Toning muscles can help, but cardio exercises are necessary to eliminate underarm fat.
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When jiggling upper arms keep women from wearing short sleeves or going sleeveless altogether, an effective upper arm workout can tighten up that area. Do exercises that target your triceps, the muscle on the back of your arms. If you're concerned about building excessive muscle, you can tone and strengthen your triceps to keep the back of your arms from sagging and shaking without bulking up.
Single Most Effective Exercise
Getting rid of flabby arms is among women's most frequently stated goals in the gym. That's one reason the American Council on Exercise devoted an entire study to finding the best triceps exercises. Out of eight exercises that focus on the triceps, only one was found to elicit significantly more triceps muscle activity than the others. The triangle pushup registered 100 on the electromyograph from both the long and lateral triceps heads. Just do a normal pushup, but place your hands flat and close together on the floor beneath your chest with your thumbs and fingertips touching to form a triangle. When you push up and are at the top of the move, your arms and chest will form a triangle, too.
There are two additional exercises that come close to triangle pushups in the amount of muscle activity elicited from your triceps. They are triceps dips and kickbacks. Though listed as the second and third most effective triceps exercises, they still only register 87 and 88 on the electromyograph. You don't need special equipment to do dips and kickbacks. Simple household items can be employed to perform them. For example, sit in a chair and place your hands on both arms, then lift your body up by extending your arms, and dip back down by bending your elbows. Or, bending over a bench or chair, hold a large can of food or a jug of water in your hand to do kickbacks. Extend your arm back until it's straight, bending only at the elbow and keeping your upper arm close to your body.
Low Weight, But Not Too Low
Doing a high amount of reps with light weights used to be the go-to strategy for women to tone muscles rather than bulk up -- but if the weight is light enough that you can do more than 20 reps, you won't see any significant effects. According to Alex Hutchinson's 2011 book "Which Comes First, Cardio or Weights?" you should use at least 50 percent of your one rep maximum weight and be able to do three to six sets of six to 12 reps each. Women's fitness magazine "Oxygen" advises working your triceps twice a week on non-consecutive days for toning.
Toned Biceps for Balance
In your quest for toned triceps, don't forget the importance of toning your biceps, too. Focusing only on the muscles at the back of your arms while ignoring the front will cause muscle imbalance and make your arms look out of proportion. Chin-ups done with an underhanded grip and curls with dumbbells, barbells or cables are the best exercises for targeting your biceps. Maintain proper form while curling by keeping your back straight, gaze forward and upper arms at your sides. Move only at the elbows, bending them to bring the weight up to just below your chin and extending them to lower the weight down.
Flab Source Matters
Flabby arms can be the result of fat, underdeveloped muscle or excessive skin. In some cases, triceps exercises will have limited results. Cardio exercises will burn fat from your entire body, including the fat on the backs of your arms. Excess skin can be a more difficult problem. In her article for the IDEA Health and Fitness Association Dr. Natalie Digate Muth says that after skin has stretched, it is limited in the amount that it can contract, and exercise cannot tighten up loose skin.