Q: I have been a runner and triathlete for 30 years. I am 45 years old now. I have read that you suggest exercising for 30-45 minutes moderately. In order to train and run marathons, I need to exercise for longer periods of up to 2.5 hours once a week during my build up. Is this unhealthly for body and brain?
A: Once a week should be fine, but beware of overtraining because of its impact on cortisol levels as they begin to rise after about 45 minutes of an intense workout. This is why many world-class athletes train twice a day but no longer than 45 minutes per session to avoid the rise in cortisol.