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Latest Clinical Research Published by ACSM

Jaworski, Carrie MD, FACSM, FAAFP

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Current Sports Medicine Reports: May/June 2012 - Volume 11 - Issue 3 - p 109-110
doi: 10.1249/JSR.0b013e318256b1a0
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What We Can Learn About Running From Barefoot Running: An Evolutionary Medical Perspective

The April 2012 issue of Exercise and Sport Sciences Reviews includes a unique piece on the topic of barefoot running written by a medical anthropologist who studies the evolution and biology of running (2). In the article, the author presents the evolutionary medical hypothesis that a barefoot running style may result in less injuries through his examination of the principles of evolutionary medicine, the evidence on how barefoot people run, and the biomechanical principles that support and refute the hypothesis. The article centers on a discussion of the main issues surrounding the current frenzy around this topic. The first issue stems from the evolutionary fact that all humans, including athletes, ran barefoot or in minimal shoes until the 1970s when the modern running shoe with a cushioned heel, arch support, and stiffened sole was invented. Based on this, would it follow that the human body must be well adapted to running barefoot as it was the natural thing to do for thousands of years and can therefore not be considered dangerous? Next is the confusion that exists between true barefoot running and running in minimalist shoes. Shoe companies and proponents of the concept often speak of barefoot running in their minimalist shoe of choice. Current theory suggests that anything on the feet negates the “barefoot” term. Can we extrapolate the barefoot running style to these minimalist shoes and/or traditional running shoes and still see the same benefits of barefoot running? Lastly, there is the fundamental concern that exists in the running community about the great number of running injuries seen per year and that, despite our best efforts through research, shoe design, and education, the numbers have remained constant during the last 30 years. While there are many theories as to why this problem exists, proponents of barefoot running suggest that this stems from poor running form. The hypothesis is that few people have been trained on how to run because most assume that one will run in a natural form that is appropriate for his or her unique anatomy and physiology. Through his careful examination of the evolution of running and the available research on barefoot running, the author proposes the following two hypotheses: 1) the human body was adapted to running in a barefoot style whose kinematic characteristics generate less forceful impact peaks, which uses more proprioception, and which strengthens the feet, and 2) these factors may help runners avoid injury, regardless of whether they are wearing shoes or not. Or more simply, how one runs is probably more important than what is on one’s feet, but what is on one’s feet may affect how one runs. The author also stresses that the data necessary to test these hypothesis are inconclusive at this time and offers questions that need to be addressed in future research on this topic.

Bottom line: The article provides an evolutionary perspective on the current debate over barefoot running with a review of the available research literature.

Exercise Dose and Insulin Sensitivity: Relevance for Diabetes Prevention

This research article in the May 2012 issue of Medicine & Science in Sports & Exercise® examines whether or not exercise dose was associated with improvements in insulin sensitivity following four months of exercise training in previously sedentary adults (1).

In the study, 55 healthy volunteers partook in a 16-wk supervised endurance exercise intervention with a pre-/postintervention design. The exercise consisted of three to five sessions per week of moderate aerobic exercise with a minimum of three sessions being supervised. A ramped exercise prescription protocol was used to achieve 75% of peak heart rate for 45 min per session. The exercise dose was computed as the product of exercise intensity, duration, and frequency. The dose was expressed as average kilocalories expended per week. Insulin sensitivity was assessed by a euglycemic hyperinsulinemic clamp, peak oxygen uptake was assessed by a graded exercise test, and body composition was assessed by dual-energy x-ray absorptiometry. The results demonstrated that an improved insulin sensitivity was related significantly to exercise dose in a graded dose-response relationship. This was a linear effect, and the researchers did not find evidence of a threshold or maximal dose-response effect. This is important clinically because of the fact that even an exercise dose of ∼400 kcal·wk−1 (about 40% to 50% of the guidelines for physical activity) was associated with a significant improvement in insulin sensitivity. Further analyses revealed that this change significantly was related to the average kilocalories expended per week and to the average kilocalories expended per minute but not to the amount of sessions per week. In other words, it was observed that exercise intensity significantly was related to improvements in insulin sensitivity but exercise frequency was not. In the aforementioned findings, neither age nor gender had an influence on this dose-response relationship.

Bottom line: This study identifies that a graded dose-response relationship exists between exercise dose and improvements in insulin sensitivity. Clinicians can use this information to adapt the exercise prescriptions they provide to their diabetic patients in the hopes of better blood sugar control.

The author declares no conflict of interest and does not have any financial disclosures.


1. Dube JJ, Fleishman L, Rousson V, et al.. Exercise dose and insulin sensitivity: relevance for diabetes prevention. Med. Sci. Sports. Exerc. 2012; 44: 793–799.
2. Lieberman DE. What we can learn about running from barefoot running: an evolutionary medical perspective. Exerc. Sport Sci. Rev. 2012; 40: 63–72.
© 2012 American College of Sports Medicine