Well, I guess it has to be "a little" hard when you work out if you want to get higher. No one will be able to tell you exactly where the limits of your body (and mind) are - it's up to you to determine that. It's even difficult to say which hart rate is "wright" (highest) for the apnea. Some say 140/min, but I can push it much higher and still progressing faster with my STA. It easy goes up to 200/min. And I am well trained (hope that doesn't sound too self-sufficient, just a fact). That is against all the rules, pulse "should be" lower for me as a long route runner. They say I should have a terrible muscle pain after holding HR on 180 for an our or two. I don't. In fact, I feel great, all the tension is out of my body, I can work more sufficient... So - what should I do? Lie in bed and trying not to get upset so my HR would'nt go to fast?
Discover. Explore. Try some different sports and training methods from there on shakedown flight. Change enviroment, intensity of training so your body doesn't get lazy. Kiss a girl, no fear :chatup And most important - have fun (it's hard to have fun when training like an animal). If you are not planinng to be a world champ next season there's no need for killing yourself, aye?
1st sentence - yes. Body accomodation has limits and we are far from reaching those limits in apnea.
The rest is just my theory and it could be wrong: walking apnea might not be all adjustable to lifting weights. Small weight + many repetions = endurance. The muscle fibre that is involved here is the slow twitch muscle which carries O2. For that aerobic training is needed -> outcome: more red muscle fiber that will store more O2. I consider aerobic training slightly more important because of that (and a good thing to start with).
With walking apnea muscles are doing anaerobic training, muscles are getting use to work with small amount of O2 in blood. That is 2nd step and also very important for spearfishing or "just" swimming under water. At the same time, of course, body starts to accomodate to higher level of CO2, but that accomodation can be done only with static as well.
And now the funny part: comparing training programmes of the greatest freedivers these days you can find out that they diverse a lot. Every athlet picks (developes) training that seems to fit (only) him best. My best guess is we just don't now (yet) how to do it so limits could be reached (as they are, for instance, in skiing).
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Ahhh... and I thought I was going to study die so-called-terrible Maschinenelemente. Très optimiste.
:duh