymes into the body. Heavy running can create enough muscle damage that urine will even change colors from hemolyzed red blood cells.
Hydration levels can fluctuate considerably depending on the environment training takes place in. And diet is another area that can affect the blood levels of various enzymes and markers.
Labs are typically ordered in groups called panels. A panel that analyzes electrolyte levels and kidney function is referred to as a basic metabolic panel or chem 7. A complete blood count or CBC delves into the body’s circulating cells. Each panel measures various biomarkers that represent indicators of different organs or functions in the body.
Each lab value has a range of accepted standard values. This range is called the reference range. Any value that falls out of the reference range is considered abnormal. As you can imagine, a larger deviation from the reference range requires more attention. Remember when you think about labs, you need to take them as one piece to the puzzle. They do not tell the whole story but provide one chapter of a story.
Commonly Abnormal Labs
Creatine kinase (CK) levels:
CK is found in the mitochondria and cytoplasm of skeletal muscle (predominantly), cardiac muscle, brain, and other visceral tissues. Its primary function is in the generation and facilitation of transportation of high-energy phosphates. Skeletal muscle, myocardium, and neuronal tissue are the primary sources of CK-MM, CK-MB, and CK-BB, respectively. It catalyzes the reaction of forming high energy molecules of ATP from ADP. ATP is the source of energy for cells to carry out various reactions, and in skeletal muscle ATP is used for contraction of muscle fibers.
Increased CK is predominantly used to diagnose neuromuscular diseases and acute myocardial infarction. Neuromuscular disorders include myopathies, muscular dystrophy, drug-induced myopathies, neuroleptic malignant syndrome, seizures.
Since it is elevated in response to muscle breakdown misdiagnosis can occur with: intense exercise, trauma, severe shivering, even EMG studies.
So, if your CK levels come back elevated there is a possibility it is from disease, but it might also be from muscle damage incurred during training. These elevations can last for up to 7 days after a bout of training. The more damage during exercise the higher the levels will rise and the longer they can stay elevated.
BUN (blood urea nitrogen):
BUN is a measure of urea levels in the blood. Urea is a compound that is made from ammonia which is toxic to the body at high levels. So, under normal PH levels ammonia is converted to urea to be filtered through the kidneys and excreted. Ammonia is generated from the disposal of nitrogen.
One place that we find nitrogen is in amino acids which, are the building blocks of protein. As more protein is broken down nitrogen, and, therefore, ammonia, is generated. This ammonia is converted into urea and excrete which is called the ammonia cycle.
When there is a diet that is high in protein, and hard training which damages muscles release protein and creating protein turnover, urea production is increased. Turnover can cause BUN levels to be elevated during hard training and high protein diets.
BUN elevations can also mean kidney dysfunction and dehydration.
You can make sure your healthcare provider knows of the possible reasons for BUN elevation, so they do not make the assumption of kidney dysfunction.
Alanine aminotransferase (ALT), Aspartate aminotransferase (AST):
The liver has many roles in the body like, store glycogen, produce glucose, produce fatty acids, produce cholesterol, and also in the conversion of amino acids. Two enzymes that are involved in the conversion of amino acids are ALT and AST. These enzymes are commonly used as a surrogate marker for damage to the liver.
ALT is found mostly in the liver so therefore is more specific to hepatocellular damage (liver damage). AST is found in the cytosol of many other cells like, muscle, brain, lung and pancreas which, makes it less specific to the liver.
AST and ALT have both been found to be elevated after acute bouts of training. One study found that levels can be elevated for up to 7 days after a bout of weight lifting in men not used to weight training.
The muscle damaged incurred during training in heavy endurance training or weight lifting releases the enzymes into the bloodstream which will then cause the blood tests to be elevated. High protein diets have also been shown to increase the concentration of these enzymes. The rise does not occur from damage but occurs because the body upregulates the production of these enzymes as someone consumes more protein.
You can see how combining hard training with a high protein diet can cause elevations in AST and ALT.
Now, of courses, there can be a disease process occurring as well. So, you should not just write off elevations especially in conjunction with other symptoms like abdominal pain, jaundice, change in stool color, darkening of the urine. Of note alcohol and medications can also cause increases in liver values.
Heavy and hard training creates lab abnormalities that must be taken into account when discussing health.
Muscle damage release enzymes like CK, ALT and AST which can also be elevated in various disease processes.
Have a discussion with your doctor about these factors to make sure they are aware you train hard and it can affect your health markers.
I hope this article has given you some insight into fundamental laboratory studies in hard training populations. I want to emphasize this is not a guide to skip labs or not look into lab aberrations. I want this to be a start of an educated conversation with your medical provider. Many medical providers are not educated in dealing with populations like this since they are a minority.