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Reduced AT load with use of heel lifts, yes/no?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markjohconley, Apr 20, 2016.

  1. markjohconley

    markjohconley Well-Known Member


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    Have got two journal articles, sure there are many more, that seem to be in conflict as to whether the use of heel lifts during gait decreases or doesn't alter the load within the Achilles tendon; 'The Effect of an In-Shoe Orthotic Heel Lift on Loading of the Achilles Tendon During Shod Walking' Mathias Wulf et al. J Orthop Sports Phys Ther, Jan 2016, which concludes, "These findings support the addition of orthotic heel lifts to footwear in the rehabilitation of Achilles tendon disorders where management aims to lower tension within the tendon"; and then 'Orthotic Heel Wedges Do Not Alter Hindfoot Kinematics and Achilles Tendon Force During Level and Inclined Walking in Healthy Individuals ' Robert A. Weinert-Aplin et al. JAB Volume 32, Issue 2, April, " These results add to the body of clinical evidence confirming that heel wedges do not reduce Achilles tendon load .."
    Couldn't find any informed opinions, any?, thanks
     
  2. Griff

    Griff Moderator

    One study says heel lifts do reduce load, one says they don't, and then this one says they INCREASE tensile load: http://europepmc.org/abstract/med/24500535

    I think comparing studies is sometimes unwise, as often different methods to quantify loads are used. I'm also wary of the pooling of data when an entire cohort has been given a raise of identical height. It's pretty fair to assume that responses will be subject specific.
     
  3. Height and stiffness of the material
     
  4. Griff

    Griff Moderator

    Yep they'll differ across studies too - another reason comparisons are almost meaningless. They'll usually be standardised within a study - but the assumption all subjects will respond to them identically is erroneous.
     
  5. N.Knight

    N.Knight Active Member

    Same issues we have in orthoses research
     
  6. Yep N= 1
     
  7. efuller

    efuller MVP

    In static stance the load on the Achilles tendon will be related to postural sway. As the center of mass moves around, the muscles have to contract to alter the location of center of pressure under the foot keep you from falling over. For example, if you have a slight anterior movement of the center of mass, you will need to contract your Achilles to shift the center of pressure anterior to the center of mass so that ground reaction force and gravity, acting on the center of mass, will create a force couple that will stop the forward rotation of the body over the stance foot.

    In gait, people will tend to use their gastroc and soleus muscles to provide motion whether or not they are on top of a heel lift. Theoretically, the effect of a heel lift in gait, on the Achilles tendon, will be random, because Achilles tendon tension is controlled by the CNS. I think you could make the case that a heel lift could reduce the force time integral in the Achilles tendon because the body can move farther over the foot before passive tension develops in the tendon. However, that would not happen for all people.

    Eric
     
  8. Eric makes an excellent point here. Tension within the Achilles tendon is absolutely necessary to provide the ankle joint plantarflexion moment that decelerates the forward acceleration of the center of mass of the body in the latter half of the stance phase of walking. This Achilles tendon tension will occur regardless of whether the person has a heel lift in their shoe or not.

    However, the passive tension within the gastrocnemius-soleus-Achilles tendon complex will likely change depending on the height of the plantar heel relative to the height of the plantar forefoot during the latter half of the stance phase of walking gait, especially in those patients who have more limited ankle joint dorsiflexion due to "equinus deformity". Passive tension will be greater in those people with limited ankle joint dorsiflexion.

    My guess is that researchers will not consistently show a decrease in Achilles tendon tension force during gait in their research studies until they segregate their subjects into two groups: those individuals with limited ankle joint dorsiflexion and those individuals with normal ankle joint dorsiflexion. I would expect those individual with limited ankle joint dorsiflexion to have a decrease in Achilles tendon tension with heel lifts and I would expect those individual with normal ankle joint dorsiflexion to have little change in Achilles tendon tension with heel lifts.

    The bottom line is that my clinical use of heel lifts in hundreds of patients with Achilles tendinitis/tendinosus over the past 30+ years has produced very consistent clinical reductions in pain in their Achilles tendon during gait. This is likely due to a reduction in Achilles tendon tension force during gait with the heel lift. The heel lift must be doing something or it wouldn't work so well at reducing the pain of walking in patients with Achilles tendinitis/tendinosus.
     
  9. It is strange such an important tendon has little research. Much of the really good research comes from the same team in Japan.
     
  10. Trevor Prior

    Trevor Prior Active Member

    Could not agree more, need to look at why we would want to use the heel lift. The effect on the force time integral will be determined by how much the heel lift affects the degree of force and the duration it loads. We apply these for symptoms or when we see early heel unweighting on inshoe analysis, looking for a change in the loading pattern.
     
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