Participants in the Great Northeast Tough Mudder obstacle race climb a muddy hill in Westbrook on Saturday. Organizers of local not-for-profit races that raise funds for charities say the incursion of such for-profit events into Maine is siphoning off their runners. Derek Davis/Staff Photographer

Participants cheer as teammates drop into a pool of muddy water at a Tough Mudder obstacle. For weekend warriors, the allure of grueling obstacle courses is irresistible, to the chagrin of local race organizers watching their numbers dwindle. Derek Davis/Staff Photographer

A field of 54 runners starts off on the course during the Craig Cup 5K trail race at Twin Brook Recreation Area. Derek Davis/Staff Photographer

Katie Perkins, 32, of Plymouth, Mass., crawls through a barbed-wire-covered mud pit during the Tough Mudder obstacle course on Saturday. Tensions are rising between longtime road race organizers and the new breed of gimmicky events, which often charge more in entry fees and contribute less to local charities. Derek Davis/Staff Photographer

The question is, who will croak first? A frog sits in a pool of muddy water as a participant passes by on mile 3 of the Tough Mudder obstacle course on Saturday. Events like Tough Mudder are seen as boons to local economies. Derek Davis/Staff Photographer

Adam Farrell, 34, of Augusta tries to see past a wave of muddy water he created while swimming through the Pitfall obstacle during Tough Mudder. Organizers were expecting about 7,500 participants this year. Derek Davis/Staff Photographer

A long line forms as participants wait to do the Tough Mudder’s Arctic Enema 2.0 obstacle. Derek Davis/Staff Photographer

Runners pass through a field during Saturday’s Craig Cup 5K trail race in Cumberland. This year’s race registered only 54 participants, down from its peak of 180 seven years ago. Derek Davis/Staff Photographer