Dennis set the record of 52.491 kilometres at the Velodrome Suisse in Grenchen, Switzerland on 8 February, but there are a host of challengers, including 2012 Tour de France champion Bradley Wiggins, lining up for their own efforts.
"I was watching people's tweets that were saying he was holding 53 kph for 30 minutes," Dennis said.
"I was thinking that was pretty quick. Then when I saw 52 a while after that, I sort of started to relax a little bit. I was thinking I don't need to watch this and stress so much anymore.
"But it was a bit of a wake-up call when I saw that he finished within about 250 meters of me, which is a lap."
Dennis will return to the road at two French one-day races this weekend, the Classic Sud ArdÃ¨che on Saturday and DrÃ´me Classic on Sunday, after he was pressed into service by his BMC squad.
"I was not initially supposed to race until Paris-Nice but the team is a little bit short and I was asked to help out," he said.
"I didn't think it would be such a bad thing to be with the guys, have some fun and get a little racing under the belt again."