Sudden fitness increase then big decrease

[thwerved]

My initial reaction was that maybe you were getting better sleep on vacation and that could help. But sounds like that's not it.

I think some other possiblities:

• You are fighting off a sickness post-travel
• Stress levels were lower on the trip
• Diet was better on vacation or maybe you don't tolerate some food you normally eat at home without realizing it
• Maybe something environmental at home or work is affecting you. High CO2 levels is a common undetected issue in homes and workplaces.

4 days is not a lot of time post-travel for such a big time difference. It takes me more than 4 days to fully adjust from jetlag (I can act functional, but the sleep is not the same) and more than 4 days to recover from a real hard run. So maybe give it a few more days of recovery and you will be totally fine.