Time limit before fitness level drops

I've also wondered this, sometimes i've had a week or two off and when i've got back on the bike i've had great form.

cheers

I have had 5 days of the bike come back and felt terrrific probably due to body having proper rest time and allows for proper adaptation. I would say anything over two weeks, would see a drop in fitness. It depends on your fitness in the first place. An unfit person will lose the gains very quickly but gain them very quickly. Top pros will lose their top end form very quickly and have to work fairly hard to regain.

The drop in fitness is quite quick, VO2 max shows significant reductions after only 3 days of no training! Given that these changes are caused by enzyme activity, plasma volume, etc. which are temporal VO2 max returns quickly once training has resumed.

Training adaptations that are more perminent (e.g. muscle changes, blood vessils, etc.) take longer to develop and take longer to go.

Some examples:

If you have trained for 8weeks and you stop you loose everyting in the same 8 weeks.
Someone who has trained several years and then stops for 8 weeks loses about 20% but is able to stay at the new 80 % level a relatively long time.

VO2 Max loss of 8-10% after 3 weeks 18-20% after 3 months
muscle strength 35-40%loss after 3 months
Energy storage in muscles 25-50%less after 3 months.

There are as 2Lap says factors that already change in a few days time.

Note that to maintain a level of fitness you don't need to train as hard as to get it. If you trained 300k a week 6 days out of 7 to get where you are. It's possible to stay at that level with training about 120k spread over 3 sessions.

Note that its important to keep the effort at the same level.
Its better to lower the volume from 300 to 120 at the same level of effort. Then to keep doing 300k but lower the intensity by 33%.

Note that some efforts are just useless If the intensity is too low the level of gain is about equal to 0.

oh man i had a 6 day layoff and my polar vo2max test went down by 11 ???? is it accurate??? how come it drops so much??? my weight did go up by 4kg so i changed the weight settings... (wonder if its fat or water weight sheez) this is scary man anyone has an explanation for this? 2lap - u mentioned that it returns quickly? meaning that when i get back to riding the vo2 max will rise fast again ?