The Achilles tendon (AT) plays a crucial role in locomotion. Differences in AT morphological and mechanical properties between men and women may therefore contribute to sex-differences in tendon behavior. This study aimed to investigate sex-based differences in AT strain behavior and derived mechanical properties during walking. Seventeen men and fifteen women walked shod at their preferred velocity on an instrumented treadmill. Gait kinematics and AT displacement were captured synchronously using 3D motion capture and ultrasound imaging, respectively. A MANOVA was used to examine sex differences in morphological and mechanical properties (AT force, stress, strain, stiffness, elastic modulus, hysteresis, strain energy) and a separate one-way ANOVA used to examine walking parameters. Time-series data (AT force, displacement, strain, AT loading rate, shortening velocity, instantaneous AT moment arm length and ankle angle) were assessed with 1D statistical parametric mapping. Results indicated that men had significantly greater AT dimensions and stiffness than women. Women exhibited greater peak AT displacement and strain during the push-off phase, while AT loading rates were higher in men in late stance. These findings suggest potential sex-specific differences in AT behavior during dynamic activities, providing further insights into tendon biomechanics. Future research should explore AT mechanics under higher loading conditions and across different age groups to comprehensively understand sex differences in tendon behaviour.

Abstract Background Familial hypercholesterolemia (FH) is a genetic condition that affects cholesterol metabolism, resulting in life-long elevated serum levels of low-density lipoprotein cholesterol. Systemically elevated cholesterol levels are associated with the onset of tendon injury and potentially lead to impaired mechanical properties. Applying a cross-sectional design, we examined whether FH patients present with altered Achilles biomechanics compared to healthy controls and conducted correlational analyses to determine the relationship between Achilles tendon biomechanics and tendon lipid or water content. Methods Patients with FH (n = 33) and healthy controls (n = 31) were recruited from the Greater Vancouver area. Achilles cross sectional area, thickness, lipid and water content was determined using Dixon method magnetic resonance imaging (3.0T). Achilles mechanical properties were determined using synchronized dynamometry, motion capture, ultrasound and electromyography during ramped maximal voluntary isometric contractions, and stiffness and Young’s modulus calculated. Between group differences were assessed with independent t-tests or Mann-Whitney U tests and Pearson’s r or Spearman’s ρ were employed for correlational analyses. Sensitivity analysis was conducted on FH patients diagnosed with Achilles xanthoma and the remaining FH patients. Results FH patients had significantly elevated Achilles total water content (p = 0.006), cross-sectional area (p = 0.006), and thickness (p = 0.019). No between-group differences were observed in any of the biomechanical parameters. In patients with FH there were significant positive relationships between tendon lipid or water content and tendon strain (ρ = 0.35, p = 0.046; r = 0.42, p = 0.02, respectively). No significant relationships were observed in control participants. In patients with FH, increased tendon cross-sectional area was associated with reduced stiffness (r=-0.371, p = 0.033) and increased strain (r = 0.48, p = 0.005). The presence of xanthoma was associated with increased Achilles dimensions (p < 0.05), total water content (p = 0.03), strain (p = 0.029), and decreased Young’s modulus (p = 0.001). Conclusion Increased Achilles lipid and water content is associated with increased tendon strain in people with FH and the presence of xanthoma might indicate altered tendon mechanics. This study holds relevance for individuals with hypercholesteremia, as best management practices advocate for physical activity as part of a healthy lifestyle.

OBJECTIVE:The aim of this study was to comprehensively examine and summarize the available in vitro evidence regarding the relationship between mechanical stimulation and biomarkers of collagen synthesis in human-derived tendon cells. METHODS:Systematic review with narrative analyses and risk of bias assessment guided by the Health Assessment and Translation tool. The electronic databases MEDLINE (Ovid), EMBASE (Ovid), CENTRAL (Ovid) and COMPENDEX (Engineering Village) were systematically searched from inception to 3 August 2023. Inclusion criteria encompassed English language, original experimental, or quasi-experimental in vitro publications that subjected human tendon cells to mechanical stimulation, with collagen synthesis (total collagen, type I, III, V, XI, XII, and XIV) and related biomarkers (matrix metalloproteinases, transforming growth factor β, scleraxis, basic fibroblast growth factor) as outcomes. RESULTS:Twenty-one publications were included. A pervasive definite high risk of bias was evident in all included studies. Owing to incomplete outcome reporting and heterogeneity in mechanical stimulation protocols, planned meta-analyses were unfeasible. Reviewed data suggested that human tendon cells respond to mechanical stimulation with increased synthesis of collagen (e.g., COL1A1, procollagen, total soluble collagen, etc.), scleraxis and several matrix metalloproteinases. Results also indicate that mechanical stimulation dose magnitude may influence synthesis in several biomarkers. CONCLUSIONS:A limited number of studies, unfortunately characterized by a definite high risk of bias, suggest that in vitro mechanical stimulation primarily increases type I collagen synthesis by human tendon cells. Findings from this systematic review provide researchers and clinicians with biological evidence concerning the possible beneficial influence of exercise and loading on cellular-level tendon adaptation.

Objective Assess the association between combined hormonal contraceptives (CHC) use and musculoskeletal tissue pathophysiology, injuries or conditions. Design Systematic review with semiquantitative analyses and certainty of evidence assessment, guided by the Grading of Recommendations Assessment, Development and Evaluation approach. Data Sources MEDLINE, EMBASE, CENTRAL, SPORTDiscus, CINAHL searched from inception to April 2022. Eligibility Intervention and cohort studies that assessed the association between new or ongoing use of CHC and an outcome of musculoskeletal tissue pathophysiology, injury or condition in postpubertal premenopausal females. Results Across 50 included studies, we assessed the effect of CHC use on 30 unique musculoskeletal outcomes (75% bone related). Serious risk of bias was judged present in 82% of studies, with 52% adequately adjusting for confounding. Meta-analyses were not possible due to poor outcome reporting, and heterogeneity in estimate statistics and comparison conditions. Based on semiquantitative synthesis, there is low certainty evidence that CHC use was associated with elevated future fracture risk (risk ratio 1.02–1.20) and total knee arthroplasty (risk ratio 1.00–1.36). There is very low certainty evidence of unclear relationships between CHC use and a wide range of bone turnover and bone health outcomes. Evidence about the effect of CHC use on musculoskeletal tissues beyond bone, and the influence of CHC use in adolescence versus adulthood, is limited. Conclusion Given a paucity of high certainty evidence that CHC use is protective against musculoskeletal pathophysiology, injury or conditions, it is premature and inappropriate to advocate, or prescribe CHC for these purposes. PROSPERO registration number This review was registered on PROSPERO CRD42021224582 on 8 January 2021.

Introduction Half of young women start combined hormonal contraceptive (CHC) use for non-contraceptive reasons including 'controlling' their menstrual cycle to prevent injuries. These decisions should be evidence-based. This study assessed the association between CHC use and musculoskeletal tissue pathophysiology, injuries, or conditions. Materials and Methods After protocol registration, five databases were searched to 04–2022. Intervention and cohort studies assessing the association between new or ongoing use of CHC and musculoskeletal tissue pathophysiology, injury, or condition outcome in post-pubertal women were included. Record screening, data extraction, and risk-of-bias assessment were duplicated (blinded). Meta-analyses were not possible. Semi-quantitative syntheses followed a modified GRADE approach. Results Across 50 included studies, we assessed the effect of CHC use on 30 unique outcomes (75% bone-related). Serious risk-of-bias was judged present in 82% of studies, with 52% adequately adjusting for confounding. Meta-analyses were not possible due to heterogeneity in outcome methods, estimate statistics, and comparison conditions. Based on semi-quantitative synthesis, there is low certainty evidence that CHC use is associated with higher future fracture risk (RR 1.02–1.20), and total knee arthroplasty (RR 1.00–1.36). There is very low certainty evidence of unclear relationships between CHC use and a wide range of bone health outcomes. Evidence about the effect of CHC use on musculoskeletal tissues beyond bone, and the influence of use in adolescence versus adulthood is limited. Conclusion Given a paucity of high-certainty evidence that CHC use is protective against musculoskeletal pathophysiology, injury, or conditions, it is premature and inappropriate to prescribe CHC for these purposes.

Familial hypercholesterolemia, a common genetic metabolic disorder characterized by high cholesterol levels, is involved in the development of atherosclerosis and other preventable diseases. Familial hypercholesterolemia can also cause tendinous abnormalities, such as thickening and xanthoma (tendon lipid accumulation) in the Achilles, which may impede tendon biomechanics. The objective of this study was to investigate the effect of cholesterol accumulation on the biomechanical performance of Achilles tendons, in vivo. 16 participants (10 men, 6 women; 37±6 years) with familial hypercholesterolemia, diagnosed with tendon xanthoma, and 16 controls (10 men, 6 women; 36±7 years) underwent Achilles biomechanical assessment. Achilles biomechanical data was obtained during preferred pace, shod, walking by analysis of lower limb kinematics and kinetics utilizing 3D motion capture and an instrumented treadmill. Gastrocnemius medialis muscle-tendon junction displacement was imaged using ultrasonography. Achilles stiffness, hysteresis, strain and force were calculated from displacement-force data acquired during loading cycles, and tested for statistical differences using one-way ANOVA. Statistical parametric mapping was used to examine group differences in temporal data. Participants with familial hypercholesterolemia displayed lower Achilles stiffness compared to the control group (familial hypercholesterolemia group: 87±20 N/mm; controls: 111±18 N/mm; p = 0.001), which appeared to be linked to Achilles loading rate rather than an increased strain (FH: 5.27±1.2%; controls: 4.95±0.9%; p = 0.413). We found different Achilles loading patterns in the familial hypercholesterolemia group, which were traced to differences in the centre of pressure progression that affected ankle moment. This finding may indicate that individuals with familial hypercholesterolemia use different Achilles loading strategies. Participants with familial hypercholesterolemia also demonstrated significantly greater Achilles hysteresis than the control group (familial hypercholesterolemia: 57.5±7.3%; controls: 43.8±10%; p<0.001), suggesting that walking may require a greater metabolic cost. Our results indicate that cholesterol accumulation could contribute to reduced Achilles function, while potentially increasing the chance of injury.

Data set for "The effects of cholesterol accumulation on Achilles tendon biomechanics: A cross-sectional study"

Persistent tendon pain that impairs function has inconsistent medical terms that can influence choice of treatment.1 When a person is told they have tendinopathy by clinician A or tendinitis by clinician B, they might feel confused or be alarmed at receiving what they might perceive as two different diagnoses. This may lead to loss of confidence in their health professional and likely adds to uncertainty if they were to search for information about their condition. Clear and uniform terminology also assists inter-professional communication. Inconsistency in terminology for painful tendon disorders is a problem at numerous anatomical sites. Historically, the term ‘tendinitis’ was first used to describe tendon pain, thickening and impaired function (online supplementary figure S1). The term ‘tendinosis’ has also been used in a small number of publications, some of which were very influential.2 3 Subsequently, ‘tendinopathy’ emerged as the most common term for persistent tendon pain.4 5 To our knowledge, experts (clinicians and researchers) or patients have never engaged in a formal process to discuss the terminology we use. We believe that health professionals have not yet agreed on the appropriate terminology for painful tendon conditions. ### Supplementary data [bjsports-2019-100885supp001.pdf] The authors of this paper, a group of international clinical and research experts from different disciplines, aimed to achieve a consensus in terminology for persistent tendon disorders. We ran a Delphi and consensus process that culminated in a face-to-face meeting at the fifth International Scientific Tendinopathy Symposium (ISTS) in Groningen, the Netherlands, on 26 September 2018 (placeholder for sentence about the other two papers and accompanying editorial if they get accepted). Here, we present the resulting consensus statements on terminology for persistent tendon pain. Our two-stage Delphi design, consensus process consisted of an online survey followed by a face-to-face meeting. One of us (AS) drafted 11 statements about terminology …

•Xanthoma is a diagnostic feature of familial hypercholesterolemia.•Ultrasound is a good alternative to radiography.•More research is needed into MRI-based tendon lipid quantification.