Sickness

It sucks to be sick on a training plan.

There are some people that try to train in any condition. They can run with fever, swollen knees or in between sessions of vomiting. This is the case mostly for "elite runners". On the other hand, some people skip training due to the smallest possible medical inconvenience. General fatigue, minor muscle stiffens, 1 cough in the morning.

None of this is good, because both are opposed to the 1st and 2nd pillar of training. Consistency.

If you train when you shouldn't, you will very likely make your illness worse which will eventually stop you from training for much longer than if you would just rest. Hence undermining the 1st pillar, consistency. Even if you will not end up in bed, you are risking to hit a plateau much sooner, an failing the 2nd pillar, progressive overload. Doing this can cost you a surprising amount of time. One week not spend at properly healing from a sickness can easily turn into 2 months of non existent progress.

On the other hand, if you could run, but didn't, you lost 1 day of training. On its own, it clearly undermines the 1st pillar, but only a little. Isolated incident is completely fine. You could move your schedule by one day, maybe skip one of the short runs to get the day back. Something like this can be absorbed, if it is an isolated incident. Like once every 2 weeks. It becomes problem if it becomes regular. Luckily catching this is not too hard if you keep a running diary.

If you are actually sick, mentally prepare for a big hit to your training plan. Personally, my sickness usually takes 1 week. 1 week during which I really consider myself sick.

TODO (next week is A, instead of A+1, I am sick, then instead of A+2 I do A-1 or A -> congratulation, lost 3 weeks of training)