The Indianapolis Colts’ quarterback, Andrew Luck, has been sidelined with a traumatic lacerated kidney. When he will return is uncertain. The quotation below comes from an article about his injury.

The Colts are handling Luck as carefully and cautiously as possible, and with good reason. Doctors know that Luck cannot risk elevating his heart rate because it would pump more blood through his kidneys, delaying the healing process, according to medical sources.

I don’t know who the unnamed medical sources are, but the renal response to exercise is to decrease renal blood flow not to increase it. The kidney receives about 20% of cardiac output. It has a great capacity to safely withstand a marked decrease in blood flow. Thus, when more blood is needed by other organs, like skeletal muscles during exercise, blood is diverted from the kidney to these organs. I have no idea when it will be safe for Mr Luck to return to action, but the explanation offered above is incorrect.