The energy-sparing spring theory of the foot’s arch has become central to interpretations of the foot’s mechanical function and evolution. Using a novel insole technique that restricted compression of the foot’s longitudinal arch, this study provides the first direct evidence that arch compression/recoil during locomotion contributes to lowering energy cost. Restricting arch compression near maximally (~80%) during moderate-speed (2.7 ms−1) level running increased metabolic cost by + 6.0% (p < 0.001, d = 0.67; unaffected by foot strike technique). A simple model shows that the metabolic energy saved by the arch is largely explained by the passive-elastic work it supplies that would otherwise be done by active muscle. Both experimental and model data confirm that it is the end-range of arch compression that dictates the energy-saving role of the arch. Restricting arch compression had no effect on the cost of walking or incline running (3°), commensurate with the smaller role of passive-elastic mechanics in these gaits. These findings substantiate the elastic energy-saving role of the longitudinal arch during running, and suggest that arch supports used in some footwear and orthotics may increase the cost of running.

Elastic energy returned from passive-elastic structures of the lower limb is fundamental in lowering the mechanical demand on muscles during running. The purpose of this study was to investigate the two length-modulating mechanisms of the plantar fascia, namely medial longitudinal arch compression and metatarsophalangeal joint (MPJ) excursion, and to determine how these mechanisms modulate strain, and thus elastic energy storage/return of the plantar fascia during running. Eighteen runners (9 forefoot and 9 rearfoot strike) performed three treadmill running trials; unrestricted shod, shod with restricted arch compression (via an orthotic-style insert), and barefoot. Three-dimensional motion capture and ground reaction force data were used to calculate lower limb kinematics and kinetics including MPJ angles, moments, powers and work. Estimates of plantar fascia strain due to arch compression and MPJ excursion were derived using a geometric model of the arch and a subject-specific musculoskeletal model of the plantar fascia, respectively. The plantar fascia exhibited a typical elastic stretch-shortening cycle with the majority of strain generated via arch compression. This strategy was similar in fore- and rear-foot strike runners. Restricting arch compression, and hence the elastic-spring function of the arch, was not compensated for by an increase in MPJ-derived strain. In the second half of stance the plantar fascia was found to transfer energy between the MPJ (energy absorption) and the arch (energy production during recoil). This previously unreported energy transfer mechanism reduces the strain required by the plantar fascia in generating useful positive mechanical work at the arch during running.

There appears to be no clear overall mechanical advantage of a habitual FFS or RFS. Switching techniques may have different injury implications given the altered distribution in loading between joints but should be weighed against the overall effects on limb mechanics; adopting an imposed RFS may prove the most beneficial given the absence of any clear mechanical performance decrements.

This study aimed to determine if a quantifiable relationship exists between the peak sound amplitude and peak vertical ground reaction force (vGRF) and vertical loading rate during running. It also investigated whether differences in peak sound amplitude, contact time, lower limb kinematics, kinetics and foot strike technique existed when participants were verbally instructed to run quietly compared to their normal running. A total of 26 males completed running trials for two sound conditions: normal running and quiet running. Simple linear regressions revealed no significant relationships between impact sound and peak vGRF in the normal and quiet conditions and vertical loading rate in the normal condition. t-Tests revealed significant within-subject decreases in peak sound, peak vGRF and vertical loading rate during the quiet compared to the normal running condition. During the normal running condition, 15.4% of participants utilised a non-rearfoot strike technique compared to 76.9% in the quiet condition, which was corroborated by an increased ankle plantarflexion angle at initial contact. This study demonstrated that quieter impact sound is not directly associated with a lower peak vGRF or vertical loading rate. However, given the instructions to run quietly, participants effectively reduced peak impact sound, peak vGRF and vertical loading rate.

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Background: Evidence supports the use of Mulligan knee taping in managing patellofemoral pain (PFP). However, no studies have compared the efficacy of rigid and elastic tape using this technique. Hypothesis: Mulligan knee taping applied with both rigid and elastic tape will produce similar reductions in knee pain, hip internal rotation, and knee flexion moments compared with no tape. Elastic tape will also be more comfortable than rigid tape. Study Design: Controlled laboratory study. Methods: A total of 19 female patients (mean age, 26.5 ± 4.5 years) with PFP performed a self-selected pain provocative task, single-leg squat (SLSq) task, and running task while wearing Mulligan knee taping applied with rigid tape, elastic tape at 100% tension, and no tape. Pain and taping comfort were recorded using 11-point numeric rating scales. An 18-camera motion capture system and in-ground force plates recorded 3-dimensional lower limb kinematics and kinetics for the SLSq and running tasks. Statistical analysis involved a series of repeated-measures analyses of variance. The Wilcoxon signed rank test was used for analyzing taping comfort. Results: Compared with no tape, both rigid and elastic tape significantly reduced pain during the pain provocative task (mean difference [MD], –0.97 [95% CI, –1.57 to –0.38] and –1.42 [95% CI, –2.20 to –0.64], respectively), SLSq (MD, –1.26 [95% CI, –2.23 to –0.30] and –1.13 [95% CI, –2.09 to –0.17], respectively), and running tasks (MD, –1.24 [95% CI, –2.11 to –0.37] and –1.16 [95% CI, –1.86 to –0.46], respectively). Elastic tape was significantly more comfortable than rigid tape generally ( P = .005) and during activity ( P = .022). Compared with no tape, both rigid and elastic tape produced increased knee internal rotation at initial contact during the running task (MD, 5.5° [95% CI, 3.6° to 7.4°] and 5.9° [95% CI, 3.9° to 7.9°], respectively) and at the commencement of knee flexion during the SLSq task (MD, 5.8° [95% CI, 4.5° to 7.0°] and 5.8° [95% CI, 4.1° to 7.4°], respectively), greater peak knee internal rotation during the running (MD, 1.8° [95% CI, 0.4° to 3.3°] and 2.2° [95% CI, 0.9° to 3.6°], respectively) and SLSq tasks (MD, 3.2° [95% CI, 2.1° to 4.3°] and 3.8° [95% CI, 2.3° to 5.2°], respectively), and decreased knee internal rotation range of motion during the running (MD, –3.6° [95% CI, –6.1° to –1.1°] and –3.7° [95% CI, –6.2° to –1.2°], respectively) and SLSq tasks (MD, –2.5° [95% CI, –3.9° to –1.2°] and –2.0° [95% CI, –3.2° to –0.9°], respectively). Conclusion: Mulligan knee taping with both rigid and elastic tape reduced pain across all 3 tasks and altered tibiofemoral rotation during the SLSq and running tasks. Clinical Relevance: Both taping methods reduced pain and altered lower limb biomechanics. Elastic tape may be chosen clinically for comfort reasons.

Context: There are three common foot strike techniques in runners. Whether these techniques generate different sounds at the point of impact with the ground may influence lower limb kinetics. No previous studies have determined whether such relationships exist. Objectives: To determine foot-ground impact sound characteristics and to compare the impact sound characteristics across foot strike techniques and the relationships between impact sound characteristics and vertical loading rates. Design: Cross-sectional study Setting: Gait analysis laboratory Patients or Other Participants: Thirty runners (50% female, age=23.5±4.0 yrs, mass=58.1±8.2kg, height=1.67±0.1m) completed overground running trials with rearfoot strike (RFS), midfoot strike (MFS) and forefoot strike (FFS) techniques in a gait analysis laboratory. Main Outcome Measure(s): Impact sound was measured by a shotgun microphone and the peak sound amplitude, median frequency and sound duration were analysed. Separate linear regression, clustering participants repeated measures were used to compare the sound parameters across foot strike techniques. Kinetic data was collected from a force plate and the vertical loading rates were calculated. Pearson's correlation was used to determine relationship between sound characteristic and kinetics. Results: Landing with a MFS or FFS resulted in greater peak sound amplitude (ps&lt;0.001) and shorter sound duration (ps&lt;0.001) than RFS. MFS exhibited the highest median frequency among the three foot strike patterns, followed by FFS (ps&lt;0.001). We did not find a significant relationship between vertical loading rates and any impact sound parameters (ps&gt;0.115). Conclusions: The results suggest that impact sound characteristics may be used to differentiate foot strike patterns in runners. However, this did not relate to lower limb kinetics. Therefore, clinicians should not solely rely on impact sound to infer impact loading.

This study examined the haemolytic effects of an interval-based running task in fore-foot and rear-foot striking runners. Nineteen male distance runners (10 fore-foot, 9 rear-foot) completed 8 × 3 min repeats at 90% vVO2peak on a motorised treadmill. Pre- and post-exercise venous blood samples were analysed for serum haptoglobin to quantify the haemolytic response to running. Vertical ground reaction forces were also captured via a force plate beneath the treadmill belt. Haptoglobin levels were significantly decreased following exercise (P = 0.001) in both groups (but not between groups), suggesting that the running task created a haemolytic stress. The ground reaction force data showed strong effect sizes for a greater peak force (d = 1.20) and impulse (d = 1.37) in fore-foot runners, and a greater rate of force development (d = 2.74) in rear-foot runners. The lack of difference in haptoglobin response between groups may be explained by the trend for fore-foot runners to experience greater peak force and impulse during the stance phase of their running gait, potentially negating any impact of the greater rate of force development occurring from the rear-foot runners' heel strike. Neither type of runner (fore-foot or rear-foot) appears more susceptible to technique-related foot-strike haemolysis.