MotoGP Under The Knife

What’s up with “arm pump”?

Dani Pedrosa race test action at Jerez

MotoGP racers Dani Pedrosa and Stefan Bradl underwent surgery recently for a particular type of injury more common in runners than motorcycle riders: arm pump. Of course, runners experience this condition in their legs, the medical term for which is chronic exertional compartment syndrome (CECS). In the paddock, however, CECS is simply called arm pump.

CECS is a type of overuse sports injury that affects men and women equally. Most reported cases are among endurance athletes in running sports. On two wheels, arm pump seems to be more prevalent in motocross than roadracing. Not surprising when you consider the hand and arm use needed to rein in such a rowdy ride.

To understand CECS (or its much more serious relative, acute compartment syndrome) requires a beyond-basic knowledge of muscle anatomy and physiology. Muscles are bundled in a strong, thin, not very stretchy membrane called fascia—like casing on a sausage. Muscle use raises energy demand. An increase in energy demand is met by increased blood flow. Increased blood flow can cause a growth in muscle volume by as much as 20 percent, but because the fascia doesn’t expand, things get tight in the compartment. When things get tight, it’s harder for energy to get where it needs to go, so the entire limb starts underperforming. An underperforming forearm means an underperforming wrist, hand, and fingers.

Stefan Bradl after surgery

Plus, arm pump hurts. In fact, that is usually how it is discovered. Pain characteristically starts within minutes of riding and disappears within 20 minutes or so afterward. There can also be transient numbness and weakness of the hand or arm, not something any rider, professional or otherwise, wants to deal with at speed.

Unlike acute compartment syndrome, a true orthopedic emergency usually associated with trauma, arm pump is not likely to cause permanent loss of function. But, it is difficult to win a race and easy to get hurt when your hand isn’t working properly.

Because symptoms are transient, a diagnosis is easy to miss and can be easily confused with less serious injuries like tendonitis. Sports-medicine specialists know that the gold standard of diagnosis is to measure compartment pressures with the muscle at rest, during exertion, and post-exertion. This is accomplished by inserting a needle attached to a pressure-reading device into the muscle. Compartment pressures that remain elevated confirm the diagnosis.

According to the latest research, the only definitive treatment for arm pump is a fasciotomy: a surgical procedure performed under general anesthesia in which the surgeon cuts a slit in the fascia to release the pressure within the affected compartment. Typically, several weeks of muscle rest are prescribed post-op. Both Pedrosa and Bradl, however, plan to compete in this weekend’s French Grand Prix, less than two weeks after their surgeries.

I guess you could say they’re, ahem, pumped.