3-weeks on, 1 week off

I received some advice from a few people who say that reducing intensity or taking the fourth week off is good for recovery, and that hammering yourself week after week with no break will come at a cost. If you are training hard, the body will see a tremendous drop off in adaptation after three consecutive weeks. Is there any truth to this? Also recommended is to down cycle in week 5, and build back up again, rather than pick back up where you left off in week 3. Anything to this?

Do you think that such a rule would be accurate and generalizable across a broad range of individuals at varying stages in their training career with varying life stressors, sleep habits, and other recovery resources, and across a broad range of training programs?

Can you see any downside to pre-emptively setting an expectation that performance / adaptation shows a “tremendous drop-off” after three consecutive weeks?

I think I see what you mean. It really depends on many different factors (calorie intake, stress levels, sleep patterns, genetics, training intensity, etc.). The downside of having a 3-week cycle is setting performance limits on myself when it may not be necessary.