They should use a foot typing system that has some theoretical explanation of why there might be a change in reaction time.
Something that has already been done along these lines is sinus tarsi syndrome.
In sinus tarsi syndrome there is an absence of peroneal activity in gait.
It has also been documented that there is an increase in peroneal reaction time in sinus tarsi syndrome.
One hypothetical cause of sinus tarsi syndrome is compression of the lateral process of the talus into the floor of the sinus tarsi that occurs when there is a high pronation moment from the ground and the floor of the sinus tarsi resists further pronation.
One way of classifying that would be to look at location of center pressure relative to the transverse plane projection of the location of STJ axis.
You could classify those into 3 groups as COP far lateral to the axis, near the axis and lateral to the axis.
Or another possible classification would be those feet that are at the end of range of motion of the STJ in static stance versus those that are not.
One could use the measurements proposed by Root et al. to calculate whether or not the STJ is at its end or range of motion.
(Calcaneal eversion to the leg and tibial varum).
Dennis, do you have any explanation of why your classification system, which doesn't use tibial varum, might be related to peroneal reaction time.
In a proposal such as this we are not looking for evidence.
We are looking for a logical hypotheses to be tested.
One of your examples does not relate to a foot typing system but to a syndrome and the other is some system that you seem to have made up but don't use.
I'm sticking to the article on this one and Robin's comment.
What system do you use was my question.
What classification system do you currently use if not navicular sag that Robin finds fault with?
Answer please and raise your interesting hypothetical elsewhere for us to consider.
Thank you, in advance.
I don't think I ever saw any replies to this thread so sorry if I never furthered the discussion
My thoughts here are that we are looking for a kinematic answer to an issue that, in my opinion, is a kinetic one
In gross terms, the activation of the peroneals is controlled by CNS and I find I it hard to believe that the feedback loop involves spacial awareness of the foot position. Moreover, I would guess that it is even less likely that it is related to a randomly assigned foot alignment
I would guess the feedback loop is a kinetic one and that the CNS response is based on tensile and compressive feedback. Something that is measurable would be supination resistance?
It can be measured on a jig with decent reliability. Might be more relevant to the problem being investigated? My guess would be that spikes would be shown at very low supination resistance and slightly higher than average supination resistance, based on clinical experience
Caveat is that there are huge numbers of other factors involved so basing on one measure, as with the original study is inherently flawed.
It's funny going back and reading a post you did a few years ago and thinking I could say more clearly what I was trying to say a couple of years ago.
It is helpful to think about ankle sprains in terms of anatomy and moments.
It's not really the ankle joint that moves with an ankle sprain it is the STJ.
The STJ supinates when there is a net supination moment.
This can occur when there is an increase in supination moment from some source or a decrease, or not enough pronation moment from some other source.
Looking at that, there could be more than one reason for an ankle sprain.
Another thought here is that the motion occurs before the STJ is anywhere near the supination end of range of motion.
This is an important point becuase lateral instability has been attributed to previously torn ligaments.
The ligaments can only limit motion when they become tight which is at the end of range of motion, after the motion has started.
One reason is that there is an unexpected change from a pronation moment from the ground to a supination moment from the ground.
For example stepping on a pebble with the medial heel which is medial to the STJ axis.
If the axis is farther lateral than average there will be a much greater supination moment from ground reaction force.
This may cause the acceleration to occur sooner than the peroneal muscles can add a pronation moment to prevent the sprain.
In the exam chair, you can push on the medial heel and see the peroneus brevis contract.
This can make it very difficult to palpate the location of the STJ axis.
Another reason that there can be a sudden inversion motion after stepping on a pebble is that the peroneal muscles do not react in time to prevent the motion.
There is literature evidence for this.
Talliard in his classic sinus tarsi pain article showed that people with sinus tarsi pain have an absence of peroneal muscle activity.
When the sinus tarsi is anesthetized, the "normal" pattern of peroneal activity is seen.
Sinus tarsi syndrome causes pain when the STJ is at its end of range of motion of pronation.
The ground is compressing the talus and calcaneus together and any increase in pronation moment from the peroneal muscles will increase the compression of those two bones together and hurt more.
So, in sinus tarsi syndrome patients, there is a good change the CNS is inhibiting peroneal activation.
This could be the reason that there is increased peroneal reaction time in those with sinus tarsi syndrome.
With inhibition of the peroneal muscles, you would expect atrophy.
On the other hand, those with a laterally deviated STJ axis, are likely to have over use of the peroneal muscles because the ground is causing a supination moment and the peroneal muscles are more likely to be contracting all the time.
So, if you did a study looking at lateral ankle instabilty and peroneal muscle cross section, you might not get very good data.
The foot type should be controlled for.
The studies mentioned in this thread should be combined and changed from looking at foot posture to looking at STJ axis position (or supination resistance) and then looking at cross sectional area of the peroneal muscles.
The coordination patterns of the foot segments in relation to lateral ankle sprain injury mechanism during unanticipated changes of direction
Carla van der Merwe et al Foot (Edinb). 2020 Sep 9;45:101745