An Austrian study carried out on Ironman finishers three weeks after they’d crossed the finish line, found biomarkers that proved muscles were still damaged and inflammation was still present in the body.
Mechanical tissue stress caused by several million contracting muscle movements during the season and competing should not be underestimated.
Every triathlete needs a physical and mental break after their last Ironman. Five weeks should be the minimum time before you return to a full training regime. If you had a tough season then give yourself at least an extra week.
If you fail to allow recuperation time away from swim-bike-run training, expect illness, injury and burnout. This will happen during the most important part of your training next season. Consistency, repeatability and recovery are the three ingredients for a healthy, fit triathlon career. You need to lose fitness to gain fitness otherwise you will simply be stuck in a plateau phase and will find it almost impossible to get to the next level.
Having five weeks off will NOT have a negative impact on going faster in the future. If you don’t schedule sufficient rest at the end of your season, expect the Ironman blues to continue.