Scientists are creating vaccinations that prevent people from getting bird flu. If the virus mutates, a new vaccine needs to be made. The vaccine needs to be tested, which can be dangerous. It also takes a long time for scientists to know whether the vaccine works.
The human movement is 4
exercises that use body weight is 5
contracting muscle is 12
holding a contraction is 8
decreasing the angle is 6
strengthening is 3
increasing is 7
lengthening of a muscle is 10
maximum amount of force is 1
isolating muscles is 15
undesirable movements is 14
shortening muscles is 9
sustained contraction is 2
opposing action is 13
increasing the weight is 16