Jens Bojsen-Møller

Jens Bojsen-Møller
Norwegian School of Sport Sciences (NIH) · Department of Physical Performance

PhD

About

58
Publications
14,716
Reads
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3,102
Citations
Additional affiliations
January 2009 - present
Norwegian School of Sport Sciences (NIH)
Position
  • professor, biomechanics
January 2002 - January 2009
Bispebjerg Hospital, Copenhagen University
Position
  • Researcher

Publications

Publications (58)
Article
Including a brief overview of current investigative approaches, the present Perspectives for Progress paper offers an overview of potential future experiments in the field of exercise-related neuroplasticity to strength training. It is proposed that the combination of specific experimental approaches and recently developed techniques holds the pote...
Article
The interaction between the Achilles tendon and the triceps surae muscles seems to be modulated differently with various task configurations. Here we tested the hypothesis that the increased forces and ankle joint work during running under contrasting conditions (altered speed or load) would be met by different, time-dependent adjustments at the mu...
Article
Full-text available
Background: During the stance phase of running, the elasticity of the Achilles tendon enables the utilisation of elastic energy and allows beneficial contractile conditions for the triceps surae muscles. However, the effect of changes in tendon mechanical properties induced by chronic loading is still poorly understood. We tested the hypothesis th...
Article
During human movement, the muscle and tendinous structures interact as a mechanical system in which forces are generated and transmitted to the bone and energy is stored and released to optimize function and economy of movement and/or to reduce risk of injury. The present review addresses certain aspects of how the anatomical design and mechanical...
Article
Full-text available
During rapid deceleration of the body, tendons buffer part of the elongation of the muscle–tendon unit (MTU), enabling safe energy dissipation via eccentric muscle contraction. Yet, the influence of changes in tendon stiffness within the physiological range upon these lengthening contractions is unknown. This study aimed to examine the effect of tr...
Article
This study compared professional ballet dancers (n=10) to non‐stretching controls (n=10) with the purpose of comparing muscle and tendon morphology, mechanical, neural and functional properties of the triceps surae and their role for ankle joint flexibility. Torque‐angle and torque‐velocity data were obtained during passive and active conditions by...
Article
It was investigated, if a newly developed discipline specific test for elite-level trapeze sailors is reli-able and sensitive. Furthermore, the physical demands of trapeze sailing were examined. In part 1, nine national team athletes were accustomed to a simulated sailing test, which subsequently was completed on four occasions to determine test re...
Article
Full-text available
The compliance of elastic elements allows muscles to dissipate energy safely during eccentric contractions. This buffering function is well documented in animal models but our understanding of its mechanism in humans is confined to non-specific tasks, requiring a subsequent acceleration of the body. The present study aimed to examine the behaviour...
Article
The hypothesis, that sailing upwind in wind speeds above 12 knots causes fatigue, which manifests as a reduction in exerted hiking strap force and/or maximal isometric voluntary contraction force (MVC) of the knee extensors, was evaluated. Additionally, it was investigated if a relationship exists between maximal exerted hiking force (hMVC) and sai...
Article
Achilles tendon rupture (ATR) is the most common tendon rupture injury. The consequences of ATR on metabolic activity of the Achilles tendon and ankle plantarflexors are unknown. Furthermore, the effects of eccentric rehabilitation on metabolic activity patterns of Achilles tendon and ankle plantarflexors in ATR patients have not been reported thus...
Article
The free Achilles tendon is considered a homogenous structure that transmits muscular force in a linear manner. However, the tendon undergoes longitudinal rotation and is separated in mechanically independent segments with distinct mechanical and material tissue properties. The present review examines the hypothesis that the human Achilles tendon i...
Article
The purpose of this study was to examine whether athletes with highly flexible hamstring muscle-tendon units display different passive and contractile mechanical properties compared with controls. Flexibility, passive, and active torque-angle properties were assessed in 21 female elite rhythmic gymnasts and 16 female age-matched athletes. Passive r...
Article
Full-text available
Background and PurposeMany studies have shown that a position task is more difficult than a force task although both are performed at a similar net muscle force. Thus, the time to task failure is consistently shown to be briefer during the position task. The contributions of the central nervous system to these two types of fatiguing contractions ar...
Article
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...
Article
Abstract Physical fitness and muscular strength are important performance parameters in Olympic sailing although their relative importance changes between classes. The Olympic format consists of eight yacht types combined into 10 so-called events with total 15 sailors (male and female) in a complete national Olympic delegation. The yachts have diff...
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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...
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Although differences in mechanical properties between symptomatic and healthy tendons have been observed for the Achilles tendon, the impact of tendinopathy on patellar tendon mechanics is not fully documented. The aim of the present case-control study was to assess the mechanical properties of the tendon and jump performance in elite athletes with...
Article
Background Rate-dependent properties of tendons have consistently been observed in vitro but in vivo studies comparing the effects of loading duration on this feature remain conflicting. The main purpose of the present study was to evaluate whether tendon loading rate per se would affect in vivo tendon mechanical properties. Methods Twenty-two phy...
Article
Full-text available
Background The Danish strategy for fighting the use of anabolic androgenic steroids in fitness centres is likely the most comprehensive of its sort in the world. It is instituted in the national anti doping organisation, Anti Doping Denmark (ADD), and consists of doping controls, educational campaigns, and anonymous counselling through a web-based...
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Fascicle angle (FA) is suggested to increase as a result of fiber hypertrophy and furthermore to serve as the explanatory link in the discrepancy in the relative adaptations in the anatomical cross-sectional area (CSA) and fiber CSA after resistance training (RT). In contrast to RT, the effects of endurance training on FA are unclear. The purpose o...
Article
Different types of contractile fatiguing tasks ("force/position tasks") have shown that the rate of neuromuscular impairment is task dependent. Whether fatigue resistance is uniform across different types of limb joints is poorly understood because the force-position paradigm has mainly been applied to upper extremity joints under unstable conditio...
Article
The purpose of this study was to test the hypothesis that remodeling of skeletal muscle extracellular matrix (ECM) is involved in protecting human muscle against injury. Biopsies were obtained from medial gastrocnemius muscles after a single bout of electrical stimulation (B) or a repeated bout (RB) 30 d later, or 30 d after a single stimulation bo...
Article
Full-text available
Due to the complexity of movement in cross-country skiing (XCS), the muscle activation patterns are not well elucidated. Previous studies have applied surface electromyography (SEMG); however, recent gains in three-dimensional (3D) imaging techniques such as positron emission tomography (PET) have rendered an alternative approach to investigate mus...
Article
The effect of a period of passive movement training on angiogenic factors and capillarization in skeletal muscle was examined. Seven young males were subjected to passive training for 90 min, four times per week in a motor-driven knee extensor device that extended one knee passively at 80 cycles min₋₁. The other leg was used as control. Muscle biop...
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Full-text available
The exact mechanical function of synergist muscles within a human limb in vivo is not well described. Recent studies indicate the existence of a mechanical interaction between muscle actuators that may have functional significance and further play a role for injury mechanisms. The purpose of the present study was to investigate if intermuscular for...
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The use of performance- and image-enhancing drugs/substances (PIED) outside elite sports appears to be increasing, although the current knowledge of the nature of PIED use among recreational athletes is scarce. The present study analyzed enquiries that were submitted to the Danish Anti Doping Agency (ADD) over an 18-month period, to gain knowledge...
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The primary aim of our study was to validate the assessment of myonuclear and satellite cell number in biopsies from human skeletal muscle. We found that 25 type I and 25 type II fibers are sufficient to estimate the mean number of myonuclei per fiber. In contrast, the assessment of satellite cells improved when more fibers were included. Second, w...
Article
To investigate variability and reproducibility of hepatic [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG) uptake in healthy individuals. Static images were obtained 70 min after the injection of 160 MBq FDG in six healthy subjects at two occasions with 13 days' interval. FDG uptake was adjusted for tissue-to-blood background ratio (T/B), or measured as st...
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It is unknown whether muscle damage at the level of the sarcomere can be induced without lengthening contractions. To investigate this, we designed a study where seven young, healthy men underwent 30 min of repeated electrical stimulated contraction of m. gastrocnemius medialis, with the ankle and leg locked in a fixed position. Two muscle biopsies...
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Full-text available
The purpose of this study was to examine patellar tendon (PT) size and mechanical properties in subjects with a side-to-side strength difference of > or =15% due to sport-induced loading. Seven elite fencers and badminton players were included. Cross-sectional area (CSA) of the PT obtained from MRI and ultrasonography-based measurement of tibial an...
Article
Whether adjacent collagen fascicles transmit force in parallel is unknown. The purpose of the present study was to examine the magnitude of lateral force transmission between adjacent collagen fascicles from the human patellar and Achilles tendon. From each sample two adjacent strands of fascicles (phi 300-530 mum) enclosed in a fascicular membrane...
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Tendon structures have been studied for decades, but over the last decade, methodological development and renewed interest for metabolic, circulatory and tissue protein turnover in tendon tissue has resulted in a rising amount of investigations. This paper will detail the various modern investigative techniques available to study tendons. There are...
Article
We examined whether long-term habitual training (a) was associated with differences in structural and mechanical properties in tendon in women and (b) yielded different tendon properties in men and women. Ten male runners, 10 female runners and 10 female non-runners were tested. Tendon cross-sectional area (CSA) and length of the patellar and Achil...
Article
Physical fitness and muscular strength are important performance factors for Olympic class sailors, but the physical demands vary greatly between yacht classes, and limited information is available regarding the physical demands for the different crew positions. In the present paper, strength and aerobic capacity data from elite Olympic sailors are...
Article
Contraction-induced glucose uptake can be imaged and quantified by the use of positron emission tomography (PET). In the human extremities, such data may reveal important information regarding the in vivo mechanical function of e.g. the force transmitting tissues such as tendons. However, to investigate structures of limited size, a PET scanner wit...
Article
The physiological factors that govern passive joint range of motion (ROM) are poorly understood. The present study investigated the relation between passive knee joint ROM and the mechanical properties of the patellar tendon. Knee joint ROM was assessed in 43 individuals, and the subjects with the greatest ROM (flexible group, n=10) and lowest ROM...
Article
The purpose of the study was to identify factors that could predict differences among individuals in the time to failure of a submaximal contraction. Twenty subjects (10 men, 25+/-6 years) supported an inertial load equivalent to 20% of the maximal voluntary contraction (MVC) force with the elbow flexor muscles for as long as possible. The time to...
Article
The metabolic activity of tendinous tissues has traditionally been considered to be of limited magnitude. However, recent studies have suggested that glucose uptake increases in the force-transmitting tissues as a response to contractile loading, which in turn indicates an elevated tissue metabolism. The purpose of the present study was to investig...
Article
The extracellular matrix (ECM) of connective tissues enables linking to other tissues, and plays a key role in force transmission and tissue structure maintenance in tendons, ligaments, bone and muscle. ECM turnover is influenced by physical activity, and both collagen synthesis and metalloprotease activity increase with mechanical loading. This ca...
Article
Mechanical properties of the human patellar tendon are largely based on cadaver studies, which may not necessarily be applicable to the human patellar tendon, in vivo. While ultrasonography is an attractive non-invasive method for studying human, in vivo, muscle-tendon behaviour, it has mostly been used to examine Achilles tendon properties. We exa...
Article
Contractile force is transmitted to the skeleton through tendons and aponeuroses, and, although it is appreciated that the mechanocharacteristics of these tissues play an important role for movement performance with respect to energy storage, the association between tendon mechanical properties and the contractile muscle output during high-force mo...
Article
To identify the underlying physiological mechanisms for the difference in the time to failure for two types of fatiguing contractions, 20 subjects performed force and position tasks with the elbow flexor muscles at a comparable net muscle torque for a similar duration. Prior to terminating each task, blood flow was occluded to estimate the relative...
Article
The human triceps surae muscle-tendon complex is a unique structure with three separate muscle compartments that merge via their aponeuroses into the Achilles tendon. The mechanical function and properties of these structures during muscular contraction are not well understood. The purpose of the study was to investigate the extent to which differe...
Article
The mechanical properties of the human vastus lateralis (VL) tendon-aponeurosis complex were investigated in eight male subjects. Knee extensor force, knee joint angle, and corresponding longitudinal VL aponeurosis displacement were monitored synchronously during graded (10-s) maximal isometric knee extension contractions. Displacement observed dur...
Article
The mechanical characteristics of the human free tendon and aponeurosis, in vivo, remains largely unknown. The present study evaluated the longitudinal displacement of the separate free Achilles tendon and distal (deep) aponeurosis of the medial gastrocnemius muscle during voluntary isometric contraction. Ultrasonography-obtained displacement of th...
Article
Full-text available
Introduction: Muscular activation is traditionally inves-tigated by use of electromyography, although inherent methodological limitations exist (1). Contraction-induced glucose uptake in muscle tissues can be imaged and quan-tified in 3D by use of positron emission tomography (PET) (2), and therefore PET may offer an alternative or supple-mental me...

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Projects

Project (1)
Project
The goal of this project is to examine the effects of long-term stretching training on muscle-tendon morphology, mechanics and function of the triceps surae and the hamstrings in young, healthy adults.