Ragnar's sluggish reflexes were not up to matching him.

"For a human, I suppose, with sluggish reflexes and the frailties of a physical body prone to infirmities."

This explains the fatigue, muscle weakness, low tone and sluggish reflexes in muscle groups.

Eventually Karr's sluggish reflexes kicked in.

Bolan moved on, seeking his targets, knowing he had only a second or two of confusion and sluggish reflexes on his side.

Tristan studied him: about twice his own weight, a couple finger-widths taller, but with sluggish reflexes.... "Hurry up," said Rajak.