question about contractions

[marindiver]

Hi, i`m rather new in freediving - spearfishing world and need some advice about training and security.
Often I read about contractions, but not sure what exactly they are.
If I uderstand correctly, durring apnea contractions occure in abdominal area and they are something like security warning : after some number of them ( individualy for each person ) one should end his apnea or risking blackout.
What I don't know or understand is : where exactly one feel contractions, why they occure. I've never felt one. I am doing spearfishing for 2 years about 20 days each year. I haven't do anny special training for freediving, just relay on cycling and workout for general fitness. For last year I am doing some dry apnea but rarely. My dry static is about 2.30 , dive to 10 m for 1.15 min. As I said newer had contractions, only in dives near to the maximum, when going up I have some numb feeling in my muscles that are working - legs, does this mean that i'm far away from blackout durring both dry apnea and diving?

Thanks
Marin

 

[Bill]

Marin
Please be careful. For twenty years, I dove 60-70 times a year. Depth to 30 meters and 2 minute max dives. Dry statics for practice, 4 min. max. I never had a contraction but I had at least two blackouts. Then I dove half as much for 5 years and seldom for another five. When I started again, 8 years ago, I could do 1;20 dynamics and 6 minute statics in about six months. Still no contractions. Some one that I trained with did statics up to 7 minutes before he had contractions. I don't know about him but now my contractions start at 3 minutes and between 5 and 5 1/2 it feels like some one jumping on my chest. What I'm trying to say is don't count on contractions as a warning signal. This is very important for experienced spear fishermen.
If I understand it right, the numb legs means that the legs are operating anaerobically. Blackout occurs when the O2 in the blood going to the brain drops below a certain level. They may or may not be related, depending on many variables.
Aloha
Bill

 

[marindiver]

Thank you very much Bill, you releeved me of a dangerous ilusion about contractions - whille waiting for them I could meet the blackout underwater.
About numbness in my legs though, I feel it durring second half of dynamic apnea - dry or in the water. You said that this means that my muscles are working anaerobically. But ones I heard that during normal dive body is first using anaerobic source of energy - ATP-KP which is the fastest way and then switching to energy source with using O2. What is meaning of this in my case ? Maybe that the numbness is a sign that I'm using very last of my O2 reservs?
You convinced me without dought that contractions are not something to releigh on as a indicator for how long one should hold breath safely, but what is ? I mean what kept you allive all these years of freediving ?

All the best.
Marin

 

[azapa]

I see/feel Marin's points. I find the contraction term confusing also. My definition is more like pangs of desire to breathe. They never feel like somebody jumping on my stomach, just spasms, very light at first, getting stronger. I always give into them before they hurt. The frequency of them is more my trigger point. I guess everyone in reality has them, but they may be too weak to detect?

 

[Bill]

Azapa
Valid observation. That is how many divers (me too) view contractions. If you continue at the same pace, the first contraction seems to occur at about 50% of your max (time/work/distance). After years it became a 'reliable' signal, too many variables to bet your life on it, though.

"....I heard that during normal dive body is first using anaerobic source of energy"

I wish that I could figure this out. You said dynamic. This is done at about 20% of max power. Not even 50% of max aerobic. Your body doesn't use the 6 seconds of sprint power unless it has to (near 150% aerobic max) and I wonder if it switches to anaerobic power at this low level before blood shift forces the issue. The other question is, on a constant dive where you use the sprint to get off the surface and cut back to below the aerobic threshold at 10-15 meters. Do the legs burn O2 at this point? If not, is the lactic acid removed during the glide to maximize anaerobic ability for the 1 1/2 minute kick to the surface? I think this would be inefficient. It seems that I'm just smart enough to find questions, not answers.

"I mean what kept you allive all these years of freediving"

A combination of very good instruction, fear and luck. The best example of all three was waking up face down and snorkel out with my gun and weight belt 20 meters below. Now when I'm the deep safety diver, I always check on the position of the surface safety in case the rescuer needs rescuing.

Aloha
Bill

 

[waxlips]

during contractions while laying down my limbs feel heavy as if i were on a gravitron(heavy gravity simulator ride) look up gravitron on wikipedia if you want to know more about it.