runner's rump

A dermatopathy seen in long-distance runners, which is characterised by small ecchymoses, which occurs on the superior portion of the gluteal clef. Runner’s rump is attributed to the flapping of the buttocks against each other with the running stride
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

runner's rump

Sports medicine A dermatopathy seen in long-distance runners, characterized by small ecchymoses, which occurs on the superior portion of the gluteal cleft; RR is attributed to the flapping of butt cheeks against each other with the running stride.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.