What is a meaning of the Physical Jerks in 1984 by George Orwell?

The Physical Jerks are a daily form of rudimentary exercise forced upon members of the Outer Party. It is equivalent to the calisthenics that physical education classes generally have students do. Every morning, the telescreen comes on and a person leads citizens through a series of stretches and light exercises. Because the telescreens are capable of broadcasting and watching, the effort of each citizen can be monitored.  

Suddenly, a voice from the telescreen interrupts him, yelling out his name and identification number and urging him to "bend lower." Feigning interest and determination, Winston complies, and succeeds in touching his toes for the first time in many years.

The Party sells the idea of mandatory exercise to the citizens by telling them the government wants to prevent weight problems, but the Party is interested in more than the general health of the population. The Physical Jerks are another way the Party displays its absolute power over the people. It is another form of repression and control. This time, though, the control is over people's physical states. The general propaganda is mental control, and the Physical Jerks is physical control. Both allow the Party to maintain total control.