No contractions
Hola
A deep salute to everyone.
On my trainings, of static apnea, when I get over 6'15" I realized a strong voluntary contraction and felt a cardiac arrythmia, at 6'45" I did it again and felt the same, when I reached 7'22" I did a smooth and slow voluntary contraction and nothing happened with my cardiac rythm.
On my training without packing nor hyperventilation, I reached 3 row static apneas of 7'06" with 1 minute surface interval. I avoided completely the contractions, and you now the results.
I think that contractions are not good, but if you can´t avoid it at all, try to make smoother and slower than usual, and try to reduce the frecuency of them. A strong contractions consumes a lot of oxygen.
I don´t have experience with contractions in constant ballast, because I only descend to 51 meters. I have never experienced a contraction at that depth, and neither at my 2 minutes hanging at 38 meters. I focus in my heart beat and avoid voluntarily the contractions.
The difference that divers experience in the onset of contractions is due to the CO2 threshold, that is different between individuals, your O2 comsumption is what gives you the performance. Ofcourse the O2 comsumption and the CO2 threshold are variables that improve with training. If you have a low CO2 threshold your contractions will come sooner.
Try to avoid the contractions, initially with low static time and go further as you feel comfortable with it. Try to focus on your feelings and your heart beat. Forget the watch and don´t set an arbitrary goal.