Elastic energy return from the plantar fascia when running

NewsBot · Feb 23, 2016

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Elastic energy within the human plantar aponeurosis contributes to arch shortening during the push-off phase of running
Justin C. Wager, , John H. Challis
Journal of Biomechanics; 17 February 2016

During locomotion, the lower limb tendons undergo stretch and recoil, functioning like springs that recycle energy with each step. Cadaveric testing has demonstrated that the arch of the foot operates in this capacity during simple loading, yet it remains unclear whether this function exists during locomotion. In this study, one of the arch?s passive elastic tissues (the plantar aponeurosis; PA) was investigated to glean insights about it and the entire arch of the foot during running. Subject specific computer models of the foot were driven using the kinematics of eight subjects running at 3.1 m/s using two initial contact patterns (rearfoot and non-rearfoot). These models were used to estimate PA strain, force, and elastic energy storage during the stance phase. To examine the release of stored energy, the foot joint moments, powers, and work created by the PA were computed. Mean elastic energy stored in the PA was 3.1?1.6 J, which was comparable to in situ testing values. Changes to the initial contact pattern did not change elastic energy storage or late stance PA function, but did alter PA pre-tensioning and function during early stance. In both initial contact patterns conditions, the PA power was positive during late stance, which reveals that the release of the stored elastic energy assists with shortening of the arch during push-off. As the PA is just one of the arch?s passive elastic tissues, the entire arch may store additional energy and impact the metabolic cost of running.
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efuller · Feb 23, 2016

NewsBot said: ↑

Elastic energy within the human plantar aponeurosis contributes to arch shortening during the push-off phase of running
Justin C. Wager, , John H. Challis
Journal of Biomechanics; 17 February 2016
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To examine the release of stored energy, the foot joint moments, powers, and work created by the PA were computed. Mean elastic energy stored in the PA was 3.1?1.6 J, which was comparable to in situ testing values. Changes to the initial contact pattern did not change elastic energy storage or late stance PA function, but did alter PA pre-tensioning and function during early stance. In both initial contact patterns conditions, the PA power was positive during late stance, which reveals that the release of the stored elastic energy assists with shortening of the arch during push-off. As the PA is just one of the arch?s passive elastic tissues, the entire arch may store additional energy and impact the metabolic cost of running.
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The last line is interesting. It almost looks as if the reviewer made them add it in. However, they should have gone a little farther. When you look at joint power, you are looking at moment produced by all structures that cross the joint. They appear to be making the assumption that all power absorption is done by the platnar fascia and not any of the other structures. If any muscle absorbed any of the energy of arch flattening, a greater percentage of that energy could be lost as heat. Also later in the gait cycle arch rise could be caused by contraction of muscles that cross the arch and not necessarily from elastic energy in the plantar fascia. If I recall correctly, there are EMG studies showing that intrinsic muscles are active in the midstance period of gait. You would think that there is some contribution to arch rise from muscular contraction.

Joint power is a very powerful tool. However, you can't go beyond the limitations of the measurements. You can know there is a net joint moment causing plantar flexion. You cannot know how much each structure contributes to the net joint moment. (Power = joint moment x angular velocity).

Eric

NewsBot · Jun 30, 2018

Experimental estimation of energy absorption during heel strike in human barefoot walking.
Baines PM et al
PLoS One. 2018 Jun 28;13(6):e0197428. doi: 10.1371/journal.pone.0197428. eCollection 2018.

Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15-20% of the overall metabolic cost of transport.
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NewsBot · Apr 21, 2020

Acute effects of long‐distance running on mechanical and morphological properties of the human plantar fascia
Hiroto Shiotani Tomohiro Mizokuchi Ryo Yamashita Munekazu Naito Yasuo Kawakami
19 April 2020 https://doi.org/10.1111/sms.13690

Long‐distance running (LDR) can induce transient lowering of the foot arch, which may be associated with mechanical fatigue of the plantar fascia (PF). However, this has not been experimentally tested in vivo. The purpose of this study was to test our hypothesis that LDR induces transient and site‐specific changes in PF stiffness and morphology, and that those changes are related to the lowering of the foot arch. Ten male recreational long‐distance runners and 10 untrained men were requested to run overground for 10km. Before and after running, shear wave velocity (SWV: an index of soft tissue stiffness) and thickness of PF at three different sites from its proximal to distal end were measured using supersonic shear imaging and B‐mode ultrasonography. Foot dimensions including the navicular height were measured using a three‐dimensional foot scanner. SWV at the proximal site of PF and navicular height were significantly decreased in both groups after running, with a higher degree in untrained men (‐21.9% and ‐14.1%, respectively) than in runners (‐4.0% and ‐6.3%, respectively). The relative change (%Δ) in SWV was positively correlated with %Δnavicular height in both groups (r = 0.69 and r = 0.65, respectively). Multiple regression analysis revealed that %ΔSWV at the proximal site solely explained 72.7% of the total variance in %Δnavicular height. It is concluded that LDR induces transient and site‐specific decreases in PF stiffness. These results suggest that the majority of running‐induced lowering of the foot arch is attributable to the reduction of PF stiffness at the proximal site.
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NewsBot · May 2, 2023

Arch Stiffness Does Not Determine Running Economy in Recreational Runners
Ian Bradford et al
Int J Exerc Sci. 2023 Mar 1;16(2):402-410

The primary purpose of this study was to determine the relationship between foot length, arch stiffness, and running economy in recreational runner at low running velocities. Sixteen trained endurance (age 20.5 ± 0.4 yrs, height 172 ± 1.8 cm, and mass 68.53 ± 2.40 kg) athletes had their foot anthropometrics and running economy measured. Foot anthropometrics including Foot Length (FL), Arch Stiffness Index (ASI), and Achilles Tendon Moment Arm Length (ATML) were assessed. Subjects then completed a maximal oxygen consumption (VO2max) test and running economy (RE) assessment. RE was measured as the oxygen consumption during running at velocities of 9.9 km/h and 11.9 km/h at a 1% grade. Data is reported as Mean ± SE, and the relationship between foot anthropometrics and running economy was assessed with linear regression (α = 0.05). Results: Absolute and relative VO2max values were 3.68 ± 0.19 L/min and 52.96 ± 1.51 mL/kg/min. ASI was 1513 ± 174.27 A.U. with a standing foot length of 25.41 ± 0.4 cm. Subject oxygen consumption at 9.9 km/h and 11.9 km/h was 34.9 ± 0.80 mL/kg/min and 41.02 ± 0.82 mL/kg/min, respectively. There was no correlation between ASI, FL, AHI, and RE (p > 0.05). Arch stiffness and Achilles tendon moment arm do not determine running economy. Therefore, running economy may be impacted by other physiological and biomechanical factors at low running velocities.
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NewsBot · Jul 20, 2023

The Exploration of Morphological and Mechanical Properties of the Plantar Fascia in Response to Imposed Running Demands
Krumpl, Lukas Daniel Dominik.
University of Idaho ProQuest Dissertations Publishing, 2023

Morphological and mechanical properties of the plantar fascia have been suggested to
play a role in developing plantar fasciitis. Clinically, plantar fasciitis has been characterized
by an increase in thickness and a decrease in stiffness of the fascia. However, the true
etiology and progression of plantar fasciitis are unknown. A more thorough knowledge of the
behavior of plantar fascia tissue properties prior to injury may establish a foundation to detail
the relationship between the tissue itself and progression of plantar fasciitis, as there are
currently no known preventative strategies. Understanding how healthy plantar fascia tissue
responds to imposed mechanical demands and stressors may bridge the literature gap
between healthy tissue and plantar fasciitis symptoms, as well as enhance understanding the
relationship between the tissue’s mechanical properties and symptoms and development of
plantar fasciitis. Therefore, there is need to determine the acute effects of imposed running
demands on mechanical and morphological properties of the PF. If these properties are
related to the progression of plantar fasciitis, these findings may move science towards
preventing plantar fasciitis, rather than merely treatment. This dissertation was designed to
explore the effects of different running demands on plantar fascia thickness and stiffness. By
evaluating the potential relationship between running and foot mechanics with their potential
association with plantar fascia.
The first manuscript details the first of the three studies conducted for the present
dissertation. It focuses on increased intensity of the mechanical loading due to running speed
and intensity, combined with acute fatigue. The purpose of the study was to evaluate the
effects of repeated 400 m sprints on plantar fascia thickness and stiffness, while a secondary
purpose was to explore the predictability of arch height index measurements on tissue
changes. Sixteen participants completed five maximal effort 400 m sprints, followed by
additional maximal effort trials until fatigue. For the first study, it is reported that plantar
fascia stiffness and thickness decreased acutely in response to a single session of high
intensity track repeats. Both properties returned to pre-run values after 30 minutes of rest.
Plantar fascia properties also appeared to have been related to arch height index, as there was
a decrease in foot arch measurements from pre-to post-run.
The second manuscript focuses on increased duration and frequency of mechanical
loading. The purpose of this study was to investigate the effects of three consecutive days of
5-km maximal effort runs on plantar fascia thickness and stiffness in healthy, active
individuals. The same 16 participants completed this protocol at least 7 days after they had
completed the protocol for study 1. It can be reported that plantar fascia thickness in a rested
state (pre-run) increased across three sessions of maximum effort 5 km running on three
consecutive days. Within each day, thickness and stiffness decreased post-run and returned to
pre-run values after 30 minutes of rest. Mechanical overloading and insufficient rest may
induce conformational change of the plantar fascia.
The third manuscript introduces a new population, new running surface, and motion
analysis. Manuscript three evaluated people with resolved plantar fasciitis to understand how
previously injured tissue recovers, and whether it recovers. Additionally, the manuscript
aimed to evaluate run and foot mechanics between aforementioned population and
individuals without history of plantar fasciitis. Thus, the purpose of that study was to
investigate the effects of 30 minutes treadmill running on plantar fascia properties and
running mechanics in individuals with resolved plantar fasciitis (RPF) and those with no
history of plantar fasciitis (NPF). It can be reported that both groups experienced the same
decrease in thickness and stiffness immediately after the run. However, people with RPF had
significantly thicker and stiffer tissue compared to never before injured individuals.
Additionally, the stiffness of the tissue appeared to alter foot mechanics as it prevented the
RPF group from undergoing vital medial longitudinal arch dorsiflexion during the stance
phase. It is unclear whether this finding increases risk of re-injury and whether plantar
fasciitis does have long-term effects on both the soft tissue, as well as foot mechanics during
running.
Questions remain regarding the possibility of utilizing the morphological and
mechanical properties of the plantar fascia to determine risk of plantar fasciitis. However, the
present series of studies affirms that the plantar fascia is a viscoelastic material in vivo due to
the change in morphological and mechanical properties in response to application and
removal of mechanical loading, and that this can be quantified via ultrasound. Individuals,
whether without plantar fasciitis history or those with resolved plantar fasciitis, displayed the
same biomechanical response to mechanical loading. This response to the plantar fascia
occurred regardless of duration, intensity, or frequency of the imposed mechanical demand.
Future explorations should strive to further evaluate the relationship between the response of
plantar fascia tissue to imposed demands and the occurrence of plantar fasciitis. While this
may require longitudinal studies, the evidence presented in this dissertation provides an
initial foundation for the continuation of research connecting plantar fascia tissue mechanics
to the etiology of plantar fasciitis.
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