Jimmy, Greg and Kim are all worried when Christine's hair starts falling out in clumps, and advise her to go to the doctor to get it checked out. The doctor tells Christine that she might be stressed out, and should exercise more. Since Kim and Greg work out at the studio gym (which offers free day care), Kim invites her to join them. Although she'd sooner go bald, Christine gives in, and Kim even manages to convince Jimmy to tag along for moral support -- by telling him that she gets hot and bothered seeing Greg work out. After the four bump into Billy and Roy at the gym -- who go to scope out the chicks -- Kim confesses to Christine that she doesn't get hot at all when Greg works out, but it's the only way she can get him to exercise. Jimmy is no happy camper when he and Roy see their masculine boss, Bess, in the middle of boxing training. Jimmy suspects that Bess hates him, which certainly seems the case after she jokes that he's fat and out-of-shape, but is too afraid to say anything out of fear that she'll fire him. After's Bess' session is over, Jimmy hops into the ring, and Christine soon follows his lead. The two decide to put up their dukes for fun, but Christine gets a little too rambunctious -- and knocks Jimmy out in front of the whole family. While nursing Jimmy at home, Christine says that she feels revitalized, but Jimmy is too sore to help her celebrate. When Bess takes potshots at Jimmy the next day at work, he challenges her to a match -- her and Christine. Bess tells him it's on, and Jimmy hopes that Bess will finally shut up after Christine whoops her butt. Jimmy tricks Christine by bringing up her health and recommending she get a new sparring partner. Why, like Bess. Jimmy acts as Christine's trainer for the big event, but Christine doesn't hit Bess anywhere near as hard as she hit him, and Bess quickly knocks her out. After the match, Bess tells Jimmy off for letting his wife fight his battles for him, which is when Christine learns of his diabolical plan. Once Bess has left, Christine shows him how hard she can hit, as she takes out all her aggression on him. Realizing that the only times she's felt good recently were when she was hitting him, Christine tells Jimmy that the cause of her stress is him. When he asks her why she hasn't been letting him know when he does something that bothers her, she says that she doesn't want to be the kind of nagging shrew wife that Kim is. But after he finds out what it is about him that bothers her, instead of changing, he suggests they go to the gym once a month so she can beat him up.