I've just started the Couch to 5K program (about three weeks ago) and I've heard in many places that you should be able to carry on a conversation fairly normally while you're exercising. If you have trouble talking normally then you are working too hard and need to turn it down a notch.

Is that true? Am I really expected to be able to talk basically normally while running? I must be much more out of shape than I thought.

The running parts of my program don't feel particularly hard (I'm not exhausted at the end and my breathing returns to normal within a minute or two of finishing the walk/run) but I can't carry on a normal converastion while exercising. I need all the oxygen I can get! I'm definitely breathing quite heavily. Does this mean I should be toning down the exercise (I'm already only running in 90 second intervals...how much more toned down can it get)?

Funny...it always seemed to me that if you could carry on talking normally while exercising...the exercise must not be that hard for you and you're perhaps not working hard enough to get all the benefits of a workout? I could be totally wrong!

Typically, when you can hold a conversation during cardio exercise, you are still operating in the aerobic zones of cardio, meaning that your body is still utilizing fats as a primary fuel source. And typically, if you cannot maintain a normal conversation during cardio, you've crossed the anaerobic threshold, meaning that your body can no longer produce any extra energy from fats and sugar becomes the primary fuel source.

It's not necessarily bad to train above your anaerobic threshold, as there is plenty of great cardiovascular adaption that occurs as a result of training at such a high intensity. Really though how much time you spend above or below the anaerobic threshold depends on your training goals.

x2 Phase is right on!

Also, if you can hold a conversation, you are not going too hard and you can go longer and burn more fat.

Great information, thanks!

Can't imagine slowing down my pace much...I'm already quite a slow runner. Much slower and I think I'd be running backwards. But I'll definitely take it under advisement.