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.
We've got some happy news that will rev up your workout routine: The moment you head out on your run, launch into your Spinning class, or start your Pilates session, the benefits of exercise kick in. "We see changes in the body within seconds," says FITNESS advisory board member Michele Olson, PhD, professor of exercise physiology at Auburn University at Montgomery in Alabama. Your heart rate increases, and blood is delivered to your muscles. You start burning calories for fuel. And you get an almost immediate mood boost.
“Being active as we age can play a role in cognitive function, and reduce the risk of disease such as dementia and Alzheimer's,” says Amanda Paluch, a postdoctoral researcher at the Northwestern University Feinberg School of Medicine. “Research has explored several mechanisms, finding that exercise can increase synaptic plasticity and strength of nerve impulses in the brain, and have a positive effect on the hippocampus.”
The skin also serves as a release point for heat. (See “Why Does My Face Turn Red When I Exercise?” for more on that.) When you exercise, your muscles generate a lot of heat, which you have to give up to the environment so your body temperature doesn’t get too high, Hackney says. The heat in the muscle transfers to the blood, which shuttles it to the skin; it can then escape into the atmosphere.