Ankle Plantarflexors as Gait compensators ?

We are always talking about compensations. We have worn out our statement “what you see in someone’s gait is not their problem, ti is their compensation stratetgy(s).”
Here is a study with an interesting thought.
Just remember, try to fix the underlying problems. But, realizing sometimes you cannot, especially in the elderly population, sometimes you have to give a strategy to help them even though it is not the solution you want. And remember also that driving the anterior compartment with appropriate exercises as our “shuffle walk” might stop any loss of ankle dorsiflexion that might be met with the extra calf work that this article seems to suggest.

From the study: “ Of particular importance were the compensatory mechanisms provided by the plantar flexors, which were shown to be able to compensate for many musculoskeletal deficits, including diminished muscle strength in the hip and knee flexors and extensors and increased hip joint stiffness. This importance was further highlighted when a normal walking pattern could not be achieved through compensatory action of other muscle groups when the uniarticular and biarticular plantar flexor strength was decreased as a group. Thus, rehabilitation or preventative exercise programs may consider focusing on increasing or maintaining plantar flexor strength, which appears critical to maintaining normal walking mechanics.”

Gait Posture. 2007 Mar;25(3):360-7. Epub 2006 May 23.
Compensatory strategies during normal walking in response to muscle weakness and increased hip joint stiffness.
Goldberg EJ1, Neptune RR.

Some Biomechanical Facts on Oscar Pistorius: 400 m London Olympic Games

Following Saturday’s 400m men’s preliminary heats Jere Longman’s wrote an article in the NYTimes entitled “Pistorius Advances to Semifinals”. In it were some interesting facts. Here is the link to the article. 

Ever since Pistorius’s shut out from the Beijing Olympics scientific and legal debate has continued about whether his prosthetic legs gave him an unfair advantage over sprinters using their natural legs. However, as we all knew, this time around would different in London 2012. Competing on carbon-fiber prosthetics called Cheetahs, Pistorius was going to get his chance and in the process further the debate on what is considered able and disabled.

Prior to Beijing the I.A.A.F. said Pistorius’ carbon-fiber blades violated its ban against springs or wheels that gave an athlete a competitive edge over able bodied athletes. The prosthetic legs allowed him to run as fast as elite sprinters while consuming less energy, the governing body concluded. None the less, the debate has continued over the past few years since Beijing pertaining to where to draw the line between fair play and the right to compete. In 2009 in The Journal of Applied Physiology a study concluded that Pistorius could take his strides more rapidly and with more power than a sprinter on biological legs.

An acquantance of ours who we talk to from time to time, Professor Peter Weyand at SMU Locomotor Performance Laboratory in 2009 looked at Oscar Pistorius-type carbon fiber Cheetah blades a little more closely. In his study (referenced below), in the Journal of Applied Physiology, he conducted three tests of functional similarity between an amputee sprinter and competitive male runners with intact limbs: the metabolic cost of running, sprinting endurance, and running mechanics. What he found was:

  • the mean gross metabolic cost of transport of the amputee sprint subject was only 3.8% lower than mean values for intact-limb elite distance runners and 6.7% lower than for subelite distance runners but 17% lower than for intact-limb 400-m specialists
  • the speeds that the amputee sprinter maintained for six all-out, constant-speed trials to failure were within 2.2 (SD 0.6)% of those predicted for intact-limb sprinters.
  • at sprinting speeds of 8.0, 9.0, and 10.0 m/s, the amputee subject had longer foot-ground contact times ,shorter aerial and swing times and lower stance-averaged vertical forces than intact-limb sprinters [top speeds = 10.8 vs. 10.8 (SD 0.6) m/s].

Weyand concluded that running on modern, lower-limb sprinting prostheses appears to be physiologically similar but mechanically different from running with intact limbs.

Longman’s article listed some of the other facts that have come up in recent years, facts that led to the eventual acceptance of Pistorius in London 2012’s Olympic events.  We have not captured these references specifically (yet, but we will) but in the mean time to keep this blog article timely, lets look at some of the other facts that Longman mentioned in his NYTimes article:

  • While calf muscles generate about 250 percent energy return with each strike of the track, propelling a runner forward, Pistorius’s carbon-fiber blades generate only 80 percent return, Gailey said.
  • Given that Pistorius has no feet or calves, he must generate his power with his hips, working harder than able-bodied athletes who use their ankles, calves and hips, Gailey said.
  • And because the blades are narrow and Pistorius essentially runs on his tip toes, he pops straight up out of the blocks instead of driving forward in a low, aerodynamic position for the first 30 or 35 meters, making him more susceptible to wind resistance, Gailey said.
  • Compared with runners with biological feet, Pistorius also must work harder against centrifugal force in the curves, and his arms and legs tend to begin flailing more in the homestretch, costing him valuable time, Gailey said. His stride is not longer than other runners, as many presume, Gailey said. “It’s not like he’s bouncing high with a giant spring,” Gailey said.
  • The blades “basically allow him to roll over the foot and get a little bounce,” Gailey said, adding: “The human foot operates like a spring, and his feet operate like a spring. But the human foot produces more power than the blades do.”

There is an abundance of interesting information here. We will likely return to some of these topics and facts in the future, but in the meantime we say that everyone has their own demons and deficits. We all have injuries and limitations we have to cope with, in life and in sport. So where the line gets drawn will always be a blurred. This debate on this specific case with Pistorius could go on for years and never reach an agreeable conclusion as to a fair playing field. So, let the games begin and may the best man or woman win, with his or her demons and deficits in tow.  Good work Oscar. Thanks for the inspiration.

Shawn and Ivo, The Gait Guys


We found 3 other journal articles on Pubmed on Oscar.

  1. Enhancing disabilities: transhumanism under the veil of inclusion? Van Hilvoorde I, Landeweerd L.   Disabil Rehabil. 2010;32(26):2222-7.

  2. Oscar Pistorius, enhancement and post-humans. Camporesi S. J Med Ethics. 2008 Sep;34(9):639.

  3. By designing ‘blades’ for Oscar Pistorius are prosthetists creating an unfair advantage for Pistorius and an uneven playing field? Chockalingam N, Thomas NB, Smith A, Dunning D. Prosthet Orthot Int. 2011 Dec;35(4):482-3.

  4. J Appl Physiol. 2009 Sep;107(3):903-11. Epub 2009 Jun 18.

    The fastest runner on artificial legs: different limbs, similar function?