Hey gang! Don't miss out on this incredible offer at www.groupon.com It lasts today only! Sweating by oneself in a gym or underground elliptical bunker can cause blinding rage or the common cold. Work out with pals in the sunshine during boot-camp classes with Gut Check Fitness. With this Groupon, $29 gets you five boot-camp classes, a $75 value. Gut Check is run by Joe Decker, who broke the Guinness World Records Physical Fitness Challenge Record in 2000 for completing 100 miles of cycling, 10 miles running, five miles of power walking, six miles kayaking, 10 miles hiking, two miles swimming, 3,000 abdominal crunches, 1,100 jumping jacks, 1,000 leg lifts, 1,100 push-ups, 10 miles on a rowing machine, 10 miles on a Nordic Track, plus 278,540 cumulative pounds of weight-lifting all at once and all in less than 24 hours. That means he's fit. Decker’s workouts are full-body, muscle-toning, fun agility exercises with heart-pumping workouts. The schedule includes classes at 6 a.m. in Torrey Hills Park, 9:30 a.m. at La Jolla Shores and Torrey Hills Park, or 5:15 p.m. at the Carmel Valley Rec Center with one of Gut Check's friendly, energetic trainers. During a workout, Gut Checkers may lift rocks majestically above their heads, flip tires, or carry each other on their backs up steep inclines simply for the love of exercising. The instructors won't make you march in step, salute them, shave your head, or do push-ups until your arms quake worse than San Francisco in 1906, but they will make you sweat buckets and challenge, tone, and trim your body. Reviews Gut Check Fitness won 10news.com's A-List award for Best Boot Camp in 2009, and it has a perfect five-star rating on Yelp: I have never had more fun getting my butt kicked in my life. If you are into fitness or want to be into fitness, look no further. – trevor h. Don't expect to pump iron in a gym, but you should expect to get in incredible shape if you let Joe and the rest of his clients motivate you to push yourself as far as you can go. – Derek L. Joe Decker runs the best boot camp in San Diego. – Brian B.