Glycogen degradation:

If glycogen degradation  and glycogen synthesis were permitted to occur concurrently,  the  net  effect  would  be  hydrolysis  of  UTP,  a  so-called  futile  cycle. To prevent this, both pathways require to be strongly controlled.  This control is  carried  out  through  allosteric  regulation  and  covalent  modification  of  both  the glycogen phosphorylase and synthase.  Additionally, the covalent modification is under close hormonal control.

Figure: Simultaneous operation of glycogen synthesis and degradation would result in net hydrolysis of UTP.