Hold your lady as if you're carrying her across the threshold. Then perform lunges, alternating legs. Three sets of 12 on each leg should be good—depending on the heft of your woman. "Any exercise where you're using her as the weight will be fun for her," says Greg Bradley-Popovich, a doctor of physical therapy in Morgantown, W.Va. "At my home gym, my wife sits atop the shrug machine for added resistance and goes for a ride."
MANUAL-RESISTANCE BICEPS CURLS
Standing face-to-face, hold a towel in your two hands and have her grab the middle of it and bring it up like a dumbbell curl. Provide just enough resistance so that it's challenging but still a smooth movement. Do three sets of 10 with both arms. Although you don't want to perform too many isolation moves with your girlfriend, this one is a good chemistry builder.
SWISS-BALL CRUNCH AND OVERHEAD TOSS
Have her lie on a Swiss ball and hold a medicine ball with her arms extended over her head. As she crunches up, have her throw the medicine ball at you, standing a few feet in front of her. Catch it, toss it back, repeat. Do two sets of 15 reps. "So she's throwing the ball at her boyfriend," says trainer Rachel Cosgrove. "What girl doesn't want to do that?"
Training Tips for Couples