Why Your Body Will Hate You If You Run 838 Kilometres in a Week

In 2019 a British runner broke a world record for amount of kilometres run on a treadmill, but here’s what he really put his body through.

Most of us have a target number of kilometres we aim to hit each week. This number can range anywhere from 24 to 96, depending on your goals and experience level.

But Jamie McDonald of Gloucester, England, ran 838 kilometres in one week—yep, you read that right, 838 kilometres—to break the world record for longest distance run on a treadmill in one week. Just three days later, Gloucestershire Live reported that McDonald was admitted to Gloucestershire Royal Hospital from complications due to this high volume in such a short amount of time.

Here at Runner’s World, we are all for running a lot, but we draw the line when running too much becomes dangerous. So we tapped Brandee Waite, M.D., a sports medicine physician at UC Davis Medical Centre, and Janet Hamilton, C.S.C.S., an Atlanta-based exercise physiologist and owner of Running Strong, to explain exactly what could happen to your body if you logged 838 kilometres in one week. (But seriously, don’t.)

1. Stress Fractures

According Gloucestershire Live, McDonald had two potential stress fractures in both of his ankles. Both Waite and Hamilton say that this is to be expected. Stress fractures typically occur in the lower legs and feet when you ramp up your mileage too quickly in a short amount of time, and is caused by putting too much repeated force on your bones. If you’re experiencing tenderness, swelling, and pain in a bone, see your doctor ASAP, as it could be a stress fracture.

2. Decreased Red Blood Cell Levels

McDonald’s blood samples, which were tested at Gloucestershire Royal Hospital, showed that his red blood cell count was half of what it was before his world record attempt.

“Red blood cells carry oxygen throughout your body,” Waite says. “People who run long distances—like ultra marathons, for instance—can get something called foot strike hemolysis, where the repeated striking of your feet can cause blood cells to rupture. Over a long period of time, this can cause anemia [or a low amount of red blood cells in your blood].” So if your red blood cell count is low, not enough oxygen is flowing to the parts of the body that need it.

3. Elevated Muscle Enzyme Levels

When your muscles are working hard during exercise, this leads to muscle breakdown, which boosts muscle enzyme—a.k.a. creatine kinase—levels, according to Waite. “But when people do a tremendous amount more than they normally do, more of their muscle product can be broken down,” she says.

If your creatine kinase levels are a little high, it’s not a big issue, Waite says—they’re typically a bit high when you’ve just finished a marathon, for instance. But if your creatine kinase levels are significantly high, that’s a problem.

While McDonald’s levels were three times the normal amount (the normal amount being anywhere from 22 to 198 units per litre, depending on factors such as gender, race, and activity level), levels that are five times more or higher can indicate rhabdomyolysis—or when your muscles get damaged to the point where some of the cell walls are disrupted, according to Hamilton. When this happens, your cells release a protein called myoglobin into your bloodstream that can cause kidney damage or failure, cardiac arrhythmia, and even death, according to Waite.

4. Exhaustion and Impaired Recovery

McDonald only got a little over 16 hours of sleep in seven days, and was, at one point, awake for 36 hours straight, according to Gloucestershire Live. Being overly fatigued can lead to not being able to maintain coordination, getting injured more easily, or errors in decision making, according to Waite.

Plus, not getting enough sleep can lead to insulin resistance, where your body can’t processes glucose for energy properly. This can negatively affect your performance and recovery. “Your body needs to sleep to be able to recuperate,” Waite says.

While McDonald’s case is extreme, we can all learn a lot from pushing the limits. Even during marathon training, it can be easy to go too hard and start to see the negative effects of overtraining take over, so be sure to take recovery runs at an actual recovery pace, and build in enough rest days to allow your body to properly recover after hard efforts.

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