Hello Eren. This is Mustafa writing to you from Miami, US. Out of respect to everybody else I figured it would be proper to communicate in English versus Turkish. However you can always write to me at my e-mail address,
[email protected]
Anyway the idea is to expose your body as much as you can to lactic acid and also to O2 deprivation to better your bodies physiological conditioning. Anyway physical activity you may choose to perform with apnea will cause a deficit, increased need for O2 and increased levels of Co2. Whether you choose to walk, run, swim etc... with apnea will have similar affects. This will improve you conditioning and also increase your mind over matter controls.
As far as the contractions are concerned, make sure you use your diaphragm to inhale and to exhale. The trick is to actively use your diaphragm yet not use so much of contraction of the muscle to avoid spasms. And always go through couple of cycles of inhalation and exhalation before you fill up to capacity for the purpose of warming up the chest cavity muscles, the kung tissue and also to stimulate the lungs into sufficient surfactent release to avoid friction and labored breathing.
Mustafa