Improved quadriceps' mechanical advantage in single radius TKRs is not due to an increased patellar tendon moment arm

Employing an arched back posture during the bench press exercise is increasingly popular. Vertical displacement of the barbell is commonly believed to be the key difference influencing strength performance between an arched and flat back bench press technique. However, comparisons between these back postures using a free weight barbell are lacking. Directly comparing performance between each posture is confounded by many variables such as proficiency and fatigue. This investigation aimed to investigate whether changing back posture alone can influence barbell kinematics, to indirectly assess potential performance differences. Twenty males performed one repetition of the bench press exercise using either an arched or flat back posture, at 25%, 50% and 75% of their one repetition maximum, in a repeated measures study design. Statistical significance was considered at p < 0.05. Changing back posture alone, reduced vertical displacement (approximately 11% average difference across all load conditions) and barbell to glenohumeral joint moment arm (approximately 20% difference) in the arched posture compared to the flat posture. These changes occurred without any specific cueing of the barbell motion and may increase the potential for lifting higher loads and decrease cumulative joint exposure. Additional cueing and training may be required to maximize the mechanical advantage available with each back posture. The arched posture appears to have an increased potential for further improvements in vertical displacement and moment arm through specific cueing. Future comparisons should consider if each back posture’s potential mechanical advantage has been maximized when assessing differences between techniques.

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Evaluation of Intrinsic Biomechanical Risk Factors in Patellar Tendinopathy: A Retrospective Radiographic Case-Control Series

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967118816038 ◽

2018 ◽

Vol 6 (12) ◽

pp. 232596711881603 ◽

Cited By ~ 6

Author(s):

Michael J. Dan ◽

James McMahon ◽

William C.H. Parr ◽

David Broe ◽

Phil Lucas ◽

...

Keyword(s):

Risk Factors ◽

Patellar Tendon ◽

Patella Alta ◽

Patellar Tendinopathy ◽

Moment Arm ◽

Control Series ◽

Pivot Point ◽

Lever Arm ◽

Radiographic Measurements ◽

Significant Difference

Background: Patellar tendinopathy is an overuse condition often affecting athletes. It has been postulated that patellar tendinopathy is associated with patella alta; however, this and any other anatomic risk factors have not been identified. Purpose: To explore whether lever arm differences from radiographic measurements exist between patients with and without tendinopathy. This may provide surgeons with a simple radiographic means to identify patients at risk. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance imaging scans of the knee from a sports imaging facility were screened and reviewed to identify 2 groups of patients: those with and those without imaging signs of patellar tendinopathy. The lateral radiographs were reviewed and measurements made to determine (1) lever arm ratio, (2) moment arm ratio, (3) angle between the moment and line of pull of the patellar tendon, (4) patellar tendon pivot point angle, and (5) patellar height (alta). Measurements were obtained directly from radiographs. The images and measurements were reviewed by 2 experienced orthopaedic clinicians. Results: A total of 105 patients were included in this study: 52 with patellar tendinopathy and 53 without patellar tendinopathy (controls). The mean age was similar between groups (23 years); females accounted for 8 of 52 patients with patellar tendinopathy and 24 of 53 patients without. The lever arm ratio in the group with patellar tendinopathy versus controls was 1.71 versus 1.01 ( P = .01), with a moment arm difference of 1.00 versus 0.80 ( P < .01), respectively. There was no difference detected between groups for patellar tendon angle, patellar tendon pivot point angle, knee flexion angle, or incidence of patella alta. No correlation was found with our measurements and the Insall-Salvati ratio. Statistical analysis was also performed according to sex, and a statistically significant difference between groups was found for differences in lever arm ratio and moment arm. Conclusion: The lever arm ratio and moment arm ratio from lateral radiographs were significantly different between patients with and without patellar tendinopathy. Further study is needed on the biomechanical implications of the pivot point and how altering it can affect stress within the patellar tendon, patellofemoral joint, and associated clinical outcomes.

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A comparison of different two-dimensional approaches for the determination of the patellar tendon moment arm length

European Journal of Applied Physiology ◽

10.1007/s00421-008-0968-3 ◽

2009 ◽

Vol 105 (5) ◽

pp. 809-814 ◽

Cited By ~ 8

Author(s):

Dimitrios E. Tsaopoulos ◽

Vasilios Baltzopoulos ◽

Paula J. Richards ◽

Constantinos N. Maganaris

Keyword(s):

Patellar Tendon ◽

Two Dimensional ◽

Moment Arm

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In vivo changes in the human patellar tendon moment arm length with different modes and intensities of muscle contraction

Journal of Biomechanics ◽

10.1016/j.jbiomech.2007.05.005 ◽

2007 ◽

Vol 40 (15) ◽

pp. 3325-3332 ◽

Cited By ~ 42

Author(s):

Dimitrios E. Tsaopoulos ◽

Vasilios Baltzopoulos ◽

Paula J. Richards ◽

Constantinos N. Maganaris

Keyword(s):

Muscle Contraction ◽

Patellar Tendon ◽

Moment Arm

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Tangential Finger Forces Use Mechanical Advantage During Static Grasping

Journal of Applied Biomechanics ◽

10.1123/jab.28.1.78 ◽

2012 ◽

Vol 28 (1) ◽

pp. 78-84 ◽

Cited By ~ 5

Author(s):

Gregory P. Slota ◽

Mark L. Latash ◽

Vladimir M. Zatsiorsky

Keyword(s):

Control Mechanism ◽

Tangential Force ◽

Moment Arm ◽

Mechanical Advantage ◽

Normal Forces ◽

Central Controller ◽

Single Finger ◽

Tangential Forces ◽

Finger Forces

When grasping and manipulating objects, the central controller utilizes the mechanical advantage of the normal forces of the fingers for torque production. Whether the same is valid for tangential forces is unknown. The main purpose of this study was to determine the patterns of finger tangential forces and the use of mechanical advantage as a control mechanism when dealing with objects of nonuniform finger positioning. A complementary goal was to explore the interaction of mechanical advantage (moment arm) and the role a finger has as a torque agonist/antagonist with respect to external torques (±0.4 N m). Five 6-dfforce/torque transducers measured finger forces while subjects held a prism handle (6 cm width × 9 cm height) with and without a single finger displaced 2 cm (handle width). The effect of increasing the tangential moment arm was significant (p< .01) for increasing tangential forces (in >70% of trials) and hence creating greater moments. Thus, the data provides evidence that the grasping system as a rule utilizes mechanical advantage for generating tangential forces. The increase in tangential force was independent of whether the finger was acting as a torque agonist or antagonist, revealing their effects to be additive.

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Variation in the Patellar Tendon Moment Arm identified with an improved measurement framework

Journal of Orthopaedic Research® ◽

10.1002/jor.25124 ◽

2021 ◽

Author(s):

Oliver Dandridge ◽

Amy Garner ◽

Andrew A. Amis ◽

Justin P. Cobb ◽

Richard J. Arkel

Keyword(s):

Patellar Tendon ◽

Moment Arm ◽

Measurement Framework

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Structure, ontogeny and evolution of the patellar tendon in emus (Dromaius novaehollandiae) and other palaeognath birds

10.7287/peerj.preprints.404v1 ◽

2014 ◽

Author(s):

Sophie Regnault ◽

Andrew A Pitsillides ◽

John R. Hutchinson

Keyword(s):

Patellar Tendon ◽

Age Groups ◽

Knee Extensor ◽

Fat Pad ◽

Mechanical Advantage ◽

Evolutionary Origins ◽

Extensor Muscles ◽

Dromaius Novaehollandiae ◽

Insight Into ◽

Knee Extensor Muscles

The patella (kneecap) exhibits multiple evolutionary origins in birds, mammals, and lizards, and is thought to increase the mechanical advantage of the knee extensor muscles. Despite appreciable interest in the specialized anatomy and locomotion of palaeognathous birds (ratites and relatives), the structure, ontogeny and evolution of the patella in these species remains poorly characterized. Within Palaeognathae, the patella has been reported to be either present, absent, or fused with other bones, but it is unclear how much of this variation is real, erroneous or ontogenetic. Clarification of the patella’s form in palaeognaths would provide insight into the early evolution of the patella in birds, in addition to the specialized locomotion of these species. Findings would also provide new character data of use in resolving the controversial evolutionary relationships of palaeognaths. In this study, we examined the gross and histological anatomy of the emu patellar tendon across several age groups from five weeks to 18 months. We combined these results with our observations and those of others regarding the patella in palaeognaths and their outgroups (both extant and extinct), to reconstruct the evolution of the patella in birds. We found no evidence of an ossified patella in emus, but noted its tendon to have a highly unusual morphology comprising large volumes of adipose tissue contained within a collagenous meshwork. The emu patellar tendon also included increasing amounts of a cartilage-like tissue throughout ontogeny. We speculate that the unusual morphology of the patellar tendon in emus results from assimilation of a peri-articular fat pad, and metaplastic formation of cartilage, both potentially as adaptations to increasing tendon load. We corroborate previous observations of a ‘double patella’ in ostriches, but in contrast to some assertions, we find independent (i.e. unfused) ossified patellae in kiwis and tinamous. Our reconstructions suggest a single evolutionary origin of the patella in birds and that the ancestral patella is likely to have been a composite structure comprising a small ossified portion, lost by some species (e.g. emus, moa) but expanded in others (e.g. ostriches).

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