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Long jump performance is, among other factors, highly dependent on the athlete's ability to generate sufficient vertical velocity during take-off. For a certain time on the take-off board the impulse-momentum relationship states that... more
Long jump performance is, among other factors, highly dependent on the athlete's ability to generate sufficient vertical velocity during take-off. For a certain time on the take-off board the impulse-momentum relationship states that vertical velocity is directly proportional to the vertical force applied to the body centre of mass and inversely proportional to the athlete's body mass. An increase in an athlete's strength is assumed to be followed by an increase in body mass. This study investigated how strength gains coupled with the ...
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Running economy (RE) at a given submaximal running velocity is defined as oxygen consumption per minute per kg body mass. We investigated RE in a group of 12 male elite runners of national class. In addition to RE at 14 and 18 km h−1 we... more
Running economy (RE) at a given submaximal running velocity is defined as oxygen consumption per minute per kg body mass. We investigated RE in a group of 12 male elite runners of national class. In addition to RE at 14 and 18 km h−1 we measured the maximal oxygen consumption (VO2max) and anthropometric measures including the moment arm of the Achilles tendon (LAch), shank and foot volumes, and muscular fascicle lengths. A 3‐D biomechanical movement analysis of treadmill running was also conducted. RE was on average 47.8 and 62.3 ml O2 min−1 kg−1 at 14 and 18 km h−1. Maximal difference between the individual athletes was 21% at 18 km h−1. Mechanical work rate was significantly correlated with VO2 measured in L min−1 at both running velocities. However, RE and relative work rate were not significantly correlated. LAch was significantly correlated with RE at 18 km h−1 implying that a short moment arm is advantageous regarding RE. Neither foot volume nor shank volume were significantly correlated to RE. Relative muscle fascicle length of m. soleus was significantly correlated with RE at 18 km h−1. Whole body stiffness and leg stiffness were significantly correlated with LAch indicating that a short moment arm coincided with high stiffness. It is concluded that a short LAch is correlated with RE. Probably, a short LAch allows for storage of a larger amount of elastic energy in the tendon and influences the force–velocity relation toward a lower contraction velocity.
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Publication in the conference proceedings of EUSIPCO, Aalborg, Denmark, 2010
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INTRODUCTION Different walking and movement patterns have been observed between anterior cruciate ligemant (ACL) deficient subjects that compensate well for their injury (copers) and those who do not (non-copers). Basically, previous... more
INTRODUCTION Different walking and movement patterns have been observed between anterior cruciate ligemant (ACL) deficient subjects that compensate well for their injury (copers) and those who do not (non-copers). Basically, previous studies observed that the movement pattern of copers was very similar to that of healthy subjects while the movement pattern observed in non-copers was different. In a previous study we observed that the walking pattern of non-copers was characterized by a significant reduction of the knee extensor moment during the stance phase but knee joint kinematics were identical to controls. In contrast, the copers walked with the same knee extensor momtent as the controls but had a greater peak knee flexion [1]. The purpose of the present study was to investigate how the different walking patterns observed between copers, non-copers and controls affected the compression and shear forces on the knee joint.
Anterior cruciate ligament injury (ACLi) reduces mechanical knee joint stability. Differences in muscle activation patterns are commonly identified between ACLi individuals and uninjured controls (CON); however, how and which of these... more
Anterior cruciate ligament injury (ACLi) reduces mechanical knee joint stability. Differences in muscle activation patterns are commonly identified between ACLi individuals and uninjured controls (CON); however, how and which of these differences are adaptations to protect the knee or adversely increase risk of joint instability remain unclear. Since the neuromuscular system integrates activity of all muscles crossing the knee to create a moment-of-force that opposes an external load, this study sought to quantify differences in individual muscle electromyography (EMG)-moment relationships between ACLi and CON. Participants isometrically modulated ground reaction forces during a standing force matching protocol to elicit combinations of sagittal, frontal and transverse plane moments. Partial least squares regressions determined which internal joint moment(s) predicted activation of 10 leg muscles for each group. Compared to CON, ACLi demonstrated greater contribution of rectus femor...
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The aim of the study was to investigate the distribution of net joint moments in the lower extremities during walking on high-heeled shoes compared with barefooted walking at identical speed. Fourteen female subjects walked at 4 km/h... more
The aim of the study was to investigate the distribution of net joint moments in the lower extremities during walking on high-heeled shoes compared with barefooted walking at identical speed. Fourteen female subjects walked at 4 km/h across three force platforms while they were filmed by five digital video cameras operating at 50 frames/second. Both barefooted walking and walking on high-heeled shoes (heel height: 9 cm) were recorded. Net joint moments were calculated by 3D inverse dynamics. EMG was recorded from eight leg muscles. The knee extensor moment peak in the first half of the stance phase was doubled when walking on high heels. The knee joint angle showed that high-heeled walking caused the subjects to flex the knee joint significantly more in the first half of the stance phase. In the frontal plane a significant increase was observed in the knee joint abductor moment and the hip joint abductor moment. Several EMG parameters increased significantly when walking on high-hee...
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Research Interests: Physiology, Skeletal muscle biology, Medicine, Physical Medicine and Rehabilitation, Biological Sciences, and 13 moreHumans, Female, The, Electromyography, Flexibility in engineering design, Skeletal Muscle, Adult, Torque, Mechanism in Biology, Hamstring, Range of Motion, Knee Joint, and Medical and Health Sciences
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The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0–200 ms). The present study... more
The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0–200 ms). The present study examined the effect of resistance training on contractile RFD and efferent motor outflow (“neural drive”) during maximal muscle contraction. Contractile RFD (slope of force-time curve), impulse (time-integrated force), electromyography (EMG) signal amplitude (mean average voltage), and rate of EMG rise (slope of EMG-time curve) were determined (1-kHz sampling rate) during maximal isometric muscle contraction (quadriceps femoris) in 15 male subjects before and after 14 wk of heavy-resistance strength training (38 sessions). Maximal isometric muscle strength [maximal voluntary contraction (MVC)] increased from 291.1 ± 9.8 to 339.0 ± 10.2 N · m after training. Contractile RFD determined within time intervals of 30, 50, 100, and 200 ms relative to onset of c...
Research Interests: Chemistry, Electrophysiology, Skeletal muscle biology, Motor Control, Medicine, and 15 moreBiological Sciences, Humans, Applied, Male, Weight Lifting, Applied Physiology, Electromyography, Adult, Leg, Force, Muscle contraction, Isometric Exercise, Physical Training, Physical Education and training, and Medical and Health Sciences
Combined V-wave and Hoffmann (H) reflex measurements were performed during maximal muscle contraction to examine the neural adaptation mechanisms induced by resistance training. The H-reflex can be used to assess the excitability of... more
Combined V-wave and Hoffmann (H) reflex measurements were performed during maximal muscle contraction to examine the neural adaptation mechanisms induced by resistance training. The H-reflex can be used to assess the excitability of spinal α-motoneurons, while also reflecting transmission efficiency (i.e., presynaptic inhibition) in Ia afferent synapses. Furthermore, the V-wave reflects the overall magnitude of efferent motor output from the α-motoneuron pool because of activation from descending central pathways. Fourteen male subjects participated in 14 wk of resistance training that involved heavy weight-lifting exercises for the muscles of the leg. Evoked V-wave, H-reflex, and maximal M-wave (Mmax) responses were recorded before and after training in the soleus muscle during maximal isometric ramp contractions. Maximal isometric, concentric, and eccentric muscle strength was measured by use of isokinetic dynamometry. V-wave amplitude increased ∼50% with training ( P < 0.01) f...
Research Interests: Chemistry, Medicine, Biological Sciences, Evoked Potentials, Humans, and 14 moreApplied, Male, Weight Lifting, Applied Physiology, Electromyography, Adult, Reflex, Isometric Exercise, Concentric, Neural Adaptation, Physical Education and training, Isometric Contraction, Motor Neurons, and Medical and Health Sciences
The rollator is a very popular walking aid. However, knowledge about how a rollator affects the walking patterns is limited. Thus, the purpose of the study was to investigate the biomechanical effects of walking with and without a... more
The rollator is a very popular walking aid. However, knowledge about how a rollator affects the walking patterns is limited. Thus, the purpose of the study was to investigate the biomechanical effects of walking with and without a rollator on the walking pattern in healthy subjects. The walking pattern during walking with and without rollator was analyzed using a three-dimensional inverse dynamics method. Sagittal joint dynamics and kinematics of the ankle, knee and hip were calculated. In addition, hip joint dynamics and kinematics in the frontal plane were calculated. Seven healthy women participated in the study. The hip was more flexed while the knee and ankle joints were less flexed/dorsiflexed during rollator walking. The ROM of the ankle and knee joints was reduced during rollator-walking. Rollator-walking caused a reduction in the knee extensor moment by 50% when compared to normal walking. The ankle plantarflexor and hip abductor moments were smaller when walking with a rol...
Research Interests: Biomedical Engineering, Biomechanics, Medicine, Physical Medicine and Rehabilitation, Biomedical, and 15 moreGait, Humans, Kinematics, Female, Inverse dynamics, Middle Aged, Adult, Ankle Joint, Long Term Effect, Ankle, Healthy Subjects, Lower Extremity, Knee Joint, Biomechanical Phenomena, and Hip Joint
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Research Interests: Physiology, Chemistry, Magnetic Resonance Imaging, Medicine, Biological Sciences, and 15 moreAnatomy, Humans, Strength Training, Male, Exercise, Myosin, The, Skeletal Muscle, Adult, Muscle contraction, Isometric Exercise, Muscle Architecture, Medical and Health Sciences, Muscle fibers skeletal, and Muscle Biopsy
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Pain is a cardinal symptom in musculoskeletal diseases involving the knee joint, and aberrant movement patterns and motor control strategies are often present in these patients. However, the underlying neuromuscular mechanisms linking... more
Pain is a cardinal symptom in musculoskeletal diseases involving the knee joint, and aberrant movement patterns and motor control strategies are often present in these patients. However, the underlying neuromuscular mechanisms linking pain to movement and motor control are unclear. To investigate the functional significance of muscle pain on knee joint control during walking, three-dimensional gait analyses were performed before, during, and after experimentally induced muscle pain by means of intramuscular injections of hypertonic saline (5.8%) into vastus medialis (VM) muscle of 20 healthy subjects. Isotonic saline (0.9%) was used as control. Surface electromyography (EMG) recordings of VM, vastus lateralis (VL), biceps femoris, and semitendinosus muscles were synchronized with the gait analyses. During experimental muscle pain, the loading response phase peak knee extensor moments were attenuated, and EMG activity in the VM and VL muscles was reduced. Compressive forces, adductio...
Research Interests: Motor Control, Medicine, Musculoskeletal Disease, Biological Sciences, Gait, and 15 moreHumans, Applied, Female, Male, Applied Physiology, Electromyography, Adult, Joint Instability, Hamstring, Healthy Subjects, Knee Joint, Motor Skills, Biomechanical Phenomena, Movement pattern, and Medical and Health Sciences
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The anatomy of the iliolumbar ligament (ILL) and the spatial orientation of the transverse process of the L5 vertebra were studied in 62 young black (n = 29) and white (n = 33) men and women during routine autopsy. The aim of the study... more
The anatomy of the iliolumbar ligament (ILL) and the spatial orientation of the transverse process of the L5 vertebra were studied in 62 young black (n = 29) and white (n = 33) men and women during routine autopsy. The aim of the study was to determine possible racial differences in the structure and attachments of the iliolumbar ligament. The present study also investigated the spatial orientation of the transverse process of the L5 vertebra since the ILL has been reported to attach to the transverse process. The measurements of the iliolumbar ligament were carried out with a digital vernier caliper while the transverse process angles were measured with an adjustable protractor. The ligament in black people was made up of a single, markedly longer band compared to white people, where the ligament was made up of two shorter bands. The ILL measured 61.8 ± 1.3 mm in black and 33.2 ± 1.5 mm white men, and in black women 61.3 ± 0.9 mm versus 32.2 ± 1.2 mm in white women (p <0.01). Fu...
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A hip joint flexor moment in the last half of the stance phase during walking has repeatedly been reported. However, the purpose of this moment remains uncertain and it is unknown how it is generated. Nine male subjects were instructed to... more
A hip joint flexor moment in the last half of the stance phase during walking has repeatedly been reported. However, the purpose of this moment remains uncertain and it is unknown how it is generated. Nine male subjects were instructed to walk at 4.5 km/h with their upper body in three different positions: normal, inclined and reclined. Net joint moments were calculated about the hip, knee and ankle joint. The peak hip joint flexor moment during late stance was significantly lower during inclined walking than in the two other conditions. During normal walking the iliacus muscle showed no or very weak activity and first at the transition from stance to swing. When walking reclined, a clear but rather low activity level of the iliacus muscle was seen in the first half of the stance phase, which could contribute to the hip moment. In the inclined condition the iliacus showed much increased activity but only in the swing phase. It is concluded that the hip flexor moment in question is l...
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Musculoskeletal shoulder load among baggage handlers measured by combining duration and intensity based on biomechanical and epidemiological information may be a stronger predictor of subacromial shoulder disorders than baggage handler... more
Musculoskeletal shoulder load among baggage handlers measured by combining duration and intensity based on biomechanical and epidemiological information may be a stronger predictor of subacromial shoulder disorders than baggage handler seniority. In 2012, a cohort of baggage handlers employed at Copenhagen Airport in 1990-2012, and a cohort of unskilled otherwise employed men answered a survey. Self-reported information on work tasks during employment in the airport in combination with work task specific biomechanically modelled forces in the shoulder joint was used to estimate shoulder load. Exposure measures were accumulated shoulder abduction moment, accumulated shoulder compression force, accumulated supraspinatus force and baggage handler seniority. The outcome was subacromial shoulder disorder registered in the Danish National Patient Register. When analyses were adjusted by all confounders except age, exposure variables showed close to significant associations with subacromial shoulder disorder. Results could not confirm our hypothesis that combined information on work task duration and shoulder load intensity was stronger associated with subacromial shoulder disorder than seniority. Practitioner Summary: In this study we sought to identify if the exposure to work-related musculoskeletal shoulder loading including duration and intensity among baggage handlers was associated with subacromial shoulder disorder. We found that there was an association but this was not stronger than that between baggage handler seniority and subacromial shoulder disorder.
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Introduction Outdoor air pollution is associated with exacerbations of obstructive lung diseases, but the role of air pollution in the incidence of these diseases is unclear. At Copenhagen Airport a high number of particles have been... more
Introduction Outdoor air pollution is associated with exacerbations of obstructive lung diseases, but the role of air pollution in the incidence of these diseases is unclear. At Copenhagen Airport a high number of particles have been measured especially on the apron at the terminal gates where many persons work with ground handling services. Aims To assess whether long-term occupational exposure to outdoor air pollution at an airport was associated with the incidence of obstructive lung disease. Methods A cohort of 6,629 male airport employees and a reference group of 62,546 men was followed from 1990 to 2012 in the Danish National Patient Register that covers all contacts to hospitals. The primary exposure measure was cumulative years of work at the airport weighted with the proportion of time spent on the apron (‘apron-years’). The outcome was a first time registration in the Patient Register of chronic obstructive pulmonary disease (COPD), asthma or all obstructive lung diseases together. Incidence rate ratios (IRR) were estimated from Poisson models adjusting for age, education, and calendar year. Results The reference group had a higher incidence rate than the group of exposed airport employees of COPD (IRR = 1.50; 95% CI: 1.21–1.85) and all obstructive lung diseases (IRR = 1.20; 1.03–1.39), but the same incidence rate of asthma (0.99; 0.81–1.20). In analyses of the internal dose-response relationship among the airport employees, we found no association between cumulated ‘apron-years’ and incidence of COPD. Regarding asthma, airport employees with 7+ apron-years had lower incidence rate (IRR = 0.57; 0.34–0.95) than airport employees with 0.1–3 years ‘apron-years’. However, we found no linear effect of cumulated ‘apron-years’ on asthma (IRR = 0.97; 0.94–1.01). Conclusions This large register-based cohort study found no evidence of associations between cumulative occupational exposure to air pollution and incidence of obstructive lung disease.
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Meniscal lesions are common and may contribute to the development of knee arthrosis. A few case-control and cross-sectional studies have identified knee-straining work as risk factors for meniscal lesions, but exposure-response relations... more
Meniscal lesions are common and may contribute to the development of knee arthrosis. A few case-control and cross-sectional studies have identified knee-straining work as risk factors for meniscal lesions, but exposure-response relations and the role of specific exposures are uncertain, and previous results may be sensitive to reporting and selection bias. We examined the relation between meniscal lesions and cumulative exposure to heavy lifting in a prospective register-based study with complete follow-up and independent information on exposure and outcome. We established a cohort of unskilled men employed at Copenhagen Airport or in other companies in the metropolitan Copenhagen area from 1990 to 2012 (the Copenhagen Airport Cohort). The cohort at risk included 3,307 airport baggage handlers with heavy lifting and kneeling or squatting work tasks and 63,934 referents with a similar socioeconomic background and less knee-straining work. Baggage handlers lifted suitcases with an ave...
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Photogrammetric measurements of bodily dimensions and analysis of gait patterns in CCTV are important tools in forensic investigations but accurate extraction of the measurements are challenging. This study tested whether manual... more
Photogrammetric measurements of bodily dimensions and analysis of gait patterns in CCTV are important tools in forensic investigations but accurate extraction of the measurements are challenging. This study tested whether manual annotation of the joint centers on 3D reconstructions could provide reliable recognition. Sixteen participants performed normal walking where 3D reconstructions were obtained continually. Segment lengths and kinematics from the extremities were manually extracted by eight expert observers. The results showed that all the participants were recognized, assuming the same expert annotated the data. Recognition based on data annotated by different experts was less reliable achieving 72.6% correct recognitions as some parameters were heavily affected by interobserver variability. This study verified that 3D reconstructions are feasible for forensic gait analysis as an improved alternative to conventional CCTV. However, further studies are needed to account for the...
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To assess the influence of cumulative employment as baggage handler on the risk of incident subacromial shoulder disorders. Baggage handling is characterized by repetitive work primarily consisting of heavy lifting in awkward positions... more
To assess the influence of cumulative employment as baggage handler on the risk of incident subacromial shoulder disorders. Baggage handling is characterized by repetitive work primarily consisting of heavy lifting in awkward positions and time pressure. This cohort study is based on the Copenhagen Airport Cohort consisting of unskilled men with employment at Copenhagen Airport and unskilled men with employment in other firms in the Greater Copenhagen area during the period 1990-2012. Only men were included. We followed the cohort in the National Patient Register and Civil Registration System. The primary exposure was cumulative years of employment as a baggage handler, and the primary outcome was diagnoses and surgical treatment of subacromial shoulder disorders. The cohort contained 3396 baggage handlers and 63,909 workers in the reference group. Baggage handlers with longer cumulative years of employment had higher incidence compared to baggage handlers with shorter employment; for example, baggage handlers with 10-19 years of employment had incidence rate ratio of 2.07 (95 % confidence interval, 1.27-3.38) compared to baggage handlers with less than 3 years of employment. Spline regression showed an increase in incidence within the first few years after employment whereupon the increased risk remained constant for longer employment. Baggage handlers had increased incidence in younger ages than the reference population. In this large cohort study, we found increased incidence of subacromial shoulder disorders for workers with longer cumulative years of employment. These results support that long-term lifting in awkward positions and time pressure influences the risk of subacromial shoulder disorders.
Research Interests: Incidence Geometry, Medicine, Denmark, Humans, Male, and 15 moreCohort Study, Incidence, Cohort, Registries, Air Travel, Middle Aged, Adult, Public health systems and services research, Age Factors, Risk Factors, Occupational Diseases, Lifting, Confidence Interval, Cumulative Incidence, and Cohort Studies
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Estimating 3D joint rotations in the lower extremities accurately and reliably remains unresolved in markerless motion capture, despite extensive studies in the past decades. The main problems have been ascribed to the limited accuracy of... more
Estimating 3D joint rotations in the lower extremities accurately and reliably remains unresolved in markerless motion capture, despite extensive studies in the past decades. The main problems have been ascribed to the limited accuracy of the 3D reconstructions. Accordingly, the purpose of the present study was to develop a new approach based on highly detailed 3D reconstructions in combination with a translational and rotational unconstrained articulated model. The highly detailed 3D reconstructions were synthesized from an eight camera setup using a stereo vision approach. The subject specific articulated model was generated with three rotational and three translational degrees of freedom for each limb segment and without any constraints to the range of motion. This approach was tested on 3D gait analysis and compared to a marker based method. The experiment included ten healthy subjects in whom hip, knee and ankle joint were analysed. Flexion/extension angles as well as hip abduc...