[Sis290025]

When glycerinated rabbit muscle fiber was placed in 10^-4 M of CaCl2 solution, the percent change in length of the muscle fiber was around 93% (decrease in length).

When glycerinated rabbit muscle fiber was placed in 30 mM ATP in 10^-2 M CaCl2 + 0.05 M KCl + 0.001 M MgCl2 solution, the percent change in length of the muscle fiber was around 51% (decrease in length).

Why does the first trial (with just the calcium ions) experience a greater contraction than the second solution with both ATP and calcium ions?

Any response is appreciated.   
Thank you.

[Arkcon]

There is a fundamental biological reason why, which is hinted at by the numbers involved.  Try writing all numbers on paper in a table and see if it jumps out at you.