Tag: military medicine

Sleepy Soldiers’ Split-Second Situation Assessment Skewed

Study demonstrates decrease in ability to make rapid judgement calls due to sleep deprivation.

   By: Nicole Myers        

          In a study conducted at the University of Texas and published in the journal Sleep, researchers found that sleep deprivation negatively impacts information-integration, the type of cognitive processing that allows fast, accurate, gut-feeling decisions.

            Soldiers in combat rely heavily on the ability to instantly make the right decisions in high pressure situations. Researcher Tom Maddox explains, “information-integration… is critical in situations when solders need to make split-second decisions about whether a potential target is an enemy soldier, a civilian, or one of their own.” Unfortunately, combat missions don’t exactly lend themselves to full nights of sleep, and soldiers in these operations are often extremely sleep- deprived.

            The study tested 49 West Point Cadets on information-integration tasks, once as a baseline and then again after 24 hours of either sleep deprivation or a normal sleep-wake cycle. While the rested cadets significantly improved their scores in the second round of testing, the sleep-deprived cadets’ scores dropped slightly. This indicates that even the mild sleep-deprivation of one night’s sleep loss impacted the cadets’ ability to use this crucial form of decision making.

          Researchers observed that one way sleep-deprivation impaired decision making was by causing subjects to shift from the fast and accurate cognitive strategy of information integration to a slower, more controlled, but less-effective rule-based approach, in which they tended to over-think the problems.

          The effect that sleep-deprivation had on decision making varied among individuals. Those who had a tendency to use a rule-based approach to problem solving in the first place were more vulnerable to the effects of sleep-deprivation. Some subjects continued to use an information-integration approach despite sleep-deprivation, and their performance showed no decline in the second set of testing. This suggests that the cognitive function necessary for information-integration strategies is not necessarily strongly affected by sleep deprivation. But, the use of an information-integration strategy in a task may require active inhibition of rule-based strategies, and this inhibitory process is what is vulnerable to the effects of sleep deprivation.

          An understanding of the effects of sleep-deprivation on various cognitive functions and decision making abilities is critical for a military in a time of war, when enormous physical demands are placed on soldiers who are often deprived of sleep and sustenance and who must make split-second life or death decisions. 

For the original research click: http://www.journalsleep.org/ViewAbstract.aspx?pid=27617

Could we re-grow lost limbs?

Researchers discover gene deletion that allows tissue regeneration in mammals.

By: Nicole M. Myers 

     Mar. 2010- Researchers at the Wistar Institute, a international leader in biomedical research, have discovered a gene that could regulate regeneration in mammals, bringing the possibility of re-growing amputated extremities one step closer to reality. The lab identified a gene called p21, that when turned off confers to mice the ability to regenerate lost tissue.

          The ability to regenerate lost appendages is common but sporadically observed in nature, as in animals such as flatworms, sponges, and salamanders, but the phenomenon was previously unknown in mammals. Mammals are capable of replacing some types of tissue, such as liver lobes, damaged skeletal muscle cells, epithelium, the gut lining, and even brain cells to some extent. Typically though, the mammalian healing process involves the formation of scar tissue, rather than new cells. Animals like salamanders begin healing with the formation of a blastema, a structure that allows cells to rapidly proliferate and differentiate as embryonic stem cells do, until the appendage is replaced without scarring.

          This research began with a chance observation in a particular strain of laboratory mice, known as MRL mice. Researchers used the standard technique of piercing holes in the mice’s ears for identification. However, within a couple weeks, the holes had unexpectedly closed without a trace. The researchers then began to investigate the genetics of the MRL mice to see what might be behind their unique healing ability, and they found that the p21 gene was inactivated. Further research indicated that mice lacking the p21 gene were able to completely regenerate lost or damaged tissue without forming a scar, re-grow cartilage, and partially regenerate amputated digits.

          The p21 gene is a cell cycle regulator that blocks the cell cycle progression when there is damage to the DNA, preventing the cells from dividing and potentially becoming cancerous. Similar to naturally regenerative creatures, mice that lack p21 show an increase in DNA damage, but also an increase in apoptosis, or the programmed death of impaired cells. Researchers suggest that “The combined effects of an increase in highly regenerative cells and apoptosis may allow the cells of these organisms to divide rapidly without getting out of control and becoming cancerous.”

         Amputation injuries are some of the most devastating and debilitating wounds soldiers sustain in combat. According to the Army Office of the Surgeon General, between September 2001 and January 2009, 1,286 soldiers suffered amputation injuries in Operation Iraqi Freedom and Operation Enduring Freedom. This is the first research to succeed in this degree of tissue regeneration in mammals, giving hope that someday, we may have the ability to restore these lost limbs.

To read the original research published in Proceedings of the National Academy of Science, click: http://www.pnas.org/content/107/13/5845.full

You Can’t Beat the Heat

Even when the body is able to maintain core body temperature, cardiovascular performance is decreased in the heat.

      Researchers from the American College of Sports Medicine conducted research in January 2010 that shows that environmental heat stress with only modest hyperthermia has a significant impact on aerobic endurance. This research is of importance to a military operating in a desert environment in which temperatures can exceed 120˚ F in the summer.

      Subjects were asked to perform fifteen minutes of cycling in a temperate (69˚F) or hot environment (104˚F). Core and skin temperature and heart rate were constantly monitored. Performance and pacing were analyzed by kJ of work completed. Core temperature was modestly elevated in both environments, with skin temperature being higher in the hot environment. While heart rate and fatigue level were consistent between the two environments, the total amount of work done in the hot environment was 17% less than in the temperate environment. Also, while the pace was maintained in the temperate climate, it dropped significantly over time in the hot environment.

      So, although excessive hyperthermia was avoided, performance was still impacted by the hot environment. While it has been established that marked hyperthermia leads to increased fatigue during exercise, it seems that a hot environment can increase fatigue even without significant increase in core temperature. There are a few theories about how this happens. One idea is that athletes use an anticipatory control mechanism during exercise to ensure maintenance of core body temperature by making unconscious adjustments in work rate. Increased cardiovascular strain resulting from the maintenance of high skin blood flow required to maintain core temperature may also explain the observed decrease in performance. So, impact aerobic ability in the heat may come from either an early modification of work output or an inability to maintain a desired work output over time. This study supported the idea that initial pace could not be maintained, as the participants in the hot group got much slower over time.

       It seems clear that cardiovascular performance is decreased in the heat even when the body is able to maintain core temperatures. Further research may elucidate whether an early modification of pace in the heat may minimize the overall decline in performance associated with environmental heat stress. This information can help athletes who must compete in the heat to pace themselves, and may also shed light on tactics the military can use to maintain optimum performance in hot climates.

 Nicole Myers

For more information visit: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA513059&Location=U2&doc=GetTRDoc.pdf

Parachuting into Combat: If the bullets don’t get you, the ground will

      When parachuting out of a plane into combat, there are two competing considerations at play. The soldier needs to reach the ground as quickly as possible (spending as little time in the air as an easy target for enemy fire as possible) without being injured on landing.

      This first goal means that military parachutes do not provide the softest possible landings, and poor landing technique often leads to injuries. What happens when you add over 100lbs. of body armor, weaponry, ammunitions, communications equipment, and other combat gear to this equation?

      A study carried out in January of 2010 at the University of Pittsburgh has demonstrated that the extra weight from combat equipment can alter soldiers’ landing mechanics and lead to increased incidence of musculoskeletal injury.

      In this study, researchers compared the kinetics (the relationship between the motion of a body and the forces acting on it) of the landings of 70 active duty Air Assault soldiers with and without equipment. High-speed cameras and computer software were used to capture and analyze the soldiers’ landing biomechanics under the two conditions, and force plates were used to measure vertical ground reaction forces (force exerted by the ground on a body in contact with it) of the landings.

      Soldiers performed two-legged drop landings from a height of less than two ft. with body armor, helmet, and rifle, weighing a total of less than 40lbs. Real parachute landings are more similar to dropping from a height of ten feet without a chute, and real weight of combat gear exceeds 100lbs. Even though experimental forces were far less than those typically experienced by soldiers in training and combat, the additional weight was still observed to significantly alter soldiers’ landings.

      It was determined that with the additional weight, soldiers experienced significantly greater maximum knee flexion, significantly greater maximum ground reaction forces, and greater time between initial ground contact and these peak values.

      These changes in landing biomechanics and force of impact increase the risk of musculoskeletal injuries in soldiers. Such injuries are a primary concern in the military. The Armed Forces Epidemiological Board reports that musculoskeletal injuries “impose a greater ongoing negative impact on the health and readiness of U.S. Armed forces than any other category of medical complaint during peacetime and combat.” According to records, 58% of hospitalization cases in 2005 in the Navy were due to musculoskeletal injuries. These types of injuries result in significant amounts of lost duty time and can often be long-lasting and difficult to make a full recovery from, so prevention is crucial.

      While jumping into combat without equipment is obviously not an option, proper strengthening and conditioning of the lower extremities, incremental increases in the weight with which soldiers train, and emphasis on proper landing technique can help mitigate the increased risk of injury associated with the weight of combat gear.

Nicole Myers

For more information follow: http://proquest.umi.com/pqdlink?Ver=1&Exp=02-21-2015&FMT=7&DID=1954679781&RQT=309