Announcement

Collapse
No announcement yet.

Impact accelerations during running

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Impact accelerations during running

    Hi Everyone

    We have completed an experiment measuring impact acceleration at both the tibia and sacrum (using Shimmer inertial sensors, Dublin) while recreational runners ran for 15 minutes on a treadmill. The sensors were attached with double sided tape, elastic tape over the sensors onto the skin and with an elastic belt wrapped firmly around the runner's waist. The sensors were aligned with the longitudinal axis of the segment (tibia, sacrum)

    While for the majority of runners the impact acceleration at the sacrum was lower than at the tibia, for a few individuals we found the opposite, the sacrum acceleration is actually higher.

    No studies to date appear to have reported this phenomenon, in stead suggesting the signal will always be lower because it is dampened as it propagates through the body.
    for example:
    Reenalda, Jasper, Erik Maartens, Jaap H. Buurke, and Allison H. Gruber. "Kinematics and shock attenuation during a prolonged run on the athletic track as measured with inertial magnetic measurement units." Gait & posture 68 (2019): 155-160. (measured at the tibia and sacrum)

    Shorten, Martyn R., and Darcy S. Winslow. "Spectral analysis of impact shock during running." International Journal of Sport Biomechanics 8, no. 4 (1992): 288-304. (measured at the tibia and head)


    We have filtered the signal at 60 Hz (with a bidirectional fourth-order Butterworth filter) and we removed any linear trend from the signal (Shorten and Winslow, 1992)

    Has anyone else experienced this situation in assessing runners?
    or/and
    Does anyone have an explanation to why the impact acceleration would be greater at the sacrum?


    Many thanks

    Kieran





    SHORTEN MR, WINSLOW DS: Spectral analysis of impact shock during running. Int J Sport Biomech 8: 288, 1992.

  • #2
    Re: Impact accelerations during running

    Hi Kieran,

    It may be related to a poor mechanical coupling between the sensor and underlying bone/body segment at that site i.e. sensor is not measuring bone accelerations on impact but is measuring large skin oscillations due to the loose skin over the bone (e.g. whip effect). Humans tend to gain mass around their torso so it could be that some of your recreational (noted recreational ��) runners have greater adipose tissue and therefore loose skin at sacrum site which is causing the sensor to oscillate more on impact as compare to the tibia.

    Also, from my experience Shimmer sensors tend to be too bulky and heavy to capture impact accelerations during running. On reading some of Joe Hamill, Martyn Shorten and Allison Gruber’s work in the past, they tended to use light and small inertial sensors (PCB sensors) to measure impact accelerations during running. These sensors allow for a better measurement of what impact accelerations the bone is experiencing during running.

    As a tip to improve the mechanical coupling between the sensor and the underlying bone, I found using kinesiology tape to stretch the skin and make it taut (although it’s more difficult to do around the torso).

    Adam
    Last edited by Adam Clansey; March 4, 2019, 01:56 PM.

    Comment


    • #3
      Re: Impact accelerations during running

      I concur with Adam's advice to use small accelerometers. Also, try to attach them at sites where there is no soft tissue between skin and bone, e.g. the anterior-medial side of the tibia. Have a large enough area of contact so the sensor can't wobble.

      I was wondering how you define "impact acceleration at the sacrum". Is there a clear impact peak? If not, you could be measuring the vertical motion of the pelvis under the influence of muscles and gravity, probably around 1 g amplitude. In that case, the acceleration at the sacrum does not necessarily need to be smaller than at the tibia.

      And a pet peeve of mine, please use the term "damping", not "dampening". The latter is about moisture, not mechanics.

      Ton van den Bogert

      Comment


      • #4
        Re: Impact accelerations during running

        Hi Kieran,

        I just wanted to add there is a chapter (think chapter 9) by Gordon Valiant in the book by Peter Cavanagh called ‘Biomechanics of Distance Running’ that nicely covers the importance of accelerometer mounting and the effect of accelerometer mass/size on impact accelerations during running. I would recommend this book to anyone who is interested in studying impact accelerations during running. Plus, it gets us humans away from the ever-increasing accumulation of daily screen time into the realms of tactile feedback and smells of a good old-fashioned hardback book! ;-)

        Adam

        Comment


        • #5
          Re: Impact accelerations during running

          Hi Adam

          Thanks for your response. Yes we suspect that the size of the sensor (and the greater adipose tissue of our participants) may be the cause. We are exploring the use of different cut of filters to see if we can distinguish between the true deceleration and that caused by skin/sensor movement relative to the underlying bone

          Many thanks

          Kieran

          Comment


          • #6
            Re: Impact accelerations during running

            Hi Ton

            Many thanks for taking the time to respond.

            When you state:
            "I was wondering how you define "impact acceleration at the sacrum". Is there a clear impact peak? If not, you could be measuring the vertical motion of the pelvis under the influence of muscles and gravity, probably around 1 g amplitude. In that case, the acceleration at the sacrum does not necessarily need to be smaller than at the tibia."

            Our signal does provide a very clear 'impact peak'

            However I am curious about your statement:
            "you could be measuring the vertical motion of the pelvis under the influence of muscles and gravity, probably around 1 g amplitude. In that case, the acceleration at the sacrum does not necessarily need to be smaller than at the tibia."

            Could you elaborate on this a little more


            Many thanks (and I promise to use the term 'damping')

            Kieran

            Comment


            • #7
              Re: Impact accelerations during running

              In running, the pelvis acceleration will be roughly a constant -1 g during the flight phase and a peak of about +1 g during the stance phases. The stance phase pattern will be similar to the vertical ground reaciton force. Because the accelerometer also senses gravity, the flight phase may show up as zero g and the stance phase as +2 g. It depends on how you "zero" the accelerometer.

              Then you have the impact peaks superimposed on this sinusoidal signal. Your accelerometer is attached well enough that the impact peaks show up, which is good, so you can measure their amplitude.

              That's what I meant.

              Ton

              Comment

              Working...
              X