September 14, 2020

Problem Solving with Your Feet

#128 – Irene Davis, Ph.D.: Evolution of the foot, running injuries, and minimalist shoes

"Rather than have the runners adapt to the running, they took the shoe and adapted it to the runner." — Irene Davis

Read Time 17 minutes

Irene Davis is the founding Director of the Spaulding National Running Center at the Harvard Medical School. In this episode, Irene describes how her research of biomechanics and clinical work with running injuries, as well as research by others, has shaped her views on maintaining body alignment and foot health. Irene discusses her argument for the role of modern footwear in running-related injuries and how minimalist footwear helps resolve the subsequent biomechanical issues.


We discuss:

  • Irene’s path to her Ph.D., her entry into physical therapy, and her interest in biomechanics [3:20];
  • How Irene’s thinking about the use of orthotics has changed [7:15];
  • The evolution of the human foot and the transition from walking to running [10:30];
  • The evolution of shoes and its impact on running injuries [17:30];
  • An overview of running injuries [26:00];
  • Cushioned running shoes, heel striking and impact forces [29:30];
  • Shin splints [33:45];
  • How heel strike patterns promotes knee stress through rate of loading [35:30];
  • The critical importance of exercise [42:15];
  • Impact forces and injury potential [45:45];
  • How shoe cushioning alters impact forces despite forefoot striking [49:00];
  • An overview of minimalist shoes [52:30];
  • Irene’s protocol for transitioning people out of orthotics [58:45];
  • Transitioning to minimalist shoes and a forefoot strike [1:05:30];
  • Foot muscle volume, minimalist shoes, and orthotics [1:07:00];
  • The recognition of the importance of foot strength in podiatry [1:09:45];
  • Minimalist shoes across the lifespan—from children to adults [1:12:30];
  • Why learning to forefoot strike on soft surfaces is not the best approach [1:20:00];
  • Knee valgus and factors related to knee injury [1:21:45];
  • IT band syndrome [1:28:30];
  • Physics and ground reaction forces [1:33:15];
  • Irene’s approach to retraining a runner’s gait [1:36:00];
  • Case study—How the transition to minimalist shoes decreased injury and improved performance [1:42:15];
  • Importance of proper movement patterns and the negative influence of our modern environment [1:45:30]; and
  • More.


Irene’s path to her Ph.D., her entry into physical therapy, and her interest in biomechanics [3:20]

The path to and focus of Irene’s Ph.D.

  • She originally wanted to be in the FBI, but at the time, women weren’t allowed
  • Classes in exercise science eventually led her to completing a degree in physical therapy
  • Her curiosity led her to complete a master’s degree and Ph.D. in biomechanics 
  • She completed her Ph.D. at Penn State under Dr. Peter Kavanaugh, who is a pioneer of running mechanics

Irene’s early work as a physical therapist

  • Watching her cousin go through physical therapy after being paralyzed in a car accident inspired her to become a physical therapist herself
  • She started her physical therapy career in spinal cord rehab
  • After starting graduate school, she shifted to outpatient physical therapy

What shifted Irene’s interest towards biomechanics

  • Quadriplegics need to move their entire body with just 25% of their muscle – they need to learn to use their bodies in atypical ways


How Irene’s thinking about the use of orthotics has changed [7:15]

Early in Irene’s career, she was a proponent of orthotics

  • She prescribed orthotics as a physical therapist
  • She taught about orthotics at the University of Delaware
  • She simply believed that some people had feet that were incapable of supporting themselves

Irene’s thinking began to change based on her research and when the book Born to Run was published

  • Her research led her to realize that people who land on their heels while running incur greater impact forces, and that footwear influences these forces
  • This, plus the message in book Born to Run, made her reflect on the traditional approach of physical therapy for other areas of the body – removing support to encourage patients to improve their intrinsic ability
  • The permanent nature of orthotics is the opposite of this approach
  • Irene says, “And it kind of brought me back to when I was a physical therapist in rehab, where we would try to take away as much support and bracing to our patients, even wheelchairs, a lower back, less lower extremity bracing so that they would use what they had. And yet my thinking in terms of feet was completely opposite. … We don’t brace anything else permanently if you have an orthopedic problem.”

Despite the common thinking that we should be prescribing a shoe type based on an individual’s need for support, a study done by Joe Knapik on thousands of military personnel found that there was no difference in injury rate


The evolution of the human foot and the transition from walking to running [10:30]

Anatomical changes from walking man (Australopithecus) to running man (Homo erectus)

{end of show notes preview}

Would you like access to extensive show notes and references for this podcast (and more)?

Check out this post to see an example of what the substantial show notes look like. Become a member today to get access.

Become a Member

Irene Davis, Ph.D.

Irene is a professor of physical medicine and rehabilitation at Harvard Medical School. She’s also the founding director of the Spaulding National Running Center—one of the premier centers in the United States devoted exclusively to the diagnosis, treatment and prevention of running injuries in runners of all ages and abilities. Irene holds two bachelor’s degrees, one in exercise science from the University of Massachusetts, and one in physical therapy from the University of Florida. She then went on to earn her master’s degree in biomechanics from the University of Virginia, before finally going on to get her PhD in biomechanics from Penn State.

Disclaimer: This blog is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this blog or materials linked from this blog is at the user's own risk. The content of this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advice for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.


  1. Peter and team,

    I just finished this podcast along with Beth Lewis. Both are great. I am a pediatric orthopaedic surgeon and so I have a significant interest in both. I want to comment on the term “knee valgus” that has been used in both of these episodes and I think is being misunderstood. Knee valgus is a skeletal alignment measure. The alignment of your knee changes dramatically throughout growth until it ends up at its adult alignment of slight valgus at around 7 years of age. From there, it can’t be changed unless there is some process changing it (ie. arthritis or fracture etc.). It is intrinsic to you. You cannot change the alignment of your knee even if you want to. The ligaments (mcl and lcl) allow for some minor varus/valgus movement to the knee but this is extremely minimal under normal conditions. So when I hear people talking about running or squatting with knee valgus that is simply not correct. I think internal rotation of the hip in combination with knee flexion looks like and is confused with knee valgus but is not. I think this is an important distinction because the answers have nothing to do with the knee but usually are problems of the foot and/or hip that cause this apparent alignment issue. Maybe we should use the term psuedovalgus or something of the like.

Facebook icon Twitter icon Instagram icon Pinterest icon Google+ icon YouTube icon LinkedIn icon Contact icon