Ground reaction forces and gait

[Gerrard Farrell]

Re: Ground reaction forces and gait

Allan
We are firmly off piste here and it would be astonishing if the vertical acceleration and deceleration of the pelvis were key to efficient gait and yet remain almost entirely unstudied , in that context , over so many years . I was aware of that when I started this thread but , as yet , have not changed my mind that this might indeed be the case .

It still seems to me , more likely than not ,that the vertical acceleration/ deceleration of the pelvis plays a vital role in co-coordinating the swinging appendages of the body during gait (arms and swing leg )

With regard to the golf swing if you look at the point of impact you can see that ,for a right handed golfer, the pivot point of the arm /club pendulum is the left shoulder , not the head ( see video and driving left leg 1 ).

I think it was Ben Hogan , a past great , who said that on the down swing he did no more than let his arms move under the force of gravity . What he might have been unaware of was vertically driving lead leg .

Finally ,did you have any thoughts on this part of post 13 ? -

"With regard to kicking a football /rugby ball after a run up , at least some of angular momentum generated in the kicking leg seems likely to be generated by the vertical deceleration of the pelvis cause by the standing /support foot meeting the ground after the final approach stride . "

I ask because it is an extreme example and therefore more likely to shed light on things .

VideoRory McIlroy - Driver Swing Slow Motion (May 2017) - YouTube

https://www.youtube.com/watch?v=fxFRXilzmAw

▶ 0:51

27 Jun 2017 - Uploaded by RollYourRock
Rory McIlroy - Driver Swing Slow Motion (May 2017). RollYourRock. Loading... Unsubscribe from ...

Gerry

[Ton van den Bogert]

Re: Ground reaction forces and gait

"at least some of angular momentum generated in the kicking leg seems likely to be generated by the vertical deceleration of the pelvis cause by the standing /support foot meeting the ground after the final approach stride."


Yes, I agree. But don't forget the horizontal deceleration of the pelvis which is equally important.

Ton

[Gerrard Farrell]

Re: Ground reaction forces and gait

"at least some of angular momentum generated in the kicking leg seems likely to be generated by the vertical deceleration of the pelvis cause by the standing /support foot meeting the ground after the final approach stride."


As the standing or supporting foot meets the ground and produces deceleration , the tissues in the supporting leg will store energy as they are stretched . Energy return will start as deceleration ends giving vertical acceleration of the pelvis and further angular acceleration of the swing leg .

I believe that the same system may be play during running . Measurement is required to confirm though .

Gerry

[Allan Carman]

Re: Ground reaction forces and gait

Gerrard,

“it would be astonishing if the vertical acceleration and deceleration of the pelvis were key to efficient gait and yet remain almost entirely unstudied”

Vertical acceleration and deceleration of the pelvis (or rather COM) do play an important role in gait efficiency. This has been widely studied in normal and pathological gait (Detrembleur et al. 2005; Nankaku et al. 2012). In normal gait, walking at your self-selected speed produces optimal gait efficiency (O2 consumption and mechanically). Reasons reported for optimal efficiency are a decreased COM vertical displacement, decreased or ‘smoother’ accelerations of the COM, and a more efficient transfer between kinetic and potential energy in an inverted pendulum model of walking. In pathological (amputee, hip replacement and Cerebral Palsy) gait analysis and research often focus on improving gait efficiency and speed. Outcome measures are often a decrease in medio-lateral and vertical COM displacements, reducing magnitude of COM accelerations and reducing right and left asymmetries.

“It still seems to me, more likely than not, that the vertical acceleration/ deceleration of the pelvis plays a vital role in co-coordinating the swinging appendages of the body during gait (arms and swing leg) “

Absolutely but now we are talking about segment coordination. Differences in COM and pelvic motion have been reported between male and female and related to anatomy and efficiency (Smith et al. 2002). In pathological gait compensatory movements of the pelvis are often described (increased hip hike and circumduction) to accommodate muscular deficiencies, contractures or limitations in joint ROM limitations.

“With regard to the golf swing if you look at the point of impact you can see that, for a right handed golfer, the pivot point of the arm /club pendulum is the left shoulder , not the head ( see video and driving left leg 1 )”

I mentioned that the head remains near stationary and from the roughly circular motion of the hands, I am presuming there would be a pivot point for the hands somewhere between the shoulders. The club follows a more elliptical path. I am not an expert in golf or golf kinematics so may well be wrong with the placement of the center of rotation of the hands and may well change during the swing.

I have attached a file describing C7 and club head speed and acceleration during the golf swing. There were very small and subtle changes in C7 position, velocity and acceleration during the swing. At impact C7 velocity was near zero (-0.13m/s) and acceleration small and negative (-5 m/s2). The large upward C7 velocity or upward acceleration of the centre of rotation of the club during the golf swing were not present.

"With regard to kicking a football /rugby ball after a run up , at least some of angular momentum generated in the kicking leg seems likely to be generated by the vertical deceleration of the pelvis cause by the standing /support foot meeting the ground after the final approach stride. "

There is a horizontal breaking force at the hip from the contra-lateral foot plant prior to foot-ball impact. This will generate an inertial or passive increase in kicking leg angular velocity. I still believe it is too small to make a ‘meaningful’ contribution to the active muscular forces involved in kicking. I see the stance leg as having at least three major roles, a stable base of support, to provide stiffness or reactive joint moments and ground reaction forces such that the muscular moments and joint velocities of the kicking leg are transferred down the linked system to enable maximal impulse to be transferred to the ball, and thirdly lowering and position the hips to aid the kicking leg to make contact with the ball.

The original question was whether the vertical velocity of the hips are responsible for bringing the leg through in walking and sprinting, producing club head speed in golf and foot velocity in kicking. In all case active muscle forces are the drivers behind these movements. Hip and COM vertical displacement do play a role in efficiency of gait and pelvic-limb coordination in walking, running and kicking activities. However the vertical accelerations of the center of rotations are either small (walking, kicking) or non-existent (golf) to make a ‘meaningful’ contribution to angular velocity of the leg or golf club.

Allan

[Gerrard Farrell]

Re: Ground reaction forces and gait

Allan
Can you use changes in C7 position as representative of hip movement within the context of the golf swing ?

With regard to the main thrust of the thread I feel that trial and measurement would be justified .

Gerry

[Gerrard Farrell]

Re: Ground reaction forces and gait

Actually Allan you might just be the man for this .
I get the impression you like to think about biomechanics , just as I do myself , and I have come across something surprising that you might like to get your teeth into .

You will be aware of the foot pump and the calf muscle pump and you might well have read texts which describe their function . In every text I have ever read the calf pump in particular is described as helping to move blood towards the heart against gravity . However what about the centripedal forces and centrifigal affect generated in the legs and vasculature during walking and running . I have never ,in years of looking ,found a paper on venous return which takes these forces into account when ,for example ,discussing venous reflux .
Surely these forces are increasingly relevant as you move from slow walking to brisk walking to jogging then running then sprinting .

It is worth noting that in individuals with previous heart failure and thus reduce cardiac capacity , poor venous return may reduce preloading (Starling mechanism ) and thus cardiac output .

What do you think . Have the vascular people missed a trick ?

Gerry

[Gerrard Farrell]

Re: Ground reaction forces and gait

Hi Allan
I have started a new thread on the subject introduced above under " Centripedal forces and the calf muscle pump " . Hope that is ok with you and if you wish to respond could you do so on new thread .

Cheers

Gerry

[Gerrard Farrell]

Re: Ground reaction forces and gait

Hi Allan

Just came across this video on sinking and then lifting the hips to create power in the golf swing . I know you don't play but thought you might find it interesting none the less .

Cheers

Gerry

• • [COLOR=#FFFFFF !important]12:20
    
    
    GOLF: How To Use Your Hips Like Dustin Johnson To Create More Power and DIstance
    
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    How To Use Your Hips Like Dustin Johnson To Create More Power AndDistance **You can get all the details about our golf ...
    
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[Gerrard Farrell]

Re: Ground reaction forces and gait

Roberto Carlos is a retired Brazilian footballer . He is 5 feet six tall but had just about the most powerful kick in the world in his day . In the video below you can see that a large proportion of the power comes from the run up , but look how high his standing leg lifts him into the air after contact . At ball contact and just after ,that's the bit to focus on . His legs were very powerful and so could rapidly , vertically accelerate the standing leg/pelvis putting power into the swing/kicking leg .

Roberto Carlos amazing free kick for Brazil - YouTube


https://www.youtube.com/watch?v=XdL7EDKr_rk

▶ 0:34

12 Aug 2012 - Uploaded by jontekahrs2
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[Gerrard Farrell]

Re: Ground reaction forces and gait

So in the first post of this thread I said this -

"Recently, I developed the idea that ground reaction forces in the stance leg can help produce vertical acceleration of the pelvis during gait which will in turn will accelerate the swing leg provided it has started on a downward arc . I feel that this might be an important part of gait and also and important part generating leg speed when it comes to kicking things like a football ."

Thanks to the helpful input of all who have contributed to the thread , I am now pretty confident that vertical accelerations of the pelvis play a major role in coordinating body segment movement during gait , with such accelerations feeding energy into the pendulums that are the swing leg and the arms .

Just a final thought . If you get someone to walk on a treadmill you will see their arms swing . Get them to put one hand in their trouser pocket , inhibiting the swing of one arm , and you will see the swing amplitude of the contralateral arm increase to maintain body segment coordination . Actually, you can see the same effect if someone is walking with a strap supported handbag . One arm/hand steadies the bag causing the other arm to have a greater swing amplitude .

Gerry