What does trajectory mean?

Trajectory means the path that something follows.

It's almost always used to describe things that are dropped, thrown, or shot,
like the trajectory of baseballs, golf balls, and canon balls, or other things moving
under the influence of gravity, like comets, asteroids, and planets.  But it doesn't
have to be the path of something sailing overhead from one place to another.
You'll also hear about a person's 'trajectory through life'.

All are great precautions but you can still lift lighter and different muscles in between hard workdays. this keeps other muscles not usually used in shape.