Ken Newgard wrote:
For an average 70 kg (155 lb.) male the cardiac output will be 5.5 liters (~1.4 gallons) per minute. His blood volume will be 60 ml per kg (0.92 fl. oz. per lb.) or 4200 ml (~1.1 gallons). Assuming his cardiac output can double under stress (as his heart beats faster and with greater force), his aortic blood flow can reach 11 liters (~2.8 gallons) per minute. If one assumes a wound that totally severs the thoracic aorta, then it would take 4.6 seconds to lose 20% of his blood volume from one point of injury. This is the minimum time in which a person could lose 20% of his blood volume. (Newgard, Ken, MD: The Physiological Effects of Handgun Bullets: The Mechanisms of Wounding and Incapacitation. Wound Ballistics Review, 1(3): 12-17; 1992.)
In some average sense, incapacitation via blood loss probably requires losing a certain percentage of blood. The more blood a living target has, the longer (on average) it will take to lose 20% of the initial blood volume.
Body builders (and people who are fit) both have a larger volume of blood AND also have more red blood cells. This suggests that they might remain conscious for a few more seconds after beginning to rapidly lose blood.
On the other hand, body builders (and people who are fit) also have higher metabolic demand for oxygen and the heart capacity to deliver blood (and oxygen) to the body. Once the plumbing springs a leak, they probably leak faster due to higher heart capacity, and their body might use what little oxygen is available more quickly.
People who are fit also have the advantage ofhaving their bodies conditioned to shift rapidly into anaerobic cellular respiration. This basically means that (on a cellular level) their bodies function better with reduced levels of oxygen.
The other factor that benefits fit people is that some of the more energetic handgun rounds produce wounds that are wider than the expanded bullet diameter early in the penetration. Bigger targets will tend to sustain these wide wounds in non-vital tissue, which will lead to slightly slower blood loss compared with sustaining the wider wound channel in vital tissue.
So, in an average sense, people who are more fit will probably remain conscious for a few seconds longer after a well-placed hit with a service caliber handgun round.
Michael Courtney