During contraction of muscles following do not take place :-

I'm sorry, but you didn't provide a specific question related to muscle contraction. However, I can tell you that during muscle contraction, the following does NOT occur:

1. Lengthening of the muscle: During contraction, muscles shorten to produce movement.

2. Decrease in calcium ion concentration: The concentration of calcium ions actually increases in the muscle cell during contraction. This is because calcium ions are necessary for the interaction between actin and myosin, the two proteins responsible for muscle contraction.

3. Separation of actin and myosin filaments: During muscle contraction, the actin and myosin filaments slide past each other, they do not separate.

4. Decrease in ATP consumption: Muscle contraction requires energy, which is provided by the breakdown of ATP. Therefore, ATP consumption increases during muscle contraction, not decreases.

Please provide a more specific question if you need more detailed information.