Starting Strength

facts, most important among them the fact that for pressure across a membrane to breach it, there must be a pressure gradient , a difference in the pressure on either side of the membrane, or movement cannot occur. When we use the Valsalva maneuver while lifting weights, the whole system is pressured up so that no gradients exist across any barriers. The same pressure being applied to the arteries in the vascular column up the neck and into the head is also being applied to the cerebrospinal fluid (CSF) in the spinal canal; this fluid transmits pressure up through the subdural space in the skull and throughout the cerebral ventricular system, balancing cardiovascular pressure across the blood/brain interface (Haykowsky, MJ et al., Medicine & Science in Sports & Exercise , 35(1):65-68, 2003)(Figure 2-55).

    Figure 2-55. Cerebral vascular pressure does increase with strain and the Valsalva maneuver. However, the likelihood of vascular rupture is mitigated by a simultaneous increase in cerebral ventricular pressure transmitted up the cerebrospinal fluid column in the spinal canal, which is under the same pressure as the vascular column. The volume of the skull limits these two pressures and stabilizes vessel structures, rather than predisposing them to rupture.

    Conventional wisdom also ignores the fact that the cranium is essentially a pressure vessel, like a propane tank, that is quite capable of containing high pressures. Imagine inserting a balloon into a glass milk bottle and trying to blow the balloon up so that it pops – obviously impossible unless you’re capable of making the milk bottle explode, too. The pressure vessel prevents a pressure gradient from developing between balloon and bottle. The pressure across the membranes within the skull is contained by the capacity of the bony encasement to control and prevent changes in pressure, and pressure changes are required for the inter-membrane disruptions of a CVA. The pressure will thus remain the same across all the structures inside the skull – unless you exhale.
    Conventional wisdom further ignores the fact that aneurysms are vessel wall defects associated with genetic predisposition and, rarely, with the response to a disease state, like tertiary syphilis, that produces chronic inflammation of the vascular walls. People with aneurysms have them for reasons other than the fact that they train with weights, and the likelihood of such a person rupturing an aneurysm while under the bar is approximately the same as the likelihood of its happening while the person is walking across the front yard.
    Now, a little empirical evidence to help make the case for breathing correctly under the bar. The actual rates of cerebrovascular accidents versus orthopedic injuries provide ample evidence that the greater risk is orthopedic. In Risser’s 1990 study ( American Journal of Diseases of Children , 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 seven 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 accidents in 2004 was about 0.000512 (150,074 total) for the entire population of the U.S. (293 million in 2004). The rate of survivable CVAs in 2004 was 0.00305 (895,000). So even if we compare the rate of orthopedic injury in a specialized small population engaging in exercise with the rate of CVA in the population of the entire United States, orthopedic injuries are still 27 times more common than survivable strokes, and you are still 94 times as likely to hurt your back in sports as you are to die from a CVA even if you don’t exercise.
    In reality, the difference is much greater because 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 buckets each year than have had barbell training-related strokes since the invention of barbells.
    The spinal support provided by the anterior thoraco-abdominal pressure is precisely why it is natural for us to use the Valsalva when we lift or push. Fighter pilots perform the Valsalva when they are subjected to