Weakened intrinsics, altered gait pattern, weaker intrinsics. A vicious circle?

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Research has demonstrated that bed rest can lead to atrophy of the intrinsic foot musculature which is then associated with compensatory changes in gait. But if gait changes to compensate for lack of toe power during toe off, do the intrinsics ever regain their full strength and is the previous gait pattern ever re-established without active intervention?

This question leads to another ,that being ,which part of the gait cycle produces/maintains strength in the intrinsic foot muscles? The answer, I believe, is toe off ,when the intrinsics are known to be most active . Merely standing on your feet or, even one foot, will not produce intrinsic strengthening.

This muscle group is crucial for balance and circulation in the lower limb . The extrinsics can't fill in for the intrinsics with regard to proprioception, balance, venous return, or arch recoil.

 

Is there any evidence that standing on one foot, or even loading up one foot whilst carrying additional mass, can strengthen the intrinsic foot muscles during the stance phase of walking? Actually, quite the opposite.

Exactly this situation is found with obese individuals (walking with additional mass) but instead of stronger intrinsics than the non obese they have weaker intrinsics. In the obese, gait is altered with shorter strides being taken and toe off reduced. The stance phase of gait is still present, with increased ground reaction forces, but the intrinsics are weaker non the less. This suggests to me that the intrinsics are not as important during stance as they are at toe off and that "foot bridges", a recent exercises, will not strengthen the intrinsics when used in isolation.

We are dependent on toe off to maintain intrinsic muscle strength and mass, and this strength and mass then allows the foot to function "properly" especially with regard to arch recoil in later stance and venous return ,a key but often neglected part of foot physiology.

 

In 2019 a paper was published in which a nerve block was used to stop the intrinsic foot muscles contributing force during walking running etc . Gait was found to change with increased stride rate and power generated at the hip . One question is, if an individual does not have use of the intrinsics for long enough, does this changed pattern become permanent, even when intrinsic function is restored.

Farris et al showed that the intrinsics really don't do much, mechanically, during midstance and that their loss is felt during toe off when they are generally most active.

Do we have the potential for a vicious circle whereby lack of intrinsic strength > gait patterns that curtail toe off > lack of stimulation of the intrinsics > intrinsic weakening > further gait changes to reduce toe of phase ?

Orthotics that use arch supports will not weaken feet since they contribute to gait mechanics during a phase of gait that does not rely on, or contribute to, intrinsic foot muscle strength maintenance, shoes which reduce toe off will likely weaken feet ( modern super shoes ).


Dominic James Farris 1 2, Luke A Kelly 2, Andrew G Cresswell 2, Glen A Lichtwark 2 2019
" However, when greater loads were experienced during ground contact in walking and running, the stiffness of the LA was not altered by the block, indicating that the PIMs' contribution to LA stiffness is minimal, probably because of their small size. With the PIMs blocked, the distal joints of the foot could not be stiffened sufficiently to provide normal push-off against the ground during late stance. This led to an increase in stride rate and compensatory power generated by the hip musculature, but no increase in the metabolic cost of transport. The results reveal that the PIMs have a minimal effect on the stiffness of the LA when absorbing high loads, but help stiffen the distal foot to aid push-off against the ground when walking or running bipedally."