Variations in jump height explain the between-sex difference in patellar tendon loading during landing

Relationships between tendon structure and clinical impairments in patients with patellar tendinopathy

The clinical relevance of altered tendon structure in patellar tendinopathy is contested since structural change persists after symptom resolution. The purpose of this study was to explore the relationships between tendon structure and clinical impairments in patellar tendinopathy. In this retrospective, secondary analysis of individuals with patellar tendinopathy (n = 41), tendon structure (thickness, cross-sectional area [CSA], shear modulus, and viscosity), symptom severity, lower extremity function (counter-movement jump [CMJ] height), and quadriceps muscle performance (knee extension force and central activation ratio [CAR]) were recorded for the symptomatic limb. Relationships among structure, symptom severity, lower extremity function, and quadriceps muscle performance were examined using sequential regression models. Adjusting for age, sex, body mass index, and pain levels, there were significant positive relationships for thickness (p < 0.001, β = 0.718) and viscosity (p = 0.006, β = 0.496) with CMJ height. There were significant negative relationships between CSA with both CMJ height (p = 0.001, β = -0.538) and CAR (p = 0.04, β = -0.517). This is the first study to demonstrate relationships between tendon structure and lower extremity function or quadriceps muscle performance in patients with patellar tendinopathy. Clinical significance: Since structural changes persist after symptom resolution, addressing these changes may assist in restoring lower extremity function and quadriceps muscle performance.

Long-term lessons learned in biomechanics: 2021 Geoffrey Dyson Lecture

After recently accepting an offer to retire, I have taken the opportunity to reflect on long-term lessons learned throughout my 40-year career as a biomechanist in academia. These lessons formed the basis of my 2021 Geoffrey Dyson Lecture and are summarised within this article. Most of these lessons are targeted at early career researchers, although my recent transition into retirement revealed some unexpected lessons that apply to senior academics. The lessons presented relate to the need to be passionate and persistent about your research, the importance of being unique and embracing failure as a mentor, as well as running with opportunities that arise. Appreciating that a career takes time to evolve, strategies to nurture a committed and supportive research team, the importance of committing to a professional society, and the need to be kind to yourself are also discussed. Why so few women receive career awards in biomechanics and when should academics retire are also addressed. I hope that highlighting lessons learned over an academic career as a biomechanist, combined with suggested practical strategies to thrive in academia, ensure academics can savour a fulfiling career in biomechanics while producing high-quality research into the future.

Changing Sagittal-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia

CONTEXT

Ground reaction force (GRF) and tibiofemoral force magnitudes and directions have been shown to affect anterior cruciate ligament loading during landing. However, the kinematic and kinetic factors modifying these 2 forces during landing are unknown.

OBJECTIVE

To clarify the intersegmental kinematic and kinetic links underlying the alteration of the GRF and tibiofemoral force vectors secondary to changes in the sagittal-plane body position during single-legged landing.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty recreationally active participants (age = 23.4 ± 3.6 years, height = 171.0 ± 9.4 cm, mass = 73.3 ± 12.7 kg).

INTERVENTION(S)

Participants performed single-legged landings using 3 landing styles: self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL). Three-dimensional kinetics and kinematics were recorded.

MAIN OUTCOME MEASURE(S)

Sagittal-plane tibial inclination and knee-flexion angles, GRF magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces.

RESULTS

The URL resulted in less time to peak tibial axial forces, smaller knee-flexion angles, and greater magnitude and a more anteriorly inclined GRF vector relative to the tibia than did the SSL. These changes led to the greatest peak tibial axial and anterior shear forces in the URL among the 3 landing styles. Conversely, the LFL resulted in longer time to peak tibial axial forces, greater knee-flexion angles, and reduced magnitude and a more posteriorly inclined GRF vector relative to the tibia than the SSL. These changes in LFL resulted in the lowest peak tibial axial and largest posterior shear forces among the 3 landing styles.

CONCLUSIONS

Sagittal-plane intersegmental kinematic and kinetic links strongly affected the magnitude and direction of GRF and tibiofemoral forces during the impact phase of single-legged landing. Therefore, improving sagittal-plane landing mechanics is important in reducing harmful magnitudes and directions of impact forces on the anterior cruciate ligament.