3-Step Arm Workout From Cameron Diaz's Trainer [2] Is it just me, or do Cameron Diaz's arms look better than ever? The Summer heat has allowed the actress to show off her toned arms while promoting My Sister's Keeper, and those sleeveless sheaths are nothing but complementary. Cameron's trainer, Teddy Bass, kindly shared a few tips on how to work your muscles to tone up for tank top season.