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OBJECTIVE: To study musculoskeletal workload in experienced surgeons during laparoscopic surgery (LS) compared with robotic assisted laparoscopy (RALS). BACKGROUND: 70-90% of surgeons who regularly perform LS report musculoskeletal symptoms, mainly in neck and shoulders. Data regarding the potential ergonomic benefits of RALS in a clinical setting is very limited. METHODS: Twelve surgeons with advanced experience in both LS and RALS each performed 2 hysterectomies on the same day. LS was performed standing, RALS sitting, the latter allowing forearm and head support. Bipolar surface electromyogram (EMG) was recorded from several muscles and was expressed relative to EMG during maximum contractions (%EMGmax). Gaps per minute plus static (p0.1), mean (p0.5), and peak (p0.9) muscle activation were calculated. Perceived exertion was rated before and just after each surgery. RESULTS: Neck muscle activity (p0.1 4.7 vs. 3.0%EMGmax, p0.5 7.4 vs. 5.3%EMGmax, p0.9 11.6 vs. 8.2%EMGmax, all P < 0.05) and static shoulder muscle activity (p0.1 5.7 vs. 2.8%EMGmax, P < 0.05) were higher for LS than for RALS. Both a higher level of gaps during RALS and a lower rating of perceived exertion, also for the legs, after RALS supported these observations. However, low back muscle activity was higher for RALS. CONCLUSIONS: RALS is significantly less physically demanding than LS, and also feels less strenuous for the surgeons. However, for both types of surgeries, there still is room for improvement of working conditions. To further optimize these, we suggest a scheme to regularly observe and advise the surgeons.

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The authors examined the associations between the performance of upper- and lower-extremity motor tasks across task complexity and motor symptom severity, overall disease severity, and the physical aspects of quality of life in persons with Parkinson's disease. The performance was assessed for three lower-extremity tasks and two upper-extremity tasks of different levels of complexity. The motor symptoms and overall disease severity correlated significantly with all motor tasks with higher correlation coefficients in the complex tasks. Thus, the strength of the association between disease severity or severity of motor symptoms and motor performance is task-specific, with higher values in complex motor tasks than in simpler motor tasks. Mobility-related and activity-of-daily-living-related quality of life correlated with lower-extremity tasks of low and medium complexity and with the complex upper-extremity task, respectively; this suggests that Parkinson's Disease Questionnaire-39 is capable of differentiating between the impact of gross and fine motor function on quality of life.

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OBJECTIVE: Developmental coordination disorder (DCD) is an innate impairment of motor coordination that affects basic locomotion and balance. This study investigated local dynamic stability of trunk accelerations during treadmill walking as an objective evaluation of gait stability and the sensitivity and specificity of this measure to discriminate children with DCD from typically developing children. METHOD: Eight children with DCD and ten age- and gender-matched typically developing children (TD) walked four minutes on a treadmill. Trunk accelerations in vertical, medio-lateral and anterior-posterior directions were recorded with a sternum mounted accelerometer at 256Hz. Short term local dynamic stability (λs), root mean square (RMS) and relative root mean square (RMSR) were calculated from measures of orthogonal trunk accelerations. Receiver operating characteristic curve (ROC) analysis was performed to discriminate between groups based on short term local dynamic stability. RESULTS: λs was significantly greater in children with DCD in the main movement direction (AP) (DCD: 1.69±0.17 λs; TD:1.41±0.17 λs; p=0.005), indicating reduced local dynamic stability. RMS and RMSR accelerations showed no difference between children with DCD and TD children in any direction. The ROC analysis of λs in separate directions and in two dimensions showed an excellent accuracy of discriminating between children with DCD and TD children. Anterior-posterior direction in combination with medio-lateral or vertical showed best performance with an area under the curve (AUC) of 0.91. CONCLUSION: We have shown that children with developmental coordination disorder have general reduced local dynamic stability and that the short term Lyapunov exponent has good power of discrimination between DCD and TD.

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The objective was to examine associations between motor and executive function across the adult lifespan and to investigate the role of motor complexity in these associations. Young, middle-aged and older adults (n = 82; 19-83y) performed two gross-motor tasks with different levels of complexity and a Stroop-like computer task. Performance was decreased in older adults. The association between motor and cognitive performance was significant for older adults in the complex motor task (p = 0.03, rs = -0.41), whereas no significant associations were found for young or middle-aged groups, suggesting that the link between gross-motor and executive function emerges with age and depends on motor complexity.

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BACKGROUND: Developmental coordination disorder (DCD) is a neurodevelopmental impairment that affects approximately 6% of children in primary school age. Children with DCD are characterized by impaired postural control. It has yet to be determined what effect peripheral and central neuromuscular control has on their balance control. OBJECTIVE: The aim of this study was to investigate the underlying mechanisms to impaired postural control in children with DCD using the rambling-trembling decomposition of the center of pressure (CoP). METHOD: Nine children with DCD (9.0±0.5years, 7 boys, 2 girls) and 10 age- and gender-matched typically developing children (TD) with normal motor proficiency (9.1±0.4years, 7 boys and 3 girls) performed 3×30s bipedal standing on a force plate in six sensory conditions following the sensory organization procedure. Sway length was measured and rambling-trembling decomposition of CoP was calculated in medio-lateral (ML) and anterior-posterior (AP) direction. RESULTS: Both rambling and trembling were larger for the children with DCD in AP (p=0.031; p=0.050) and ML direction (p=0.025; p=0.007), respectively. ML rambling trajectories did not differ in any conditions with fixed support surface. In ML direction children with DCD had a lower relative contribution of rambling to total sway (p=0.013). CONCLUSION: This study showed that impaired postural control in children with DCD is associated with less efficient supraspinal control represented by increased rambling, but also by reduced spinal feedback control or peripheral control manifested as increased trembling.

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Running on a lower-body positive-pressure (LBPP) treadmill allows effects of weight support on leg muscle activation to be assessed systematically, and has the potential to facilitate rehabilitation and prevent overloading. The aim was to study the effect of running with weight support on leg muscle activation and to estimate relative knee and ankle joint forces. Runners performed 6-min running sessions at 2.22 m/s and 3.33 m/s, at 100%, 80%, 60%, 40%, and 20% body weight (BW). Surface electromyography, ground reaction force, and running characteristics were measured. Relative knee and ankle joint forces were estimated. Leg muscles responded differently to unweighting during running, reflecting different relative contribution to propulsion and antigravity forces. At 20% BW, knee extensor EMGpeak decreased to 22% at 2.22 m/s and 28% at 3.33 m/s of 100% BW values. Plantar flexors decreased to 52% and 58% at 20% BW, while activity of biceps femoris muscle remained unchanged. Unweighting with LBPP reduced estimated joint force significantly although less than proportional to the degree of weight support (ankle). It was concluded that leg muscle activation adapted to the new biomechanical environment, and the effect of unweighting on estimated knee force was more pronounced than on ankle force.

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INTRODUCTION: We studied the functional effects of combined strength and aerobic anti-gravity training in severely affected patients with Becker and Limb-Girdle muscular dystrophies. METHODS: Eight patients performed 10-week progressive combined strength (squats, calf raises, lunges) and aerobic (walk/run, jogging in place or high knee-lift) training 3 times/week in a lower-body positive pressure environment. Closed-kinetic-chain leg muscle strength, isometric knee strength, rate of force development (RFD), and reaction time were evaluated. RESULTS: Baseline data indicated an intact neural activation pattern but showed compromised muscle contractile properties. Training (compliance 91%) improved functional leg muscle strength. Squat series performance increased 30%, calf raises 45%, and lunges 23%. CONCLUSIONS: Anti-gravity training improved closed-kinetic-chain leg muscle strength despite no changes in isometric knee extension strength and absolute RFD. The improved closed-kinetic-chain performance may relate to neural adaptation involving motor learning and/or improved muscle strength of other muscles than the weak knee extensors. Muscle Nerve 54: 239-243, 2016.

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Recent studies indicate that the effect of training on motor performance in persons with Parkinson's disease (PDP) is dependent on motor intensity. However, training of high motor intensity can be hard to apply in PDP due to e.g. bradykinesia, rigidity, tremor and postural instability. Therefore, the aim was to study the effect of motor intensive training performed in a safe anti-gravity environment using lower-body positive pressure (LBPP) technology on performance during dynamic balance related tasks. Thirteen male PDP went through an 8-week control period followed by 8 weeks of motor intensive antigravity training. Seventeen healthy males constituted a control group (CON). Performance during a five repetition sit-to-stand test (STS; sagittal plane) and a dynamic postural balance test (DPB; transversal plane) was evaluated. Effect measures were completion time, functional rates of force development, directional changes and force variance. STS completion time improved by 24% to the level of CON which was explained by shorter sitting-time and standing-time and larger numeric rate of force change during lowering to the chair, indicating faster vertical directional change and improved relaxation. DPB completion time tended to improve and was accompanied by improvements of functional medial and lateral rates of force development and higher vertical force variance during DPB. Our results suggest that the performance improvements may relate to improved inter-limb coordination. It is concluded that 8 weeks of motor intensive training in a safe LBPP environment improved performance during dynamic balance related tasks in PDP.

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BACKGROUND: Critical illness is associated with muscle weakness leading to long-term functional limitations. OBJECTIVES: To assess the reliability of a novel method for evaluating fatigability of the quadriceps muscle in noncooperating healthy subjects. METHODS: On two occasions, separated by seven days, nonvoluntary isometric contractions (twitch and tetanic) of the quadriceps femoris muscle evoked by transcutaneous electrical muscle stimulation were recorded in twelve healthy adults. For tetanic contractions, the Fatigue Index (ratio of peak torque values) and the slope of the regression line of peak torque values were primary outcome measures. For twitch contractions, maximum peak torque and rise time were calculated. Relative (intraclass correlation, ICC3.1) and absolute (standard error of measurement, SEM) reliability were assessed and minimum detectable change was calculated using a 95% confidence interval (MDC95%). RESULTS: The Fatigue Index (ICC3.1, 0.84; MDC95%, 0.12) and the slope of the regression line (ICC3.1, 0.99; MDC95%, 0.03) showed substantial relative and absolute reliability during the first 15 and 30 contractions, respectively. CONCLUSION: This method for assessing fatigability of the quadriceps muscle produces reliable results in healthy subjects and may provide valuable data on quantitative changes in muscle working capacity and treatment effects in patients who are incapable of producing voluntary muscle contractions.

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This study examined the ability of the Acti4 software for identifying physical activity types from accelerometers during free-living with different levels of movement complexity compared with video observations. Nineteen aircraft cabin cleaners with ActiGraph GT3X+ accelerometer at the thigh and hip performed one semi-standardised and two non-standardised sessions (outside and inside aircraft) with different levels of movement complexity during working hours. The sensitivity for identifying different activity types was 75.4-99.4% for the semi-standardised session, 54.6-98.5% outside the aircraft and 49.9-90.2% inside the aircraft. The specificity was above 90% for all activities, except 'moving' inside the aircraft. These findings indicate that Acti4 provides good estimates of time spent in different activity types during semi-standardised conditions, and for sitting, standing and walking during non-standardised conditions with normal level of movement complexity. The Acti4 software may be a useful tool for researchers and practitioners in the field of ergonomics, occupational and public health. Practitioner Summary: Being inexpensive, small, water-resistant and without wires, the ActiGraph GT3X+ by applying the Acti4 software may be a useful tool for long-term field measurements of physical activity types for researchers and practitioners in the field of ergonomics, occupational and public health.

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Local dynamic stability has been assessed by the short-term local divergence exponent (λS), which quantifies the average rate of logarithmic divergence of infinitesimally close trajectories in state space. Both increased and decreased local dynamic stability at faster walking speeds have been reported. This might pertain to methodological differences in calculating λS. Therefore, the aim was to test if different calculation methods would induce different effects of walking speed on local dynamic stability. Ten young healthy participants walked on a treadmill at five speeds (60%, 80%, 100%, 120% and 140% of preferred walking speed) for 3min each, while upper body accelerations in three directions were sampled. From these time-series, λS was calculated by three different methods using: (a) a fixed time interval and expressed as logarithmic divergence per stride-time (λS-a), (b) a fixed number of strides and expressed as logarithmic divergence per time (λS-b) and (c) a fixed number of strides and expressed as logarithmic divergence per stride-time (λS-c). Mean preferred walking speed was 1.16±0.09m/s. There was only a minor effect of walking speed on λS-a. λS-b increased with increasing walking speed indicating decreased local dynamic stability at faster walking speeds, whereas λS-c decreased with increasing walking speed indicating increased local dynamic stability at faster walking speeds. Thus, the effect of walking speed on calculated local dynamic stability was significantly different between methods used to calculate local dynamic stability. Therefore, inferences and comparisons of studies employing λS should be made with careful consideration of the calculation method.

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The purpose of the present study was to investigate muscle mechanical properties and mechanical interaction between muscles in the lower hindlimb of the spastic mutant rat. Length-force characteristics of gastrocnemius (GA), soleus (SO), and plantaris (PL) were assessed in anesthetized spastic and normally developed Han-Wistar rats. In addition, the extent of epimuscular myofascial force transmission between synergistic GA, SO, and PL, as well as between the calf muscles and antagonistic tibialis anterior (TA), was investigated. Active length-force curves of spastic GA and PL were narrower with a reduced maximal active force. In contrast, active length-force characteristics of spastic SO were similar to those of controls. In reference position (90° ankle and knee angle), higher resistance to ankle dorsiflexion and increased passive stiffness was found for the spastic calf muscle group. At optimum length, passive stiffness and passive force of spastic GA were decreased, whereas those of spastic SO were increased. No mechanical interaction between the calf muscles and TA was found. As GA was lengthened, force from SO and PL declined despite a constant muscle-tendon unit length of SO and PL. However, the extent of this interaction was not different in spastic rats. In conclusion, the effects of spasticity on length-force characteristics were muscle specific. The changes observed for GA and PL muscles are consistent with the changes in limb mechanics reported for human patients. Our results indicate that altered mechanics in spastic rats cannot be attributed to differences in mechanical interaction, but originate from individual muscular structures.

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Intense neuromuscular blockade (NMB) measured by post tetanic count (PTC) was monitored, reversed and verified in this pig model. In a cross-over assessor blinded design six pigs were randomized to either no NMB followed by intense NMB, or intense NMB followed by no NMB. Neuromuscular measurements were performed with acceleromyography [train-of-four (TOF) Watch SX]. In all pigs, the response to TOF nerve stimulation was stable and intense NMB (PTC 0-1) was established with rocuronium 3 mg/kg. For reversal, the pigs received sugammadex 20-35 mg/kg and returned to TOF-ratio above 0.90 within 2.15 min after injection. We established a pig model for monitoring intense NMB with surface stimulation electrodes and acceleromyography. We verified total relaxation of the diaphragm and the abdominal muscles at the PTC 0-1 by suction test and with surface electromyography. This pig model is suitable for studies with experimental abdominal surgery with monitoring of intense NMB, and where relaxation of the diaphragm and the abdominal muscles are required.

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INTRODUCTION: We investigated muscle activation strategy and performance of knee extensor and flexor muscles in children and adults with generalized joint hypermobility (GJH) and compared them with controls. METHODS: Muscle activation, torque steadiness, electromechanical delay, and muscle strength were evaluated in 39 children and 36 adults during isometric knee extension and flexion. Subjects performed isometric maximum contractions, submaximal contractions at 25% maximum voluntary contraction (MVC), and explosive contractions. RESULTS: Agonist activation was reduced, and coactivation ratio was greater in GJH during knee flexion compared with controls. Torque steadiness was impaired in adults with GJH during knee flexion. No effect of GJH was found on muscle strength or electromechanical delay. Correlation analysis revealed an association between GJH severity and function in adults. CONCLUSIONS: The results indicate that muscle activation strategy and quality of force control were significantly affected in adults with GJH during knee flexion, whereas only muscle activation strategy was affected in children with GJH.

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The aim of this study was to investigate the effect of high-intensity locomotor training on knee extensor and flexor muscle activation and adaptability to increased body-weight (BW) support during walking in patients with Parkinson's disease (PD). Thirteen male patients with idiopathic PD and eight healthy participants were included. The PD patients completed an 8-week training program on a lower-body, positive-pressure treadmill. Knee extensor and flexor muscles activation during steady treadmill walking (3 km/h) were measured before, at the mid-point, and after training. Increasing BW support decreased knee extensor muscle activation (normalization) and increased knee flexor muscle activation (abnormal) in PD patients when compared to healthy participants. Training improved flexor peak muscle activation adaptability to increased (BW) support during walking in PD patients. During walking without BW support shorter knee extensor muscle off-activation time and increased relative peak muscle activation was observed in PD patients and did not improve with 8 weeks of training. In conclusion, patients with PD walked with excessive activation of the knee extensor and flexor muscles when compared to healthy participants. Specialized locomotor training may facilitate adaptive processes related to motor control of walking in PD patients.

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OBJECTIVE: To describe CT image reconstruction criteria for measurement of the tibial tuberosity-trochlear groove (TT-TG) offset distance, evaluate intra- and inter-reconstruction repeatability, and identify key sources of error in the measurement technique, as determined in vulpine hind limbs. ANIMALS: 12 red fox (Vulpes vulpes) cadavers. PROCEDURES: CT images of each hind limb in intact cadavers were obtained; at 1-week intervals, 3 reconstructions were performed that were based on 1 plane passing through the centers of the femoral head and medial condyle and parallel to the caudal femoral condyles, 1 plane aligned with the femoral trochlea, and a third orthogonal plane. Randomized and anonymized reconstructions were assessed for TT-TG offset distance with a single-image technique by 1 observer, and inter-reconstruction repeatability and intra- and inter-reconstruction measurement repeatability were assessed via the repeatability coefficient and intraclass correlation coefficient. RESULTS: Multiplanar reconstructions of hind limb images were repeatedly made to within a few degrees of each other. Intra- and inter-reconstruction repeatability for TT-TG offset distance measurement was good. Repeatability was most affected by accurate identification of the tibial tuberosity and femoral trochlea landmarks. CONCLUSIONS AND CLINICAL RELEVANCE: Results obtained from vulpine hind limb CT images indicated that reconstructions can be made with a high degree of repeatability when based on strictly defined and applied criteria. The TT-TG offset distance has potential as an objective assessment of alignment of the distal portion of the quadriceps mechanism; its use as an aid in case selection for corrective femoral osteotomy among dogs with medial patellar luxation warrants investigation.

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We investigated lower-extremity isometric tremor Approximate Entropy (irregularity), torque steadiness and rate of force development (RFD) and their associations to muscle activation strategy during isometric knee extensions in patients with Parkinson's disease (PD). Thirteen male patients with idiopathic PD and 15 neurologically healthy matched controls performed isometric maximal contractions (extension/flexion) as well as steady submaximal and powerful isometric knee extensions. The patients with PD showed decreased isometric tremor irregularity. Torque steadiness was reduced in PD and the patients had increased muscle coactivation. A markedly lower RFD was found in PD and the decreased RFD correlated with reduced agonist muscle activation. Furthermore, patient RFD correlated with the Movement-Disorder-Society-Unified-Parkinson's-Disease-Rating-Scale 3 (motor part) scores. We concluded that both knee isometric tremor Approximate Entropy and torque steadiness clearly differentiate between patients with PD and healthy controls. Furthermore, severely compromised RFD was found in patients with PD and was associated with decreased agonist muscle activation.

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OBJECTIVE: To evaluate the effect of body weight-supported progressive high-intensity locomotor training in Parkinson's disease (PD) on (1) clinical status; (2) quality of life; and (3) gait capacity. DESIGN: Open-label, fixed sequence crossover study. SETTING: University motor control laboratory. PARTICIPANTS: Patients (N=13) with idiopathic PD (Hoehn and Yahr stage 2 or 3) and stable medication use. INTERVENTIONS: Patients completed an 8-week (3 × 1h/wk) training program on a lower-body positive-pressure treadmill. Body weight support was used to facilitate increased intensity and motor challenges during treadmill training. The training program contained combinations of (1) running and walking intervals, (2) the use of sudden changes (eg, in body weight support and speed), (3) different types of locomotion (eg, chassé, skipping, and jumps), and (4) sprints at 50 percent body weight. MAIN OUTCOME MEASURES: The Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Parkinson's Disease Questionnaire-39 items (PDQ-39), and the six-minute walk test were conducted 8 weeks before and pre- and posttraining. RESULTS: At the end of training, statistically significant improvements were found in all outcome measures compared with the control period. Total MDS-UPDRS score changed from (mean ± 1SD) 58±18 to 47±18, MDS-UPDRS motor part score changed from 35±10 to 29±12, PDQ-39 summary index score changed from 22±13 to 13±12, and the six-minute walking distance changed from 576±93 to 637±90m. CONCLUSIONS: Body weight-supported progressive high-intensity locomotor training is feasible and well tolerated by patients with PD. The training improved clinical status, quality of life, and gait capacity significantly.

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OBJECTIVES: ICU admission is associated with decreased physical function for years after discharge. The underlying mechanisms responsible for this muscle function impairment are undescribed. The aim of this study was to describe the biomechanical properties of the quadriceps muscle in ICU survivors 12 months after ICU discharge. DESIGN: Case-control study with consecutive inclusion of ICU survivors and age- and sex-matched controls. SETTING: Patients were treated at a mixed 18-bed ICU at a tertiary care university hospital and tested at a biomechanical university laboratory. PATIENTS: We included 16 male ICU patients (Acute Physiology and Chronic Health Evaluation II score 20 ± 7, mean ± SD), who had stayed in the ICU >72 hrs and survived to 12 months and 15 age- and sex-matched controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: An extensive battery of biomechanical tests, including maximum, fast, and endurance contractions, was administered during isometric knee extensions while simultaneously recording surface electromyography (quadriceps and hamstrings). Compared to controls, ICU survivors had reduced maximal voluntary torque (22%, 179 ± 64 Nm vs. 230 ± 57 Nm, p = 0.03), absolute rate of force development (50%, 868 ± 372 Nm/sec vs. 1739 ± 470 Nm/sec, p < 0.001) and relative rate of force development (32%, 512 ± 260% maximum voluntary contraction/sec vs. 754 ± 189% maximum voluntary contraction/sec, p < 0.01), and endurance time (40%, 136 ± 84 sec vs. 226 ± 111 sec, p < 0.02). Rate of force development, but not maximal voluntary torque, was significantly reduced after adjusting for muscle mass. Electromyography data indicated no impairment of motor activation strategy or central motor drive. Also, no difference in reaction time was found between patients and controls. CONCLUSIONS: ICU survivors had reduced rate of force development and muscular endurance 1 yr after ICU discharge. Our data indicate that the functional deficits experienced by ICU survivors originate in muscle tissue rather than the nervous system. Also, increased attention to velocity-orientated exercise during rehabilitation of ICU patients may have the potential to better physical outcome after critical illness.

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