The 38 year old Radio Shack rider struggled today on the eighth stage which was won by Andy Schleck.
Armstrong finished close to twelve minutes behind the rider from Luxembourg but said on his Twitter page: "When it rains it pours I guess.. Today was not my day needless to say. Quite banged but gonna hang in here and enjoy my last 2 weeks."
Armstrong is in 39th place on the first rest day and is 13 minutes 26 seconds behind the lead Cadel Evans.
The current placings for the British and Irish riders are:
Bradley Wiggins is 14th, Nicholas Roche is 16th, Geraint Thomas 69th, Charles Weglius 83rd, David Millar 117th, Steve Cummings 135th, Mark Cavendish 149th, Daniel Lloyd 159, Jeremy Hunt 160
Picture copyright of Covsupport News Service. Credit CNS/KM