There’s a bit of a (dare we say it) call-to-arms situation happening this fall. Wedding season seems to be lasting longer than ever, and holiday season is (somehow) already around the corner, so it’s like we're still going sleeveless every weekend. Plus, if you’re like us, MObama’s presence on the campaign trail is probably inspiring you to blaze a trail straight to the gym, because... Damn. Those guns!But, the thing that sucks about arm exercises is that they’re boring beyond belief, not to mention frustratingly complicated: You’re afraid to add bulk but desperate to banish that bleepin’ bicep blob and tighten up that weird underarm waddle. We’re right there with you. That’s why we called on Ary Nunez, founder of Gotham Global Fitness and Rihanna’s trainer of the past three years. Her top five “Ninja” moves for sculpting sleek, sexy arms are all martial-arts inspired — and designed to give you major definition (and each move comes with the option to do it with or without weights — which really makes this the ultimate at-home workout).