The 50-year-old Illinois man is trying to reclaim his world's record for continuous exercise.
He's riding a stationary bike in a YMCA and hopes to keep spinning until Sunday morning.
That would be more than 132 hours straight.
Until last summer, Hood held the record of 111 hours, 11 minutes and 11 seconds on a stationary bike.
It was passed by a cyclist from Tasmania.
Hood, who's a retired Drug Enforcement Agency investigator, says his record attempt will also raise $50,000 for the YMCA.
