Caesar reminds Antony to touch Calpurnia as he runs today. It was a superstition that if the runner touched the woman who is trying to get pregnant, that she will become pregnant and the sterile curse will be broken:

Forget not, in your speed, Antonio, 
To touch Calpurnia, for our elders say, 
The barren, touched in this holy chase,(10) 
Shake off their sterile curse. 

Truly, this is a superstition or a wive's tale, but still Caesar instructs Antony to touch his wife Calpurnia as he runs by. Marc Antony is a military commander who fought against Pompey. He is running the course which is a ritual performed during Lupercalia Festival in which a runner strips naked and races throught the streets wearing only a thong that is cut from a sacrificial goat. 

Caesar tells Antony to be sure and touch his wife to make sure she will get pregnant in the near future. By touching Calpurnia, Antony is breaking the sterile curse. He is blessing Calpurnia with fertility to become pregnant. Along the way, the runner strikes any woman he encounters, thus ensuring her fertility. Caesar tells him to be sure to strike Calpurnia, the wife of Caesar, and Antony assures him that he will.