Possible Clues:

• Athletic
• Ignited high explosive, getting to flex with no difficulty
• Being agile, he put the light on first
• Like an acrobat
• Being lissom turned on the man
• Supple man got down first
• Not inflexible - still, it helps a bit
• Fired by fellow of flexible frame
• Are you the big stiff after fiftyone? On the contrary
• Physically supple, agile