With my all respect for your knowledge, expercience, for a 40 year old man to run longer and longer distance with 200 beats per minutes is NOT an example of Muscular Endurance training done with Cardiorespiratory Endurance training, but an example of a very questionable training programme.

All the running literature I have ever read, repeat the SAME advice: keep 90% of your running milage/time in the under 85% max heart rate zone, and run in the 90+ % zone ONLY during short intervalls as part of the - usually once or twice a week - speed work. Doing MORE in the 90+% zone will NOT improve either endurance or speed, only the chance to injure yourself. Running in the 80-85% already improve your cardio health - but without damaging your legs.

The sign of good cardiovascular health is NOT the ability of enduring longer distance in the 90%+ zone, but the ability to keep your heart rate DOWN for extended period, while running faster and faster.

(I have never met any veteran runners bragging about how HIGH his heart rate is. They always proud to show how LOW it is. While "jogging" with 5-6 min/mile pace .)

Please feel free to post any new research on runners showing your point. I am ready to learn new ideas.

If you feel comfortable with this - it is ok, go for it - but before anybody else try your method, I would recommend to check some other resources.

Btw Jeff, I am very happy to see that despite of your injury you are back on the road. Good luck for your running carreer.

Cheers:

Eva