S P Magnusson

IT University of Copenhagen, København, Capital Region, Denmark

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Publications (170)546.08 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In the past twenty years, the use of ultrasound-based methods has become a standard approach to measure tendon mechanical properties in vivo. Yet, the multitude of methodological approaches adopted by various research groups probably contributes to the large variability of reported values. The technique of obtaining and relating tendon deformation to tensile force in vivo has been applied differently, depending on practical constraints or scientific points of view. Divergence can be seen in i) methodological considerations such as the choice of anatomical features to scan and to track, force measurements or signal synchronisation and ii), in physiological considerations related to the viscoelastic behaviour or length measurements of tendons. Hence, the purpose of the present review is to assess and discuss the physiological and technical aspects connected to in vivo testing of tendon mechanical properties. In doing so, our aim is to provide the reader with a systematic, qualitative analysis of ultrasound-based techniques. Finally, a list of recommendations is proposed for a number of selected issues. Copyright © 2014, Journal of Applied Physiology.
    Journal of Applied Physiology 11/2014; 118(2):jap.00849.2014. DOI:10.1152/japplphysiol.00849.2014 · 3.43 Impact Factor
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    ABSTRACT: (1) Objective Isolated human tendon cells form 3D tendon constructs that demonstrate collagen fibrillogenesis and feature structural similarities to tendon when cultured under tensile load. The exact role of circulating growth factors for collagen formation in tendon is sparsely examined. We investigated the influence of insulin-like growth factor I (IGF-I) on tendon construct formation in 3D cell culture. (2) Design Tendon constructs were grown in 0.5 or 10% FBS with or without IGF-I (250 mg/ml) supplementation. Collagen content (fluorometric), mRNA levels (PCR) and fibril diameter (transmission electron microscopy) were determined at 7, 10, 14, 21 and 28 days. (3) Results IGF-I revealed a stimulating effect on fibril diameter (up to day 21), mRNA for collagen (to day 28), tenomodulin (to day 28) and scleraxis (at days 10 and 14), and on overall collagen content. 10% FBS diminished the development of fibril diameter (day 14), collagen content (at days 21 and 28), and mRNA expression for collagen, tenomodulin and scleraxis. (4) Conclusion IGF-I supplementation promotes early onset of tensile load induced collagen formation and tendon structural arrangement, whereas the FBS concentration routinely used in cultures diminishes collagen expression, collagen content and fibril formation.
    Growth Hormone & IGF Research 09/2014; 25(1). DOI:10.1016/j.ghir.2014.09.001 · 1.33 Impact Factor
  • Theresa Bieler, S Peter Magnusson, Michael Kjaer, Nina Beyer
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    ABSTRACT: Objective: To investigate the reliability and agreement of measures of lower extremity muscle strength, power and functional performance in patients with hip osteoarthritis at different time intervals, and to compare these with the same measures in healthy peers. Design: Intra-rater test-retest separated by 1, 2, or 2.5 weeks in patients, and 1 week in healthy peers. Subjects: Patients with hip osteoarthritis (age range 61-83 years) with 1 (n = 37), 2 (n = 35), or 2.5 weeks (n = 15) between tests, and 35 healthy peers (age range 63-82 years). Methods: Maximal isometric hip and thigh strength, leg extensor power, and functional performance (8-foot up and go, stair climbing, chair stand and 6-min walk) were measured in patients, and quadriceps strength, leg extensor power and functional performance were measured in healthy peers. Systematic error, reliability and agreement were calculated. Results: Most hip strength measurements for the most symptomatic extremity, and nearly all strength measurements for the least symptomatic lower extremity, declined after 1 week (p < 0.05), but not after a 2.5-week interval. In healthy peers, quadriceps strength was unchanged. Regardless of the time interval, leg extensor power was unchanged, while functional performances improved at retest for all participants. Conclusion: In patients with hip osteoarthritis leg extensor power is unaffected by the time interval between tests, in contrast to muscle strength and functional performance.
    Journal of Rehabilitation Medicine 08/2014; DOI:10.2340/16501977-1864 · 1.90 Impact Factor
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    ABSTRACT: Life-long regular endurance exercise is known to counteract the deterioration of cardiovascular and metabolic function and overall mortality. Yet it remains unknown if life-long regular endurance exercise can influence the connective tissue accumulation of advanced glycation endproducts (AGEs) that is associated with aging and lifestyle-related diseases. We therefore examined two groups of healthy elderly men: 15 master athletes (64 ± 4 years) who had been engaged in life-long endurance running and 12 old untrained (66 ± 4 years) together with two groups of healthy young men; ten young athletes matched for running distance (26 ± 4 years), and 12 young untrained (24 ± 3 years). AGE cross-links (pentosidine) of the patellar tendon were measured biochemically, and in the skin, it was assessed by a fluorometric method. In addition, we determined mechanical properties and microstructure of the patellar tendon. Life-long regular endurance runners (master athletes) had a 21 % lower AGE cross-link density compared to old untrained. Furthermore, both master athletes and young athletes displayed a thicker patellar tendon. These cross-sectional data suggest that life-long regular endurance running can partly counteract the aging process in connective tissue by reducing age-related accumulation of AGEs. This may not only benefit skin and tendon but also other long-lived protein tissues in the body. Furthermore, it appears that endurance running yields tendon tissue hypertrophy that may serve to lower the stress on the tendon and thereby reduce the risk of injury.
    Journal of the American Aging Association 08/2014; 36(4):9665. DOI:10.1007/s11357-014-9665-9 · 3.45 Impact Factor
  • T. Bieler, S. P. Magnusson, M. Kjaer, N. Beyer
    Annals of the Rheumatic Diseases 06/2014; 73(Suppl 2):757-757. DOI:10.1136/annrheumdis-2014-eular.2360 · 9.27 Impact Factor
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    ABSTRACT: The objective of this study was to investigate the relative contributions of superficial and deep ankle plantarflexors during repetitive submaximal isometric contractions using surface electromyography (SEMG) and positron emission tomography (PET). Myoelectric signals were obtained from twelve healthy volunteers (27.3 ± 4.2 yrs). A tracer ([18F]-FDG) was injected during the exercise and PET scanning was done immediately afterwards. The examined muscles included soleus (Sol), medial gastrocnemius (MG), lateral gastrocnemius (LG), and flexor hallucis longus (FHL). It was found that isometric maximal voluntary contraction (MVC) force, muscle glucose uptake (GU) rate, and SEMG of various plantarflexors were comparable bilaterally. In terms of%EMG MVC, FHL and MG displayed the highest activity (∼34%), while LG (∼21%) had the lowest activity. Cumulative SEMG from all parts of the triceps surae (TS) muscle accounted for ∼70% of the combined EMG signal of all four plantarflexors. As for GU, the highest quantity was observed in MG (2.4 ± 0.8 μmol∗100g-1∗min-1), whereas FHL (1.8 ± 0.6 μmol∗100g-1∗min-1) had the lowest uptake. Cumulative GU of TS constituted nearly 80% of the combined GU. The findings of this study provide valuable reference for studies where individual muscle contributions are estimated using models and simulations.
    Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology 06/2014; DOI:10.1016/j.jelekin.2014.03.002 · 1.73 Impact Factor
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    ABSTRACT: High-load eccentric exercises have been a key component in the conservative management of chronic Achilles tendinopathy. This study investigated the effects of a 12-week progressive, home-based eccentric rehabilitation program on ankle plantarflexors' glucose uptake (GU) and myoelectric activity, and Achilles tendon GU. A longitudinal study design with control (N = 10) and patient (N = 10) groups was used. Surface electromyography (SEMG) from four ankle plantarflexors and glucose uptake from the same muscles and the Achilles tendon were measured during submaximal intermittent isometric plantarflexion task. The results indicated that the symptomatic leg was weaker (P<0.05) than the asymptomatic leg at baseline but improved (P<0.001) with eccentric rehabilitation. Additionally, the rehabilitation resulted in greater GU in both soleus (P < 0.01) and lateral gastrocnemius (P < 0.001) in the symptomatic leg while the asymptomatic leg displayed higher uptake for medial gastrocnemius and flexor hallucis longus (P<0.05). While both patient legs had higher tendon GU than the controls (P<0.05), there was no rehabilitation effect on the tendon GU. Concerning SEMG, at baseline, soleus showed more relative activity in the symptomatic leg compared to both the asymptomatic and control legs (P<0.05) probably reflecting an effort to compensate for the decreased force potential. The rehabilitation resulted in greater SEMG activity in the lateral gastrocnemius (P<0.01) of the symptomatic leg with no other within- or between-group differences. Eccentric rehabilitation was effective in decreasing subjective severity of Achilles tendinopathy. It also resulted in redistribution of relative electrical activity, but not metabolic activity, within the triceps surae muscle.
    Journal of Applied Physiology 05/2014; 117(2). DOI:10.1152/japplphysiol.00113.2014 · 3.43 Impact Factor
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    ABSTRACT: Background Achilles tendon pathologies may alter the coordinative strategies of synergistic calf muscles. We hypothesized that both surface electromyography and positron emission tomography would reveal differences between symptomatic and asymptomatic legs in Achilles tendinopathy patients and between healthy controls. Methods Eleven subjects with unilateral chronic Achilles tendon pain (28 yr) and eleven matched controls (28 yr) were studied for triceps surae and flexor hallucis longus muscle activity in response to repetitive isometric plantarflexion tasks performed at 30% of maximal voluntary contraction using surface electromyography and glucose uptake using positron emission tomography. Additionally, Achilles tendon glucose uptake was quantified. Findings Normalized myoelectric activity of soleus was higher (P < 0.05) in the symptomatic leg versus the contralateral and control legs despite lower absolute force level maintained (P < 0.005). Electromyography amplitude of flexor hallucis longus was also greater on the symptomatic side compared to the healthy leg (P < 0.05). Both the symptomatic and asymptomatic legs tended to have higher glucose uptake compared to the control legs (overall effect size: 0.9 and 1.3, respectively). Achilles tendon glucose uptake was greater in both legs of the patient group (P < 0.05) compared to controls. Maximal plantarflexion force was ~ 14% greater in the healthier leg compared to the injured leg in the patient group. Interpretations While the electromyography showed greater relative amplitude in the symptomatic leg, the results based on muscle glucose uptake suggested relatively similar behavior of both legs in the patient group. Higher glucose uptake in the symptomatic Achilles tendon suggests a higher metabolic demand.
    Clinical biomechanics (Bristol, Avon) 05/2014; DOI:10.1016/j.clinbiomech.2014.03.003 · 1.88 Impact Factor
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    ABSTRACT: Objective. Persistent weakness is a common problem after anterior cruciate ligament- (ACL-) reconstruction. This study investigated the effects of high-intensity (HRT) versus low-intensity (LRT) resistance training on leg extensor power and recovery of knee function after ACL-reconstruction. Methods. 31 males and 19 females were randomized to HRT (n = 24) or LRT (n = 26) from week 8-20 after ACL-reconstruction. Leg extensor power, joint laxity, and self-reported knee function were measured before and 7, 14, and 20 weeks after surgery. Hop tests were assessed before and after 20 weeks. Results. Power in the injured leg was 90% (95% CI 86-94%) of the noninjured leg, decreasing to 64% (95% CI 60-69%) 7 weeks after surgery. During the resistance training phase there was a significant group by time interaction for power (P = 0.020). Power was regained more with HRT compared to LRT at week 14 (84% versus 73% of noninjured leg, resp.; P = 0.027) and at week 20 (98% versus 83% of noninjured leg, resp.; P = 0.006) without adverse effects on joint laxity. No other between-group differences were found. Conclusion. High-intensity resistance training during rehabilitation after ACL-reconstruction can improve muscle power without adverse effects on joint laxity.
    BioMed Research International 04/2014; 2014:278512. DOI:10.1155/2014/278512 · 2.71 Impact Factor
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    ABSTRACT: Human aging is associated with a loss of skeletal muscle and an increase in circulating inflammatory markers. It is unknown whether endurance training (Tr) can prevent these changes. Therefore we studied 15 old trained (O-Tr) healthy males and, for comparison, 12 old untrained (O-Un), 10 Young-Tr (Y-Tr) and 12 Young-Un (Y-Un). Quadriceps size, VO2 peak, CRP, IL-6, TNF-α and its receptors, suPAR, lipid profile, leucocytes and glucose homeostasis were measured. Tr was associated with an improved insulin profile (p<0.05), and lower leucocyte (p<0.05) and triglyceride levels (p<0.05), independent of age. Aging was associated with poorer glucose control (p<0.05), independent of training. The age-related changes in waist circumference, VO2 peak, cholesterol, LDL, leg muscle size, CRP and IL-6 were counteracted by physical activity (p<0.05). A significant increase in suPAR with age was observed (p<0.05). Most importantly, life-long endurance exercise was associated with a lower level of the inflammatory markers CRP and IL-6 (p<0.05), and with a greater thigh muscle area (p<0.05), compared to age-matched untrained counterparts. These findings in a limited group of individuals suggest that regular physical endurance activity may play a role in reducing some markers of systemic inflammation, even within the normal range, and in maintaining muscle mass with aging.
    Mechanisms of ageing and development 11/2013; DOI:10.1016/j.mad.2013.11.004 · 3.51 Impact Factor
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    ABSTRACT: Achilles tendinopathy is a highly prevalent sports injury. Animal studies show a growth response in tendons in response to loading in the immature phase but not after puberty maturation. The aim of this investigation was to examine the structural and material properties in long distance runners who were either physically active (HAY) or inactive (LAY) in young age. Twelve men in HAY group and eight men in LAY group participated. Structural, functional, and biochemical properties of Achilles tendon were estimated from magnetic resonance imaging, ultrasound video recordings, mechanical tests, and tendon biopsies, respectively. There was no difference between the groups with respect to tendon cross-sectional area or tendon free length. There was no difference between the groups with respect to maximal force or mechanical properties. The collagen content, enzymatic and nonenzymatic cross-link density did not differ between the groups, nor did collagen fibril density, diameter, and area. There was a correlation between age and pentosidine/collagen within the groups [(HAY: P < 0.05 and r(2) = 0.47) and (LAY: P < 0.05 and r(2) = 0.52)]. The data suggest that high or low activity during youth did not appreciably influence the mechanical, structural, or biochemical properties of the Achilles tendon in adult long distance runners.
    Scandinavian Journal of Medicine and Science in Sports 11/2013; DOI:10.1111/sms.12143 · 3.17 Impact Factor
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    ABSTRACT: It is unknown whether loss in musculo-tendinous tissue during inactivity can be counteracted by growth hormone(GH), and whether GH accelerate rehabilitation in aging individuals. Elderly men (65-75 years; n=12) had one leg immobilized two weeks followed by six weeks re-training, and were randomly assigned to daily injections of recombinant GH(rhGH, n=6) or placebo(Plc, n=6). Cross sectional area(CSA), muscle strength(MVC) and biomechanical properties of m. quadriceps and patellar tendon were determined. Muscle and tendon biopsies were analyzed for gene expressions (mRNA) of collagen(COL1A1/3A1) and insulin-like growth factors(IGF-1Ea/Ec). Fibril morphology was analyzed by transmission electron microscope(TEM). In tendon, CSA and biomechanical properties did not change following immobilization, but an increase in CSA was found after 6 weeks of rehabilitation in both groups. The changes were more pronounced when GH was injected. Furthermore, tendon stiffness increased in GH group. Muscle CSA declined after immobilization in Plc but not in GH group. Muscle CSA increased during re-training with a significant larger increase in GH group compared to Plc. Both a time and group effect was seen for IGF-1Ea/Ec and COL1A1/3A1 mRNA expression in muscle with a difference between GH and Plc. IGF-1Ea/Ec and COL-1A1/3A1 mRNA expression increased in muscle following immobilization and re-training in subjects receiving GH, whereas an increase in IGF-1Ec mRNA expression was seen in the Plc group only after re-training. In conclusion, in elderly humans GH seems to have a matrix stabilizing effect during inactivity and rehabilitation by stimulating collagen expression in the musculo-tendinous tissue and increasing tendon CSA and stiffness.
    Journal of Applied Physiology 11/2013; 116(2). DOI:10.1152/japplphysiol.01077.2013 · 3.43 Impact Factor
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    ABSTRACT: To investigate the influence of lifelong endurance running on the satellite cell pool of type I and type II fibres in healthy human skeletal muscle. Muscle biopsies were collected from 15 healthy old trained men (O-Tr) who had been running 43±16 (mean±SD) kilometres a week for 28±9 years. 12 age-matched untrained men (O-Un) and a group of young trained and young untrained men were recruited for comparison. Frozen sections were immunohistochemically stained for Pax7, type I myosin and laminin, from which fibre area, the number of satellite cells, and the relationship between these variables were determined. In O-Un and O-Tr, type II fibres were smaller and contained fewer satellite cells than type I fibres. However, when expressed relative to fibre area, the difference in satellite cell content between fibre types was eliminated in O-Tr, but not O-Un. A strong positive relationship between fibre size and satellite cell content was detected in trained individuals. In line with a history of myofibre repair, a greater number of fibres with centrally located myonuclei was detected in O-Tr. Lifelong endurance training 1) does not deplete the satellite cell pool and 2) is associated with a similar density of satellite cells in type I and II fibres despite a failure to preserve the equal fibre type distribution of satellite cells observed in young individuals. Taken together, these data reveal a differential regulation of satellite cell content between fibre types, in young and old healthy men with dramatically different training histories. This article is protected by copyright. All rights reserved.
    Acta Physiologica 11/2013; DOI:10.1111/apha.12195 · 4.25 Impact Factor
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    ABSTRACT: Magnetic resonance imaging (MRI) has commonly been applied to determine tendon cross-sectional area (CSA) and length either to measure structural changes or to normalize mechanical measurements to stress and strain. The ability to reproduce CSA measurements on MRI images has been reported, but the accuracy in relation to actual tendon dimensions has never been investigated. The purpose of this study was to compare tendon CSA measured by MRI with that measured in vitro with the mould casting technique. The knee of a horse was MRI-scanned with 1.5 and 3 tesla, and two examiners measured the patellar tendon CSA. Thereafter, the patellar tendon of the horse was completely dissected and embedded in an alginate cast. The CSA of the embedded tendon was measured directly by optical imaging of the cast impression. 1.5 tesla grey tendon CSA and 3 tesla grey tendon CSA were 16.5% and 13.2% higher than the mould tendon CSA, respectively. Also, 3 tesla tendon CSA, based on the red-green border on the National Institute of Health (NIH) colour scale, was higher than the mould tendon CSA by 2.8%. The typical error between examiners was below 2% for all the measured CSA. The typical error between examiners was below 2% for all the measured CSA. These data show that measuring tendon CSA on the grey-scale MRI images is associated with an underestimation, but by optimizing the measurement using a 3 tesla MRI and the appropriate NIH colour scale, this underestimation could be reduced to 2.8% compared with the direct measurements on the mould.
    Clinical Physiology and Functional Imaging 09/2013; DOI:10.1111/cpf.12086 · 1.33 Impact Factor
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    ABSTRACT: Introduction: Osteoarthritis (OA) is the most common form of arthritis and the most common chronic joint disease in individuals over the age of 65 years. The condition is often associated with significant pain, stiffness, fatigue, and has a strong impact on physical function, mobility and quality of life. Objectives: The aim of the present study was to investigate the associations between health-related quality of life (HRQL), physical function and self-efficacy (the sense of being able to perform specific tasks), in individuals with X-ray-verified hip OA. The aim was also to determine factors explaining good perceived HRQL. Participants: Eighty-nine individuals with X-ray-verified hip OA in the age group 40–75 years participated in this study. The study sample predominantly consisted of females, n = 61 (69%), and the mean age was 62.5 years, range 39–76. Main outcome measures: For assessment of HRQL, the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), which is divided into the Physical Component Scale (PCS) and the Mental Component Scale (MCS), was used. Physical function was measured with one self-recorded instrument, the Hip Osteoarthritis Outcomes Score (HOOS Swedish version L.K 1.1), and two instruments using observation – the Body Awareness Scale – Movement Quality (BAS-MQ) and the Six Minute Walk Test (6MWT). Self-efficacy was evaluated using the Arthritis Self-Efficacy Scale (ASES). Results: The data indicated that HRQL (SF-36 PCS) had a significant correlation with both observed physical function and self-reported physical function. SF-36 PCS correlated significantly to all five subscales in HOOS, two of three subscales in BAS-MQ, 6MWT and all three subscales in ASES. Three subscales in HOOS, one subscale in ASES and the 6MWT together explained 58% (R2) of the variance in SF-36 PCS. Conclusion: The results of the current study indicated that good physical ability and good self-efficacy are important for HRQL in subjects with hip OA. This knowledge ought to influence future rehabilitation strategies. The treatment strategies for individuals with OA ought to be directed not only to the symptoms of the disease, but also to the individual's possibilities of gaining perceived control over the consequences of the disease including the HRQL.
    08/2013; 15(3). DOI:10.3109/21679169.2013.830331
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    ABSTRACT: Tendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH4 reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human collagen fibrils. There was an initial rise in modulus followed by a plateau with reduced modulus, which was finally followed by an even greater increase in stress and modulus before failure. The RTTs also displayed the initial increase and plateau phase, but the third region was virtually absent and the plateau continued until failure. The importance of cross-link lability was investigated by NaBH4 reduction of the rat-tail fibrils, which did not alter their behavior. These findings shed light on the function of cross-links at the fibril level, but further studies will be required to establish the underlying mechanisms.
    Biophysical Journal 06/2013; 104(11):2476-84. DOI:10.1016/j.bpj.2013.04.033 · 3.83 Impact Factor
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    ABSTRACT: This study explored the age-related deterioration in stretch-shortening cycle (SSC) muscle power and concurrent force-velocity properties in women and men across the adult life span. A total of 315 participants (women: n = 188; men: n = 127) aged 18-81 years performed maximal countermovement jumps on an instrumented force plate. Maximal SSC leg extension power expressed per kg body mass (Ppeak) was greater in men than in women across the adult age span (P < 0.001); however, this gender difference was progressively reduced with increasing age, because men showed an ∼50% faster rate of decline in SSC power than women (P < 0.001). Velocity at peak power (VPpeak) was greater in men than in women (P < 0.001) but declined at a greater rate in men than in women (P = 0.002). Vertical ground reaction force at peak power (FPpeak) was higher in men than in women in younger adults only (P < 0.001) and the age-related decline was steeper in men than in women (P < 0.001). Men demonstrated a steeper rate of decline in Ppeak than women with progressive aging. This novel finding emerged as a result of greater age-related losses in men for both force and velocity. Consequently, maximal SSC power production was observed to converge between genders when approaching old age.
    Scandinavian Journal of Medicine and Science in Sports 03/2013; DOI:10.1111/sms.12066 · 3.17 Impact Factor
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    ABSTRACT: Introduction: Gender differences exist with regards to ligament and tendon injuries. Lower collagen synthesis has been observed in exercising females vs. males, and in users of oral contraceptives (OC) vs non-users, but it is unknown if OC will influence tendon biomechanics of females undergoing regular training. Material and Method: 30 female athletes (handball players, 18-30 yrs) were recruited: Fifteen long-term users of OC (7.0±0.6 yrs) and 15 non-users (> 5 yrs). Synchronized values of patellar tendon elongation (obtained by ultrasonography) and tendon force were sampled during ramped isometric knee extensor MVC to estimate mechanical tendon properties. Further, tendon cross-sectional area and length were measured from MRI images, and tendon biopsies were obtained for analysis of tendon fibril characteristics and collagen cross-linking. Results: Overall, no difference in tendon biomechanical properties, tendon fibril characteristics or collagen cross-linking was observed between the OC-users and non-users, or between the different phases of the menstrual cycle. In athletes, tendon CSA in the preferred jumping leg tended to be larger than the contra-lateral leg (p=0.09), and a greater absolute (p=0.01) and normalized tendon stiffness (p=0.02), as well as a lower strain (p=0.04) were observed in the jumping leg compared to the contra-lateral leg. Conclusion: The results indicate that long-term OC use or menstrual phases does not influence structure or mechanical properties of the patellar tendon in female team handball athletes.
    Journal of Applied Physiology 02/2013; 114(8). DOI:10.1152/japplphysiol.01255.2012 · 3.43 Impact Factor
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    Journal of Applied Physiology 02/2013; 114(4):518-20. DOI:10.1152/japplphysiol.01525.2012 · 3.43 Impact Factor
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    ABSTRACT: Background Collagen-rich tendons and ligaments are important for joint stability and force transmission, but the capacity to form new tendon is poorly understood. In the present study we investigated mechanical strength, fibril size and structure during development of tendon like tissue from adult human tenocytes (termed tendon constructs) in vitro over 5 weeks in 3D tissue culture. Results The constructs displayed large elongated tendon cells aligned along the tendon axis together with collagen fibrils that increased in diameter by 50% from day 14 to 35, which approaches that observed in adult human tendon in vivo. The increase in diameter was accompanied by a 5-fold increase in mechanical strength (0.9±0.1 MPa to 4.9±0.6 MPa) and Young's modulus (5.8±0.9 MPa to 32.3±4.2 MPa), while the maximal strain at failure (16%) remained constant throughout the 5-week culture period. Conclusions The present study demonstrates that 3D tendon constructs can be formed by isolated human tendon fibroblasts, and when these constructs are subjected to static self-generated tension, the fibrils will grow in size and strength approaching that of adult human tendon in vivo. Developmental Dynamics, 2012. © 2012 Wiley Periodicals, Inc.
    Developmental Dynamics 01/2013; 242(1). DOI:10.1002/dvdy.23896 · 2.67 Impact Factor

Publication Stats

6k Citations
546.08 Total Impact Points


  • 1997–2014
    • IT University of Copenhagen
      København, Capital Region, Denmark
    • Copenhagen University Hospital Gentofte
      Hellebæk, Capital Region, Denmark
  • 1996–2014
    • Bispebjerg Hospital, Copenhagen University
      • Institute for Sports Medicine
      København, Capital Region, Denmark
  • 2013
    • Lund University
      Lund, Skåne, Sweden
  • 1998–2013
    • Institute of Sports Medicine Copenhagen
      København, Capital Region, Denmark
  • 2012
    • University of North Carolina at Charlotte
      Charlotte, North Carolina, United States
  • 2008
    • Ball State University
      • Human Performance Laboratory
      Muncie, Indiana, United States
  • 2006
    • University of Turku
      • Turku PET Centre
      Turku, Varsinais-Suomi, Finland
  • 2004
    • University of Gothenburg
      Goeteborg, Västra Götaland, Sweden
  • 2003
    • University of Copenhagen
      København, Capital Region, Denmark
  • 1993–1994
    • Lenox Hill Hospital
      New York, New York, United States