Kinesiology Research & Publications

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    Are subject-specific models necessary to predict patellar tendon fatigue life? A finite element modelling study
    (Taylor & Francis, 2021-09-11) Firminger, Colin R.; Haider, Ifaz T.; Bruce, Olivia L.; Wannop, John W.; Stefanyshyn, Darren J.; Edwards, W Brent
    Patellar tendinopathy is an overuse injury that occurs from repetitive loading of the patellar tendon in a scenario resembling that of mechanical fatigue. As such, fatigue-life estimates provide a quantifiable approach to assess tendinopathy risk and may be tabulated using nominal strain (NS) or finite element (FE) models with varied subject-specificity. We compared patellar tendon fatigue-life estimates from NS and FE models of twenty-nine athletes performing countermovement jumps with subject-specific versus generic geometry and material properties. Subject-specific patellar tendon material properties and geometry were obtained using a data collection protocol of dynamometry, ultrasound, and magnetic resonance imaging. Three FE models were created for each subject, with: subject-specific (hyperelastic) material properties and geometry, subject-specific material properties and generic geometry, and generic material properties and subject-specific geometry. Four NS models were created for each subject, with: subject-specific (linear elastic) material properties and moment arm, generic material properties and subject-specific moment arm, subject-specific material properties and generic moment arm, and generic material properties and moment arm. NS- and FE-modelled fatigue-life estimates with generic material properties were poorly correlated with their subject-specific counterparts (r2≤0.073), while all NS models overestimated fatigue life compared to the subject-specific FE model (r2≤0.223). Furthermore, FE models with generic tendon geometry were unable to accurately represent the heterogeneous strain distributions found in the subject-specific FE models or those with generic material properties. These findings illustrate the importance of incorporating subject-specific material properties and FE-modelled strain distributions into fatigue-life estimations.
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    Effects of cyclic loading on the mechanical properties and failure of human patellar tendon
    (Journal of Biomechanics, 2021) Firminger, Colin R.; Edwards, W. Brent
    Patellar tendinopathy is a common overuse injury in sports such as volleyball, basketball, and long-distance running. Microdamage accumulation, in response to repetitive loading of the tendon, plays an important role in the pathophysiology of patellar tendinopathy. This damage presents mechanically as a reduction in Young’s modulus and an increase in residual strain. In this study, 19 human patellar tendon samples underwent cyclic testing in load control until failure, segmented by four ramped tests where digital image correlation (DIC) was used to assess anterior surface strain distributions. Ramped tests were performed prior to cyclic testing and at timepoints corresponding to 10%, 20%, and 30% of cyclic stiffness reduction. Young’s modulus significantly decreased and cyclic energy dissipation significantly increased over the course of cyclic testing. The DIC analysis illustrated a heterogeneous strain distribution, with strain concentrations increasing in magnitude and size over the course of cyclic testing. Peak stress and initial peak strain magnitudes significantly correlated with the number of cycles to failure (r2 = 0.65 and r2 = 0.57, respectively, p < 0.001); however, the rates of peak cyclic strain and modulus loss displayed the highest correlations with the number of cycles to failure (r2 = 96% and r2 = 86%, respectively, p < 0.001). The high correlation between the rates of peak cyclic strain and modulus loss suggest that non-invasive methods to continuously monitor tendon strain may provide meaningful predictions of overuse injury in the patellar tendon.
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    A biomechanical study of clamping technique on patellar tendon surface strain and material properties using digital image correlation
    (Elsevier, 2021-01-01) Firminger, Colin R.; Edwards, W. Brent
    Several clamping techniques exist for ex vivo mechanical testing of tendon. For the patellar tendon, one can choose to clamp directly to the bony attachment sites, the tendon itself, or a combination of the two; however, the influence of these techniques on localized strains and gross material properties is unknown. To this end, uniaxial tensile tests were performed on eleven porcine patellar tendons in three clamping setups while digital image correlation was used to measure axial and transverse strains, Young's modulus, and Poisson's ratio. The setups involved clamping to: 1) the patella and tibia, 2) the patella and the dissected distal tendon, and 3) the dissected proximal and distal tendon. Axial strains in the tendon-tendon clamping setup were 181% higher than patella-tibia clamping (p = 0.002) and 131% higher than patella-tendon clamping (p = 0.006). Transverse strains were not significantly different between clamping conditions (p ≥ 0.118). Young's modulus was 50% (p < 0.001) greater for patella-tibia clamping and 42% (p < 0.001) greater for patella-tendon clamping when compared to tendon-tendon clamping. For all clamping setups, the tendon illustrated auxetic behaviour (i.e., negative Poisson's ratio); however, the Poisson's ratios were 80% smaller in the patella-tibia setup (p = 0.006) and 71% smaller patella-tendon setup (p = 0.007) compared to the tendon-tendon setup. These results illustrate that discretion should be utilized when reporting material properties derived from mechanical tests involving direct clamping to the dissected patellar tendon at both ends, as this clamping technique significantly increases axial strains, reduces Young's modulus, and alters the tendon's natural auxetic behaviour.
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    Female athletes’ decisions to use hormonal contraceptives: a scoping review protocol.
    (2024) Suarez Moreno, Paula; Van Den Berg, Carla; Hayden, K. Alix; Doyle-Baker, Patricia K.
    Female athletes from a variety of sports indicate a perceived impact of the menstrual cycle (MC) on their performance (Brown et al., 2021; Ekenros et al., 2022; Findlay et al., 2020). Female athletes often choose to use hormonal contraceptives (HC’s) and although their reasons vary, the most consistent one is related to the impact of the MC on performance and training. For example, in a study by Martin et al., (2018) a third of 145 combined oral contraceptive athlete users perceived that cycle manipulation to avoid menstruation can be considered a positive outcome of oral contraceptive use. Therefore, the objective of this scoping review is to investigate the extent of evidence associated with the reasons behind female athletes’ decision to use or discontinue use of hormonal contraceptives. The inclusion criteria included a) female (sex assigned at birth), b) athletes actively participating in competition, of which the majority are competing at least a regional level (Swann et al., 2015), c) sample is mostly age 18 years or older, d) discusses knowledge, reasons, perceptions, attitudes, beliefs of the athletes as related to their decisions regarding HC use and e) discusses history of hormonal contraceptive use either current or previous as an athlete. The JBI guidelines for scoping reviews found in the JBI Manual for Evidence Synthesis (2020) will be followed and this review will be reported in accordance with the PRISMA –SCr extension (Peters et al., 2020; Tricco et al., 2018).