This podcast thoroughly examines the Supination Resistance Test (SRT), a clinical assessment used to estimate the force required to invert a patient's foot. While the test aims to quantify pronation forces and assist in prescribing foot orthoses, renown podiatrist Andy Horwood questions its overall validity and relationship to dynamic movement. The analysis highlights that SRT results are heavily influenced by body weight, standing posture, and individual muscle activity, which may not reflect how the foot functions during gait. Furthermore, the text critiques recent research suggesting the SRT can predict orthotic success, arguing that these studies often overlook basic engineering principles and beam mechanics. Instead of relying on static tests, Horwood advocates for a comprehensive clinical assessment involving gait analysis and functional strength testing. Ultimately, Horwood suggest that the SRT should be viewed with healthy skepticism until more robust evidence links it to actual pathological risks.

This presentation provides a biomechanical deconstruction of the Blake Inverted Orthosis, a specialized foot device designed to treat excessive pronation through extreme orthotic inversion. While the technique assumes that steeply inverting the heel cup will proportionally limit foot pronation, the presenters argue that these kinematic claims lack experimental validation and standardized manufacturing protocols. Scientific evaluations, such as the study by Williams et al. (2003), suggest that highly inverted devices fail to significantly reduce rearfoot eversion, instead primarily affecting joint moments and mechanical forces. The presenters conclude that the device’s popularity persists despite a lack of empirical data supporting its original geometric rationale. Ultimately, the kinetic benefits of such complex designs have not been experimentally shown to surpass those of standard, less aggressive orthotic options.

While conventional orthoses focus on correcting foot posture and alignment, research indicates these devices produce only negligible changes in actual skeletal motion. Instead, research suggests that orthotic efficacy stems from the modulation of ground reaction forces and internal joint moments rather than postural repositioning. By utilizing flat kinetic insoles with varied material stiffness, practitioners can directly manage tissue stress and load distribution to treat conditions like plantar fasciopathy. Ultimately, the presentation argues that engineering the magnitude and timing of forces is more therapeutically significant than attempting to control the foot's geometric form.

This addendum to Episode 19(3) in the SHIFT project clarifies that plantar heel pain is a broad clinical category rather than a single, specific diagnosis. Research indicates that discomfort can arise from a variety of tissues, including the plantar fascia, the heel fat pad, and local nerves. While, as we have discussed in the first 3 episodes, some patients experience pain from repetitive tension on the fascia, others suffer due to compressive stress or nerve entrapment. Imaging reveals that these conditions often overlap, with features like calcaneal spurs and fascial thickening frequently appearing together. Despite these distinct causes, all variations are ultimately driven by how mechanical forces are distributed during walking. Therefore, effective treatment depends on identifying the specific loading pathway and tissue involvement unique to each individual.

Presentation 3 in the 4 parts series on plantar fasciopathy advocates for a kinetic approach to the orhtotic management of plantar fasciopathy, shifting the focus from foot alignment to the distribution of forces. Traditional orthoses based on the Root and alligned paradigms prioritize correcting motion and posture, yet the published research ambigiously demonstrated that tissue strain is driven by ground reaction forces and lever arms -- M=Fxd. Specific legacy orthotic modifications, such as forefoot varus posting, may unintentionally increase tension on the plantar fascia by elevating pressure under the medial forefoot. The presenters concludes that effective orthotic design must prioritize modulating external moments rather than simply aiming for geometric symmetry. Consequently, clinical success depends on repositioning force rather than merely repositioning the foot itself.

This podcast, episode 2 in a 4 part series on plantar fasciopathy, explores the evolution of Twisted Plate Theory (TPT), a biomechanical model that views the human foot as a torsionally integrated structure rather than a simple hinge. While historical and contemporary research validates this theory as a kinematic description of foot motion, the presenters question its application as a primary explanation for plantar fasciopathy. Instead of focusing solely on the "unwinding" of the foot's plates, modern evidence suggests that plantar fascia strain is more accurately driven by kinetic factors, such as ground reaction force, CoP, and the stiffness of the medial column. The podcast concludes that while TPT effectively describes how the foot moves, pathological loading is better understood through the relationship between pressure distribution and structural moments. Ultimately, the presenters advocate for a nuanced perspective that distinguishes structural orientation from the mechanical forces that actually cause injury.

This podcast -- part 1 of a 4 part series, argues that chronic plantar "fasciitis" (fasciosis) should be understood as a degenerative condition caused by excessive physical load rather than an inflammatory issue caused by poor foot posture. While traditional theories blame the shape of the arch or "excessive" foot pronation, research suggests that the condition affects people with all foot types by subjecting the tissue to repetitive mechanical stress from high magnitudes of dorsiflexion moment at the forefoot. A key contributor to this pathology is ankle equinus, a limitation in flexibility that acts as a moment multiplier, significantly increasing the tension placed through the fascia. Consequently, the clinicians are encoraged to take a kinetic approach to treatment that focuses on managing how force is distributed during movement. This framework suggests that gastrocnemius recession may be more effective than a plantar fascia release because it address the underlying mechanical drivers of the strain. Ultimately, chronic plantar fasciosis is failure of the fascia to tolerate cumulative stress over time.

The SHIFT Project proposes a kinetic paradigm for orthotic therapy, moving away from kinematic models based on geometric correction of foot posture. It defines foot orthoses as devices that modulate ground reaction forces and joint moments—often without altering observable foot posture. Rather than relying on highly contoured designs, flat insoles with regionally varied stiffness can modify ground reaction force vectors, shift the center of pressure relative to joint axes, alter internal joint moments, and thereby reduce tissue stress.