Get in plank position with your hands wider than shoulder-width apart (A). Lower your chest as close to the floor as you can. Holding that position, lift your right knee to the outside of your right elbow (B). Return to plank position, then push back up to start; repeat on the other side. That's one rep. Do three sets of 12 to 15 reps, resting for 30 seconds between sets.
Get out of the medicine cabinet and reduce your risk of heart disease the natural way. A meta-review of a variety of studies and trials conducted by researchers in 2013 — encompassing 305 trials with more than 339,000 participants — found that no statistically detectable differences existed between those who exercised and those who were given medications in the prevention of coronary heart disease and prediabetes. (4)
You'll also build muscle to fill out your arms and firm them up. “Generally, when people are complaining about underarm jiggle, they’re usually referring to the area that is governed by the tricep,” says Williams. “If the jiggle or looseness in that part of your arm is due to a lack of muscle, then strengthening and building muscle in your tricep will also create some change in the aesthetic of that area.” She recommends performing triceps push-ups, extensions, and dips to hone in on that area and add some muscular definition to your arms.