Shorter work boot shaft height improves ankle range of motion and decreases the oxygen cost of work.

Work boots featuring design elements implemented to protect the foot and lower limb are common in many industries. However, boot design can have negative unintended consequences such as increases in work related fatigue and injury risk. This study compared joint kinematics and the physiological cost of two commercially available steel-toed work boots with different shaft designs worn throughout a simulated work task. A boot with a lower-cut and scalloped shaft allowed greater sagittal plane range of motion at the ankle joint compared to a boot with a higher-cut straight shaft, particularly in the late stance phase of the gait cycle. This was coupled with a decreased physiological cost of treadmill walking (2.6 and 3.1% improvement in oxygen consumption and walking economy, respectively), likely caused by a more efficient gait pattern. A lower-cut and scalloped shaft could lead to decreases in work-related fatigue and the subsequent risk of injuries in workers. Practitioner summary: Gait kinematics and the physiological cost of work boots with different shaft heights has not previously been investigated. A randomised cross-over study design found that a boot with a lower shaft height and scalloped collar improved ankle range of motion and reduced the physiological cost experienced by the wearers. Abbreviations: ROM: range of motion; FS: full shaft; SS: scalloped shaft; COM: centre of mass; HR: heart rate; RPE: rating of perceived exertion; ES: effect size.

From the field of play to the laboratory: Recreating the demands of competition with augmented reality simulated sport.

Biomechanical analysis has typically been confined to a laboratory setting. While attempts have been made to take laboratory testing into the field, this study was designed to assess whether augmented reality (AR) could be used to bring the field into the laboratory. This study aimed to measure knee load in volleyball players through a jump task incorporating AR while maintaining the perception-action couplings by replicating the visual features of a volleyball court. Twelve male volleyball athletes completed four tasks: drop landing, hop jump, spike jump, and spike jump while wearing AR smart glasses. Biomechanical variables included patellar tendon force, knee moment and kinematics of the ankle, knee, hip, pelvis and thorax. The drop landing showed differences in patellar tendon force and knee moment when compared to the other conditions. The hop jump did not present differences in kinetics when compared to the spike conditions, instead of displaying the greatest kinematic differences. As a measure of patellar tendon loading the AR condition showed a close approximation to the spike jump, with no differences present when comparing landing forces and mechanics. Thus, AR may be used in a clinical assessment to better replicate information from the competitive environment.

Free Achilles tendon strain during selected rehabilitation, locomotor, jumping, and landing tasks.

A better understanding of the strains experienced by the Achilles tendon during commonly prescribed exercises and locomotor tasks is needed to improve efficacy of Achilles tendon training and rehabilitation programs. The aim of this study was to estimate in vivo free Achilles tendon strain during selected rehabilitation, locomotor, jumping, and landing tasks. Sixteen trained runners with no symptoms of Achilles tendinopathy participated in this study. Personalized free Achilles tendon moment arm and force-strain curve were obtained from imaging data and used in conjunction with motion capture and surface electromyography to estimate free Achilles tendon strain using electromyogram-informed neuromusculoskeletal modeling. There was a strong correspondence between Achilles tendon force estimates from the present study and experimental data reported in the literature (R2 > 0.85). The average tendon strain was highest for maximal hop landing (8.8 ± 1.6%), lowest for walking at 1.4 m/s (3.1 ± 0.8%), and increased with locomotor speed during running (run 3.0 m/s: 6.5 ± 1.6%; run 5.0 m/s: 7.9 ± 1.7%) and during heel rise exercise with added mass (BW: 5.8 ± 1.3%; 1.2 BW: 6.9 ± 1.7%). The peak tendon strain was highest during running (5 m/s: 13.7 ± 2.5%) and lowest during walking (1.4 m/s: 7 ± 1.8%). Overall findings provide a preliminary evidence base for exercise selection to maximize anabolic tendon remodeling during training and rehabilitation of the Achilles tendon.NEW & NOTEWORTHY Our work combines medical imaging and electromyogram-informed neuromusculoskeletal modeling data to estimate free Achilles tendon strain during selected rehabilitation, locomotor, jumping, and landing tasks in trained middle-distance runners. These data may potentially be used to inform Achilles tendon training and rehabilitation to maximize anabolic tendon remodeling.

The Free Achilles Tendon Is Shorter, Stiffer, Has Larger Cross-Sectional Area and Longer T2* Relaxation Time in Trained Middle-Distance Runners Compared to Healthy Controls.

Tendon geometry and tissue properties are important determinants of tendon function and injury risk and are altered in response to ageing, disease, and physical activity levels. The purpose of this study was to compare free Achilles tendon geometry and mechanical properties between trained elite/sub-elite middle-distance runners and a healthy control group. Magnetic resonance imaging (MRI) was used to measure free Achilles tendon volume, length, average cross-sectional area (CSA), regional CSA, moment arm, and T2* relaxation time at rest, while freehand three-dimensional ultrasound (3DUS) was used to quantify free Achilles tendon mechanical stiffness, Young's modulus, and length normalised mechanical stiffness. The free Achilles tendon in trained runners was significantly shorter and the average and regional CSA (distal end) were significantly larger compared to the control group. Mechanical stiffness of the free Achilles tendon was also significantly higher in trained runners compared to controls, which was explained by the group differences in tendon CSA and length. T2* relaxation time was significantly longer in trained middle-distance runners when compared to healthy controls. There was no relationship between T2* relaxation time and Young's modulus. The longer T2* relaxation time in trained runners may be indicative of accumulated damage, disorganised collagen, and increased water content in the free Achilles tendon. A short free Achilles tendon with large CSA and higher mechanical stiffness may enable trained runners to rapidly transfer high muscle forces and possibly reduce the risk of tendon damage from mechanical fatigue.

Magnetic Resonance Imaging and Freehand 3-D Ultrasound Provide Similar Estimates of Free Achilles Tendon Shape and 3-D Geometry.

The purpose of this study was to assess the similarity of free Achilles tendon shape and 3-D geometry between magnetic resonance imaging (MRI) and freehand 3-D ultrasound (3-DUS) imaging methods. Fourteen elite/sub-elite middle-distance runners participated in the study. MRI and 3-DUS scans of the Achilles tendon were acquired on two separate imaging sessions, and all 3-D reconstructions were performed using identical methods. Shape similarity of free Achilles tendon reconstructed from MRI and 3-DUS data was assessed using Jaccard index, Hausdorff distance and root mean square error (RMSE). The Jaccard index, Hausdorff distance and RMSE values were 0.76 ± 0.05, 2.70 ± 0.70 and 0.61 ± 0.10 mm, respectively. The level of agreement between MRI and 3-DUS for free Achilles tendon volume, length and average cross-sectional area (CSA) was assessed using Bland-Altman analysis. Compared to MRI, freehand 3-DUS overestimated volume, length and average CSA by 30.6 ± 15.8 mm3 (1.1% ± 0.6%), 0.3 ± 0.7 mm (0.6% ± 1.9%) and 0.3 ± 1.42 mm2 (0.4% ± 2.0%), respectively. The upper and lower limits of agreement between MRI and 3-DUS for volume, length and average CSA were -0.4 to 61.7 mm3 (-0.2% to 2.3%), -1.0 to 1.5 mm (-3.2% to 4.5%) and -2.5 to 3.1 mm2 (-3.5% to 4.3%), respectively. There were no significant differences between imaging methods in CSA along the length of the tendon. In conclusion, MRI and freehand 3-DUS may be considered equivalent methods for estimating shape and 3-D geometry of the free Achilles tendon. These findings, together with the practical benefits of being able to assess 3-D Achilles tendon shape and geometry in a laboratory environment and under isometric loading, make 3-DUS an attractive alternative to MRI for assessing 3-D free Achilles tendon macro-structure in future studies.