Most think that time cannot speed up or slow down. I have found that during intervals, time is variable. During the force part of the interval, time seems to stand still and 10 seconds seems like a minute. During the rest interval, time speeds up. I look at the time and 30 seconds have passed and I am still tired. The next 30 seconds are over in what seems like 10 seconds.
My perception of Now while on the bike must be different when I am suffering or I am in recovery.