See the rest of Slate's Fitness Issue.
Also in Slate's Fitness issue, Emily Yoffe gets shredded by Jillian Michaels and coddled by Jack LaLanne and our foreign correspondents reveal the latest global workout trends.
Listen to Our January Music Roundup Beat the chill with our winter playlist, exclusively for Slate Plus members.
Is Snapchat Really Confusing, or Am I Just Old? A 32-year-old’s hopeless quest to understand America’s fastest-growing social app.
Another Data Point New England’s incredible ball security is not impossible, but also not meaningless.