Exercise ball standard exercises, such as a push-up, on an unstable surface can be used to increase activation of core trunk stabilizers and in turn provide increased trunk strength and greater resistance to injury. Fitness Experts and some doctors also recommend sitting on an exercise ball instead of an office chair. That is based on the theory that the abdominal and back muscles are constantly engaged and active to maintain proper posture and balance on the ball. There is no scientific evidence of those benefits occurring by just sitting without additional exercises. However, some people warn against using a Swiss ball as
Q-ball can have an energy per unit charge that is less than formula_21, meaning that it cannot decay into a gas of individual particles. Such a region is a Q-ball. If it is large enough, its interior is uniform, and is called "Q-matter". (For a review see Lee "et al." (1992). The thin-wall Q-ball was the first to be studied, and this pioneering work was carried out by Sidney Coleman in 1986. For this reason, Q-balls of the thin-wall variety are sometimes called "Coleman Q-balls". We can think of this type of Q-ball a spherical ball of nonzero vacuum expectation value.