This is not actual battle, but arm wrestling. Matches like this cant ve decides in one second, if one one side has much more strenght than the other, like in this case. She can broke Kisames arm in few places in one moment - she has more time than enough to definietly win this.
But as soon as the power is released she has to go through the process all over again, and if your vastly superior, physically to your opponent the match can end in a matter of a second. It could be as simple as
Ref: Alright and begin!
*Kisame slams Sakura's hand to the ground*
Kisame: Done.
Sakura's base strength is very much below's Kisame's for that to be a possiblity and chakra enhanced strength wont' work in this situation.
that's not how chakra control works, you exert chakra into your body parts, that's how its always worked. Back in part 1, she would exert chakra to her legs to move faster. Chakra bursting at points of impact is how gentle fist works, not chakra control.
That's how Sakura's technique works as well, she focuses the chakra into a point and then releases it at that one point. Difference between gentle fist and this technique, chakra goes into opponent's body with the gentle fist and Sakura's technique releases externally into physical power.
Here's the concept of Sakura's technique. When you throw a punch you generate your power into your fist by taking your power from the ground and channeling it through your body into your fist and then when you hit something, you release all that power. That's what Sakura's technique is based on, the simplicities on throwing an actual punch however your generated power would be chakra instead starting from the ground.
She's focusing the chakra all the time maybe but she's not releasing it in the same way when in an arm wrestling match and even if it's all stored it's nothing until it's exited the body in some way.