Tag: athletics

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.”

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