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Papers by Jakob Lorentzen
Sensors
Monitoring and quantifying movement behavior is crucial for improving the health of individuals w... more Monitoring and quantifying movement behavior is crucial for improving the health of individuals with cerebral palsy (CP). We have modeled and trained an image-based Convolutional Neural Network (CNN) to recognize specific movement classifiers relevant to individuals with CP. This study evaluates CNN’s performance and determines the feasibility of 24-h recordings. Seven sensors provided accelerometer and gyroscope data from 14 typically developed adults during videotaped physical activity. The performance of the CNN was assessed against test data and human video annotation. For feasibility testing, one typically developed adult and one adult with CP wore sensors for 24 h. The CNN demonstrated exceptional performance against test data, with a mean accuracy of 99.7%. Its general true positives (TP) and true negatives (TN) were 1.00. Against human annotators, performance was high, with mean accuracy at 83.4%, TP 0.84, and TN 0.83. Twenty-four-hour recordings were successful without data...
Brain, 2019
Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order... more Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order to ensure optimal stability of the ankle joint at ground impact. Toe walking is frequently observed in children with cerebral palsy, but the mechanisms involved have not been clarified. Here, we investigated maturation of voluntary toe walking in typically-developing children and typically-developed adults and compared it to involuntary toe walking in children with cerebral palsy. Twenty-eight children with cerebral palsy (age 3-14 years), 24 typically-developing children (age 2-14 years) and 15 adults (mean age 30.7 years) participated in the study. EMG activity was measured from the tibialis anterior and soleus muscles together with knee and ankle joint position during treadmill walking. In typically-developed adults, low step-to-step variability of the drop of the heel after ground impact was correlated with low tibialis anterior and high soleus EMG with no significant coupling between the antagonist muscle EMGs. Typically-developing children showed a significant age-related decline in EMG amplitude reaching an adult level at 10-12 years of age. The youngest typically-developing children showed a broad peak EMG-EMG synchronization (4100 ms) associated with large 5-15 Hz coherence between antagonist muscle activities. EMG coherence declined with age and at the age of 10-12 years no correlation was observed similar to adults. This reduction in coherence was closely related to improved step-to-step stability of the ankle joint position. Children with cerebral palsy generally showed lower EMG levels than typically-developing children and larger step-to-step variability in ankle joint position. In contrast to typically-developing children, children with cerebral palsy showed no age-related decline in tibialis anterior EMG amplitude. Motor unit synchronization and 5-15 Hz coherence between antagonist EMGs was observed more frequently in children with cerebral palsy when compared to typically-developing children and in contrast to typically-developing participants there was no age-related decline. We conclude that typically-developing children develop mature feedforward control of ankle muscle activity as they age, such that at age 10-12 years there is little agonistantagonist muscle co-contraction around the time of foot-ground contact during toe walking. Children with cerebral palsy, in contrast, continue to co-contract agonist and antagonist ankle muscles when toe walking. We speculate that children with cerebral palsy maintain a co-contraction activation pattern when toe walking due to weak muscles and insufficient motor and sensory signalling necessary for optimization of feedforward motor programs. These findings are important for understanding of the pathophysiology and treatment of toe walking.
European Journal of Applied Physiology
PURPOSE Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is ... more PURPOSE Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is due to altered corticospinal drive. We aimed to compare changes in corticospinal drive following sustained muscle contractions in adults with CP and neurologically intact (NI) adults. METHODS Fourteen adults with CP [age 37.6 (10.1), seven females, GMFCS levels I-II] and ten NI adults [age 35.4 (10.3), 6 females] performed 1-min static dorsiflexion at 30% of maximal voluntary contraction (MVC) before and after a submaximal contraction at 60% MVC. Electroencephalography (EEG) and electromyography (EMG) from the anterior tibial muscle were analyzed to quantify the coupling, expressed by corticomuscular coherence (CMC). RESULTS Adults with CP had lower MVCs but similar time to exhaustion during the relative load of the fatigability trial. Both groups exhibited fatigability-related changes in EMG median frequency and EMG amplitude. The CP group showed lower beta band (16-35 Hz) CMC before fatigability, but both groups decreased beta band CMC following fatigability. There was a linear correlation between decrease of beta band CMC and fatigability-related increase in EMG. CONCLUSION Fatigability following static contraction until failure was related to decreased beta band CMC in both NI adults and adults with CP. Our findings indicate that compensatory mechanisms to fatigability are present in both groups, and that fatigability affects the corticospinal drive in the same way. We suggest that the perceived physical fatigue in CP is related to the high relative load of activities of daily living rather than any particular physiological mechanism.
Journal of Neurophysiology
Sensory feedback through spinal reflex pathways makes only a minor contribution to neural drive t... more Sensory feedback through spinal reflex pathways makes only a minor contribution to neural drive to muscles during voluntary ankle plantar flexion. This differs distinctly from observations during walking and suggests that the neural drive to ankle plantar flexors during voluntary contraction do not rely on sensory feedback through similar spinal interneuronal networks as during walking. In line with animal studies this suggests that the integration of sensory feedback in CNS is task specific.
Functional tests. These data describes the results of the Sit-to-stand- and the Romberg tests. S2... more Functional tests. These data describes the results of the Sit-to-stand- and the Romberg tests. S2. Whole Hand strength and pinch strength. These data describes the results of the Hand strength and Pinch strength. S3. Pinch rate of force development. These data describes the results of RFD 0-30 ms; RFD 0-50 ms; RFD 0-100 ms; RFD 0-200 ms for the least and most affected arm. S4. Ankle joint measurements. These data describes the results of the ankle joint stiffness and ROM measurements. S5. Ankle strength measurements. These data describes the results of the ankle strength measurements in TA. S6. Cognitive and Psychological test. These data describes the data of cardbased CogState computerized tests and test of the spatial location based tasks. S7. Evaluation of personal and social competencies. These data summarize the results of the evaluation of personal and social competencies separated in sections including Overall; Physical abilities; Skills and abilities; Mental well-being; Rel...
Background: Effective science-based motor rehabilitation requires high volume of individualized, ... more Background: Effective science-based motor rehabilitation requires high volume of individualized, intense physical training, which can be difficult to achieve exclusively through physical 1-on-1 sessions with a therapist. Home-based training, enhanced by technological solutions, could be a tool to help facilitate the important factors for neuroplastic motor improvements. Objectives: This review aimed to discover how the inclusion of modern information and communications technology in home-based training programs can promote key neuroplastic factors associated with motor learning in neurological disabilities and identify which challenges are still needed to overcome. Methods: We conducted a thorough literature search on technological home-based training solutions and categorized the different fundamental approaches that were used. We then analyzed how these approaches can be used to promote certain key factors of neuroplasticity and which challenges still need to be solved or require ...
Ultrasound in Medicine & Biology, 2022
We used ultrasound-derived echo intensity and hand-held dynamometry to characterize plantar flexo... more We used ultrasound-derived echo intensity and hand-held dynamometry to characterize plantar flexor muscle contractures in adults with cerebral palsy (CP). Eleven adults with CP (aged 41 ± 12 y, Gross Motor Function Classification System I-II) and 11 neurologically intact adults (aged 35 ± 10 y) participated in the study. Echo intensity was measured from the medial gastrocnemius muscle using brightness mode ultrasound. Hand-held dynamometry was used to quantify plantar flexor passive muscle stiffness and ankle joint passive range of motion (pROM). Echo intensity correlated with both passive muscle stiffness (r = 0.57, p = 0.006) and pROM (r = -0.56, p = 0.006). Ultrasound echo intensity (p = 0.02, standardized mean difference [SMD] = 1.13) and passive muscle stiffness (p < 0.001, SMD = 1.99) were higher and ankle joint pROM (p < 0.001, SMD = 2.69) was lower in adults with CP than in neurologically intact adults. We conclude that combined ultrasound-derived echo intensity and hand-held dynamometry may be used to provide an objective characterization of muscle contractures.
Disability and Rehabilitation, 2012
Archives of Rehabilitation Research and Clinical Translation, 2021
Background: Home-based training is becoming ever more important with increasing demands on the pu... more Background: Home-based training is becoming ever more important with increasing demands on the public health systems. We investigated whether individualized and supervised interactive home-based training delivered through the internet improves functional abilities in children with cerebral palsy (CP). Methods: Thirty four children with CP (aged 9–16; mean age 10.9 ± 2.4 years) (GMFCS I-II; MACS I-II) were included in this non-randomized controlled clinical training study. 12 children (aged 7–16; mean age: 11.3+/−0.9 years) were allocated to a control group in which measurements were performed with 20 weeks interval without any intervening training. Daily activities, functional abilities of upperand lower limbs, and balance were evaluated before, immediately after training and 12 weeks after training. The training consisted of 30 min daily home-based training for 20 weeks delivered through the internet. Results: The training group on average completed 17 min daily training for the 20...
Ugeskrift for laeger, 2013
Neurological Rehabilitation
Ugeskrift for Læger, 2013
Aims: One of the impairments evaluated in children with cerebral palsy (CP), which perhaps has be... more Aims: One of the impairments evaluated in children with cerebral palsy (CP), which perhaps has been least investigated, is reduced selective motor control. The aim of the present study was to determine construct validity, discriminative validity, and intraand interrater reliability of the Selective Control of the Upper Extremity Scale (SCUES). Methods: Thirty-three children with unilateral CP, with a mean age of 11.5 ± 3.3 years, at level I to IV according to the Manual Ability Classification System (MACS), participated. The children were video-recorded and scored using the SCUES. The videos were scored twice to determine the intraand interrater reliability. Reliability was assessed using the intraclass correlation coefficient, the standard error of the measurement (SEM), and the smallest real difference (SRD). Differences in the SCUES scores were determined between the lessand more-affected arm and across all MACS levels for discriminative validity. Construct validity of the SCUES ...
Spasticity is a frequently used diagnosis, and anti-spastic medication is used widespread. In thi... more Spasticity is a frequently used diagnosis, and anti-spastic medication is used widespread. In this systematic review article we highlight difficulties in diagnosing spasticity correctly and thus limit the value of the diagnosis in ensuring the best possible treatment. We review recent neuroscience research and conclude that it is necessary to develop better tools for clinical diagnosis of spasticity in order to avoid potential malpractice and to limit treatment with anti-spastic drugs for patients with documented increased reflex-mediated muscle tone as their main annoyance.
Sensors
Monitoring and quantifying movement behavior is crucial for improving the health of individuals w... more Monitoring and quantifying movement behavior is crucial for improving the health of individuals with cerebral palsy (CP). We have modeled and trained an image-based Convolutional Neural Network (CNN) to recognize specific movement classifiers relevant to individuals with CP. This study evaluates CNN’s performance and determines the feasibility of 24-h recordings. Seven sensors provided accelerometer and gyroscope data from 14 typically developed adults during videotaped physical activity. The performance of the CNN was assessed against test data and human video annotation. For feasibility testing, one typically developed adult and one adult with CP wore sensors for 24 h. The CNN demonstrated exceptional performance against test data, with a mean accuracy of 99.7%. Its general true positives (TP) and true negatives (TN) were 1.00. Against human annotators, performance was high, with mean accuracy at 83.4%, TP 0.84, and TN 0.83. Twenty-four-hour recordings were successful without data...
Brain, 2019
Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order... more Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order to ensure optimal stability of the ankle joint at ground impact. Toe walking is frequently observed in children with cerebral palsy, but the mechanisms involved have not been clarified. Here, we investigated maturation of voluntary toe walking in typically-developing children and typically-developed adults and compared it to involuntary toe walking in children with cerebral palsy. Twenty-eight children with cerebral palsy (age 3-14 years), 24 typically-developing children (age 2-14 years) and 15 adults (mean age 30.7 years) participated in the study. EMG activity was measured from the tibialis anterior and soleus muscles together with knee and ankle joint position during treadmill walking. In typically-developed adults, low step-to-step variability of the drop of the heel after ground impact was correlated with low tibialis anterior and high soleus EMG with no significant coupling between the antagonist muscle EMGs. Typically-developing children showed a significant age-related decline in EMG amplitude reaching an adult level at 10-12 years of age. The youngest typically-developing children showed a broad peak EMG-EMG synchronization (4100 ms) associated with large 5-15 Hz coherence between antagonist muscle activities. EMG coherence declined with age and at the age of 10-12 years no correlation was observed similar to adults. This reduction in coherence was closely related to improved step-to-step stability of the ankle joint position. Children with cerebral palsy generally showed lower EMG levels than typically-developing children and larger step-to-step variability in ankle joint position. In contrast to typically-developing children, children with cerebral palsy showed no age-related decline in tibialis anterior EMG amplitude. Motor unit synchronization and 5-15 Hz coherence between antagonist EMGs was observed more frequently in children with cerebral palsy when compared to typically-developing children and in contrast to typically-developing participants there was no age-related decline. We conclude that typically-developing children develop mature feedforward control of ankle muscle activity as they age, such that at age 10-12 years there is little agonistantagonist muscle co-contraction around the time of foot-ground contact during toe walking. Children with cerebral palsy, in contrast, continue to co-contract agonist and antagonist ankle muscles when toe walking. We speculate that children with cerebral palsy maintain a co-contraction activation pattern when toe walking due to weak muscles and insufficient motor and sensory signalling necessary for optimization of feedforward motor programs. These findings are important for understanding of the pathophysiology and treatment of toe walking.
European Journal of Applied Physiology
PURPOSE Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is ... more PURPOSE Fatigue is frequent in adults with cerebral palsy (CP) and it is unclear whether this is due to altered corticospinal drive. We aimed to compare changes in corticospinal drive following sustained muscle contractions in adults with CP and neurologically intact (NI) adults. METHODS Fourteen adults with CP [age 37.6 (10.1), seven females, GMFCS levels I-II] and ten NI adults [age 35.4 (10.3), 6 females] performed 1-min static dorsiflexion at 30% of maximal voluntary contraction (MVC) before and after a submaximal contraction at 60% MVC. Electroencephalography (EEG) and electromyography (EMG) from the anterior tibial muscle were analyzed to quantify the coupling, expressed by corticomuscular coherence (CMC). RESULTS Adults with CP had lower MVCs but similar time to exhaustion during the relative load of the fatigability trial. Both groups exhibited fatigability-related changes in EMG median frequency and EMG amplitude. The CP group showed lower beta band (16-35 Hz) CMC before fatigability, but both groups decreased beta band CMC following fatigability. There was a linear correlation between decrease of beta band CMC and fatigability-related increase in EMG. CONCLUSION Fatigability following static contraction until failure was related to decreased beta band CMC in both NI adults and adults with CP. Our findings indicate that compensatory mechanisms to fatigability are present in both groups, and that fatigability affects the corticospinal drive in the same way. We suggest that the perceived physical fatigue in CP is related to the high relative load of activities of daily living rather than any particular physiological mechanism.
Journal of Neurophysiology
Sensory feedback through spinal reflex pathways makes only a minor contribution to neural drive t... more Sensory feedback through spinal reflex pathways makes only a minor contribution to neural drive to muscles during voluntary ankle plantar flexion. This differs distinctly from observations during walking and suggests that the neural drive to ankle plantar flexors during voluntary contraction do not rely on sensory feedback through similar spinal interneuronal networks as during walking. In line with animal studies this suggests that the integration of sensory feedback in CNS is task specific.
Functional tests. These data describes the results of the Sit-to-stand- and the Romberg tests. S2... more Functional tests. These data describes the results of the Sit-to-stand- and the Romberg tests. S2. Whole Hand strength and pinch strength. These data describes the results of the Hand strength and Pinch strength. S3. Pinch rate of force development. These data describes the results of RFD 0-30 ms; RFD 0-50 ms; RFD 0-100 ms; RFD 0-200 ms for the least and most affected arm. S4. Ankle joint measurements. These data describes the results of the ankle joint stiffness and ROM measurements. S5. Ankle strength measurements. These data describes the results of the ankle strength measurements in TA. S6. Cognitive and Psychological test. These data describes the data of cardbased CogState computerized tests and test of the spatial location based tasks. S7. Evaluation of personal and social competencies. These data summarize the results of the evaluation of personal and social competencies separated in sections including Overall; Physical abilities; Skills and abilities; Mental well-being; Rel...
Background: Effective science-based motor rehabilitation requires high volume of individualized, ... more Background: Effective science-based motor rehabilitation requires high volume of individualized, intense physical training, which can be difficult to achieve exclusively through physical 1-on-1 sessions with a therapist. Home-based training, enhanced by technological solutions, could be a tool to help facilitate the important factors for neuroplastic motor improvements. Objectives: This review aimed to discover how the inclusion of modern information and communications technology in home-based training programs can promote key neuroplastic factors associated with motor learning in neurological disabilities and identify which challenges are still needed to overcome. Methods: We conducted a thorough literature search on technological home-based training solutions and categorized the different fundamental approaches that were used. We then analyzed how these approaches can be used to promote certain key factors of neuroplasticity and which challenges still need to be solved or require ...
Ultrasound in Medicine & Biology, 2022
We used ultrasound-derived echo intensity and hand-held dynamometry to characterize plantar flexo... more We used ultrasound-derived echo intensity and hand-held dynamometry to characterize plantar flexor muscle contractures in adults with cerebral palsy (CP). Eleven adults with CP (aged 41 ± 12 y, Gross Motor Function Classification System I-II) and 11 neurologically intact adults (aged 35 ± 10 y) participated in the study. Echo intensity was measured from the medial gastrocnemius muscle using brightness mode ultrasound. Hand-held dynamometry was used to quantify plantar flexor passive muscle stiffness and ankle joint passive range of motion (pROM). Echo intensity correlated with both passive muscle stiffness (r = 0.57, p = 0.006) and pROM (r = -0.56, p = 0.006). Ultrasound echo intensity (p = 0.02, standardized mean difference [SMD] = 1.13) and passive muscle stiffness (p < 0.001, SMD = 1.99) were higher and ankle joint pROM (p < 0.001, SMD = 2.69) was lower in adults with CP than in neurologically intact adults. We conclude that combined ultrasound-derived echo intensity and hand-held dynamometry may be used to provide an objective characterization of muscle contractures.
Disability and Rehabilitation, 2012
Archives of Rehabilitation Research and Clinical Translation, 2021
Background: Home-based training is becoming ever more important with increasing demands on the pu... more Background: Home-based training is becoming ever more important with increasing demands on the public health systems. We investigated whether individualized and supervised interactive home-based training delivered through the internet improves functional abilities in children with cerebral palsy (CP). Methods: Thirty four children with CP (aged 9–16; mean age 10.9 ± 2.4 years) (GMFCS I-II; MACS I-II) were included in this non-randomized controlled clinical training study. 12 children (aged 7–16; mean age: 11.3+/−0.9 years) were allocated to a control group in which measurements were performed with 20 weeks interval without any intervening training. Daily activities, functional abilities of upperand lower limbs, and balance were evaluated before, immediately after training and 12 weeks after training. The training consisted of 30 min daily home-based training for 20 weeks delivered through the internet. Results: The training group on average completed 17 min daily training for the 20...
Ugeskrift for laeger, 2013
Neurological Rehabilitation
Ugeskrift for Læger, 2013
Aims: One of the impairments evaluated in children with cerebral palsy (CP), which perhaps has be... more Aims: One of the impairments evaluated in children with cerebral palsy (CP), which perhaps has been least investigated, is reduced selective motor control. The aim of the present study was to determine construct validity, discriminative validity, and intraand interrater reliability of the Selective Control of the Upper Extremity Scale (SCUES). Methods: Thirty-three children with unilateral CP, with a mean age of 11.5 ± 3.3 years, at level I to IV according to the Manual Ability Classification System (MACS), participated. The children were video-recorded and scored using the SCUES. The videos were scored twice to determine the intraand interrater reliability. Reliability was assessed using the intraclass correlation coefficient, the standard error of the measurement (SEM), and the smallest real difference (SRD). Differences in the SCUES scores were determined between the lessand more-affected arm and across all MACS levels for discriminative validity. Construct validity of the SCUES ...
Spasticity is a frequently used diagnosis, and anti-spastic medication is used widespread. In thi... more Spasticity is a frequently used diagnosis, and anti-spastic medication is used widespread. In this systematic review article we highlight difficulties in diagnosing spasticity correctly and thus limit the value of the diagnosis in ensuring the best possible treatment. We review recent neuroscience research and conclude that it is necessary to develop better tools for clinical diagnosis of spasticity in order to avoid potential malpractice and to limit treatment with anti-spastic drugs for patients with documented increased reflex-mediated muscle tone as their main annoyance.