Long-term treatment with transcranial pulsed electromagnetic fields improves movement speed and elevates cerebrospinal erythropoietin in Parkinson's disease.

BACKGROUND: Parkinson's disease is characterized by motor dysfunctions including bradykinesia. In a recent study, eight weeks of daily transcranial stimulation with bipolar pulsed electromagnetic fields improved functional rate of force development and decreased inter-hand tremor coherence in patients with mild Parkinson's disease. OBJECTIVE: To investigate the effect of long-term treatment with transcranial bipolar pulsed electromagnetic fields on motor performance in terms of movement speed and on neurotrophic and angiogenic factors. METHODS: Patients diagnosed with idiopathic Parkinson's disease had either daily 30-min treatment with bipolar (±50 V) transcranial pulsed electromagnetic stimulation (squared pulses, 3ms duration) for three eight-week periods separated by one-week pauses (T-PEMF group) (n = 16) or were included in a PD-control group (n = 8). Movement speed was assessed in a six-cycle sit-to-stand task performed on a force plate. Cerebrospinal fluid and venous blood were collected and analyzed for erythropoietin and vascular endothelial growth factor. RESULTS: Major significant improvement of movement speed compared to the natural development of the disease was found (p = 0.001). Thus, task completion time decreased gradually during the treatment period from 10.10s to 8.23s (p<0.001). The untreated PD-control group did not change (p = 0.458). The treated group did not differ statistically from that of a healthy age matched reference group at completion of treatment. Erythropoietin concentration in the cerebrospinal fluid also increased significantly in the treated group (p = 0.012). CONCLUSION: Long-term treatment with transcranial bipolar pulsed electromagnetic fields increased movement speed markedly and elevated erythropoietin levels. We hypothesize that treatment with transcranial bipolar pulsed electromagnetic fields improved functional performance by increasing dopamine levels in the brain, possibly through erythropoietin induced neural repair and/or protection of dopaminergic neurons.

No difference in knee muscle activation and kinematics during treadmill walking between adolescent girls with and without asymptomatic Generalised Joint Hypermobility.

BACKGROUND: Altered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait. Therefore, the aim was to investigate group differences in knee muscle activity simultaneously with knee joint kinematics during treadmill walking between children with and without GJH. METHODS: Girls 14-15 years of age with GJH (inclusion criteria: Beighton score ≥6 of 9 and positive hyperextension ≥10° (one/both knees)) and a matched control group without GJH (inclusion criteria: Beighton score ≤5 and no knee hyperextension ≥10° ) were recruited. In total 16 participants with GJH and 10 non-GJH participants were included in the study. Surface electromyography (sEMG) was measured from the quadriceps, hamstrings and gastrocnemius muscles of the dominant leg during treadmill walking. Maximal voluntary isometric contractions while sitting were used for normalisation of sEMG to % of Maximum Voluntary EMG (%MVE). Knee joint angles during treadmill walking were measured by electrogoniometer. Furthermore, co-contraction index (CCI) was calculated, and presented for muscle groups of hamstrings-quadriceps (HQ) and gastrocnemius-quadriceps (GQ). CCI of medial and lateral sides of the knee, including ratio of the medial and lateral CCI for HQ and GQ were calculated. RESULTS: No group differences were found in demographics, muscle activation level, nor CCI and CCI ratios. However, participants with GJH displayed significantly decreased knee joint angle, mean (153º vs. 156º; p =0.03) and minimum (105º vs. 111º; p=0.01), during treadmill walking compared with controls. CONCLUSION: Muscle activity during gait was not different between participants with GJH and non-GJH participants. However, participants with GJH displayed minor but statistically significant increased knee flexion during gait. Since the clinical consequences of increased knee joint flexion during gait are unknown, future studies should follow a larger cohort longitudinally during overground walking for development of clinical complications in this group.

The influence of posture duration on hand tremor during tasks with attention-distraction in persons with Parkinson's disease.

BACKGROUND: Tremor is one of the hallmarks and most bothersome symptoms in Parkinson's disease (PD). The classical PD tremor is present at rest, but postural tremor also occurs. PD tremor can be continuous or intermittently present and can have a re-emergent nature. The tremor intensity is affected by attention and stress level. Observations of PD tremor have indicated increased tremor intensity with time during 30-s tremor assessments. This phenomenon has not previously been studied systematically. Thus, in order to contribute to our understanding of the mechanisms associated with PD tremor, our aim was to investigate the influence of time during a posture holding and a resting task on hand tremor characteristics in persons with PD compared to healthy peers. METHOD: Fifty persons with PD and at least one tremoring hand (tremor intensity exceeding mean + 2SD of a healthy reference group (REF), N = 40) were included from a clinical trial population. Hand accelerations in a rest and postural condition were measured in 30-s assessments while the participants performed a self-paced simple subtraction task with eyes closed to standardize attention without inducing stress. Tremor intensity, maximal power, frequency of maximal power and tremor onset time was calculated for three consecutive 10-s time intervals. RESULTS: Tremor intensity and maximal power increased significantly during the 30-s recording in the PD-group in both conditions (1st-3rd time-interval, tremor intensity: rest + 65% p < 0.0001, postural + 55% p < 0.0001; maximal power: rest + 93% p < 0.0001, postural + 82% p < 0.001). No effect of time was found on frequency of maximal power in the PD-group or on any effect measure in the REF-group. CONCLUSION: Tremor intensity and maximal power increased with time in the PD-group during 30-s tasks, while no change with time was found in the REF-group. In contrast, frequency of maximal power remained unchanged, which may suggest that the same neural circuits were responsible for the tremor generation throughout the tasks. The increase in tremor intensity and maximal power could not solely be explained by re-emergence of tremor. This suggests an increasing or gradually more synchronized cortico-spinal drive throughout the tasks. However, this requires further studies to determine.

The effect of 8 weeks of treatment with transcranial pulsed electromagnetic fields on hand tremor and inter-hand coherence in persons with Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) tremor comprises asymmetric rest and postural tremor with unilateral onset. Tremor intensity can be amplified by stress and reduced by attention, and the medical treatment is complex. Mirror movements and unintentional synchronization of bimanual movements, possibly caused by insufficient inhibition of inter-hemispheric crosstalk, have been reported in PD, indicating a lag of lateralization. Potential neuroprotective effects of pulsed electromagnetic fields (PEMF) have been reported in-vitro and in rodents, as have influences of PEMF on human tremor. The aim was to investigate the effect of 8 weeks daily transcranial PEMF treatment (T-PEMF) of persons with PD on rest and postural hand tremor characteristics and on inter-hand coherence. METHODS: Hand accelerations of 50 PD participants with uni- or bilateral tremor participating in a clinical trial were analysed. A rest and postural tremor task performed during serial subtraction was assessed before and after 8 weeks of T-PEMF (30 min/day, 50 Hz, ±50 V, 3 ms squared pulses) or placebo treatment (sham stimulation 30 min/day). Forty matched healthy persons (no treatment) were included as reference. Intensity and inter-hand coherence related measures were extracted. RESULTS: The T-PEMF treatment decreased the inter-hand coherence in the PD group with unilateral postural tremor. The PD group with unilateral postural tremor was less clinically affected by the disease than the PD group with bilateral postural tremor. However, no differences between T-PEMF and placebo treatment on either intensity related or coherence related measures were found when all persons with PD were included in the analyses. The peak power decreased and the tremor intensity tended to decrease in both treatment groups. CONCLUSIONS: Eight weeks of T-PEMF treatment decreased inter-hand coherence in the PD group with unilateral postural tremor, while no effects of T-PEMF treatment were found for the entire PD group. The unilateral postural tremor group was less clinically affected than the bilateral postural tremor group, suggesting that early treatment initiation may be beneficial. In theory, a reduced inter-hand coherence could result from a neuronal treatment response increasing inter-hemispheric inhibition. However, this requires further studies to determine. Studies of even longer treatment periods would be of interest. TRIAL REGISTRATION: ClinicalTrials.gov , NCT02125032. Registered 29 April 2014, https://clinicaltrials.gov/ct2/show/NCT02125032?term=NCT02125032&rank=1.

Increased EMG intermuscular coherence and reduced signal complexity in Parkinson's disease.

OBJECTIVES: To investigate differences in surface electromyography (EMG) features in individuals with idiopathic Parkinson's disease (PD) and aged-matched controls. METHODS: Surface EMG was recorded during isometric leg extension in PD patients prior to, and after undergoing a locomotor training programme, and in aged-matched controls. Differences in EMG structure were quantified using determinism (%DET), sample entropy (SampEn) and intermuscular coherence. RESULTS: %DET was significantly higher, and SampEn significantly lower, in PD patients. Intermuscular coherence was also significantly higher in the PD group in theta, alpha and beta frequency bands. %DET increased and SampEn decreased with increasing Movement-Disorder-Society UPDRS scores, while theta band coherence was significantly correlated with total MDS-UPDRS scores and torque variance. Neither %DET, SampEn nor intermuscular coherence changed in response to training. CONCLUSIONS: The differences observed are consistent with increased synchrony among motor units within and across leg muscles in PD. Differences between EMG signals recorded from the PD and control groups persisted post-therapy, after improvements in walking capacity occurred. SIGNIFICANCE: These results provide insight into changes in motoneuron activity in PD, demonstrate increased beta band intramuscular coherence in PD for the first time, and support the development of quantitative biomarkers for PD based on advanced surface EMG features.

Effects of Long-Term Treatment with T-PEMF on Forearm Muscle Activation and Motor Function in Parkinson's Disease.

Bipolar pulsed electromagnetic stimulation applied to the brain (T-PEMF) is a non-pharmacological treatment which has been shown to stimulate nerve growth, attenuate nerve abnormalities, and improve microcirculation. We report on a 62-year-old, medically well-treated man with idiopathic Parkinson's disease. He was treated with T-PEMF, 30 min per day for three 8-week periods separated by two 1-week breaks. The disease made his handwriting impossible to read mainly due to small letters and lack of fluency. Forearm EMG measured during standardized conditions showed an involuntary spiky EMG pattern with regular burst activity (on his left side) at baseline. The intervention normalized the handwriting and forearm EMG. The UPDRS-motor score decreased from 25 to 17, and UPDRS-II-handwriting decreased from a pre-intervention value of 3 to 0 after the intervention. Finally, the patient reported improved fine motor function, less muscle stiffness, less muscle cramps and tingling, and less fatigue during the day in response to the T-PEMF treatment. The improved handwriting lasted for approximately 3 months after the treatment. Our results should be considered as preliminary, and large-scale, controlled studies are recommended to elucidate the therapeutic potential of long-term treatment with T-PEMF.

Effect of transcranial pulsed electromagnetic fields (T-PEMF) on functional rate of force development and movement speed in persons with Parkinson's disease: A randomized clinical trial.

BACKGROUND: Parkinson's disease is caused by dopaminergic neurodegeneration resulting in motor impairments as slow movement speed and impaired balance and coordination. Pulsed electromagnetic fields are suggested to have neuroprotective effects, and could alleviate symptoms. OBJECTIVE: To study 1) effects of 8-week daily transcranial pulsed electromagnetic field treatment on functional rate of force development and movement speed during two motor tasks with different levels of complexity, 2) if treatment effects depend on motor performance at baseline. METHODS: Ninety-seven persons with Parkinson's disease were randomized to active transcranial pulsed electromagnetic field (squared bipolar 3 ms pulses, 50 Hz) or placebo treatment with homebased treatment 30 min/day for 8 weeks. Functional rate of force development and completion time of a sit-to-stand and a dynamic postural balance task were assessed pre and post intervention. Participants were sub-grouped in high- and low-performers according to their baseline motor performance level. Repeated measure ANOVAs were used. RESULTS: Active treatment tended to improve rate of force development during chair rise more than placebo (P = 0.064). High-performers receiving active treatment improved rate of force development during chair rise more than high-performers receiving placebo treatment (P = 0.049, active/placebo: 11.9±1.1 to 12.5±1.9 BW/s ≈ 5% / 12.4±1.3 to 12.2±1.3 BW/s, no change). No other between-treatment-group or between-treatment-subgroup differences were found. Data on rate of force development of the dynamic balance task and completion times of both motor tasks improved but did not allow for between-treatment differentiation. CONCLUSION: Treatment with transcranial pulsed electromagnetic fields was superior to placebo regarding functional rate of force development during chair rise among high-performers. Active treatment tended to increase functional rate of force development while placebo did not. Our results suggest that mildly affected persons with Parkinson's disease have a larger potential for neural rehabilitation than more severely affected persons and indicate that early treatment initiation may be beneficial.

The Hawthorne effect as a pre-placebo expectation in Parkinsons disease patients participating in a randomized placebo-controlled clinical study.

BACKGROUND: The Hawthorne effect on clinical studies in Parkinson's disease has not been thoroughly investigated. Evidently the Hawthorne effect may have impact on study outcomes acting as a 'pre-placebo' effect in the recruitment phase, hence before inclusion. AIM: The aim of this study was to discuss the Hawthorne effect in relation to clinical and self-reported outcome measures in a randomized clinical study in the recruitment phase and during the study. METHODS: Data from 97 participants with Parkinson's disease treated with Transcranial Pulsed Electromagnetic Fields were applied, randomized to an active (n = 49) or a placebo treated group (n = 48). The participants received one home treatment session, for eight consecutive weeks. Outcome measures were the Unified Parkinson's Disease Rating Scale, The 39-item Parkinson's Disease Questionnaire and the WHO-5. RESULTS: No difference in treatment effect between the two groups was found pertaining the Unified Parkinson's Disease Rating Scale. No difference in treatment effect between the two groups was found pertaining the 39-item Parkinson's Disease Questionnaire, apart from the dimension mobility. No difference in treatment effect between the two groups was found pertaining the WHO-5 scale. CONCLUSIONS: The Hawthorne effect may have caused a 'pre-placebo' effect on the outcome measures even before obtaining baseline outcomes measures. This study may have been particularly prone to a Hawthorne effect due to the intense contact with the participants before and during the study. Moreover, the Hawthorne effect should not be viewed upon as a single entity but rather as entities affecting outcome measures throughout the full study period.

Alterations in neuromuscular function in girls with generalized joint hypermobility.

BACKGROUND: Generalized Joint Hypermobility (GJH) is associated with increased risk of musculoskeletal joint pain. We investigated neuromuscular performance and muscle activation strategy. METHODS: Girls with GJH and non-GJH (NGJH) performed isometric knee flexions (90°,110°,130°), and extensions (90°) at 20 % Maximum Voluntary Contraction, and explosive isometric knee flexions while sitting. EMG was recorded from knee flexor and extensor muscles. RESULTS: Early rate of torque development was 53 % faster for GJH. Reduced hamstring muscle activation in girls with GJH was found while knee extensor and calf muscle activation did not differ between groups. Flexion-extension and medial-lateral co-activation ratio during flexions were higher for girls with GJH than NGJH girls. CONCLUSIONS: Girls with GJH had higher capacity to rapidly generate force than NGJH girls which may reflect motor adaptation to compensate for hypermobility. Higher medial muscle activation indicated higher levels of medial knee joint compression in girls with GJH. Increased flexion-extension co-activation ratios in GJH were explained by decreased agonist drive to the hamstrings.

Influence of intense neuromuscular blockade on surgical conditions during laparotomy: a pig model.

PURPOSE: Intense neuromuscular block may improve surgical conditions in ileus laparotomies; however, it is difficult to evaluate. The aim of this study was to investigate if neuromuscular block improved surgical conditions in pigs with artificial ileus laparotomy. METHODS: Six pigs were endotracheally intubated, mechanically ventilated, anesthetized with propofol and fentanyl, and randomized into two groups in a cross-over assessor-blinded design. Neuromuscular block was established with rocuronium. Artificial laparotomy for ileus was performed. We investigated the influence of intense neuromuscular block on surgical conditions with a subjective rating scale, force needed to close the fascia, incidences of abdominal contractions while suctioning the lungs, width of the wound diastase and operating time as outcome parameters. RESULTS: In all six pigs no abdominal contractions occurred while suctioning the lungs at intense neuromuscular block. Without neuromuscular block we detected abdominal contractions seen as hiccups and bucking. In all six pigs during intense neuromuscular block we found no visible electromyographic (EMG) activity in the abdominal muscles while suctioning the lungs. Without neuromuscular block suctioning the lungs elicited brief periods of abdominal EMG activity. No difference was found in the force needed to close the fascia when comparing no neuromuscular block with intense neuromuscular block. Furthermore, no significant differences were found in the width of the diastase, operating time and subjective ratings using a four-point rating scale when comparing no neuromuscular block with intense neuromuscular block. However, these outcomes were related to the order of the suturing round. CONCLUSION: Intense neuromuscular block prevented abdominal muscle contractions but did not influence the force needed to close the fascia.

Anti-gravity training improves walking capacity and postural balance in patients with muscular dystrophy.

Recent studies in patients with muscular dystrophies suggest positive effects of aerobic and strength training. These studies focused training on using bicycle ergometers and conventional strength training, which precludes more severely affected patients from participating, because of their weakness. We investigated the functional effects of combined aerobic and strength training in patients with Becker and limb-girdle muscular dystrophies with knee muscle strength levels as low as 3% of normal strength. Eight patients performed 10 weeks of aerobic and strength training on an anti-gravity treadmill, which offered weight support up to 80% of their body weight. Six minute walking distance, dynamic postural balance, and plasma creatine kinase were assessed 10 weeks prior to training, immediately before training and after 10 weeks of training. Training elicited an improvement of walking distance by 8±2% and dynamic postural balance by 13±4%, indicating an improved physical function. Plasma creatine kinase remained unchanged. These results provide evidence that a combination of aerobic and strength training during anti-gravity has the potential to safely improve functional ability in severely affected patients with Becker and limb-girdle muscular dystrophies.

L4-L5 compression and anterior/posterior joint shear forces in cabin attendants during the initial push/pull actions of airplane meal carts.

The aim of the present study was to assess the acute low back load of cabin attendants during cart handling and to identify working situations which present the highest strain on the worker. In a setup, 17 cabin attendants (ten females and seven males) pushed, pulled and turned a 20 kg standard meal cart (L: 0.5m × W: 0.3 m × H: 0.92 m) loaded with extra 20 kg and 40 kg, respectively on two different surfaces (carpet and linoleum) and at three floor inclinations (-2°, 0° and +2°). Two force transducers were mounted as handles. Two-dimensional movement analysis was performed and a 4D WATBAK modelling tool was used to calculate the acute L4-L5 load. No working situations created loads greater than the accepted values for single exertions, however compression and anterior/posterior shear forces during pulling and turning were much higher when compared with pushing. There were significant effects of handling the cart on different floor types, at the varying inclinations and with different cart weights. Additionally, when external forces were reduced, the cabin attendants did not decrease push/pull force proportionally and thus the L4-L5 load did not decrease as much as expected.

Gait pattern in 9-11-year-old children with generalized joint hypermobility compared with controls; a cross-sectional study.

BACKGROUND: To study differences in gait patterns in 10-year-old children with Generalized Joint Hypermobility (GJH) and with no GJH (NGJH). METHODS: A total of 37 children participated (19 GJH, 18 NGJH, mean age 10.2 (SD 0.5) years). Inclusion criteria for GJH were a Beighton score of ≥5, with at least one hypermobile knee joint; for NGJH a Beighton score of ≤4, and no hypermobile knees and for both groups no knee pain during the previous week. All children were recorded by five video cameras, while they walked across three force platforms. Net joint moments were calculated in 3D by inverse dynamics and peak values provided input to statistical analyses. RESULTS: In the frontal plane, children with GJH had a significantly lower peak knee abductor moment and peak hip abductor moment. In the sagittal plane, the peak knee flexor moment and the peak hip extensor moment were significantly lower in the GJH group although the absolute difference was small. CONCLUSIONS: The walking pattern was the same for children with GJH and for healthy children, as there were no differences in kinematics, but it was, however, performed with different kinetics. Children with GJH walked with lower ankle, knee and hip joint moments compared to children with NGJH. However, the clinical importance of these differences during normal gait is unknown. To obtain this knowledge, children with GJH must be followed longitudinally. TRIAL REGISTRATION: The study was approved by the Committee on Biomedical Research Ethics for Copenhagen and Frederiksberg, Denmark (jnr. KF01-2006-178).

Running on a lower-body positive pressure treadmill: VO2max, respiratory response, and vertical ground reaction force.

PURPOSE: This study investigated maximal oxygen consumption (VO2max) and time to exhaustion while running on a lower-body positive pressure treadmill (LBPPT) at normal body weight (BW) as well as how BW support affects respiratory responses, ground reaction forces, and stride characteristics. METHOD: Twelve runners performed VO2max tests on a regular treadmill and an LBPPT. Furthermore, they performed steady-state running (10km/hr, 14 km/hr, and 18 km/hr) and high-speed running (20km/hr and 22 km/hr) at four different BWs on the LBPPT. VO2, heart rate, ventilation, and breathing frequency as well as vertical ground reaction force (vGRF) and stride characteristics were measured. RESULTS: VO2max could be obtained on both treadmills, although time to exhaustion was 34.5% longer on the LBPPT. VO2, ventilation, and heart rate decreased linearly with increasing BW support at steady-state running, while breathing rate remained unaffected by increasing BW support. Ground reaction force was markedly reduced with increasing BW support. The contact time decreased and flight time increased with increasing BW support. The step frequency decreased and step length increased to some extent with increasing BW support. CONCLUSIONS: VO2max can be achieved on an LBPPT at 100% BW with an incline-running protocol. The LBPPT is a suitable training device for athletes and allows training at high running speeds and high aerobic stimuli with the benefit of low vGRF and a near-normal movement pattern, although manipulation of gravitational weight causes some adaptations in locomotion.

Muscle oxygenation, EMG, and cardiovascular responses for cabin attendants vs. controls.

INTRODUCTION: The goal was to investigate the effect of acute moderate hypobaric exposure on the physiological responses to sustained contractions (local) and light to moderate dynamic exercise (systemic) for cabin attendants (CAB) and a matched control group (CON). METHOD: There were 14 CAB and 13 CON who participated. The experimental protocol was designed as a 2 x 2 randomized crossover study for which subjects performed a forearm isometric test and a cycling test in normobaric (NORM) and hypobaric [HYPO; 574 mmHg approximately 8000 ft (2440 m) above sea level (ASL)] conditions. Oxygen saturation (StO2%) was measured in the extensor carpi radialis muscle at rest and during an isometric wrist extension (20% MVC). Heart rate (HR), ventilation (V(E)), and oxygen uptake (VO2) were measured at rest, during cycling exercise at intensities of 50 W and 100 W, and during recovery. Blood samples were collected and analyzed for hemoglobin concentrations. RESULTS: Local response: There was a significant effect of HYPO for both CAB and CON with a decrease in StO2% of 6.5% both at rest and during contraction. Systemic response: there was no general effect of HYPO on HR, VE, or VO2. No differences were found between groups in either the local or systemic response or in the blood parameters. CONCLUSION: This study shows an effect of moderate hypobaric exposure on local muscle oxygenation during rest and sustained contraction. Whether this has an impact on fatigue development during work among cabin attendants is discussed.

Changes in human muscle oxygen saturation and mean fiber conduction velocity during intense dynamic exercise--effect of muscular training status.

INTRODUCTION: In this study we investigated whether an association exists between muscle fiber conduction velocity (MFCV) and local muscle oxygen saturation (StO(2)) in the superficial part of the latissimus dorsi muscle of runners and swimmers during exhaustive dynamic exercise. METHODS: Participants performed arm cranking with increasing intensity until exhaustion. RESULTS: Runners' MFCV was unchanged with increasing arm-cranking exercise intensity, but was higher (P < 0.05) than swimmers' MFCV at the same workload. Swimmers' MFCV increased (P < 0.05) with increasing exercise intensity and reached values at exhaustion similar to those of the runners. StO(2) was similar in swimmers and runners at rest and decreased with increasing exercise intensity. StO(2) was higher (P < 0.05) at the same workload in swimmers compared with runners. StO(2) and MFCV were significantly but very weakly correlated in both swimmers and runners. CONCLUSION: No association exists between surface MFCV and StO(2) in either trained or untrained human skeletal muscle during exhaustive intense dynamic exercise.

Knee function in 10-year-old children and adults with Generalised Joint Hypermobility.

PURPOSE: Knee function is reduced in patients with Benign Joint Hypermobility Syndrome. The aim was to study knee function in children and adults with Generalised Joint Hypermobility (GJH) and Non-GJH (NGJH)). MATERIALS AND METHODS: In a matched comparative study, 39 children and 36 adults (mean age children 10.2 years; adults 40.3 years) were included, comprising 19 children and 18 adults with GJH (Beighton ≥ 5/9; Beighton ≥ 4/9), minimum one hypermobile knee, no knee pain (children), and 20 children and 18 adults with NGJH (Beighton <5; Beighton <4). Totally, 85% of the adults were parents to these children. Knee function was determined by self-reported physical fitness (100mm VAS), Knee injury and Osteoarthritis Outcome Score (KOOS) (only adults), measured maximum isokinetic knee strength (60°/s) and peak vertical jump displacement (PVJD), with calculated knee strength balance, Hamstring/Quadriceps (H/Q) ratio and peak rate of force development (PRFD). RESULTS: Adults with GJH had lower knee function (KOOS: pain, p=0.001; symptoms, p=0.001; Activities of Daily Living, p=0.001; Sport/Recreation, p=0.003; knee-related quality of life, p<0.001), and H/Q ratio (0.46 vs. 0.54, p=0.046) than adults with NGJH, regardless of age and knee pain. Both GJH groups had normal physical fitness, isokinetic knee strength, and (only children) H/Q ratio. CONCLUSIONS: Children at 10 years with GJH have normal, but adults with GJH have impaired knee function. To track the risk of developing impaired knee function, children with GJH must be followed longitudinally. Meanwhile, attention to knee function may be given to children with GJH who have parents presenting GJH.

Approximate entropy based on attempted steady isometric contractions with the ankle dorsal- and plantarflexors: reliability and optimal sampling frequency.

The aim of this study was to (1) examine the test-retest reliability of approximate entropy (ApEn) calculated for torque time-series from attempted steady isometric contractions performed at two different days, and (2) examine the significance of the sampling frequency for the ApEn values. Eighteen healthy young subjects (13+/-3 years, mean+/-1 S.D.) performed attempted steady isometric submaximal contractions with the ankle dorsal- and plantarflexors at two different days. Relative (ICC(3.1)) and absolute (standard error of measurement [S.E.M.], and S.E.M.%) test-retest reliability was assessed for the ApEn values calculated for torque time-series down-sampled to 30 and 100Hz, respectively. The relative reliability was generally moderate (0.360< or =ICC(3.1)< or =0.897), with an absolute reliability (S.E.M.%) of 6-14%. The mean ApEn values varied considerably depending on the applied down-sampling frequency (5-200Hz). When ApEn was used to quantify structure in the torque time-series, the relative and absolute reliability of steady isometric contractions with the ankle proved to be good in healthy young subjects. We propose that an optimal time-series down-sampling frequency exists for ApEn calculations, which will increase the sensitivity for biological system-changes, reduce adverse effects of random noise, and ensure that biological information in the signal is preserved. We recommend estimating this frequency using a variable high-pass filter-method for frequency analysis. Based on this method, the optimized time-series down-sampling frequency was around 30Hz for the isometric contractions performed with the ankle in the present study.

Assessment of torque-steadiness reliability at the ankle level in healthy young subjects: implications for cerebral palsy.

It was the primary objective of this study to investigate whether quantifying fluctuations in dorsi and plantarflexor torque during submaximal isometric contractions is a reliable measurement in young healthy subjects. A secondary objective was to investigate the reliability of the associated muscle activity (EMG) data. Eighteen young subjects (12.8 +/- 3.1 years, mean +/- 1 SD) were examined twice. At each visit, fluctuations in exerted torque (torque steadiness) and muscle activity from the tibialis anterior, gastrocnemius and soleus muscles were determined during submaximal isometric dorsi and plantarflexions. The relative reliability of the torque steadiness variables was substantial (0.80 < ICC(3.1) < 0.92), with an absolute reliability (average coefficient of variation) of 13-17%. The relative reliability of the muscle activity data was generally moderate (0.51 < ICC(3.1) < 0.90), with an absolute reliability of 6-26%. The reliability of dorsi and plantarflexion torque-steadiness measurements proved to be good in young healthy subjects.