'fast' is a terrible word, IMHO. Denying yourself food for a handful of hours is not the same as denying yourself food for several days, and yet both are considered fasting.
How long were the fasts you took? I am curious because my lifts suffer when I have not eaten breakfast, and I'm pretty sure it's because of the exhausted feeling in my muscles, which I attribute to the lack of food.
denying yourself food for days is starving not fasting HaHa.
I fast every day, 16-19 hrs at a time. I train completely for strength rather than endurance, so lift super heavy for 4-5. Max 2-3 sets. If you are going for muscle endurance (8reps+) then some food prior to training.
How close to your workout is your eating window? I was doing 23/1 intermittent fasting and my coach told me it would interfere with my strength training. I'm also training for strength/max lifts, not endurance.
I'm pretty sure aerobic exercise is better for the brain than strength training. Aerobic exercise increases oxygen flow to the brain and it directly improves creation and survival of neurons. Effectively it acts as a drug for your brain.
It has the additional benefit that it alters your mood, aerobic exercise makes you happy :)
Strength training may boost testosterone, but the effects of aerobic exercise is well established. Several comparisons have been done between aerobic and strength training and the conclusions have been that strength training have little effect on executive function.
My source for this is the book "Brain Rules" by John Medina [1]. Also check out his presentation on exercise [2] and his Authors@Google talk [3].
I'm really struggling to think of a strength training scenario where your heart rate wouldn't be elevated (thus increasing blood flow). Consider a max. back squat, where all your muscles are contracting to the maximum degree that they can for several seconds. I'd say that'll make your heart pump.
(Thanks for the citations. That's awesome, and I wish more people would do it.)
Weight training and cardio training have different effects on the heart. Weight training forces the heart to pump against resistance, leadening to a thickening of aorta walls. Cardio requires blood to be circulated more frequently, leading to an enlargement of some heart chambers.
The effects I'm talking about are not during the actual exercise, it's more long term. Note that even though they are long term (~12 weeks I think) they are not permanent, if you stop exercising soon there will be no benefit.
I've noticed that when I run my breathing speed and heart rate increase up to 5 km, then stays pretty much constant. I don't know why this is though. If you do strength training you probably stop long before this point.
I'm friends with several people who fast for religious reasons. For them that means not eating during the day time, it does not mean starving for days.
That is one definition of fasting, I guess a lot of people are only exposed to the story of Jesus "fasting" for 40 days where he ate nothing at all (if I remember the story right, if I have that wrong please correct me, I don't know the Bible all that well).
How long were the fasts you took? I am curious because my lifts suffer when I have not eaten breakfast, and I'm pretty sure it's because of the exhausted feeling in my muscles, which I attribute to the lack of food.