Explain what is happening at the level of individual sarcomeres when a person is using his or her biceps brachii muscle to hold a weight in constant position. Contrast this with what is happening at the level of individual sarcomeres when an individual lowers the weight, as well as when the individual raises the weight.

The Z disk closer together when the position constantly crossing the bridges. The weight pull forced apart from each other by equal forces.

Sarcomeres are the same in the length. When the lower weight of the bridges occurs than the original weight, the sarcomeres get lengthen.

On the other hand when the weight raises the forces than the weight will increase and sarcomere get shorten.