I did not think I would ever be writing about blood clots, aka thrombi, for OTM. But when John Speare came to see me, saying his calf hurt after a hard ride, and asked, “Could it be a blood clot?” and I said “NO way!”—considering what he normally does for fun—I learned a valuable lesson.

Go figure, athletes can get blood clots, although thankfully it’s uncommon. But John knew things weren’t normal and that’s the first take-home message: listen to your body, even if your healthcare provider tells you “It’s normal…don’t worry.”

But I know you want to learn more about clots. Blood is composed of fluid (plasma), cells and platelets (cell fragments). Normally, it maintains a fine balance between flowing and clotting; it needs to flow smoothly to do what it does—transport oxygen and nutrients throughout the body and remove metabolic wastes from organs and tissues. It also needs to clot when a vessel is damaged. This occurs through an elaborate cascading system of clotting factors and platelets that, in most cases, work well to ensure you don’t bleed out when you crash. But sometimes things don’t work quite right and clots form when and where they’re not supposed to. Most commonly, this occurs in the deep veins of the leg and is referred to as a “deep venous thrombosis,” or a DVT. The big concern is having a piece of the clot break off, or embolize, and travel to the lung (pulmony embolus), the brain (embolic stroke) or other organs—all potentially life threatening events and, at the minimum, not good.

In people who commonly push their bodies to the limits (sound familiar?), these pains may be gaffed off as simply a cramp or strain—take a few Advil and see what happens. But in John’s case, dehydration provided the deal-breaker for him as he had an unknown genetic risk factor making him more susceptible. Dehydration can make your blood relatively thicker than normal, and increases the risk for clots. Again, however, it’s not common enough to worry about a clot every time your legs feel like #*&%. But if it’s a recurring theme of your workouts, then it’s something to think about and you should be aware of the major risk factors:

• Age (typically >60)
• Tobacco
• Prolonged sitting (e.g., traveling) and inactivity
• Obesity
• Medications (e.g., birth control pills)
• Recent surgery
• Family history and/or clotting disorders

When clots do occur, the most common symptoms are pain—typically in the calf, thigh or behind the knee—swelling and tenderness. It may feel like a cramp at first, but if it’s there for a while, the pain can get a lot worse. Thankfully, most people don’t wait this long and look for an answer that a good physical exam can often diagnose and confirm with an ultrasound. Once diagnosed, “blood thinners” are used to both dissolve the clot and prevent another from forming. Activity, as John learned, is often backed off a bit.

Then the reason for the clot and the potential for recurrence need to be determined. If the first question is answered and there is low risk for recurrence, then typically a few months of medications are called for and that will probably be it. If no obvious explanation is found and/or there is risk for recurrence, then meds and/or activity modifications may be the long course of action.

So what is the second take-home message? Blood clots are rare but do occur, even in athletes and others who don’t fit the picture I learned in medical school, as there’s sometimes the unknown risk factor that has to be factored into the equation. So if you find yourself, like John did, with more questions than answers and it’s because of pain in your calf or leg and/or swelling in your ankle, then remember his story. Don’t wait for it to get better on its own. Listen to your body. You may be wrong, but this is one of those times when it’s better having someone tell you you’re wrong than finding out the hard way.

Read the second part of this story in Everyday Cyclist” on page 13 where John Speare gives a first-person account of his blood clot.

By Bob Lutz