is harder on the soles of your shoes
than on the knees of your trousers.
The patella, otherwise known as the knee cap, is a free moving bone; that is, it is not attached directly to any other bone and it moves with the leg to protect the knee. But it doesn't go all the way down. Even at its lowest point it still leaves some of the muscles and tendons exposed. Which means the human body was not designed to kneel. Thus many churches have prayer cushions so that worshipers won't hurt themselves while kneeling in prayer.
But that does not mean the human was not designed to pray. There are many ways of praying. In some areas of the world it's still done by animal sacrifice or self flagellation. Some write their prayers on paper and hang them on trees or stuff them into walls Some churches use incense "the prayers of the saints," Rev. 5:8. There's a fishing village somewhere in Italy that takes the statue of its patron saint down to the sea once a year and threatens to throw it in the water if the harvest isn't good. I don't think they ever carried out that threat, good harvest or bad. And Thomas Merton found that for him jazz was prayer.
I think what O'Malley is saying is that once you've prayed for what you need, kneeling, sitting, standing or lying down, then put on your shoes and go help the heavenly powers to get it done.
DB - Vagabond Journeys