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The purpose of this study was to compare the effects of a task-oriented exercise program with and without altered sensory input on postural stability in subjects with stroke. Sixteen hemiparetic subjects, at least 6 months post-stroke, were randomly assigned to the experimental or control group, and participated in an 8-week task-oriented exercise program focusing on balance and mobility exercises. Exercises were performed under normal conditions by the control group, and under conditions of vision and surface manipulation by the experimental group. Pre- and post-test assessments involved the measurement of the center of pressure (COP) displacement during double-legged stance and sit-to-stand under four sensory conditions: (1) eyes open, normal surface; (2) eyes open, soft surface; (3) eyes closed, normal surface; and (4) eyes closed, soft surface, as well as the 10-m walking test. Results showed significant improvements (P<0.05) in COP displacement under sensory conditions (1) and (2) for the experimental group only, and limited changes for the sit-to-stand in both groups after training. Significant improvements (P<0.05) were also found in both groups for the walking test. It is concluded that a task-oriented exercise program, assisted by sensory manipulation, is more effective at improving the standing balance of stroke subjects than a conventional task-oriented program. [ABSTRACT FROM AUTHOR]

Objective: Patellofemoral dysfunctions are associated with problems in the knee extensor mechanism, including specific atrophy of the distal fibers of the vastus medialis, also known as the vastus medialis oblique. Rehabilitation of the vastus medialis in patellofemoral dysfunctions has been shown to be ineffective. This limitation had stemmed from the lack of understanding of the vastus medialis' specific functions. The purpose of this project was to investigate the role of four portions of the quadriceps femoris using surface electrical stimulation. Design and Setting: Single-group and single-test (repeated measures on muscle portions) design. All tests were performed in a university laboratory. Subjects: Eight healthy university students received electrical stimulation. Measurements: Subjects were seated with the knee at 90 degrees of flexion and the leg pushing against a strain gauge that measured the force exerted. Electrical stimulation was administered on the vastus lateralis, rectus femoris, and proximal and distal fibers of the vastus medialis to quantify the torque produced by the knee extensors. The electrical stimulation maximum intensity was adjusted to achieve specific fiber recruitment and the highest isolated contraction. Force was measured with a strain gauge placed on the anterior aspect of the distal end of the tibia. Force was recorded in two levels: force applied before the onset of electrical stimulation and force produced by the stimulation. Subjects also performed two maximum isometric knee extensions before and after electrical stimulation for normalization. Results: Electrical stimulation elicited mean torques of 6.31%, 14.0%, 20.2%, and 28.0% of maximum isometric voluntary contractions of the distal and proximal fibers of the vastus medialis, the vastus lateralis, and rectus femoris, respectively. Conclusions: The distal fibers of the vastus medialis do not contribute significantly to knee extension. [ABSTRACT FROM AUTHOR]

Ground reaction forces (GRF) have been widely studied in football to prevent injury. However, ambulatory tools are missing, posing methodological limitations. The purpose of this study was to assess the validity of an innovative football shoe measuring normal GRF (nGRF) directly on the field through instrumented studs. A laboratory-based experiment was first conducted to compare nGRF obtained with the instrumented shoe (IS) to vertical GRF (vGRF) obtained with force platform (FP) data, the gold standard to measure vGRF. To this aim, three subjects performed 50 steps and 18 counter-movement jumps (CMJs). Secondly, eleven subjects completed running sprints at different velocities on a football field, as well as CMJs, while wearing the IS. Good to excellent agreement was found between the vGRF parameters measured with the FP and the nGRF measured by the IS (ICC > 0.75 for 9 out of 11 parameters). Moreover, on-field nGRF patterns demonstrated a progressive and significant increase in relation with the running velocity (p < 0.001). This study demonstrated that the IS is a highly valid tool to assess vGRF patterns on a football field. This innovative way to measure vGRF in situ could give new insights to quantify training load and detect neuromuscular fatigue., Competing Interests: The authors declare no conflicts of interest.

The cobra wave is a popular physical phenomenon arising from the explosion of a metastable grillage made of popsicle sticks. The sticks are expelled from the mesh by releasing the elastic energy stored during the weaving of the structure. Here we analyze both experimentally and theoretically the propagation of the wave front depending on the properties of the sticks and the pattern of the mesh. We show that its velocity and its shape are directly related to the recoil imparted to the structure by the expelled sticks. Finally, we show that the cobra wave can only exist for a narrow range of parameters constrained by gravity and rupture of the sticks.

Methods for analysing dental caries and associated risk indicators have evolved considerably in recent decades. The use of zero-inflated or hurdle models is increasing so as to take account of the decayed, missing, and filled teeth (DMFT) distribution, which is positively skewed and has a high proportion of zero scores. However, there is a need to develop new statistical models that involve pragmatic biological considerations on dental caries in epidemiological surveys. In this paper, we show that the zero-inflated and the hurdle models can both be expressed as a compound sum. Using the same compound sum, we then present the generalized negative binomial (GNB) distribution for dental caries count data, and provide a numerical application using the data of the EPIPAP study. The GNB model generates the best score functions while handling the lifetime dental caries disease process better. In conclusion, the GNB model suits the nature of some count data, in particular when structural zeros are unlikely to occur and when several latent spells can lead to new countable events. For these reasons, the use of the GNB distribution appears to be relevant for the modelling of dental caries count data., (© 2016 S. Karger AG, Basel.)

Objective: The purpose of this study was to evaluate the effects of chiropractic manipulative treatment on paraspinal cutaneous temperature (PCT) for subjects with chronic low back pain and compare these PCT findings to subjects without chronic low back pain., Methods: Two groups were created, a symptomatic treatment group (subjects with chronic low back pain, n = 11, 7 males, 4 females) and an asymptomatic, nontreatment group (asymptomatic subjects, n = 10, 6 males, 4 females). Outcomes included the modified Oswestry questionnaire and PCT measurements in the prone position after an 8-minute acclimation period. The treatment group received 9 chiropractic spinal instrument-based manipulative treatments over 2 weeks. Reevaluation was done 2 weeks after the initial evaluation for both groups., Results: The preintervention Oswestry results (29.8% ± 11.8%) for the treatment group were higher than the asymptomatic group (10.2% ± 10.6%). The postintervention Oswestry results for the treatment group were 14.20 % ± 11.5%. The resulting Cohen's effect size of the spinal manipulation on the Oswestry evaluation is 0.58. The preintervention PCT showed higher temperature for the nontreatment group compared with the treatment group. Comparing the levels associated with low back pain, the nontreatment group PCT was stable, varying from 0.01°C to 0.02°C, whereas the treatment group PCT varied from 0.10°C to 0.18°C. The treatment group postintervention PCT showed an increase in temperature after the 9 visits; however, this did not reach the values of the asymptomatic group., Conclusion: The PCT readings for subjects with chronic low back pain were lower than the asymptomatic, nontreatment group. The PCT temperature of the treatment group increased after 9 treatments., (Copyright © 2013 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.)

The goal of the present study was to investigate the effect of 30 min of electrical stimulation on the activation of lipolysis in human white adipocytes. Two stimulation protocols (S1, S2) were conducted in vitro on isolated human white adipocytes. Subcutaneous adipose tissue was obtained from female subjects undergoing abdominal adipose tissue reduction. Adipose tissue of 10 female subjects (mean age, 38.7 ± 9.1 years) and 6 female subjects (mean age, 37.2 ± 11.3 years) was obtained for S1 and S2, respectively. All subjects fasted overnight before tissue removal. The control conditions were a basal and a β-adrenergic stimulation (isoproterenol (ISO), 10(-6) mol·L(-1)) of lipolysis. For S1, the 3 electrostimulation conditions consisted of a monopolar square-wave pulse current for 30 min at intensities of 4, 8, and 20 mA, respectively. In S2, the 2 electrostimulation conditions consisted of a bipolar square-wave alternating current for 30 min at intensities of 4 and 6 mA, respectively. Fat cell lipolysis was measured by quantifying the release of glycerol from adipocytes for 3 trials in each experimental condition. For S1, 4 mA significantly increased lipolysis 1.5 times over basal values (p ≤ 0.01), 8 mA and 20 mA did not increase lipolysis significantly, and no significant difference (p > 0.05) was found between ISO and 4 mA. For S2, 4 mA (p ≤ 0.05) and 6 mA (p ≤ 0.01) significantly increased lipolysis by 1.8 and 2.3 times above basal, respectively. Our results demonstrate that both monopolar (4 mA) and bipolar (4 and 6 mA) electrical stimulations significantly activated in vitro lipolysis. Our findings suggest the existence of a new lipolytic pathway that may involve K(v) channels shown to exist in human white adipocytes.

Many European countries apply score systems to evaluate the disability severity of non-fatal motor victims under the law of third-party liability. The score is a non-negative integer with an upper bound at 100 that increases with severity. It may be automatically converted into financial terms and thus also reflects the compensation cost for disability. In this paper, standard and zero-altered discrete regression models are applied to model the disability severity score of victims. An application using data from Spain is provided in which the hurdle-Negative Binomial regression was the preferred method. The effects of victims' characteristics, type of road user and recovery duration are examined. The results suggest that the expected permanent disability severity is higher for older women with long recovery periods. The results provide traffic decision makers with a model to quantify the compensation cost savings due to disability severity reductions., (2010 Elsevier Ltd. All rights reserved.)

Objective: Inflammatory markers interleukin-6 (IL-6) and C-reactive protein (CRP) have not been evaluated in response to a short course of lumbar spinal manipulation. The purpose of this study is to observe the responses of inflammatory markers (IL-6 and CRP) after a series of 9 chiropractic spinal manipulations., Methods: Twenty-one participants were assigned to a treatment or a control group. Only the treatment group received 9 chiropractic interventions. Pre- and postintervention measures were recorded for blood samples for detection of proinflammatory cytokines IL-6 and CRP., Results: Mediators of inflammation (IL-6 and high-sensitivity CRP) were modified by the intervention received in the treatment group, and the effect size demonstrated a tendency toward the control group values., Conclusion: A total of 9 chiropractic lower back manipulations caused the mediators of inflammation to present a normalization response in individuals suffering from chronic low back pain., (Copyright © 2010 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this study was to investigate local paraspinal cutaneous temperature (CT) modifications after spinal manipulative therapy at L5., Methods: Twenty subjects with acute low back symptoms were randomly assigned to either a treatment or a sham group (n = 10 per group). Subjects underwent an 8-minute acclimatizing period. Temperature was measured bilaterally with infrared cameras at the L5 level. In the treatment group, a traditional chiropractic manipulation (lumbar roll technique with a pisiform contact on the ipsilateral mamillary of L5) was delivered, whereas with the sham group, the same technique was used, but no thrust was applied. Cutaneous temperature control measurements were taken 2 minutes before (t(-2)) and immediately after the intervention (t(0)) and at 1, 3, 5, and 10 minutes postintervention (t(1), t(3), t(5), and t(10), respectively)., Results: At t(0), CT in the treatment group on the treatment side (ipsilateral side) warmed up by 0.2 degrees F, whereas in the sham group, there were no significant temperature modifications on either side. At t(3) relative to t(0), CT in the treatment group on the treatment side warmed by approximately 0.6 degrees F, whereas the contralateral side (nontreatment side) cooled. In the treatment group, significant differences were noted between sides (F = 13.36, P = .002, P = .932) and sides x times (F = 2.97, P = .016, P = .838)., Conclusion: The effects of a lumbar spine manipulation appear noticeable by changes in paraspinal CT measurements at the level of L5. However, the meaning and mechanisms of CT modifications at L5 are still being investigated.

Objective: The goal of this pilot study was to measure paraspinal cutaneous temperature (PCT) in the prone vs standing position., Methods: Ten symptom-free participants were evaluated. Paraspinal cutaneous temperature was recorded. Subjects were acclimated to the treatment room in a prone position for 8 minutes before the PCT was measured. After the prone PCT reading, patients stood. A standing PCT measurement was then taken., Results: Paraspinal cutaneous temperature was marginally warmer when subjects were standing vs prone (PCT difference, 0.25 degrees C +/- 0.64 degrees C and 0.62 degrees C +/- 0.67 degrees C for left and right sides, respectively). The right and left side differential was the same in the prone and standing positions. There was a positive Pearson correlation (0.802-0.803; P < .000) between the standing and prone positions for both left and right sides., Conclusion: There are no differences between the prone or standing PCT measures if symptom-free subjects are given 8 minutes to acclimate before recording PCT measures., (Copyright 2010 National University of Health Sciences. Published by Mosby, Inc. All rights reserved.)

Background: The purpose of this study was to examine heart rate variability (HRV) in the presence or the absence of pain in the lower back, while receiving one chiropractic treatment at L5 from either a manually assisted mechanical force (Activator) or a traditional diversified technique spinal manipulation., Methods: A total of 51 participants were randomly assigned to a control (n = 11), 2 treatment, or 2 sham groups (n = 10 per group). Participants underwent an 8-minute acclimatizing period. The HRV tachygram (RR interval) data were recorded directly into a Suunto watch (model T6; FitzWright Company Ltd, Langley, British Columbia, Canada). We analyzed the 5-minute pretreatment and posttreatment intervals. The spectral analysis of the tachygram was performed with Kubios software., Results: All groups decreased in value except the control group that reacted in the opposite direction, when comparing the pretests and posttests for the high-frequency component. The very low frequency increased in all groups except the control group. The low frequency decreased in all groups except the sham pain-free group. The low frequency-high frequency ratio decreased in the treatment pain group by 0.46 and in the sham pain-free group by 0.26. The low frequency-high frequency ratio increase was 0.13 for the sham pain group, 0.04 for the control group, and 0.34 for the treatment pain-free group. The mean RR increased by 11.89 milliseconds in the sham pain-free group, 18.65 milliseconds in the treatment pain group, and 13.14 milliseconds in the control group. The mean RR decreased in the treatment pain-free group by 1.75 milliseconds and by 0.01 milliseconds in the sham pain group., Conclusion: Adjusting the lumbar vertebrae affected the lumbar parasympathetic nervous system output for this group of participants. Adaptation in the parasympathetic output, reflected by changes in high frequency, low frequency, and very low frequency, may be independent of type of adjustment. Therefore, the group differences found in the modulation of the HRV would seem to be related to the presence or absence of pain. The autonomic nervous system response may be specific and sensitive to its effectors organ.

Objective: Digitized infrared segmental thermometry (DIST) is a tool used for measuring cutaneous temperature (CT). This project ascertains the effect of a manually assisted mechanical force producing a chiropractic adjustment in the lumbar spine after the Activator Methods Chiropractic Technique on CT during 2 different time recording periods (TRPs)., Methods: Sixty-six healthy subjects (36 women and 30 men) without acute low back conditions or symptoms were recruited. Subjects were randomly divided into 2 groups based on the length of the acclimatization period (8 or 30 minutes; TRP(8) and TRP(30), respectively). In turn, each recording period group was divided into 3 subgroups (n = 11 per subgroup): treatment, sham, and control subgroups. Bilateral DIST was conducted at L-4 (TRP(30)) and L-5 (TRP(8)) using infrared cameras (Subluxation Station Insight 7000; Chiropractic Leadership Alliance, Mahwah, NJ)., Results: Before treatment (t(-0.5)), the TRP(8) CT was significantly different between the ipsilateral and the contralateral sides for all subgroups. At 10 minutes (t(10)) after intervention, CT increased significantly (P < .05) for the treatment group but not for the sham and control groups. In contrast, there were no significant differences in the TRP(30) CT before treatment between the ipsilateral and the contralateral sides; but at t(10), CT was significantly (P < .05) greater for all 3 subgroups compared with preintervention CT., Conclusion: Contacting the skin with the instrument with (treatment group TRP(30)) or without (sham group TRP(30)) a thrust with a sustained pressure stronger than the loading principle taught in the Activator Methods Chiropractic Technique protocol or a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument produced a CT cooling immediately after the adjustment. Furthermore, we observed that when contacting the skin with the instrument with a thrust respecting the standard loading principle (treatment group TRP(8)) of the instrument, it produced a secondary cooling at t(5) followed by a rewarming at t(10). Finally, contacting the skin with the instrument without a thrust and respecting the standard loading principle (sham TRP(8)) of the instrument did not produce a CT change.

Objectives: Digitized infrared segmental thermometry (DIST) is a method for measuring and recording skin surface body temperatures. The project evaluated the required length of time for patients to acclimatize their core body temperature to ambient conditions to obtain stable DIST readings., Methods: Seventeen subjects were allowed a 20-minute acclimatizing period in a temperature-controlled room. The bilateral DIST temperature was measured with thermistors in combination with infrared cameras (IRCs) at the C4 and L4 levels. All IRC temperatures were recorded after a 20-minute stabilization period. The room temperature and relative humidity were recorded throughout all trials. The acclimatization trend was computed from the 20- to 24-minute period for the IRCs, and the acclimatization trend was computed continuously for a total of 30 minutes (at 2-minute intervals) for 5 days., Results: We discovered a stabilization trend in the early trial stages, with the thermistor recordings between 8 and 16 minutes. The IRC trend was also conclusive for the core temperature requirements., Conclusions: This study determined a core body temperature acclimatization trend tested among patients using thermistor recordings in a controlled environment. Based on these findings, we recommend acclimatization in a temperature- and humidity-controlled environment for a minimum 8-minute period, followed by an 8-minute maximum recording period with the patient in a prone position to obtain accurate DIST recordings.

Objective: The purpose of this study was to evaluate the validity of thermal measurements by infrared camera thermometry., Methods: Seventeen subjects underwent a 30-minute acclimatizing period in a controlled environment room. Thermal recordings were executed at the levels of C4 and L4. Fifteen recordings per segment were acquired in an alternating mode that always started at L4. Each subject was required to participate on 5 occasions. The exclusion criteria for the subjects included the following: no inflammatory disease or fever, no consumption of beverages containing caffeine, and no participation in physical activity 2 hours before the recording session; female subjects could not be menstruating on a day of recording., Results: A total of 2550 recordings for the cervical area and the lumbar area was recorded. Strong significant correlations were found for the left (r = .77) and right (r = .71) lumbar sections (P < .0001) whereas weaker significant correlations were observed for the left (r = .56) and right (r = .63) cervical areas (P < .0001). The limits of agreement (Bland-Altman) showed good relationships but poor interchangeability., Conclusions: In this study, the infrared cameras showed that they were valid tools in a controlled environment; however, the technique for the cervical measurements needs to be reassessed.

Objective: To provide an electrophysiological and functional description of the vastus medialis (VM) and contrast it to an anatomical description., Methods: Motor points of all superficial portions of the quadriceps were identified on the dominant side of 8 human subjects and electrically stimulated to achieve a light contraction to trace and measure the orientation of the fibers. Electromyography of the VM was then recorded over 2 motor points during isometric and isokinetic maximum knee extensions. An independent laboratory dissected 39 cadaveric specimens focusing on fiber orientations and distal insertions of the VM., Results: Results revealed 5 motor points for the quadriceps: 1 point for the vastus lateralis, 1 point for the rectus femoris (RF), and 3 points for the VM. The 3 VM motor points suggest 3 separate groups of fibers: proximal (pf), median (mf), distal (df). Fiber orientations ranged from 45 degrees for VMpfs to 55 degrees for VMdfs. Motor point stimulation and anatomical dissection clearly showed that the VMpfs and VMmfs were inserted on a tendon common to the RF, whereas VMdfs were attached directly to the medial aspect of the patella. Furthermore, the VMpfs were more active (P < .05) than VMdfs during maximum knee extensions., Conclusion: The anatomy, motor points, and electromyography clearly support an important distinction between the VMpfs and VMdfs. The role of the VMpfs would be one of assisting the RF in knee extension, whereas the VMdfs would track the patella medially without participating in knee extension. Because of these anatomical and functional differences, the VMpfs and VMdfs should be addressed very differently during quadriceps rehabilitation in patellofemoral dysfunctions.

Field-induced magnetic order has been investigated in detail in the interacting spin 3/2 dimer system Cs3Cr2Br9. Elastic and inelastic neutron scattering measurements were performed up to H=6 T, well above the critical field H(c1) approximately 1.5 T. The ordering displays incommensurabilities and a large hysteresis before a commensurate structure is reached. This structure is fully determined. Surprisingly, the lowest excitation branch never closes. Above H(c1), the gap increases slowly with the field. An analysis in terms of projected pseudospins is given.

Background: Motor evoked potentials (MEPs) obtained from magnetic stimulation allow the measurement of the excitability of motor nerve cells. Although this technique is becoming widely used, its reliability has yet to be established., Objective: To determine the reliability of MEPs and evaluate their stability., Design: Subjects received magnetic stimulation at 3 different sites: cranial, cervical, and peripheral. Three stimulations were given at each site. Stimulations were given under 4 conditions: eyes open or closed and with or without controlled mental activity., Setting: The study was performed in a research laboratory setting., Participants: Nine healthy subjects (mean age = 21 years +/- 0.9), asymptomatic of any neural or musculoskeletal dysfunctions., Main Outcome Measures: Normalized peak-to-peak amplitude of MEPs at the opponens pollicis muscle., Results: Intraclass correlations were high for all conditions (R > 0.90). The amplitude of the MEPs elicited from the transcranial site during the controlled mental activity condition was increased by 26.6% (P =.017). No other significant differences (P >.05) were obtained among the other conditions., Conclusion: Intraclass correlation results reveal that MEP measurements are highly reliable in a controlled environment. The increase of MEPs during the controlled mental activity condition could be attributed to an elevation of neural activity of different nonmotor areas of the brain increasing corticospinal excitability.

Objective: To quantify changes of evoked stretch responses (ESR) in the most rigid arm of patients with Parkinson's disease (PD) after Trager therapy., Methods: Gentle rocking motion associated with this type of manual therapy was imparted to the upper limbs and body of 30 patients for 20 minutes. A pretest and 2 posttests (at 1 and 11 minutes after the treatment, respectively) were performed, consisting of electromyographic (EMG) recordings of the flexor carpi radialis and extensor digitorum communis while the patient's wrist was passively flexed and extended with an amplitude of 60 degrees and a frequency of 1 Hz. Patients received the treatment on the most rigid side of their bodies (ipsi-group) or on the contralateral side (contra-group). Half of patients in each group received the treatment while lying supine on a massage table (ipsi- and contra-supine) or sitting in a chair (ipsi- and contra-sitting)., Results: In general, the level of ESR were reduced by 36% immediately after treatment and remained 32% lower than pretest values 11 minutes after treatment (F = 41.45, P <.05). Patients who received the treatment lying supine benefited from a 42% reduction of ESR (F = 4.07, P <.05). The side on which the treatment was performed did not significantly influence the outcome of the treatment (F = 0.50, P >.05). However, post hoc analysis of the triple interaction (test x side x position) indicated that the sitting position was much less efficient for sustained contralateral effect (P >.05)., Conclusions: Results from the present study strongly suggest that it is possible to modify the level of ESR by using Trager therapy. This stretch reflex inhibition may induce a reduction of the muscle rigidity seen in these patients. The present results may eventually lead to the development of a specific complementary therapy for patients with Parkinson's disease and rigidity.

The Dzyaloshinski-Moriya interaction partially lifts the magnetic frustration of the spin-1/2 oxide SrCu(2)(BO(3))(2). It explains the fine structure of the excited triplet state and its unusual magnetic field dependence, as observed in previous ESR and new neutron inelastic scattering experiments. We claim that it is mainly responsible for the dispersion. We propose also a new mechanism for the observed ESR transitions forbidden by standard selection rules, which relies on an instantaneous Dzyaloshinski-Moriya interaction induced by spin-phonon couplings.

We report high-resolution neutron inelastic scattering experiments on the spin excitations of NaV(2)O(5). Below T(c), two branches with distinct energy gaps are identified. From the dispersion and intensity of the spin excitation modes, we deduce the precise zigzag charge distribution on the ladder rungs and the corresponding charge order: Delta(c) approximately 0.6. We argue that the spin gaps observed in the low-T phase of this compound are primarily due to the charge transfer.

The effect of practice on predicting elbow flexion movement time was studied. Participants (N = 18) performed 400 elbow flexion trials to a target in the horizontal plane. The trials were distributed equally over four sessions. The goal was to decrease the movement time (MT) for the same degree of accuracy. The electromyographic (EMG) activity of the biceps and triceps brachii was monitored with standard Beckman Ag/AgCl surface electrodes. The EMG measures formed two variable sets within one prediction equation. One variable set was composed of the onset of muscle activity relative to the start of movement (motor time) and the duration of muscle activity. The other variable set consisted of the mean amplitude value of the entire burst and of the first 30 ms (Q30) of activity. As the maximal speed of limb movement increased, the duration of muscle activity (motor time and EMG duration) decreased, and the magnitude of muscle activity (MAV and Q30) increased. Most of the change in the duration of muscle activity occurred in Session 1, while the magnitude of muscle activity continued to increase until Session 3. Multiple regression analysis revealed a cooperative strategy between the magnitude and duration of muscle activity. Early in learning, participants adjusted the magnitude of muscle activity to increase limb movement speed. As practice continued, alterations in the duration of muscle activity became more important, while the magnitude changes were less involved. Late in learning, both dimensions of muscle activity were used to decrease MT. We suggest that the interplay between the magnitude and duration of muscle activity may be due to: (a) cognitive factors related to the division of attention in a motor skill, (b) an increase in the frequency of motor unit firing that affects both dimensions of muscle activity, or (c) some combination of (a) and (b).

A "breather excitation" is observed directly by electron spin resonance in the quantum spin chain Cu benzoate, in which an unexpected field-induced gap has recently been found. The nonlinear field dependence of the resonance field agrees well with the formula based on a quantum sine-Gordon model. The power-law temperature dependence of the linewidth is observed in the gapless spinon regime while the width decreases exponentially for the gapped breather regime. In the intermediate range, a distinct anomaly is found, which is the manifestation of "the spinon-breather dynamical crossover."

Objective: To evaluate the influence of pelvic restraint on electromyographic activation (neural drive) of the lumbar extensor, gluteal, and hamstring muscles during submaximal dynamic lumbar extension in an upright seated position., Design: Randomized, balanced, crossover trial comparing the electromyographic activation of the lumbar, gluteal, and hamstring muscles during dynamic lumbar extension exercise with and without pelvic restraint., Setting: Research laboratory at a private research university., Subjects: Twelve apparently healthy men (ages 18 to 50 yrs)., Intervention: Dynamic lumbar extension exercises., Main Outcome Measure: Electromyographic recordings., Results: Pelvic restraint did not influence the relative activation of the lumbar, gluteal, or hamstring muscle groups (p< or =.05) during submaximal dynamic lumbar extension exercise. The relative activation of the gluteal muscles was significantly lower than that of the lumbar extensor and hamstring muscle groups., Conclusions: Pelvic restraint is not a requirement to promote neural drive to the lumbar musculature during submaximal dynamic lumbar extension exercise performed in an upright seated position. Submaximal lumbar extension exercise reduces the relative contribution of the gluteal muscles compared with a maximal voluntary isometric contraction.

The effect of repeated maximal effort isotonic contractions on electromechanical delay was studied. Over 4 days, 17 male subjects performed 400 rapid elbow flexion trials. The kinematics and surface electromyographic (EMG) activity of the biceps brachii of these subjects were recorded. The period from the onset of the EMG until the beginning of movement was defined as the electromechanical delay. The period from the beginning of movement until the end of the EMG was defined as the second component of the contraction. Over the 4 day period there was an increase in the speed of limb movement. The mean power frequency and the duration of the EMG during the electromechanical delay did not change, while the root-mean-square amplitude increased. The duration of the EMG during the second component of the contraction remained stable. The mean power frequency and the root-mean-square amplitude of the EMG during the second component of the contraction increased with the speed of limb movement. We conclude that the faster contractions were a result of changes in motor unit recruitment during the second component of the contraction, rather than in the electromechanical delay.

Objective: To measure the effects of manual segmental vibration (MSV) on motoneuron pool excitability., Methods: Seven healthy subjects were tested under five conditions: pretest, upholding static knee position (USKP), MSV, posttest 1 and posttest 2. Each test lasted 2 min, and a 2-min rest was given between pretest, USKP and MSV, whereas the last two tests were consecutive. Cutaneous pressure and vibration frequency were stabilized through training periods. The effects of MSV on motoneuron excitability were investigated by measuring the H-reflex peak-to-peak amplitude., Measures: The H-reflex and M response were taken from the medial gastrocnemius electromyogram and elicited every 7 sec by a 1 ms square wave pulses to the tibial nerve. Fifteen trials were recorded for each condition. Stimulation intensity was set at 10% (+/- 2.5%) of Mmax stimulus., Results: Repeated-measures analysis of variance comparing conditions revealed no significant differences in M response [F(4,24) = 2.37, p > .05, beta = .35]. H-reflex comparisons revealed significant differences [F(4,24) = 30.39, p < .05, beta = .01] between conditions. Duncan post hoc analysis showed that MSV produced the greatest inhibition (decreases 95%) and USKP also elicited a significant inhibition (decreases 41%)., Conclusions: The inhibition may be the result of the following mechanisms: the reflex inhibition, the implication of cutaneous afferences and the higher control mechanism. Because MSV produces a reduction in neuromuscular excitability, it could also play a role in predisposing the system for changes to occur and therefore be used as an adjunct for other therapeutic applications.

This study examined changes in antagonist timing and magnitude in response to ballistic elbow flexion practice. Seventeen men performed 400 ballistic elbow flexion trials to a target in the horizontal plane over 4 days of testing. A potentiometer and microswitch system at the elbow axis of rotation of a manipulandum recorded angular displacement and movement onset. Surface electrodes (Beckman Ag/AgCl) monitored the triceps brachii lateral head, and the electromyographic (EMG) signals were bandpassed between 20 and 300 Hz. The antagonist EMG burst was divided in two: early low-level activity (ANT1), and the large portion of the burst which occurs near target achievement (ANT2). Movement time decreased from 178 ms on the first test day to 136 ms on the last session. As practice improved the speed of limb movement, onset of the first component (ANT1) remained unchanged, while the second component (ANT2) started earlier. The magnitude of both portions of the antagonist burst increased from the first to last test day, but the change in ANT2 relative to ANT1 was more pronounced. These findings are used to explain discrepant observations in the literature for the temporal measure.

Objective: Determine the electrophysiological effects of anterior knee pain using monosynaptic and polysynaptic reflexes., Design: A pretest/posttest control group experimental design with repeated measures., Setting: All tests were performed in a university laboratory., Participants: Six subjects suffering from patello-femoral dysfunction (PFD) composed the experimental group. These patients were diagnosed and referred by medical and chiropractic doctors. Six healthy subjects were recruited for the control group., Intervention: Pain relief by cold application (10 minutes) on the knee., Main Outcome Measures: Monosynaptic reflex: H reflex of the superficial portions of the quadriceps femoris. Polysynaptic reflexes: nociceptive flexion response (NFR) of the long head of the biceps femoris., Results: Cold application, producing significant pain relief (p < 0.05), did not change H-reflex amplitude (p > 0.05) for both groups and did not show modulation of the NFR. However, the PFD group showed significantly lower pain (p < 0.05) and NFR thresholds (p < 0.05) than the control group. Finally, nociceptive stimulation was applied at the sural nerve during an isometric extension of the knee (20% of maximum electromyographic contraction). After this stimulation, uni-articular extensors, especially the distal fibers of the vastus medialis, showed a longer and stronger inhibition than the bi-articular rectus femoris., Conclusions: Pain episodes do not appear to affect monosynaptic responses. NFR threshold differences found between PFD and control group could be explained by the increased excitability of the nervous system in subjects experimenting painful bouts. Functional implications of these findings are discussed.

Objective: The aim of this article is to review the basic research concerned with force and fatigue induced by electrical stimulation. Specific reports on human and animal models are covered. Articles dealing with specific afflictions of the neuromuscular system are also reviewed., Data Sources: The main sources for article retrieval were the classic bibliographic data bases in the exercise, rehabilitation and physiological science fields such as Index Medicus and Medline. Indexing terms used included human and animal in conjunction with electrical stimulation, force and fatigue. Language and time constraints limited the search to French and English texts of this century. Proceedings of different electrical stimulation conferences were also covered., Study Selection: All authors had to approve the selection of the articles to be included in this review. The narrow scope of the review made it possible to include most of the articles investigated. Redundancy of information was the only rejection criterion., Data Extraction: Initially, the first author collated the articles and extracted the relevant data. This collation was then verified with respect to the original information and approved by all authors., Data Synthesis: Possible sites of the fatigue mechanisms may include the central nervous system, the peripheral nervous system, the neuromuscular junction, and the muscle excitation-contraction coupling. Even though not unanimous, data gathered from normal muscles seem to support that the major contributor to fatigue is the muscle fiber and not the nervous system or the neuromuscular junction. Other work involving paralyzed muscles suggest that electrically induced exercise alters the contractile properties of the muscle more specifically., Conclusions: It appears that muscle intracellular processes dominate the force decrease associated with muscular fatigue. Accordingly, when dealing with a problem involving loss of force and hyperfatigability, the metabolic aspects and muscle physiology should be prime considerations in choosing a therapeutic approach. The nervous and/or neuromuscular implications are, however, not to be discarded.

To elucidate and attempt to dissociate the two mechanisms, neuromuscular and mechanical, underlying patellofemoral pain syndrome, 18 subjects, divided into two groups based on a diagnosis of patellofemoral pain syndrome and the knee Q angle, were studied. The control group was asymptomatic and exhibited a normal Q angle (mean, 8.25 degrees), whereas the other group, diagnosed as patellofemoral pain syndrome patients, reported knee pain and had an above-normal Q angle (mean, 21.05 degrees). All subjects were tested for isometric maximum knee extension at 90 degrees, 30 degrees, and 15 degrees of knee flexion while they were seated in a special restraining chair. During testing, surface electromyography at the oblique and long fibers of the vastus medialis, and at the vastus lateralis were recorded along with the knee moment of force. The integrated electromyographic signals associated with the peak torque for all of the vastus muscles, along with the vastus medialis obliquus:vastus lateralis and vastus medialis longus:vastus lateralis activity ratios showed no significant differences between groups nor between the three angles, suggesting that all vasti measured were consistently active throughout the studied range of motion. This suggests that the neural drive was not affected in the patellofemoral pain syndrome patients. However, when the five patients showing the largest Q angles were isolated, they revealed a significantly smaller vastus medialis obliquus:vastus lateralis ratio when compared to the other group. The same ratio was also significantly smaller at 15 degrees compared to 90 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinematic and electromyographic (EMG) parameters were analyzed on phase plane diagrams of human stepping motions performed over an obstacle of varying height. A videomotion analysis system was used to record the displacement of 5 reflective markers placed on the subject's lower limb joints. Surface bipolar electrodes were placed on the rectus and biceps femoris muscles. Results revealed systematic differences in the EMG patterns of the rectus femoris between initial and subsequent trials in the 3 conditions of obstacle height. In the initial trials there was an episode of EMG activity right before or during the transition from knee flexion to extension. In the subsequent trials this episode was shifted toward maximum knee extension velocity, leaving a period of silence between the initial burst and this episode. On the other hand, the biceps femoris was rarely silent and particularly active during the flexion phase, reflecting its possible role in active knee flexion and postural control during the dynamic phase of stepping. The increase in phase plane size with obstacle height appears related to the amplitude of the initial EMG burst of the rectus femoris. Phase plane diagrams combined with EMG appear to be an appropriate approach to explore the dynamics of human movement strategies. The results suggest that control mechanisms for the flexion and extension phases are different and may be involved in fine tuning the stepping strategy for subsequent trials.