I've been trying to get into the practice of cycling regularly. I got a great deal on a K2 Sidewinder mtb and have been slowly converting it to a street bike. I find that after 2 or 3 days of cycling it becomes noticeably more difficult as my legs become much stiffer and don't relax until I do. My endurance hasn't seemed to change at all, but my speed definitely has. I generally only ride for half an hour to an hour at a time, but my distance traveled has more than tripled in that time. (Only been riding regularly for about a month)
Switching from mtb tires to road tires has made a huge difference in my avg speed and I'm sure that plays a large part in how much distance I cover, but I also believe that my legs have been getting much stronger. I still have yet to quit due to any respiratory issues, but rather it seems my legs just lose their strength over the course of the ride. (Possibly due to lactic acid buildup or lack or proper oxidation). It's probably just something I'll overcome with more time.
Haven't noticed an increase or descrease in performance since I started using e-cigs, however, I never smoked too many real cigs. (On average 1-2 per week, lol) I regularly used my homemade vaporizer pipe and dried hooka
tobacco though (once or twice daily).
