By Cindy Kuzma, Runner's World
If there's one time to brag about being a runner or staying active, it's at the doctor's office--especially when your appointment includes blood or urine analyses. "Let your physician know if you are exercising heavily, and also how often and how recently you did tough workouts; it can influence how we interpret tests," says William Roberts, M.D., a family physician and medical director for the Twin Cities Marathon. If you recently ran hard--or even ran to your appointment, which Dr. Roberts's patients have been known to do--your doc might elect to reschedule some lab work. Here's a quick report of some exercise-influenced workups.
PLUS: The 5 Health Tests You Need to Ace This Year
CREATINE KINASE (CK)
Tells your doc: Whether you've had a heart attack or other type of muscle breakdown; often done if you've experienced unexplained muscle pain or weakness or chest pain or tightness
Running's effects: Tough runs--especially ones that incorporate lots of downhills, which cause more microtears in your muscle fibers--can elevate these levels for a day or two, which isn't typically a cause for concern. However, it may make it impossible for your doctor to tell if you've also sustained muscle damage from a heart problem or as a side effect of medications like statins. He or she may want to repeat the test at another time.
CREATININE WITH EGFR
Tells your doc: How well your kidneys are functioning; often done when you experience fatigue or trouble sleeping
Running's effects: Too much ibuprofen or other anti-inflammatories can damage your kidneys; abnormal results on this test could mean you should cut back. (Instead, try these 7 Natural Ways to Get More Sleep.)
PLUS: How Fit Are You? 10 Ways To Find Out
Tells your doc: The levels of sodium, potassium, and other electrolytes in your blood; sometimes done as part of a regular check-up or to monitor diabetes or heart conditions
Workout's effects: A workout can leave you temporarily depleted, so if your complaint isn't running-related, it may be best to do this test another time. However, if you frequently develop post-workout headaches, your doctor may ask you to run before your appointment--if your levels are very low afterward, you may be overhydrating.
RELATED: 7 Habits of Highly Effective Runners and Eaters
Tells your doc: If you have low iron levels; sometimes done if you're experiencing tiredness, weakness, or headaches
Running's effects: Low levels, when combined with fatigue and low hemoglobin (see below), may mean you need iron supplements. However, ferritin also increases with inflammation. A recent cold or flu can artificially inflate your numbers, masking the underlying problem.
FIND OUT: Should You Workout When You're Sick?
Tells your doc: If you have anemia or a low red-blood-cell count; sometimes done as part of a regular check-up or if you have unexplained tiredness
Running's effects: Slightly lower levels can actually be normal in a runner; your body produces extra fluid to keep your sweat and blood flowing freely, diluting your red blood cells. But iron-deficiency anemia is common, especially in women, and can cause fatigue that hampers your running. If your hemoglobin is low, your doctor may also want to run a ferritin test.
Tells your doc: Whether you have kidney disease, a metabolic disorder, or urinary-tract infection; sometimes part of a wellness exam
Workout's effects: Blood and protein in your urine--normally red flags for kidney disease or even cancer--can occur for up to a day or two following a long or fast workout.
Tells your doc: Your blood levels of this nutrient; sometimes tested if you're experiencing frequent fractures, low energy, or sleep issues
Running's effects: Outdoor runners in warm climates often get plenty of the "sunshine vitamin." But if you live north of Nashville, have dark skin, or are supervigilant about your SPF, you could be deficient. Low levels are thought to contribute to muscle pain, insomnia, and a greater risk for stress fractures.