<13 post viral under performing

How much under 13 is he? To have someone that young running 400-800m track reps seems quite severe, especially a month or so after a viral infection. How much and how hard does he train, and more importantly, is it through his own motivation? What sort of infection was it and how long did it last?

If you can establish whether or not he has fully recovered physically, there is always a chance that he is worried about becoming ill again. He might interpret signs of tiredness inappropriately and slow down. Has he said what he is actually experiencing before or as he slows down? Have you asked? Does he think there is a risk of falling ill again?

Have you checked his iron stores level. I realize he is a boy but this is common in girls of that age and I have also known it to be a problem with slight boys. They may have the desire to go in a race but towards the end there is nothing left. Check the ferritin level, add Slow FE if it is low and expect it to take at least 6 weeks to make a difference. Also talk to him about his diet - does he eat red meat?

Anyone know of anything better to get iron stores back up than Slow FE and red meat?

I am a 33 year old man, 10k pb 35mins. My training has been going fantastically well all of 2003 - I credit pponline and sports coach for this - my race times in the autumn relays were 45 - 150 secs better than 2002 on the same courses of 3000 - 6000m. I was on track to smash my 10km pb in mid Feb - I was aiming for 33ish mins.
I too contracted the flu in mid November and even with almost 2 weeks off, and a slow build up until Xmas I have been unable to return the same training performances. My efforts have been laclustre at best and I am finding great difficulty in motivating myself to train.
3 times in my life I've had Post Viral Syndrome or Chronic Fatigue Syndrome - at 16, 19 and 25. The last time was the worst - I finished my usual 4 mile Tempo run in 20mins 12 secs, next day the flu started to work on me 6 weeks later the same run at a greater effort took me 29:30. I took me almost 4 years to fully recover my energy and that same tempo run now is done in sub 23.
I sincerely hope your boy does not go into this spiral, it is your duty to make sure he doesn't overtrain, eats properly and maintains an enthusiastic approach to training.
Best Regards

ps. Overtraining is only under-recovery