Achilles tendon loading during weight bearing exercises

Running-related Achilles tendon injuries have been observed more frequently in males, which may reflect sex differences in tendon morphology or mechanics during running. Males exhibit a larger Achilles tendon cross-sectional area and some measures of Achilles tendon loading in running, but sex differences in measures of tendon loading have not been thoroughly characterized. This study examines sex differences in the Achilles tendon cross-sectional area and Achilles tendon loading variables associated with running kinetics and kinematics. Cross-sectional. Recruited from a university population, 26 female and 23 male healthy recreational runners ran at 3.35m/s on an instrumented treadmill and were assessed using 3-dimensional motion capture, musculoskeletal modeling, and diagnostic ultrasound. A multivariate analysis examined differences between sexes in Achilles tendon loading and additional running variables with alpha set to .05. Mean differences (MD) and confidence intervals (CIs) were reported. Males displayed greater peak Achilles tendon force (MD = 0.94 body weight [BW]; 95% CI, -1.48 to -0.33), peak gastrocnemius force (MD = 0.52 BW; 95% CI, -0.75 to -0.29), and Achilles tendon cross-sectional area (MD = 0.1cm2; 95% CI, -0.15 to 0.04) compared with females (P < .05). No group differences were observed in peak Achilles tendon stress (MD = 4.13 kPa; 95% CI, -16.25 to 7.98), peak Achilles tendon strain (MD = 0.41; 95% CI, -1.60 to 0.78), peak soleus force (MD = 0.34 BW; 95% CI, -0.76 to 0.078), foot strike angle (MD = 3.1; 95% CI, -1.65 to 7.85), or peak vertical ground reaction force (MD = 0.106; 95% CI, -0.24 to 0.03) (P > .05). Male runners produced greater peak Achilles tendon force when running at the same speed, but similar peak Achilles tendon stress was observed between male and female recreation runners. Male runners had a greater Achilles tendon cross-sectional area. These findings may have implications to running-related injury based on sex.

IntroductionThis study aimed to investigate the differences in the loading characteristics of the patellofemoral joint (PFJ) and the Achilles tendon (AT) between novice and experienced runners across different footwear conditions (conventional vs. minimalist shoes) with rearfoot striking (RFS) and forefoot striking (FFS).MethodsEleven male RFS novice runners and experienced runners were randomly asked to run across a force platform at 12 km/h when wearing conventional and minimalist shoes with RFS and FFS, respectively. AT and PFJ loading were estimated from kinematic and kinetic data. The morphological (length and cross-sectional area) of AT in vivo were recorded using ultrasound imaging. Three-way ANOVA was used to determine differences in PFJ and AT loading characteristics.ResultsPatellofemoral contact force and AT impulses were significantly greater (p < 0.05) in novice runners than in experienced runners, regardless of footwear or the foot strike pattern. Regardless of running level, patellofemoral contact force and PFJ stress were significantly lower in FFS than in RFS, whereas AT force, AT impulse, and peak AT stress were significantly greater in FFS than in RFS. Peak impact loading rates were significantly lower in conventional shoes with RFS than in minimalist shoes (p < 0.05).DiscussionNovice runners experienced a significant increase in PFJ and AT loads during running. In addition, FFS increased the impulse, force, and stress on the AT and decreased the PFJ stress. Therefore, novice runners need to gradually adjust their foot strike pattern according to the loading capacity of different joints to reduce the corresponding injury risk.

The effects of habitual foot strike patterns on Achilles tendon loading in female runners

Effect of Achilles tendon loading on plantar fascia tension in the standing foot

Achilles tendon loading is lower in older adults than young adults across a broad range of walking speeds.

(1) Achilles tendon rupture is one of the most severe lower-limb injuries, frequently occurring during movements involving maximal dorsiflexion with the knee at near-full extension. Preventive strategies are crucial, particularly for athletes engaged in high-risk sports such as basketball. (2) In this work, we examined the effect of a novel Achilles brace on Achilles tendon loading during concentric and eccentric mechanisms associated with tendon rupture. (3) Twenty-eight young basketball players performed tests under two conditions: with the adaptive brace and without it (control). Participants were divided into two groups (n = 14 in both). The first group assessed concentric Achilles loading by performing three plantar-flexor strength tests in three different joint configurations: maximal dorsiflexion with the knee flexed (FKF); injury mechanism position-full plantar flexion with the knee extended (FKE); and neutral ankle position with the knee extended (NKE). The number of maximal heel-raise repetitions performed before onset of fatigue was recorded. The second group assessed eccentric tendon loading by performing single-leg forced maximal-velocity dorsiflexion with the knee extended. In all tests, the time between maximal plantar flexion and maximal dorsiflexion, as well as the ankle range of motion, was analyzed using 2D video. Paired t-tests were used to compare braced and control conditions. In all tests, the ankle range of motion (ROM) did not differ significantly between brace and control conditions. Wearing the brace significantly improved plantar-flexor muscle strength only in the FKE test (31 ± 1.3 repetitions with brace vs. 21 ± 1.3 in control, p < 0.05). No significant differences were found for the FKF (27 ± 1.3 vs. 25 ± 1.3) or NKE (25 ± 1.3 vs. 24 ± 1.3) positions. During drop eccentric loading, wearing the brace resulted in a significantly slower transition time from plantar flexion to dorsiflexion (460 ± 60 ms with brace vs. 320 ± 30 ms in control, p < 0.001). (4) In brief, the novel Achilles brace was found to significantly reduces Achilles tendon load during both concentric and eccentric activities, but only in high-risk joint positions. These findings suggest that the brace provides mechanical protection, and may reduce the risk of Achilles tendon rupture, in athletes exposed to high tendon stress.

The purpose of this study is to develop a wearable paradigm to accurately monitor Achilles tendon loading and walking speed using wearable sensors that reduce subject burden. Ten healthy adults walked in an immobilizing boot under various heel wedge conditions (30°, 5°, 0°) and walking speeds. Three-dimensional motion capture, ground reaction force, and 6-axis inertial measurement unit (IMU) signals were collected. We used a Least Absolute Shrinkage and Selection Operator (LASSO) regression to predict peak Achilles tendon load and walking speed. The effects of altering sensor parameters were also explored. Walking speed models (mean absolute percentage error (MAPE): 8.81 ± 4.29%) outperformed tendon load models (MAPE: 34.93 ± 26.3%). Models trained with subject-specific data performed better than models trained without subject-specific data. Removing the gyroscope, decreasing the sampling frequency, and using combinations of sensors did not change the usability of the models, having inconsequential effects on model performance. We developed a simple monitoring paradigm that uses LASSO regression and wearable sensors to accurately predict (MAPE ≤ 12.6%) Achilles tendon loading and walking speed while ambulating in an immobilizing boot. This paradigm provides a clinically implementable strategy to longitudinally monitor patient loading and activity while recovering from Achilles tendon injuries.

Standing balance performance is often characterized by sway, as measured via fluctuations of the center of pressure (COP) under the feet. For example, COP metrics can effectively delineate changes in balance under altered sensory conditions. However, COP is a global metric of whole‐body dynamics and thus does not necessarily lend insight into the underlying musculotendon control. We have previously shown that shear wave tensiometers can track wave speeds in tendon as a surrogate measure of the load transmitted by the muscle‐tendon unit. The purpose of this study was to investigate whether shear wave metrics have sufficient sensitivity to track subtle variations in Achilles tendon loading that correspond with postural sway. Sixteen healthy young adults (26 ± 5 years) stood for 10 s with their eyes open and closed. We simultaneously recorded COP under the feet and shear wave speed in the right Achilles tendon. We found that Achilles tendon shear wave speed closely tracked (r > 0.95) dynamic fluctuations of the COP in the anteroposterior direction. Achilles tendon wave speed fluctuations significantly increased during standing with eyes closed, mirroring increases in COP fluctuations. These results demonstrate that tendon wave speed can track the subtle variations in Achilles tendon loading that modulate COP in standing. Hence, shear wave tensiometry exhibits the sensitivity to investigate the muscular control of quiet standing, and may also be useful for investigating other fine motor and force steadiness tasks.

Effects of foot orthoses on Achilles tendon load in recreational runners

BackroundIt is expected that every second runner has a running-related overuse injury each year. The knee joint and Achilles tendon are the most commonly injured sites covering both about one...

Human tendons adapt to mechanical loading, yet there is little information on the effect of the temporal coordination of loading and recovery or the dose–response relationship. For this reason, we assigned adult men to either a control or intervention group. In the intervention group, the two legs were randomly assigned to one of five high-intensity Achilles tendon (AT) loading protocols (i.e., 90% maximum voluntary contraction and approximately 4.5 to 6.5% tendon strain) that were systematically modified in terms of loading frequency (i.e., sessions per week) and overall loading volume (i.e., total time under loading). Before, at mid-term (8 weeks) and after completion of the 16 weeks intervention, AT mechanical properties were determined using a combination of inverse dynamics and ultrasonography. The cross-sectional area (CSA) and length of the free AT were measured using magnetic resonance imaging pre- and post-intervention. The data analysis with a linear mixed model showed significant increases in muscle strength, rest length-normalized AT stiffness, and CSA of the free AT in the intervention group (p < 0.05), yet with no marked differences between protocols. No systematic effects were found considering the temporal coordination of loading and overall loading volume. In all protocols, the major changes in normalized AT stiffness occurred within the first 8 weeks and were mostly due to material rather than morphological changes. Our findings suggest that—in the range of 2.5–5 sessions per week and 180–300 s total high strain loading—the temporal coordination of loading and recovery and overall loading volume is rather secondary for tendon adaptation.

BackgroundShear wave tensiometry is a recent promising technology which can be used to evaluate tendon loading. Knowing the clinimetric features (e.g., reliability) of this technology is important for use in clinical and research settings. ObjectivesTo evaluate the inter-session reliability of a novel shear wave tensiometer for the assessment of Achilles tendon loading. A further aim was to test the construct validity of this device by evaluating its precision in detecting Achilles tendon loading changes induced by a plantar flexor isometric contraction of increasing intensity. MethodTen healthy participants were recruited. Five measurements were performed at different time points to evaluate inter-session reliability. Shear wave speed along the Achilles tendon was evaluated during different isometric contractions using a shear wave tensiometer composed of an array of four accelerometers fixed on the tendon, ranging from 4 to 8.5 cm from the calcaneal insertion of the tendon. Test-retest, intra- and inter-session reliability were determined using intraclass correlation coefficient (ICC3.1). Absolute reliability was calculated using the standard error of measurement and minimal detectable change. ResultsTest-retest reliability was good to excellent (ICC3.1 0.87–0.99) for each of the contraction levels examined. Intra-session reliability was good to excellent (ICC3.1 0.85–0.96) and inter-session reliability was also good to excellent (ICC3.1 0.75–0.93) for each of the contraction levels. ConclusionsThis study confirms the reliability of this novel device. Future studies analyzing participants with Achilles tendinopathy are needed to evaluate the capability of shear wave tensiometry to detect transient changes in loading due to pathology.

Effect of Ankle Motion and Tensile Stress at the Achilles Tendon on the Contact Pressure Between the Achilles Tendon and the Calcaneus

Added mass increases Achilles tendon stress in female runners

The interaction effects of rocker angle and apex location in rocker shoe design on foot biomechanics and Achilles tendon loading