Cardio, weights, or sex? If you've ever been curious about the caloric burn of sex -- or the average duration -- this episode is for you. Arnold also shares his perspective on days when you don't want to workout, and how often you should be hitting PRs in the gym. In nutrition news, if you've ever tried to cut carbs, you'll want to hear about a study that revealed a surprising downside that might make you think twice about saying goodbye to bread.