Tag: physiology

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

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

Running in Genes

By Abby Larson

Can someone really be born to be an athlete?  Science says so.  The idea of a genetic basis to exercise is a fairly new area of science, but it makes sense based on how the human body works. The expression of genes controls the function of human physiology: muscle development, capillary growth, hemoglobin concentration in red blood cells, etc.   After strenuous exercise, gene expression fires up to control muscle tissue repair due to increased forces on the body and tissue metabolic demand.  Capillaries feeding the muscles grow and become more efficient at delivering oxygen to tissues.  All of this is controlled by gene expression, the cellular switchboard of the human body.

Recent studies have identified over 200 genes that can determine the body’s ability to adapt quickly to exercise.  Based on this, training and conditioning could only take an athlete up to his or her genetically predetermined potential.  Does this mean that children can be genetically tested to see if they will be good at sports?  Is there a gene that makes a good football player versus a good runner? It’s more complicated than saying if a person has a specific gene, he or she can be a top athlete.  Like all processes in the human body, multiple genes are involved in adaptation to exercise and gene interactions play a large role.   Gene products don’t interact in a linear fashion, but in pathways and networks.  This makes genes harder to understand, and our knowledge of the interactions is in its infancy.  Once these pathways are discovered, scientists can begin to understand the extent to genetic determination of athletic ability.

These studies on the genetic basis of exercise are not going to benefit  just athletes—physical activity is one of the greatest preventative medicines for obesity, diabetes, and heart disease.  It is likely that genes correlated with exercise response could be mutated in people that have obesity or heart disease, which proposes new options of drug and gene therapy as preventative medicine.  The more we understand the benefits and mechanisms of exercise, the better we can understand how exercise can be used to improve public health.  So next time you go to the gym or run outside, think to yourself, “this is science.”

For more information