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PubMed1999

Identification of the cerebral loci processing human swallowing with H2(15)O PET activation.

Lesional and electrophysiological data implicate a role for the cerebral cortex in the initiation and modulation of human swallowing, and yet its functional neuroanatomy remains undefined. We therefore conducted a functional study of the cerebral loci processing human volitional swallowing with 15O-labeled water positron emission tomography (PET) activation imaging. Regional cerebral activation was investigated in 8 healthy right handed male volunteers with a randomized 12-scan paradigm of rest and water swallows (5 ml/bolus, continuous infusion) at increasing frequencies of 0.1, 0.2, and 0.3 Hz, which were visually cued and monitored with submental electromyogram (EMG). Group and individual linear covariate analyses were performed with SPM96. In five of eight subjects, the cortical motor representation of pharynx was subsequently mapped with transcranial magnetic stimulation (TMS) in a posthoc manner to substantiate findings of hemispheric differences in sensorimotor cortex activation seen with PET. During swallowing, group PET analysis identified increased regional cerebral blood flow (rCBF) (P < 0.001) within bilateral caudolateral sensorimotor cortex [Brodmann's area (BA) 3, 4, and 6], right anterior insula (BA 16), right orbitofrontal and temporopolar cortex (BA 11 and 38), left mesial premotor cortex (BA 6 and 24), left temporopolar cortex and amygdala (BA 38 and 34), left superiomedial cerebellum, and dorsal brain stem. Decreased rCBF (P < 0.001) was also observed within bilateral posterior parietal cortex (BA 7), right anterior occipital cortex (BA 19), left superior frontal cortex (BA 8), right prefrontal cortex (BA 9), and bilateral superiomedial temporal cortex (BA 41 and 42). Individual PET analysis revealed asymmetric representation within sensorimotor cortex in six of eight subjects, four lateralizing to right hemisphere and two to left hemisphere. TMS mapping in the five subjects identified condordant interhemisphere asymmetries in the motor representation for pharynx, consistent with the PET findings. We conclude that volitional swallowing recruits multiple cerebral regions, in particular sensorimotor cortex, insula, temporopolar cortex, cerebellum, and brain stem, the sensorimotor cortex displaying strong degrees of interhemispheric asymmetry, further substantiated with TMS. Such findings may help explain the variable nature of swallowing disorders after stroke and other focal lesions to the cerebral cortex.

Adult↗
PubMed2000

Responses to efferent activation and excitatory response-intensity relations of turtle posterior-crista afferents.

Multivariate statistical formulas were used to infer the morphological type and longitudinal position of extracellularly recorded afferents. Efferent fibers were stimulated electrically in the nerve branch interconnecting the anterior and posterior VIIIth nerves. Responses of bouton (B) units depended on their inferred position: BP units (near the planum semilunatum) showed small excitatory responses; BT units (near the torus) were inhibited; BM units (in an intermediate position) had a mixed response, including an initial inhibition and a delayed excitation. Calyx-bearing (CD-high) units with an appreciable background discharge showed large per-train excitatory responses followed by smaller post-train responses that could outlast the shock train by 100 s. Excitatory responses were smaller in calyx-bearing (CD-low) units having little or no background activity than in CD-high units. Excitatory response-intensity functions, derived from the discharge during 2-s angular-velocity ramps varying in intensity, were fit by empirical functions that gave estimates of the maximal response (r(MAX)), a threshold velocity (v(T)), and the velocity producing a half-maximal response (v(1/2)). Linear gain is equal to r(MAX)/v(S), v(S) = v(1/2) - v(T). v(S) provides a measure of the velocity range over which the response is nearly linear. For B units, r(MAX) declines by as much as twofold over the 2-s ramp, whereas for CD units, r(MAX) increases by 15% during the same time period. At the end of the ramp, r(MAX) is on average twice as high in CD as in B units. Thresholds are negligible in most spontaneously active units, including almost all B and CD-high units. Silent CD-low units typically have thresholds of 10-100 deg/s. BT units have very high linear gains and v(S) < 10 deg/s. Linear gains are considerably lower in BP units and v(S) > 150 deg/s. CD-high units have intermediate gains and near 100 deg/s v(S) values. CD-low units have low gains and v(S) values ranging from 150 to more than 300 deg/s. The results suggest that BT units are designed to measure the small head movements involved in postural control, whereas BP and CD units are more appropriate for monitoring large volitional head movements. The former units are silenced by efferent activation, whereas the latter units are excited. This suggests that the efferent system switches the turtle posterior crista from a "postural" to a "volitional" mode.

Algorithms↗
PubMed1992

Evidence that circulatory oscillations accompany ventilatory oscillations during exercise in patients with heart failure.

Periodic breathing (PB) during exercise in patients with congestive heart failure (CHF) is associated with prominent oscillations (OSC) of O2 uptake (VO2). We hypothesized that the VO2 OSC represent OSC in true O2 exchange, resulting from concomitant cardiac output fluctuations and are not merely due to OSC of lung O2 stores. We compared the amplitude of the OSC of VO2, ventilation (VE), and end-expiratory lung volume (EELV) in 17 patients with CHF and PB and in seven healthy control subjects who volitionally simulated PB. Subjects underwent an incremental and/or a constant work-rate exercise test. VE and VO2 were measured breath by breath. EELV change was estimated by summing the difference between inspiratory and expiratory tidal volumes for each breath. The amplitude of the OSC, delta, is expressed as the ratio of the difference between the peak and nadir of the oscillating variable divided by its mean [delta = (peak - nadir)/mean]. In CHF, during incremental testing, the amplitude of the VE OSC was smaller than that of the VO2 OSC (delta VE = 49 +/- 15% [SD], delta VO2 = 63 +/- 25%, p less than 0.01). In contrast, during volitional PB in the control subjects, VE OSC were larger than VO2 OSC (delta VE = 48 +/- 12%, delta VO2 = 25 +/- 11%, p less than 0.01). This suggests that changing VE itself cannot account for the marked VO2 OSC seen in CHF. In the patients, EELV showed no systematic OSC, did not correlate with delta VO2, and was not significantly different from zero.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Diaphragmatic fatigue after exercise in healthy human subjects.

The purpose of this study was to determine whether diaphragmatic fatigue occurs after high-intensity constant-load whole-body exercise to volitional exhaustion. Ten sedentary subjects with a maximal oxygen uptake of 2.52 +/- 0.47 L/min were studied. Subjects exercised on a bicycle ergometer at 80% of their maximal working capacity until volitional exhaustion. Minute ventilation during the last minute of exercise was 89.9 +/- 13.6 L/min, which represented 50 +/- 6% of the subjects' 12-s maximal voluntary ventilation. During the last minute of exercise, mean inspiratory esophageal pressure was 18.1 +/- 5.3 cm H2O, which represented only 15 +/- 4% of the subjects' maximal static inspiratory pressure. Bilateral transcutaneous supramaximal phrenic nerve stimulation was performed before and 10, 30, 45 and 60 min after exercise. Twitch diaphragmatic pressure (twitch Pdi) was significantly decreased after exercise in seven of the 10 subjects. For the group as a whole, twitch Pdi fell from 28.9 +/- 3.7 cm H2O during control to 23.9 +/- 5.1 cm H2O at 10 min after exercise (p < 0.005). The fall in twitch Pdi was due to a significant decrease in twitch esophageal pressure from 19.6 +/- 4.3 cm H2O during control to 15.5 +/- 4.9 cm H2O (p < 0.001). Twitch gastric pressure was not significantly different: 8.7 +/- 4.0 cm H2O, compared with 9.2 +/- 3.8 cm H2O during control. Twitch Pdi recovered to 93 +/- 7% of control values at 60 min after exercise. The fall in twitch Pdi after exercise indicates that diaphragmatic fatigue can occur following heavy endurance exercise in sedentary healthy persons.

Adult↗
PubMed1999

Ocular and oculomotor signs in Joubert syndrome.

A number of oculomotor defects have been described in Joubert syndrome. This study systematically examined the oculomotor systems of 13 individuals previously diagnosed with Joubert syndrome. Twelve had the characteristic "molar tooth sign" seen on magnetic resonance imaging scan. In all individuals, smooth pursuit gain and vestibulo-ocular reflex cancellation were decreased in the horizontal and vertical directions and volitional saccades, when generated, were hypometric. We believe that these defects arise from a disorder in the posterior cerebellar vermis. All individuals also had partial to complete oculomotor apraxia in which initiation of saccades was prolonged or impaired. The oculomotor apraxia in Joubert syndrome differs from congenital idiopathic oculomotor apraxia in that both volitional saccades and quick phases of nystagmus were impaired both in the horizontal and vertical directions, and the defects did not resolve with time. We believe that the oculomotor apraxia arises from a disorder involving the projections from the superior colliculus to the parapontine reticular formation and rostral interstitial nucleus of the medial longitudinal fasciculus. A subset of individuals also had severe visual loss, pendular nystagmus, pigmentary changes in the fundus, and decreased vestibulo-ocular reflexes. We believe that this is a form of Leber's amaurosis occasionally associated with Joubert syndrome. In summary, key oculomotor features of Joubert syndrome are decreased smooth pursuit and vestibulo-ocular reflex cancellation, partial to complete oculomotor apraxia both in the horizontal and vertical directions, and hypometric saccades if oculomotor apraxia is not complete.

Adolescent↗
PubMed2004

Clinical neurophysiological assessment of residual motor control in post-spinal cord injury paralysis.

OBJECTIVE: This study was designed to characterize the rudimentary residual lower-limb motor control that can exist in clinically paralyzed spinal-cord-injured individuals. METHODS: Sixty-seven paralyzed spinal-cord-injured subjects were studied using surface electromyography recorded from muscles of the lower limbs and analyzed for responses to a rigidly administered protocol of reinforcement maneuvers, voluntary movement attempts, vibration, or the ability to volitionally suppress withdrawal evoked by plantar surface stimulation. RESULTS: Markers for the subclinical discomplete motor syndrome were found in 64% of the subjects. The tonic vibration response was recorded in 37%, volitional plantar surface stimulation response suppression in 27%, and reinforcement maneuver responses in 6% of the subjects. Three subjects, 4%, produced reliable but very low amplitude surface electromyography during the voluntary movement segment of the protocol. Surface electromyography recorded during passive leg movement was related to Ashworth scores as was the tonic vibration response marker (P < 0.05). CONCLUSIONS: Multimuscle surface electromyography patterns recorded during a rigidly administered protocol of motor tasks can be used to differentiate between clinically paralyzed spinal-cord-injured individuals using subclinical motor output to identify the translesional neural connections that remain available for intervention testing and treatment planning after spinal cord injury.

Adult↗
PubMed1999

Are aerobically fit older individuals more physically active in their free-living time? A doubly labeled water approach.

There is considerable controversy regarding factors regulating free-living physical activity energy expenditure (PAEE) in older individuals. This component is highly variable, is difficult to accurately assess, and reflects both volitional and nonvolitional activities. We examined the association between maximal aerobic fitness (peak VO2) and free-living PAEE in older individuals. One hundred and eighty healthy older patients (96 females and 84 males) between 45-90 yr of age were studied. Total energy expenditure was measured from doubly labeled water. PAEE was calculated as the difference between total energy expenditure, resting metabolic rate, and estimated thermic effect of a meal. Peak VO2 was assessed from an exercise test to volitional fatigue. Fat mass and fat-free mass were assessed from dual energy x-ray absorptiometry. After correction for age, fat mass, and fat-free mass, significant correlations were observed between peak VO2 and PAEE for older males (r = 0.42; P < 0.0001) and females (r = 0.24; P < 0.05), although significant variation among volunteers was noted. When subjects were subdivided by tertiles based on their peak VO2 (liters per min), males with the highest peak VO2 showed greater free-living PAEE than individuals with low peak VO2 (P < 0.01). Similar results were observed in females (P < 0.05). Our results suggest a positive association between higher levels of peak VO2 and greater free-living PAEE in older individuals. This relationship is stronger in older men than in women. These additional energy-dissipating properties during their free-living time may serve to preserve leanness and buffer fat gain with age.

Absorptiometry, Photon↗
PubMed1999

Oculomotor evidence for neocortical systems but not cerebellar dysfunction in autism.

OBJECTIVE: To investigate the functional integrity of cerebellar and frontal systems in autism using oculomotor paradigms. BACKGROUND: Cerebellar and neocortical systems models of autism have been proposed. Courchesne and colleagues have argued that cognitive deficits such as shifting attention disturbances result from dysfunction of vermal lobules VI and VII. Such a vermal deficit should be associated with dysmetric saccadic eye movements because of the major role these areas play in guiding the motor precision of saccades. In contrast, neocortical models of autism predict intact saccade metrics, but impairments on tasks requiring the higher cognitive control of saccades. METHODS: A total of 26 rigorously diagnosed nonmentally retarded autistic subjects and 26 matched healthy control subjects were assessed with a visually guided saccade task and two volitional saccade tasks, the oculomotor delayed-response task and the antisaccade task. RESULTS: Metrics and dynamics of the visually guided saccades were normal in autistic subjects, documenting the absence of disturbances in cerebellar vermal lobules VI and VII and in automatic shifts of visual attention. Deficits were demonstrated on both volitional saccade tasks, indicating dysfunction in the circuitry of prefrontal cortex and its connections with the parietal cortex, and associated cognitive impairments in spatial working memory and in the ability to voluntarily suppress context-inappropriate responses. CONCLUSIONS: These findings demonstrate intrinsic neocortical, not cerebellar, dysfunction in autism, and parallel deficits in higher order cognitive mechanisms and not in elementary attentional and sensorimotor systems in autism.

Adolescent↗
PubMed1993

Effect of training on the relationship between maximal and submaximal strength.

The purpose of this study was to evaluate the validity of a dynamic seven to 10 repetition maximum (7-10 RM) test to estimate maximal knee extension strength (1-RM) in untrained and trained subjects. Thirty-three men and 25 women (25 +/- 5 yr) were randomly assigned to a group that trained two or three times.wk-1 for 18 wk (N = 47) or a control group (N = 11). Training included one set of 7-10 repetitions to volitional fatigue on a Nautilus knee extension machine. Prior to (T1) and after training (T2) dynamic strength was evaluated by 1-RM and 7-10 RM tests. The 7-10 RM test consisted of one set of variable resistance knee extension exercise performed to volitional fatigue with a weight that allowed 7-10 repetitions. The training group improved their 1-RM and 7-10 RM strength (by 31.7 and 51.4%, respectively) (P < or = 0.01) while the control group did not change. Training increased relative 7-10 RM strength (68.4% of 1-RM at T1 and 79.1% of 1-RM at T2) (P < or = 0.01). The relationship between the 7-10 RM weight and 1-RM at T1 was linear: 1-RM = 1.554 (7-10 RM weight)-5.181; R2 = 0.89; SEE = 9.3 kg. Application of this equation following training resulted in a systematic overprediction (p < or = 0.01) of 1-RM (21.2 kg) in trained subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2007

Estimation of oxygen uptake during fast running using accelerometry and heart rate.

UNLABELLED: Previous investigations have reported that accelerometer counts plateau during running at increasingly faster speeds. PURPOSE: To assess whether biomechanical and/or device limitations cause this phenomenon and the feasibility of generating oxygen uptake (.VO2) prediction equations from the combined use of accelerometry and heart rate during walking and running. METHODS: : Sixteen endurance-trained subjects completed two exercise tests on a treadmill. The first was a continuous incremental test to volitional exhaustion to determine ventilatory threshold and peak .VO2. The second was a discontinuous incremental exercise test while walking (3, 5, and 7 km.h(-1)) and running (8, 10, 12, 14, 16, 18, and 20 km.h(-1), or until volitional exhaustion). Subjects completed 3 min of exercise at each speed, followed by 3-5 min of recovery. Activity counts from uni- and triaxial accelerometers, heart rate, and gas exchange were measured throughout exercise. RESULTS: All accelerometer outputs rose linearly with speed during walking. During running, uniaxial accelerometer outputs plateaued, whereas triaxial output rose linearly with speed up to and including 20 km.h(-1). Prediction of .VO2 during walking and running using heart rate (R2 = 0.42 and 0.59, respectively), accelerometer counts (R2 = 0.48-0.83 and 0.76, respectively), the combined methodologies (R2 = 0.54-0.85 and 0.80, respectively), and the combined methodologies calibrated with individual data (R2 = 0.99-1.00 and 0.99, respectively) was completed by linear regression. CONCLUSIONS: Uni- and triaxial accelerometer outputs have a linear relationship with speed during walking. During running, uniaxial accelerometer outputs plateau because of the biomechanics of running, whereas triaxial accelerometer output has a linear relationship. The combined methodologies predict .VO2 better than either predictor alone; a subject's individually calibrated data further improves .VO2 estimation.

Acceleration↗
PubMed1988

Surgical treatment of pharyngoesophageal spasm.

The clinical course of 17 laryngectomees with pharyngoesophageal spasm who underwent pharyngeal myotomy was studied to determine clinical response and complications. The influence of speech therapy on the development of volitional control of pharyngoesophageal spasm, tracheoesophageal speech fluency, and the efficacy and complications of surgical treatment for pharyngoesophageal spasm were assessed. Volitional control of tracheoesophageal speech was never achieved. Ninety-four percent of the patients (16/17) were successfully rehabilitated following surgical therapy. The complications following pharyngeal myotomy were acceptable.

Esophageal Spasm, Diffuse↗
PubMed2003

High-frequency modulation of heart rate variability during exercise in patients with COPD.

STUDY OBJECTIVES: To evaluate cardiac autonomic modulation in patients with COPD during peak exercise. METHODS: Fifty-three patients with COPD (mean FEV(1), 35% predicted [SD, 11% predicted]; mean PaO(2), 68 mm Hg [SD, 11 mm Hg]; mean PaCO(2), 40 mm Hg [SD, 7 mm Hg]; mean age, 61 years [SD, 10 years]; 26 women and 27 men) and 14 healthy control subjects aged 60 years (SD, 8 years) [seven women and seven men] were studied at rest and during ramped bicycle ergometry to their volitional peak. Patients were not receiving autonomic medications other than inhaled beta-agonist agents and/or anticholinergic agents. Control subjects were not receiving any medications. Cardiac autonomic modulation was assessed via time-frequency analysis (Wigner-Ville) of ECG-derived heart rate variability as the power in the low-frequency (LF) band (ie, 0.04 to 0.15 Hz) and the high-frequency (HF) band (ie, > 0.15 to 0.4 Hz) averaged from > 3 min at rest and minutes 2 through 5 of their exercise period. RESULTS: Patients with COPD had a significantly increased mean, ln-transformed HF band from rest to peak exercise (9.9 ms(2) [SD, 1.4 ms(2)] vs 10.7 ms(2) [SD, 1.4 ms(2)], respectively; p < 0.01), while the HF band was unchanged for the control group (10.7 ms(2) [SD, 1.5 ms(2)] vs 10.4 ms(2) [1.3 ms(2)], respectively; difference not significant). The mean ln-transformed LF band was significantly increased from rest to peak exercise in patients with COPD (10.9 ms(2) [SD, 1.5 ms(2)] vs 11.5 ms(2) [SD, 1.4 ms(2)], respectively; p < 0.01) and in control subjects (10.9 ms(2) [SD, 1.5 ms(2)] vs 11.5 ms(2) [SD, 1.3 ms(2)], respectively; p < 0.01). The mean LF/HF ratio was significantly decreased from rest to peak exercise in patients with COPD (3.1 [SD, 1.5] vs 2.5 [SD, 1.0], respectively; p < 0.01) and was increased in control subjects (1.9 [SD, 0.8] vs 2.4 [1.0], respectively; p < 0.01). When expressed in normalized units ([absolute power of the components]/[total power - very low frequency power] x 100), the HF band was again significantly greater during peak exercise than at rest in the patients with COPD and was unchanged during peak exercise for the control group. Autonomic changes were not significantly correlated with age, gender, body mass index, spirometry, lung volumes, resting gas exchange, or oxygen saturation during exercise. CONCLUSION: These data suggest that, in contrast to control subjects, the balance of sympathetic to parasympathetic cardiac modulation decreases in patients with COPD during maximal volitional exercise.

Aged↗
PubMed2005

Effects of imposed pursed-lips breathing on respiratory mechanics and dyspnea at rest and during exercise in COPD.

STUDY OBJECTIVES: To investigate the effect of volitional pursed-lips breathing (PLB) on breathing pattern, respiratory mechanics, operational lung volumes, and dyspnea in patients with COPD. SUBJECTS: Eight COPD patients (6 male and 2 female) with a mean (+/-SD) age of 58 +/- 11 years and a mean FEV1 of 1.34 +/- 0.44 L (50 +/- 21% predicted). METHODS: Wearing a tight-fitting transparent facemask, patients breathed for 8 min each, with and without PLB at rest and during constant-work-rate bicycle exercise (60% of maximum). RESULTS: PLB promoted a slower and deeper breathing pattern both at rest and during exercise. Whereas patients had no dyspnea with or without PLB at rest, during exercise dyspnea was variably affected by PLB across patients. Changes in the individual dyspnea scores with PLB during exercise were significantly correlated with changes in the end-expiratory lung volume (EELV) values estimated from inspiratory capacity maneuvers (as a percentage of total lung capacity; r2 = 0.82, p = 0.002) and with changes in the mean inspiratory ratio of pleural pressure to the maximal static inspiratory pressure-generating capacity (PcapI) [r2 = 0.84; p = 0.001], measured using an esophageal balloon, where PcapI was determined over the range of inspiratory lung volumes and adjusted for flow. CONCLUSION: PLB can have a variable effect on dyspnea when performed volitionally during exercise by patients with COPD. The effect of PLB on dyspnea is related to the combined change that it promotes in the tidal volume and EELV and their impact on the available capacity of the respiratory muscles to meet the demands placed on them in terms of pressure generation.

Adult↗
PubMed2004

The effects of varied rest periods between sets to failure using the bench press in recreationally trained men.

The purpose of this study was to determine the rate of recovery for recreational weight trainers between 2 sets of bench press to volitional exhaustion. Twenty-eight men performed 2 sets of the bench press at 75% of their previously determined 1 repetition maximum (1RM) to volitional exhaustion. Rest periods of 1, 3, or 5 minutes between sets were utilized on the 3 separate testing days. There was a significant decrease in the number of repetitions performed between the second sets at all rest periods. There were no significant differences in work performed (repetitions x weight) during the second set with the 3- and 5-minute rest periods, but the total work with a 1-minute rest period (1,389.1 +/- 529.9) was significantly less than both the 3- (1,494.9 +/- 451.0) and 5-minute (1,711.4 +/- 478.0) rest period. The data indicated that subjects were unable to fully recover between the first and second sets of maximal resistance exercise, regardless of the rest period. However, subjects were able to maintain a performance level of 8-12 repetitions and sustain the total work performed per set with as little as 3 minutes rest between sets.

Adult↗
PubMed2006

Response of gait deficits to neuromuscular electrical stimulation for stroke survivors.

Persistent gait deficits after stroke can cause falls, elevated energy cost and poor endurance. Coordination impairment is an underlying cause of gait deficits. Few efficacious interventions have been described that have targeted and measured restoration of coordinated gait components. Neuromuscular electrical stimulation can provide the critical gait practice characteristic of close-to-normal movements, by electrically inducing muscle contractions and coordinated movements that are not possible under volitional effort. Two-channel, surface neuromuscular electrical stimulation can be synchronized with phases of gait and can provide faster, more symmetrical neuromuscular electrical stimulation-assisted gait than gait with no neuromuscular electrical stimulation. Difficulties encountered during the use of surface neuromuscular electrical stimulation for gait training led to the development of neuromuscular electrical stimulation with implanted technologies. Implanted electrodes and/or stimulators proved to be feasible for gait training in stroke survivors. Gait training with a multichannel neuromuscular electrical stimulation system with implanted electrodes proved more advantageous than gait training without neuromuscular electrical stimulation, according to measures of volitional coordinated gait components (neuromuscular electrical stimulation deactivated).

Electric Stimulation Therapy↗
PubMed1995

Strength of the quadriceps femoris muscle and functional recovery after reconstruction of the anterior cruciate ligament. A prospective, randomized clinical trial of electrical stimulation.

Immediately after reconstruction of the anterior cruciate ligament, 110 patients were randomly assigned to treatment with high-intensity neuromuscular electrical stimulation (thirty-one patients), high-level volitional exercise (thirty-four patients), low-intensity neuromuscular electrical stimulation (twenty-five patients), or combined high and low-intensity neuromuscular electrical stimulation (twenty patients). All treatment was performed isometrically with the knee in 65 degrees of flexion. All of the patients participated in an intensive program of closed-kinetic-chain exercise. After four weeks of treatment, the strength of the quadriceps femoris muscle and the kinematics of the knee during stance phase were measured. Quadriceps strength averaged 70 per cent or more of the strength on the uninvolved side in the two groups that were treated with high-intensity electrical stimulation (either alone or combined with low-intensity electrical stimulation), 57 per cent in the group that was treated with high-level volitional exercise, and 51 per cent in the group that was treated with low-intensity electrical stimulation. The kinematics of the knee joint were directly and significantly (p < 0.05) correlated with the strength of the quadriceps. There was a clinically and statistically significant (p < 0.05) difference in the recovery of the quadriceps and the gait parameters according to the type of operation that had been performed: the patients who had had reconstruction of the anterior cruciate ligament with use of an autologous patellar-ligament graft did poorly compared with the other patients.

Adult↗
PubMed2002

A gender-related difference in the contribution of the knee musculature to sagittal-plane shear stiffness in subjects with similar knee laxity.

BACKGROUND: Women's susceptibility to injuries involving the anterior cruciate ligament remains unexplained. Volitional contraction of the knee musculature is known to increase the resistance of the knee to shear deformation, raising the possibility that muscles play a part in protecting the anterior cruciate ligament during hazardous activities. We therefore tested the hypothesis that a volitional co-contraction of the knee muscles increases the sagittal-plane shear stiffness (or resistance to anterior tibial translation) of the knee more in men than in women. METHODS: Twenty-three volunteers (ten men and thirteen women; mean age, 24.7 +/- 5.4 years), all with anterior tibial translation of 6 mm, agreed to participate in the study. Each subject underwent a subjective evaluation of knee function and activity level, an arthrometric measurement of passive anterior tibial translation, and an isokinetic dynamometer strength test at 60 degrees/sec. A dynamic stress test was then performed to measure anterior tibial translation while simultaneously monitoring lower-extremity muscle response. RESULTS: Maximum co-contraction of the knee musculature significantly decreased mean anterior tibial translation in both men and women (from 7.8 mm to 2.2 mm in men and from 6.5 mm to 3.1 mm in women). The corresponding percentage increase in shear stiffness of the knee was significantly greater (p = 0.003) in men (379%) than in women (212%). CONCLUSIONS: The results suggested that women have a diminished potential for muscular protection of passive structures of the knee in anterior tibial translation. CLINICAL RELEVANCE: Maximal muscular protection of the anterior cruciate ligament in women may be less than that in men. This may be one factor explaining why more women than men are apt to sustain injuries to the anterior cruciate ligament.

Adult↗
PubMed1989

Recognition and differential diagnosis of tardive dyskinesia.

Tardive dyskinesia (TD) is a consequence of chronic neuroleptic therapy. It is an irregular stereotyped movement disorder that is usually choreic in appearance, and is subject to temporary volitional control. Dystonia, akathisia, and tics are uncommon variants of the classic tardive syndrome. Characteristic clinical features including amelioration by action, augementation by distraction, partial volitional suppressibility, and lack of subjective distress help differentiate TD from other movement disorders such as resting tremor, Huntington's disease, spontaneous dyskinesias, and abnormal movements accompanying psychiatric illnesses.

Antipsychotic Agents↗