# The Effect of Custom Insoles on Muscle Activity in Diabetic Individuals with Neuropathy
## 4 Discussion  
There is a general consensus [3] on adopting various offloading techniques (i.e., casting, specific footwear, plantar orthotics, and surgical interventions such as callus debridement) to prevent foot ulcers in patients with diabetes. CIs in particular are among the most commonly used approaches to treat or prevent diabetic foot pathology [22]. CIs have been proven to provide a beneficial effect by reducing localized excessive mechanical stresses [37; 38; 39; 40] and promoting a load redistribution on the plantar aspect of the foot, thus reducing the soft tissue strain [39]. In particular there is an agreement on the consideration of custom therapeutic insoles as being more effective than over-the-counter insoles in diabetic foot prevention [22]. The standard methodology for assessing the efficacy of CIs is through kinetic measurements [6; 38; 41; 42] with mean pressure, peak pressure, pressure-time integral and force-time integral as the most frequently used parameters [6]. In agreement with previous studies, our results showed a reduction in peak pressure through a redistribution of contact surface (i.e., increased contact surface was registered in our sample subject) in the CI condition. However, reducing high plantar loads or foot pressures should not be considered a standalone mechanism. There is agreement in the literature that PN generates functional gait variations related to the altered lower limb joint range of movement, reduced active muscle power, reductions in spatiotemporal parameters, increased kinetics (i.e., GRFs and joint moments), and altered EMG [43]. Although it has been demonstrated that in PN subjects an altered dynamic plantar pressure might be the result (or might be the cause) of altered muscle activity, there is limited research data on the assessment of the effect of CIs on PN subjects' sEMG. The aim of this study was to investigate if the biomechanical effects of CIs (measured in terms of dynamic plantar pressure, GRFs, and COP displacement) were associated with the neuromuscular effects (assessed in terms of muscular function) in subjects at risk of diabetic foot. In respect to this aim, our results indicated a reduction in the activity of the lower limb distal muscles. TA sEMG activity in particular was reduced at loading response and between pushoff and initial swing, which are the phases wherein muscles should provide the necessary support to the plantar surface in order to reduce the impact with the ground. The results were similar for GL, but only for what concerns terminal stance. At the level of proximal muscles, a reduction has been observed on the RF from loading response up to midstance, similarly to what is detected on the GM, again confirming a reduction in the support provided by the muscles during the landing phase. Our results demonstrate agreement with the current literature reporting muscle weakness and atrophy of the lower limbs as a consequence of PN [43; 44; 45], which is further exacerbated when sarcopenia is present. This has also been reported in association with a reduction of maximum voluntary isometric contractions and a reduced number of motor units recruitment [46]. These characteristic alterations have also been documented in terms of decreased flexor and extensor concentric torque at the knee and ankle joints in people with type 2 diabetes with more severe PN [47; 48]. With that said, recently, the inclusion of rehabilitation approaches such as foot and ankle exercises have been suggested as preventive strategies for diabetic foot individuals. In this respect, the following foot-related outcomes were indicated: an increased nerve velocity conduction of the lower limbs, skin sensitivity and intraepidermal nerve fiber density, delayed skin damage and ulceration [49], and improved foot-ankle range of motion and PN symptoms [50]. Furthermore, a positive impact on muscle weakness, foot deformities, the rigidity of connective tissue, poor balance, foot rollover, dynamic plantar pressure distribution, and coordination have been detected [51].