​Study Title: 
Stiffness of the human foot and evolution of the transverse arch

Authors: 
Venkadesan, M. et al. 

Publication Information: 
Nature (2020) Vol. 579: 97-100.

Background Information: 
The importance of midfoot stiffness for propulsion of human locomotion has been extensively studied. Much of the research however, has centered around the role of the medial longitudinal arch, with little investigation into the role of the transverse tarsal arch (TTA).

Considering a model similar in conceptualization to that of the increasing stiffness properties of a sheet of paper when curled longitudinally, the role of the TTA in contributing to midfoot stiffness via bony and soft tissue configuration can be similarly applied.
The purpose of this study was to examine the relationship between curvature and stiffness of the TTA. 

Study Methods:
The TTA was modelled during both computer simulations and physical experiments. Three-point bending tests were performed on arched continuum shells, mechanical mimics of the midfoot, and on human cadaveric feet.

Results:
Shells with greater transverse curvature were found to be stiffer in longitudinal bending.
Noted was that stiffness also depended the thickness, length, width, Young’s modulus, and Poisson’s ratio of the material. 

The three-point bending tests on the foot models (3 metatarsals with springs mimicking intermetatarsal tissues plus hinges towards the midfoot), demonstrated results similar to the shells based on degree of transverse curvature.
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The cadaveric feet demonstrated that intermetatarsal tissues significantly contributed to foot stiffness and greater than that of the longitudinal arch (LA) and plantar fascia.
 
Conclusions:
The structural curvature of the TTA, as well as the stiffness and slack contributed by intermetatarsal tissues, were found important for the longitudinal stiffness of the foot. Thus, the authors demonstrated that biomechanical understanding of the feet should expand beyond that of the longitudinal arch and include that of the transverse arch and its related soft tissues.
 
Personal Interpretation and Significance:
Like demonstrated in previous studies, it is important for us to look beyond static architecture of the foot and more toward the role dynamic activity plays in arch stiffness. Through this study, it is apparent that we must look at multiple planes and not ignore the role that soft tissues play in contributing to human locomotion. ​

Study Title: 
The functional importance of human foot muscles for bipedal locomotion 

Authors: 
Farris, DJ. et al. 

Publication Information: 
PNAS (2019) Vol. 116: 5. 1645-1650.

Background Information: 
One of the most significant developments in the evolution of the human foot is replacement of an opposable first digit in favor of a longitudinal arch (LA). Research has shown that the purpose of this LA, via the restructuring of the bones within the foot, is to stiffen the foot to enable bipedalism by providing leverage for propulsion to the ground. It has also been demonstrated that the LA exhibits elastic mechanics and is able to act in a spring-like manner to minimize energy cost in running.

Recent research has since focused on the intrinsic muscles of the feet, investigating their role in supportive foot mechanics during static and dynamic weightbearing.

The purpose of this study was to test the importance of the plantar intrinsic muscles (PIMS) for stiffening of the foot, for providing LA support, and for propulsion generation during walking and running.
 
Study Methods:
Two experiments were performed in which posterior tibial nerve blocks were used to prevent PIM activation in each. The first experiment examined controlled loading of the lower leg via linear actuator with and without nerve block. The second experiment examined walking and running on a treadmill with and without nerve block. The effect of the nerve block on LA deformation was measured by changes in the Cal-Met angle formed between the calcaneus and metatarsal segments.
 
Results:
- There was a significant effect on LA deformation via nerve block, particularly during peak force.
- No significant changes in LA deformation were found between the conditions (with and without nerve block) during the initial loading of the midfoot.
- A significant effect of the nerve block in reducing angular impulse generated by the midfoot moment during arch recoil was present. Propulsive impulses during walking and running were also negatively affected by nerve block.
- The nerve block also significantly reduced stiffness of the MTP joint during late stance leading to a drop in vertical ground reaction forces and MTP dorsiflexion.
- The ability to generate power and work through the foot and ankle during late stance was significantly affected by the nerve block. 
- Interestingly, the ability to generate power about the hip during walking and faster running (not slow walking) was also negatively affected by the nerve block.
- In contrast to the “lengthening” of the plantar aponeurosis via the windlass mechanism, tension of the PIMs occurred both isometrically and concentrically.
 
Conclusions:
While it is known that the longitudinal arch of the human foot has evolved for the purposes of both energy absorption and force transfer, this study demonstrated that the contributions of the plantar intrinsic muscles are load and activity specific. LA absorption of energy was only minimally supported by PIM activity, particularly in midstance, yet stiffness of the foot during push-off was highly dependent for the purposes of propulsion. 

Personal Interpretation and Significance:
In simplest terms, strengthening of the plantar intrinsic muscles may do very little to improve the shape and height of the arch of the foot. Instead, the focus of plantar intrinsic muscle strength should be placed on its role in contributing to lever rigidity and dynamic foot stiffness for the purposes of propulsion in late stance of higher speed walking and running. 

For introductory ideas on how to strengthen the plantar intrinsic muscles, this post might help.

Study Title: Association between post-game recovery protocols, physical and perceived recovery, and performance in elite Australian Football League players
Authors: A. Bahnert, K. Norton & P. Lock
Journal: Journal of Science and Medicine in Sport
Date: 2013
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Summary:

• Similar to my recent post on perception of recovery and performance, this study looked specifically at the associations between post-game recovery interventions chosen by players and their subsequent physical and perceptual recovery, and game performances. But in contrast to the last paper, which described a short 3-week study, the authors of this paper undertook a season long project with members (n=44) of an  Australian Football team. Allowing these elite players to be their own controls, the players participated in mandatory post-game (within 10-20 min) recovery sessions whereby the given intervention was self-chosen. The modalities included: floor stretching, pool stretching, bike active recovery, pool active recovery, cold water immersion, contrast therapy, and compression garments. Again, the athletes were permitted to utilize any of the above (plus other modalities) on each given week. Their vertical jump (5 repeated countermovement jumps) was tested weekly to assess recovery, and the athletes reported their perceptions of recovery regularly. Asked of them was their daily rating (1-5 scale) of recovery, fatigue, muscle soreness, stress levels, sleep quality and 'hardness' of the previous session/game. Perceptions of recovery were combined to form a single Recovery Index score. Also collected regularly was a coaching-staff assessment of individual player game performance on a 0-4 scale.
• Results of this study demonstrated that floor stretching, cold water immersion, and compression garments were the most utilized (preferred and self-chosen) forms of interventions while active recovery (bike or pool) were least utilized.  Additionally, those players who chose CWI, floor stretching and/or no active recovery demonstrated an increased probability of reporting greater perceptual recovery the following week. Interestingly, no association was found between the indicator of performance (vertical jump tests) and any of the recovery interventions.
• To me, this paper sheds even more light to the importance of the cognitive component of "physical preparation". Again, far too often we think of the body as a machine, yet these results show that "the mental" is what may matter most in elite sport. We all know the old adage, yet millions of dollars are still spent on technology.  This is not to say that other modalities are not important, because I do administer my MARC-PRO quite regularly, but coaching and "performance engineering" are dynamic processes, so we really should be listening to our athletes better and engaging them in the decision making process.

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Bahnert, A., Norton, K. & Lock, P. (2013). Association between post-game recovery protocols, physical and perceived recovery, and performance in elite Australian Football League players. Journal of Science and Medicine in Sport, Vol. 16; 151-156.
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Study Title: Differences in Static and Dynamic Balance Task Performance After 4 Weeks of Intrinsic Foot Muscle Training: The Short-Foot Exercise Versus the Towel-Curl Exercise
Authors: S. Lynn, R. Padilla & K. Tsang
Journal: Journal of Sport Rehabilitation
Date: 2012
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Summary:

• This study, from Cal State-Fullerton, compared the effects of towel curls and the short-foot exercise on static and dynamic single-leg balance tasks. Towel curls have traditionally been used for foot muscle strengthening however, such exercises theoretically may actually recruit more of the extrinsic foot musculature rather than the intrinsics.
• A RCT was used in this study whereby 30 healthy university students (24 completed the study) were assigned to either the short-foot exercise group, the towel-curl exercise group or a control group. The dependent variables of the study were range of mediolateral movement of the center of pressure during static and dynamic balance tests and standing navicular height. The center of pressure was measured via forceplate while performing a modified Y-balance test (without the test device).
• The participants performing the short foot exercise were instructed to raise the medial longitudinal arch by drawing in the metatarsal heads toward the calcaneus without flexing the toes and holding this position for 5 seconds each repetition. The participants performing the towel curl exercise were instructed to drag a towel (placed on a slick surface) under their foot via toe flexion to generate a strong grip for 5 seconds per repetition. Each group performed 100 repetitions daily for 4 weeks, progressing from seated to standing positions.
• During the static tasks, no differences were found. During the dynamic balance test, both intervention groups demonstrated a significant decrease in movement of the COP of both the dominant and non-dominant limbs however, the short foot group demonstrated much greater improvement (an average decrease by 9.3 mm). This was a large effect size.
• To me, this paper wasn't very impressive. It seemed like a mountain was made out of a molehill with their results. I do prefer the short foot exercise over the towel curl exercise but I generally use an integrated approach as demonstrated in this post. I do understand that variables need to be isolated for the purposes of research, but a static hold and dynamic contractions to me are quite different.

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Lynn, SK., Padilla, RA., & Tsang, KW. (2012). Differences in static- and dynamic-balance task performance after 4 weeks of intrinsic-foot-muscle training: The short-foot exercise versus the towel-curl exercise. Journal of Sport Rehabilitation, vol 21; 327-333

​

Study Title: Which physical examination tests provide clinicians with the most value when examining the shoulder? Update of a systematic review with meta-analysis of individual tests
Authors: E. Hegedus
Journal: British Journal of Sports Medicine
Date: October 2012
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Summary:

• Although high quality open access journal articles aren't common - yet - they still do occur. This systematic review with meta-analysis by Hegedus is one such paper for example, and is one that is essentially an updated version of his 2008 review. With a surplus of orthopaedic tests for the shoulder and an equally great number of review papers investigating such tests, it can be very simple for clinicians who a) take a less than adequate history and b) are unfamiliar with the accuracy of the arsenal of tests to fall into the trap of utilizing inappropriate tests for given clinical presentations.
• Hegedus' review provides us with an update of his original article, based on the fact that since his original article was published, not only have new studies been published, but also the methodologies behind systematic reviews and meta-analyses have been updated as well.
• Without going into great detail, the protocol used in this review was that of the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). The original paper examined studies from 1966-October, 2006 while this paper confined it's Medline and CINAHL search to November, 2006-February, 2012. Additionally, EMBASE and the Cochrane Library were added as databases as well. 2x2 tables were used for meta-analysis and quality was assesed via the QUADAS-2 tool.
• In total, 32 new studies addressing diagnostic accuracy were revealed in this new time frame with 12 of these studies added 13 new tests to the literature. And the majority of these tests pertained to the diagnosis of SLAP tears. What this updated paper adds to the literature include the following:

• Biceps Load II seems to be less diagnostic for SLAP lesions
• The belly-off and modified belly press tests may add to subscapularis tendinopathy diagnosis
• The olecranon-manubrium percussion test may be useful in traumatic cases for requiring imaging
• The passive compression test may be helpful in diagnosing a SLAP lesion
• The modified dynamic labral shear test may be helpful for SLAP lesions
• The lateral Jobe test for diagnosing rotator cuff tears
• The passive distraction test may assis in ruling in a SLAP tear if possible

• With the information provided above, it is still very reasonable to assume that rather than clarifying the application of orthopaedic testing for the shoulder, we may be no further from a practicality standpoint. I, myself, firmly believe that although there are numerous tests for the shoulder, a detailed clinical history combined with a good understanding of the mechanisms behind shoulder pathologies hold more value than the testing itself. Essentially, orthopaedic tests should confirm or deny your differentials but your differentials will always be based on your investigative and listening skills, as well as your understanding of the body (and mind).
• So with that said, I want to leave you with a snippet of an email discussion I had several months back with a colleague of mine who is an orthopaedic surgeon that specializes in the upper extremity.

"Sorry, but I won't be much help with the biceps/slap debate.  My own personal view is that all the tests are pretty useless and I've not found much predictive value with any of them.  Most of them put the arm in significant flexion or adduction and these are essentially the impingement or AC compression testing positions, so I feel they overlap siginificantly with eliciting the much more common cuff and AC pathology.  I also refuse to do multiple tests to evaluate the same structure, I pick the one that is the best (even if it's the best of a bunch of bad tests).  So for superior labrum I do the crank test, because it is past the painful arc and mimics the peel back meneuvre that we do intra-operatively to visualize an unstable II slap if it's there.  

Combine that diagnostic dilema with the fact that most slap repairs either don't heal or cause significant stiffness and essentially I only repair slaps in combination with a pan labral injury during instability surgery.  Final caveat though is that I definitely don't have a very young sportsy practice, so maybe others are seeing the real deal, for me it's all hocus pocus."
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Hegedus, E. (2012). Which physical examination tests provide clinicians with the most value when examining the shoulder? Update of a systematic review with meta-analysis of individual tests. British Journal of Sports Medicine, vol 46; 964-978
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Study Title: Spinal manipulation, medication, or home exercise with advice for acute and subacute neck pain: a randomized trial
Authors: G. Bronfort, R. Evans, A. Anderson, K. Svendson, Y. Bracha, R. Grimm
Journal: Annals of Internal Medicine
Date: 2012
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My thoughts

• First of all, seeing this study capture the attention of many manual and rehabilitation therapists through the power of the internet reminded me of the old "Start the Car" ikea commercial.
• As a chiropractor that highly values exercise and rehabilitation, most would assume that I too would take this paper, "start the car", and run away with it. Unfortunately, I wanted to read the actual paper and see what all the hype was about beyond the good publicity from the New York Times.
• There's no question that I strongly believe manipulation and exercise may be better alternatives to medication in some if not many "pain" presentations, however, overtime I have learned to become more attached to patient-specific care more than anything else. Patient-specific care may indeed call for meds, manipulation and exercise - but patient-specific care may also call for reassurance, education, and / or soft tissue therapy.
• Now having read the actual study, the authors did do a relatively good job to prescribe individually based exercises but I do think they could have been more thorough. Gentle stretching and scapular retraction exercises, as well as neck and possibly (although not convincing in this paper) thoracic manipulations don't cut it when it comes to sending a message that SMT and exercise are better than meds. I understand that this is a research paper so I will accept some limitations in the study.
• While there was significant difference in follow up at 6 months, no significant differences were found at the 1 year mark of follow up when compared to baseline. To me, this likely indicates symptomatic relief or treating the DP (which I think is ok)...but what about the root cause? And what about integrated care? Because how often do you just manipulate or just rehab? I know quite well many of you who read this blog also combine the two. But you probably combine other therapeutic approaches as well. What I don't want to see is manipulating people's necks for the simple reason that this paper said it was more beneficial. If it is indicated, and the patient consents, then by all means. But if not, don't "start the car". We need to be more precise and we need to be accountable.
• Again, it is a research study and I get that we can't control for everything in research but I do think we can be a little more responsible when drinking the kool-aid. And responsibility means taking an objective, rather than emotional opinion...especially on social media. So please feel free to advocate that SMT and Exercise may sometimes be better a alternative than medication for neck pain (and that meds are often unnecessary), but please also recognize that generalizing the study's results to all of your patients is an act that is no different than advocating for meds alone.

Bronfort, G et al. (2012). Spinal manipulation, medication, or home exercise with advice for acute and subacute neck pain: a randomized trial. Annals of Internal Medicine, vol 156; 1-10....