Physics and animation

Hi to everyone!

Im creating a 2d Platformer game with cocos2dx and im starting to understand the physics but I have a problem when I combining the animation with the gravity.
In my game when I press the right key of the keyboard, the character start to run, for that animation I use this code:
{
auto animation = Animation::create();

	for (int i = 1; i <= 14; i++)
	{
		char szName[100] = { 0 };
		sprintf(szName, "mov%d.png", i);
		animation->addSpriteFrame(SpriteFrameCache::getInstance()->spriteFrameByName(szName));
	}

	animation->setDelayPerUnit(0.1f);
	personaje->runAction(CCRepeatForever::create(CCAnimate::create(animation)));
}

The problem is that my character rises up when the animation start, I found that the problem is when i put the DelayPerUnit.

animation->setDelayPerUnit(0.1f);