Flip Flops not so bad? We still think they suck and here's why...

We have talked about the dangers of open back shoes (Including flip-flops)  and loss of ankle rocker as well as changes in forefoot rocker and great toe dorsiflexion on our blog many times.

The findings of this study, with slower cadence and shortened stance are not surprising (especially since you need to fire your long flexors to keep them on!) nor are ankle joint kinematics (flip flops have no heel counter and are not torsionally rigid, so naturally there would be increseased subtalar motion), however we really question the interpretation.

 "Many have long suspected the answer, but a new study would appear to resolve the question: Are flip flops really that bad for your feet? According to Chen and colleagues from the Department of Biomedical Engineering at The Hong Kong Polytechnic University, flip flops are most likely no better than barefoot when it comes to lower-limb co-contraction and joint contact force in the ankle. The authors had hypothesized that the popular rubber footwear would increase co-contraction of the muscles between the knee and ankle joints in what they thought was a compensatory mechanism for the unstable foot–sole interface and would affect gait kinematics and kinetics.

In the study, the researchers had 10 healthy males perform 6 walking trials under 3 conditions: barefoot, sports shoes, and thong-type flip flops. Participants, who reported they were not “regular flip flop wearers,” were fitted with numerous markers that were monitored while they walked on a 10-meter pathway. The study looked at several muscle pairings that stabilize the knee, ankle, and subtalar joints, including vastus lateralis and gastrocnemius medialis; vastus lateralis and biceps femoris; and peroneus longus and tibialis anterior.

In pairwise comparisons, the walking velocity of flip flops was lower than that of sports shoes (p<0.01) but comparable to barefoot (p>0.05), findings that were consistent with the published literature. Although not significant, the minimalist footwear produced a slower cadence and shortened stance phase in walking trials compared to the other 2 types of footwear. Joint kinematics differed significantly in the ankle joint (F[2,18]=6.73, P<.05) and subtalar joint (F[2,18]=4.45; P<.05); Furthermore, ankle and subtalar range of motion was higher for flip flops than for sports shoes. However, co-contraction was not enhanced. The authors propose that walking speed does not need to be consistent for real-world activities and the slower speed could be a natural approach to avoid injury.

The authors conclude that the slowed walking speed of flip flop users could account for the comparable joint biomechanics between flip flop use and barefoot. They note, however, that, for injury prevention, the closed-toe design of the sports shoe would provide better support for joint motion and loading compared to the other 2 options."

Source:

Chen TL, Wong DW, Xu Z, Tan Q, Wang Y, Luximon A, Zhang M. Lower limb muscle co-contraction and joint loading of flip-flops walking in male wearers. PLoS One. 2018;13(3):e0193653."

image and article source: http://lermagazine.com/issues/may/flip-flops-bare-feet-or-sports-shoes-which-are-best-and-which-are-worst

Parkinsons Patients? How about textured insoles or walking barefoot more?

Is it at all surprising that increasing afferent input (in this case: textured insoles) to one of the areas in the brain (parasaggital sulcus in the post central gyrus) from one of the structures that has the greatest cortical representation (ie the feet) can improve gait on folks that have a disorder with their basal ganglia (which provides background positioning of joints)?

"After one week of insole wear, plantar sensation and stride length were significantly improved relative to baseline; the improvement in plantar sensation was maintained after another week of wearing conventional insoles."

Lirani-Silva E, Vitorio R, Barbieri FA, et al. Continuous use of textured insole improve plantar sensation and stride length of people with Parkinson disease: A pilot study. Gait Posture 2017;58:495-497.

Being a gait geek offers you a unique perspective in many situations.

Perhaps you have been with us for some time now and would like to check your gait acumen. If you are new, or these terms are foreign to you; search here on our blog through hundreds of posts to become more comfortable with some of the vocabulary.

Watch this video a few times (we slowed it down for you) and write down what you see.

Did you see all of these in this brief video?

• bilateral loss of hip extension

• bilateral loss of ankle rocker

• less ankle rocker on right

• bilateral increased progression angle  

• dip in right pelvis at right heel strike

• arm swing increased on R

The Gait Guys. Increasing your gait competency each and every day.

special thanks to NL for allowing us to use this video footage.

On the topic of endurance training.....

On the topic of endurance training (which we discussed on this weeks PODcast, forthcoming in the next day or so; we have both been extraordinarily busy in our clinics); if you are a well trained athlete (ie endurance junkie), how might this effect your running gait?

So, you run 103 miles with an elevation change of over 31,000 feet, how do you think you would fare? These folks were tested pre and 3 hours post race on a 22 foot long pressure walkway at about 7.5 miles per hour. Here’s how this group of 18 folks did:

1. increased step frequency
2. decreased “aerial” time
3. no change in contact time
4. decrease in downward displacement of the center of mass
5. decrease in peak vertical ground reactive force
6. increased vertical oscillation
7. leg stiffness remained unchanged

So what does this tell us?

• wow, that is a lot of vertical
• holy smokes, that is really far
• don’t know how I would do with a race like that
• they are fatigued (1, 2, 6)
• they are trying to attenuate impact forces (2, 3, 4, 5, 7)

The system is trying to adapt the best it can. If you were to do a standard hip screen test (like we spoke about here)  you would probably see increased horizontal drift due to proprioceptive fatigue. Remember that proprioception (our bodies ability to sense its position in space) makes the world go round. Proprioception is dependent on an intact visual system (see our post yesterday) , an intact vestibular system and muscle and joint mechanoreceptors functioning appropriately). We would add here that central nervous system fatigue (ie central processing both at the cord and in the cortex) would probably play a role as well.

The take home message? The human machine is a neuro mechanical marvel and much more complex than having the right shoe or the right running technique. Training often makes us more competent and efficient, but everything has it limits.

The Gait Guys. Making it real with each and every post.

all material copyright 2013 The Gait Guys/ The Homunculus Group

J Biomech. 2011 Apr 7;44(6):1104-7. doi: 10.1016/j.jbiomech.2011.01.028. Epub 2011 Feb 20.

Changes in running mechanics and spring-mass behavior induced by a mountain ultra-marathon race.

Morin JB, Tomazin K, Edouard P, Millet GY.

Source

Université de Lyon, F-42023 Saint-Etienne, France. jean.benoit.morin@univ-st-etienne.fr

Abstract

Changes in running mechanics and spring-mass behavior due to fatigue induced by a mountain ultra-marathon race (MUM, 166km, total positive and negative elevation of 9500m) were studied in 18 ultra-marathon runners. Mechanical measurements were undertaken pre- and 3h post-MUM at 12km h(-1) on a 7m long pressure walkway: contact (t©), aerial (t(a)) times, step frequency (f), and running velocity (v) were sampled and averaged over 5-8 steps. From these variables, spring-mass parameters of peak vertical ground reaction force (F(max)), vertical downward displacement of the center of mass (Δz), leg length change (ΔL), vertical (k(vert)) and leg (k(leg)) stiffness were computed. After the MUM, there was a significant increase in f (5.9±5.5%; P<0.001) associated with reduced t(a) (-18.5±17.4%; P<0.001) with no change in t©, and a significant decrease in both Δz and F(max) (-11.6±10.5 and -6.3±7.3%, respectively; P<0.001). k(vert) increased by 5.6±11.7% (P=0.053), and k(leg) remained unchanged. These results show that 3h post-MUM, subjects ran with a reduced vertical oscillation of their spring-mass system. This is consistent with (i) previous studies concerning muscular structure/function impairment in running and (ii) the hypothesis that these changes in the running pattern could be associated with lower overall impact (especially during the braking phase) supported by the locomotor system at each step, potentially leading to reduced pain during running.

Copyright © 2011 Elsevier Ltd. All rights reserved.

http://www.ncbi.nlm.nih.gov/pubmed/21342691

The Windmill Pitch: Fastpitch Softball. More proof that arm swing and opposite leg swing are powerfully coordinated and neurologically paired.

Step length and power can affect opposite arm power and speed.

You have heard us talk often about opposite arm and leg swing pairing and how important they are from a neurological coordination issue. We have also talked about energy conservation and transmission in prior blog posts when it comes to arm swing. Good arm swing will lead to energy conservation.  A reduction in arm swing leads to a poor gait economy.  Check out this study here and the statistics. 

Collins et al Proc Biol Sci, 2009, Oct 22 “Dynamic arm swinging in human walking.”

“normal arm swinging requires minimal shoulder torque, while volitionally holding the arms still requires 12 % more metabolic energy.  Among measures of gait mechanics, vertical ground reactive moments are most affected by arm swinging and increased by 63% without arm swing.”

* type in “arm swing” into our blog SEARCH box and you will see 14 articles we have written on arm swing in human locomotion.

Gait is in every sport, just about.  Here we see a beautiful depiction of the opposite arm and leg pairing neuro-biomechanically, albeit not gait here it is still in her movement.  The larger a first step , whether the pitcher is a overhead hardball thrower or underarm fastball pitcher, the concept remains preserved.  I was a pitcher for over 10 years in the Ontario Fastball league back in Canada when I was a youth and teenager.  I was not a big speed pitcher, but what I had troubles coming up with in speed I was able to make up in putting “junk” on the ball.  My first step was large, and the larger the left step length (as seen in this video here), the more pelvic obliquity that could be achieved, which in turn enabled an opposite “anti-phase” rotation of the shoulder girdle.  When you add increased shoulder girdle obliquity with full arm rotation speed losses can be contained and limited.  Hypothetically, ball speed in a smaller player with a large first step can be heightened to the point of a that of a larger stronger pitcher with a smaller step.

Here you can see a great demonstration of this large step length the video.  They are using the tilt board to facilitate a faster downward plantarflexion of the right foot to drive a larger faster left step. It is the same principle as if you stepped off a curb or into a hole unexpectedly, the body’s natural reaction is to step out quickly with the other limb to catch the body’s forward fall. The board is used to achieve the same result with control. This is why you will see pitchers dig out a trench immediately in front of the pitchers rubber, to create this same plantarflexion drop of the right foot (in this case, the right foot for a right handed pitcher).  The deeper the trench, the more aggressive that left step.

Shawn and Ivo………..digging deep trenches today…….. and finding gait theory everywhere, even in fastball.

http://youtu.be/QzojfAUcGEI

http://youtu.be/0OA6RfTre6M

This week we will focus on the basics of gait and the gait cycle in our attempt to assist in gait literacy

Gait Cycle Basics: Part 1

Steps and strides….

What does the gait cycle that have to do with therapy or rehabilitation? Well, most people walk at some point in the day, and most have walked into your office. If people can’t carry the changes you made on the table and incorporate it into walking, then what you do will have limited effectiveness. Thus, the need for understanding the gait cycle as it relates to rehabilitation or how it can give you clues to the biomechanical faults present. An example is a loss of functional hip extension and chronic LBP/ SI dysfunction. This could be due to a myriad of reasons, from weak glutes, loss of ankle dorsiflexion, or even a dysfunctional shoulder. Understanding how these seemingly unrelated body parts integrate into the kinetic chain, especially while moving upright through the gravitational plane.

One gait cycle consists of the events from heel strike to heel strike on one side. A step length is the distance traveled from one heel strike to the next (on the opposite side). Comparing right to left step lengths can give the evaluator insight into the symmetry of the gait.  Differences in step length, on the simplest level, should cause the individual to deviate consistently from a straight line (technically it should cause the individual to eventually walk in a large circle!).  Often, compensations occur functionally in the lower kinetic chain to compensate for the differences in step length to ensure that you walk in a straight line.  It is these longstanding complex compensations that are the generators of many of our patient’s complaints.

A stride length is the distance from heel strike to heel strike on the ipsilateral side (the distance covered in one gait cycle.  Step width, or base of gait, is the lateral distance between the heel centers of two consecutive foot contacts (this typically measures 6-10 cm).  Foot progression angle is the angle of deviation of the long axis of the foot from the line of progression (typically 7-10 degrees). Çhanges in the progression angle can be due to both congenital (torsions, versions) as well as developmental reasons.

Next time we will take a closer look at the gait cycle itself. Yup, we are still…The Gait Guys

special thanks to Dr. Tom Michaud, who has allowed us to use these images in our book