Sudden Fatigue During Workout

[Longstreet]

I have included running in my workouts my whole adult life (I'm 79 years old). Currently, I do two sets of pushups (79) before mounting the treadmill. I run two-minute intervals (10) and one-minute intervals (20) on alternative days. At the end of April, I was running 7.0 mph and walking 3.6 mph on the two-minutes, and running 7.5 mph; walking 3.6 on the one-minutes. Since the beginning of May, my performance has plummeted. In fact, I am now "trying" to do 6.0-3.6 on the two's, and 6.5-3.6 on the ones, but not able to complete the 10/20 intervals, as I hit the wall at about 2/3-3/4 of the schedule. I can sometimes will myself to finish, but usually, have to give it up, as I just can't push through it.

I have changed nothing in my diet, my exercise program, nor my daily activity, yet I have gained abut 10 lbs (from 165). I've never experienced this before, so I'm completely baffled. Anyone have any ideas?

[napalm]

Could be cardiac in nature, go get checked out...