This study showed that an increase in the coefficient of friction between the ball and the foot caused the ball to acquire more spin.

这项研究表明，脚和球之间的摩擦系数的增加导致了球获得更多的角动能。

youdao

If your foot feels tense, stand with one hand on a wall for support and place the arch of one foot on top of the ball.

如果你的脚很紧张，一只手倒站在墙面支撑着把一只脚放在球上形成一个拱门。

youdao

If you notice that your shoes are wearing in the normal pattern, from the outside of the heel to the ball of the foot, that means you are a normal pronator.

如果你找不到好的跑鞋商店，以下是如何分析你鞋的方法。首先为了分析你的鞋，找一双穿破的鞋，看看鞋的鞋底，注意破损的模式。

youdao

Then he would fall down on the floor again like a ball of dirt and start rubbing the side of his head with his back foot as if he had no idea he had been doing any more than any frog might do.

VOA: special.2009.08.29

Indeed, it's the support at the ball of the foot that gave my pair their distinct feel.

FORBES: The Sole of Stefano Bemer

Lance Allred remembers pre-season tryouts for the Stampede, when bad shoes literally ripped the skin off the ball of his foot.

NPR: Almost-NBA Players Take Home Paltry Salaries

Ja added the third in the 53rd minute with a touch of individual brilliance, twisting past two defenders and hitting the ball home on the outside of his foot from an acute angle.

BBC: Etoile edge closer to semis