I have spent the last 6 weeks getting back into form, ready for winter training. After a period of almost 12 months without any training. Prior to that I was doing hard 5hr rides most weekends and 11-12hrs of structured training a week and my peak FTP was about 290w. I am not a racer. I didn't seed my CTL when I got back into training, I figured I was in pretty poor shape and started from zero. After a month got to a CTL of 45 and had been liberal with rest days. I started to up the intensity and keep an eye on my TSB, RHR and general fatigue. My goal being to get my FTP to around the 260 mark and work on getting my CV system restarted. I have found that a TSB of -50 or worse is about the time I need to take a rest of more than one day and that at -30 I should take it a bit easier taking perhaps a recovery ride or something. This has lead me to wonder -- how low is too low for TSB? As you become better trained can you do more work with less rest? What do you guys here think? How low have you taken your TSB? Did you get any adverse effects?