Monday, March 26, 2012

Ischemic Preconditioning

   John Hobbs, MS         

One interesting aspect of studying exercise physiology is the ability to incorporate a multi-discipline approach to developing new ideas.  The major underlying theme is the body being placed under a form of stress and monitoring the response.  The crossover between exercise science and medical research is well founded as it’s not uncommon to see researchers in Exercise Physiology performing studies regarding heart disease, modalities to simulate bleeding, sub-cellular changes to tissue, to a further variety of topics.    With these relationships in mind, an anesthesiologist brought up the topic of a surgical technique called ischemic preconditioning.    Essentially, the blood flow to a limb is temporarily occluded and then allowed to re-purfuse for a short duration.  Several cycles of this treatment serves to protect the heart during surgery. The concept is intriguing due to its mechanism and questions regarding implementation with the limited research on athletes currently available.
            Specificity is an attribute that is highly stressed to athletes.  If you want to run faster, you have to actually run fast and any other training has to closely mimic the demands placed by running.  The medical background of ischemic preconditioning is similar.  It is well documented that by stressing the heart, various proteins are produced to serve as protective mechanisms, such as heat shock proteins.  The stress required is small and relatively long lasting with single bouts of exercise producing benefits lasting weeks.  The cascade of events leading to this protective mechanism is involved with a variety of variables including gender based hormone production and age.   The end result is increased protection against what is called ischemic-reperfusion injury—essentially the heart cells being starved of oxygen, becoming damaged, and then rupturing once oxygen is re-introduced. 
            The method used preoperatively seems to negate the concept of specificity.  In a pre-operative hospital setting, a protocol occluding a patient’s arm with a blood pressure cuff can be applied resulting in better outcomes in procedures involving the heart.  What is novel about the procedure is that the stress applied to a remote site provides benefits to a distant location.  While systemic messengers in the body are nothing new with basic hormones being taught in high school biology, the signaling with this protocol does not follow the same  principals.  It could be equated to doing bicep curls to increase your 40K time trial.
            Limited research is available on the topic regarding athletic performance.  Two recent publications by Jean-St-Michel et al. (2011) and Groot et al. (2010) evaluate the application of the concept to exercise performance.  While the tendency is to find all the holes in the research and conclusions and question validity, the limited work available on this topic would favor time spent delving deeper in to the mechanisms and  implementation of the practice.
            Both Jean-St-Michel et al. and Patricia et al. implemented  ischemic preconditioning prior immediately prior to exercise testing.  The former utilized the arm as the treatment site in swimmers with the latter performing the treatment on the legs of cyclists.  Both showed benefits due to the treatment.
            In evaluating the swimmers, the researchers found a benefit to maximal intensity exercise illustrated by 100 meter swim times.  The authors noted, the benefit seen was relatively small, being less than a second, but competitively significant as top level events over that distance.  An increase in the stroke count was also noted in the treatment data.  This could be significant as swimming speed relies on the relationship of the distance covered per stroke and the speed of the stroke (Jean-St-Michel et al. 2011).  A question emerges if the alteration of stroke count is a physiological response allowing for a faster stroke rate with decreased fatigue, or an alteration in form due to the preconditioning.  Regardless, the end result in an increase is swim performance.
            The cycling group showed improvement in VO2 max and in the maximal power output achieved during the testing.  The researchers attributed this to improved endothelial function, essentially the diameter of the blood vessels, for a partial cause of the improvement (Groot et al. 2010).  It must be noted that this theory contradicts data and commonly taught limiters to VO2max in athletes.  But, that is the nature of science with constant remodeling and invalidating of theories.  Additionally, the research methods may not have been conducive to the highest level of validity.  The end result of the study, however is the same—increased performance.  Further work will provide reinforcement or dismissal of the theory regarding the mechanism.
            When evaluating the studies presented, an important note is the fact that the benefits were seen only in maximal exercise efforts.  While this could provide a benefit to events specializing in a maximal effort only, such as a 100 meter swim, the benefits have yet to be evaluated across endurance activities.  Based on the various differences in limiters of performance, the protocol may or may not be effective.  Additionally, duration and intensity of exercise prior to the maximal exercise testing has not been evaluated.   This is to say that a cyclist attacking two miles from the finish may have the benefit “washed out” by the previous sixty miles of racing.
            One interesting note is the fact that both of the studies regard exercise as a possible ischemic event whose stress contributes to fatigue.  So, in a more practical application than bringing a blood pressure cuff to competition maybe to utilize high intensity bouts of exercise as the means to illicit ischemic preconditioning.  While neither of the articles directly associates this concept with their findings, this could add to data supporting high intensity intervals in to a warm-up prior to a race.
            A final note on the research procedure is the fact that the ischemic event was utilized in a limb directly implemented in the exercise.  The cycling study utilized both legs which allowed to demonstrate the existence of a benefit, but not isolate it to the legs.  The work by Jean-St-Michel et al. attempted to focus in on the possible cause of the benefits.  By using one arm, they hoped to demonstrate a positive effect at a site other than the occluded arm.  This closely mirrors the ischemic precondition previously presented as being used in surgical procedures.  The researchers went a step further by using the blood from the swimmers before and after conditioning in rat hearts undergoing ischemia.  The results showed that the blood drawn after the ischemic conditioning served to protect the rat heart. 
            These data serve as starting points for evaluating the use of a possible supplement to training.  Athletes must use caution however, before incorporating these practices in to training as extrapolating benefits of medical practices to the athletic arena routinely occurs with no other significant benefit shown other than separating athletes from their dollar.  As with any novel theory or application, further study is required.  While these initial studies show possible promise further work may reveal a cumulative effect that could allow for training with a blood pressure cuff while you lounge on the couch or the fact that a quick bout of push-ups during staging at a race could provide a small benefit.


Jean-St-Michel, E., et al. (2011).  Remote Preconditioning Improves Maximal Performance in Highly Trained Athletes.  Medicine and Science in Sports and Exercise, 43(7) 1280-1286.

Groot, P., Thijssen, D., Sanchez,M., Ellenkamp, R., Hopman, M. (2010).  Ischemic preconditioning improves maximal performance in humans. European Journal of Applied Physiology, 108(1) 140-146.