Definitiv Luft anhalten. Ein / Ausatmen auf dem Weg nach unten und nach oben ist quatsch. Rippetoe hat das sehr schön beschrieben und er hat auch mit Statistiken erwiesen, dass davon praktisch keine gesundheitliche Gefahr einhergeht. Ist so ein Mythos.

Hab gerade extra im Buch nachgeschaut, ich hoffe mal, es ist ok hier einen kleinen Ausschnitt zu posten:

Furthermore, no one gets under 405 lbs. and squats it without having trained enough to be
able to do so. The cardiovascular system adapts to resistance training just like all of the other
tissues and systems in the body, and this adaptation occurs as strength increases. Anyone who is
capable of squatting extremely heavy weights is adapted for it in all the necessary ways. And no
lifter has ever pulled 800 lbs. off the floor while exhaling. For the athlete using more than 5 lb.
chrome dumbbells, it is far, far more likely that following the advice to "inhale on the way down
and exhale on the way u p " will actually cause an orthopedic injury than prevent a stroke.

In fact, it is a good practice to take and hold the biggest breath you can before each rep of
your heaviest sets. Get in the habit of breathing correctly during your lighter sets, so that when
the weight gets heavy the pattern will be established. The Valsalva maneuver will prevent far more
problems that it has the potential to cause. It is a necessary and important technique for safety in
the weight room
.
The actual rates of cerebrovascular accidents (CVA) versus orthopedic injuries provide ample evidence
that the greater risk is orthopedic. In Risser's 1990 study (Am J Dis Child. 144(9):1015-7,1990) of junior high
and high school athletes from all sports, 7.6% of all athletes incurred injuries that kept them out of training for 7
days. The rate of injury from all causes was 0.082 injuries per training year; 74% of all injuries were simple
sprains and strains, and 59% of all injuries were classified as back injuries.
In contrast, the death rate from cerebrovascular accident in 2004 was about 0.000512 deaths per year
(150,074 total) for the entire population of the US (293 million in 2004). The rate of survivable CVA in 2004 was
0JQO3O5 incidents per year (895,000). So even if we compare the rates of orthopedic injury in a specialized small
population engaging in exercise with the rate of CVA of the population of the entire United States, orthopedic
injuries are still twenty-seven times more common than survivable strokes, and you are still ninety-four rimes as
likely to hurt your back in sports as you are to die from a CVA if you don't even exercise. In reality, the
difference is much greater, since athletes are far less likely than the general population to have cerebrovascular
problems they have not inherited. There are no actual data for the rates of CVA in the weight room, because
they occur so infrequently as to be statistically unmeasurable. More people drown in 5-gallon backets each year
than have had strokes in the weight room in the past decade.
Das ist sehr gut argumentiert, wer also was dagegen setzen will bitte mit entsprechender Begründung und nicht "einfach nur so halt weils mein Fitnesstrainer gesagt hat".