You don't have to suffer through stationary, hours-long flights.

Struggling to reach common fitness goals doesn’t mean you’re failing—according to U.S. training experts, it may be the smartest way to build long-term strength and endurance.

So, your diet has been on point, and you've been cranking out tons of situps at the end of your lifts, but still, the set of defined washboard abs you were promised has yet to show up. What gives? You ...