HI!

This was a conversation on this board and I can't for the life of me remember WHO asked me whether we destroyed heart muscle by exercising above our recommended target heart rate zone.

This question was very relevant to me because I jog at 170-180, well above my target heart rate zone of 155. 

I asked my personal trainer and this is what she said: 1) go ahead and work out above your target heart rate zone PROVIDED you dont have any heart issues. If you (i.e. me) feels tired/exhausted/over-exerted, drop down to the recommended heart rate.

When I pointed out that I wanted to be FASTER for my 5 and 10Ks and that when I exercise to the target heart rate zone I am going a slow 3.2 mph, she pointed out that as ones heart becomes better conditioned, the heart rate will lower and I will have to run FASTER to achieve the target heart rate.

She did not say anything about destroying heart muscle by exercising above the target heart rate zone.

I hope this helps.

First, let me say that the following may be wrong. But, it is my understanding that all muscle (all cells, for that matter) are always breaking down and being replaced. Cells don't last forever. This is one reason we need protein, since only protein can build muscle.

Normal activity replaces old cells with new. Activity that stresses muscles over time, such as lifting heavy weights with low repetitions, will not only replace worn and damaged cells, but build new, extra muscle. Stressing your heart muscle will cause damage. Too much, obviously, is bad. But proper stress will strengthen and build heart muscle.

You are correct. When we lift, run, etc...we are breaking down muscle and rebuilding it.

I think what Grim Traveller said is true. It was my understanding that you get maximum fat burn by staying in your target zone. Something to investigate.