[Terra Nova]

Originally Posted by Trevor M.

Moderate intensity assumes cellular respiration aerobic metabolism. The substrate utilization for ATP formation would be split between both fat and glucose molecules(mainly from glycogenlysis reactions). The overall ratio of fat to glucose molecules used depends on the overall relative intensity and duration of the given exercise.

In which case, this means that so long as liver and muscle glycogen stores remain sufficiently stocked. Blood glucose levels should remain somewhat elevated, but, stable throughout such a short duration.

Thanks for the detailed reply Trevor ...really appreciate it.

The ratio, intensity and adequate energy stores issues you cited make perfect sense.

On this issue of blood glucose and the ' 2 minutes ' . In this example I gave, of where I might do a fasted session of 30 minutes of moderate intensity cardio, do you any any idea what the bio-chemical / physiological rationale is for the author to make the claim that the glucose in my blood would only provide about 2 minutes of glucose energy to fuel the fasted cardio ?

Any thoughts as to why it isn't longer than 2 minutes - for example, maybe 5 - 10 minutes ?

Originally Posted by Trevor M.

Of course, a diabetic has an increased likely hood of having a hypoglycemic episode during exercise or a person who ate a very high GI meal before exercise, Or the person who started exercise with an already reduced glycogen storage.

Again....makes sense.

Originally Posted by Trevor M.

Yes, Pre-exercise and during exercise snacks can reduce glycogenlysis reaction thus sparing glycogen and increasing exercise duration.

I've read many studies that show snacking during marathons and so on can extend the marathoners capacity to continue.
Of course, the breakdown of glycogen in such a situation far out paces the formation of it. So the benefit is limited.

Interesting.

So, going back to my session of 30 minutes of moderate intensity cardio...and assume for argument's sake it burns 250 calories over the 30 minutes. And lets say I did have that pre-workout snack of about 150 calories ( mostly carbs ) about an hour before ....and it's digested before I train.

My general understanding based on what you've said is that my body will fuel that cardio ' primarily ' with energy sources derived from some combination fat and glycogen. Would those 150 calories I have before cardio be reflected primarily as a bump in blood glucose ? And would my body preferentially access this excess blood glucose first before it taps ' stored ' energy sources such as fat and glycogen ?

Originally Posted by Trevor M.

However, in such a short workout time as you described. A mid exercise snack would be unnecessary.
The average person can carry a max of 1,400-2,000calories of glycogen. I highly doubt this could be depleted in 30 minutes by just about anyone.
muscular fatigue sets in before glycogen depletion occurs anyway so again it is unlikely.

So, is it safe to say, assuming stored energy source are topped up, that a small pre workout snack's primary purpose before something like a 30 minute moderate intensity cardio session is to simply ensure blood sugar levels are / remain stable and the pre workout snack should not be considered as a significant source of fuel for the cardio session itself ?

Originally Posted by Trevor M.;522313I'm a bit in a hurry and kinda rushed through this. If you need to know something else or have something explained a tad more in detail [I

feel free to ask[/i].

Will do ...thanks again for all your help in trying to help me sort out this issue in my mind.