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PubMed2003

Gender differences in muscular protection of the knee in torsion in size-matched athletes.

BACKGROUND: Female athletes who participate in sports involving jumping and cutting maneuvers are up to eight times more likely to sustain a rupture of the anterior cruciate ligament than are men participating in the same sports. We tested the hypothesis that healthy young women are able to volitionally increase the apparent torsional stiffness of the knee, by maximally activating the knee muscles, significantly less than are size-matched men participating in the same type of sport. METHODS: Twenty-four NCAA (National Collegiate Athletic Association) Division-I athletes (twelve men and twelve women) competing in sports associated with a high risk of injury to the anterior cruciate ligament (basketball, volleyball, and soccer) were compared with twenty-eight collegiate endurance athletes (fourteen men and fourteen women) participating in sports associated with a low risk of such injuries (bicycling, crew, and running). Male and female pairs were matched for age, height, weight, body mass index, shoe size, and activity level. Testing was performed with a weighted pendulum that applied a medially directed 80-N impulse force to the lateral aspect of the right forefoot. The resulting internal rotation of the leg was measured optically, to the nearest 0.25 degrees, at 30 degrees and 60 degrees of knee flexion, both with and without maximal activation of the knee muscles. RESULTS: Maximal rotations of the leg were greater in women than in men in both the passive and the active muscle state (16% and 27% greater [p = 0.01 and p = 0.02], respectively). Moreover, female athletes exhibited a significantly (18%) smaller volitional increase in apparent torsional stiffness of the knee under internal rotation loading than did the matched male athletes (p = 0.014); this was particularly the case for those who participated in sports involving jumping and pivoting maneuvers (42% difference between genders, p = 0.001). CONCLUSIONS: The collegiate female athletes involved in high-risk sports exhibited less muscular protection of the knee ligaments during external loading of the knee than did size and sport-matched male athletes.

Analysis of Variance↗
PubMed1998

Application of functional electrical stimulation to the paralyzed extremities.

This paper describes restoration of motor function in patients with paralyzed extremities due to upper motor neuron disorders by functional electrical stimulation (FES). Percutaneously indwelling intramuscular electrodes were implanted into the muscles of the paralyzed upper and lower extremities to be controlled by FES. Stimulation patterns for extremity FES were created from electromyography (EMG) during motion in healthy subjects. By using a percutaneous FES system, all of the joint movement in the extremities could be controlled as long as severe lower motor neuron damage did not exist. In the paralyzed upper extremity, motor function of not only the hand but also the wrist, elbow, and shoulder could be restored with well-coordinated manner by EMG-based stimulation data and utilized for vocational tasks in the hemiplegic and quadriplegic patients. Continuous bias stimulation to the paralyzed muscle in combination with volitional contraction of its antagonistic muscles provided the patient with more volitional and natural control of the upper extremity. Restoration of locomotive movement in the paraplegics at around T-8 level was also achieved by FES under the usage of a walker.

Electric Stimulation Therapy↗
PubMed1978

The training of coordination.

The training of coordination is generally considered a volitional activity, during which, by trial and perception of results, an individual selects the muscular activity resulting in the desired performance. This concept of volitionally directed complex coordination of multiple muscles with speed, skill, and strength does not stand the test of thorough evaluation. Attention is limited to 1 activity at a time, with the ability to shift attention not more frequently than 3 times per second. Only under special conditions can activity be limited to specific muscles during an untrained contraction without cocontraction of other muscles. However, with repeated practice of the desired activity, a pattern of performance is developed which can be carried out rapidly and forcefully without activation of other muscles. At that time, the consciousness is no longer directing the components of the activity but merely starting, maintaining, and stopping the performance. The development of these patterns, or engrams, by practice develops the capacity to automatically inhibit muscles that do not contribute to the performance of the desired pattern. The capacity for inhibition results in coordinated activation of the muscles contributing to the performance desired. Investigation of the development of coordination in many types of normal activities, as well as in neuromuscularly impaired patients, shows that engrams develop progressively by slow, precise practice of simple patterns, combined as they develop into more and more complex patterns, until the final skill is attained.

Attention↗
PubMed1998

Effects of pramipexole on contraversive rotation and functional motor impairments in 1-methyl-4-phenyl1,2,3, 6-tetrahydropyridine-induced chronic hemiparkinsonian monkeys.

Rotational and functional motor behavioral changes were studied in five MPTP lesioned chronic hemiparkinsonian Macaca nemestrina monkeys after i.m. pramipexole, a predominant D2 subfamily agonist. Pramipexole induced contraversive rotations in a dose-dependent manner with an optimal dose of 56 microg/kg for approximately 2 to 4 hr after injection. Three different rating scales were used to determine drug-induced functional improvement. They included a monkey parkinsonism rating scale, volitional responses to fruit presentations, and number of hand movements that appeared volitional. A dose of 56 microg/kg of pramipexole produced functional improvements on hand disability, and on a parkinsonian rating scale for monkeys in a dose-dependent manner from 32 to 100 microg/kg. These doses produced an increase in significant hand movements in the affected (contralateral) as well as in the normal (ipsilateral) hand to the side of the brain lesion compared with 5% dextrose in water vehicle control. With a dose of 100 microg/kg, the therapeutic effects of pramipexole on hand movements were less than with 56 microg/kg, due to side effects such as scratching.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1986

Swallowing and speech production in Parkinson's disease.

Videofluoroscopy was used to examine movement patterns during swallowing and speech production in 6 parkinsonian subjects and 6 age-matched controls. Motility patterns for liquid and semisolid swallows were documented. We performed temporospatial analyses of oropharyngeal structures, particularly the velum, which is prominently involved in both motor speech production and swallowing. Differences were found between groups and conditions. All of the parkinsonian subjects exhibited abnormal oropharyngeal movement patterns and timing during the volitional oral as well as the pharyngeal stage of swallowing; only 50% of these subjects admitted to any swallowing difficulty upon questioning. Two of the subjects with Parkinson's disease aspirated liquids. Duration of velar movement during speech production significantly differentiated the groups (p less than 0.01), reflecting reduced range of velar motion. Our findings suggest that rigidity and bradykinesia underlie the volitional speech abnormality as well as the disordered oral and pharyngeal stages of swallowing. Findings indicate that parkinsonian patients may be "silent aspirators" with decreased cough reflexes and lack of awareness of aspiration. The clinical value of videofluoroscopic monitoring of swallowing is that aspiration may be detected and managed early.

Adult↗
PubMed1987

Functional electrical stimulation for the control of the upper extremities.

A multi-channel functional electrical stimulation (FES) system for the restoration of hand function of the quadriplegic is described. The system is composed of a personal computer NEC PC-880lmkII, peripheral electronic circuits and two kinds of sensors, i.e. an analog displacement sensor for volitional control (channel 1) and a logical sensor (high pitch sound or head switch, channel 2). Combination of the two channel signals allow three major function: 1) designation of the desired prehension pattern among cylindrical grasp, key grip and parallel extension grip; 2) selection of the operation status--'start', 'proportional control', 'hold', 'stop'--and, 3) volitional control which can be controlled by the shoulder movement. In the clinical application, Caldwell-Reswick type multistrand stainless steel percutaneous electrodes were used. In this FES system, standard multi-channel stimulation patterns were obtained from electromyographical analysis of joint movement of the upper extremities in normal subjects which gave us precise information about a role of each muscle during various kinds of motion. Such stimulation patterns have enabled us to restore motor function of the paralyzed upper extremities for activities of daily living (ADL).

Electric Stimulation↗
PubMed2002

Control of a hand grasp neuroprosthesis using an electroencephalogram-triggered switch: demonstration of improvements in performance using wavepacket analysis.

Volitionally modulated electroencephalographic (EEG) waves were monitored for the purpose of controlling a hand neuroprosthesis in people with tetraplegia. The region of the EEG signal spectrum monitored was the occipital alpha wave (8-13 Hz), and volitional modulation was achieved with the opening and closing of the eyes. In a set of 13 trials evaluated, a subject with tetraplegia successfully completed ten trials undertaking stimulated grasp and release using the EEG-triggered switch. EEG signal data recorded during the 13 trials were also post-processed off-line using wavepacket analysis. Following this signal processing, the speed and reliability of the EEG-triggered switch, when operated by the subject with tetraplegia, was significantly improved (p < 0.002). Such improvements provide system performance that is likely to be acceptable to a neuroprosthesis user during activities of daily life.

Electric Stimulation↗
PubMed2004

Oxygen uptake kinetics and maximal aerobic power are unaffected by inspiratory muscle training in healthy subjects where time to exhaustion is extended.

The aim of this study was to determine whether 4 weeks of inspiratory muscle training (IMT) would be accompanied by alteration in cardiopulmonary fitness as assessed through moderate intensity oxygen uptake (V(.)O(2)) kinetics and maximal aerobic power (V(.)O(2max)). Eighteen healthy males agreed to participate in the study [training group (Tra) n=10, control group (Con) n=8]. Measurements of spirometry and maximal static inspiratory mouth pressure ( PI(max)) were taken pre- and post-training in addition to: (1) an incremental test to volitional exhaustion, (2) three square-wave transitions from walking to running at a moderate intensity (80% ventilatory threshold) and (3) a maximal aerobic constant-load running test to volitional fatigue for the determination of time to exhaustion ( T(lim)). Training was performed using an inspiratory muscle trainer (Powerbreathe). There were no significant differences in spirometry either between the two groups or when comparing the post- to pre-training results within each group. Mean PI(max) increased significantly in Tra ( P<0.01) and showed a trend for improvement ( P<0.08) in Con. Post-training T(lim) was significantly extended in both Tra [232.4 (22.8) s and 242.8 (20.1) s] ( P<0.01) and Con [224.5 (19.6) and 233.5 (12.7) s] ( P<0.05). Post-training T(lim) was significantly extended in Tra compared to Con ( P<0.05). In conclusion, the most plausible explanation for the stability in V(.)O(2) kinetics and V(.)O(2max) following IMT is that it is due to insufficient whole-body stress to elicit either central or peripheral cardiopulmonary adaptation. The extension of post-training T(lim) suggests that IMT might be useful as a stratagem for producing greater volumes of endurance work at high ventilatory loads, which in turn could improve cardiopulmonary fitness.

Adaptation, Physiological↗
PubMed2004

Relationship between stress hormones and testosterone with prolonged endurance exercise.

Previous pharmacological and pathological studies have reported negative relationships between circulating testosterone and certain stress hormones (i.e., cortisol and prolactin) in humans. These relationships have subsequently been used in hypotheses explaining the subclinical resting testosterone levels often found in some endurance-trained males, but as of yet no one has specifically examined these relationships as they relate to exercise. Thus, we examined the relationship between total and free testosterone levels and cortisol, and between total and free testosterone and prolactin following prolonged endurance exercise in trained males. Twenty-two endurance-trained males volunteered to run at 100% of their ventilatory threshold (VT) on a treadmill until volitional fatigue. Blood samples were taken at pre-exercise baseline (B0); volitional fatigue (F0); 30 min (F30), 60 min (F60), and 90 min (F90) into recovery; and at 24 h post-baseline (P24 h). At F0 [mean running time = 84.8 (3.8) min], exercise induced significant changes (P<0.05) from B0 in total testosterone, cortisol and prolactin. All three of these hormones were still significantly elevated at F30; but at F60 only cortisol and prolactin were greater than their respective B0 values. Free testosterone displayed no significant changes from B0 at F0, F30, or the F60 time point. At F90, neither cortisol nor prolactin was significantly different from their B0 values, but total and free testosterone were reduced significantly from B0. Cortisol, total testosterone and free testosterone at P24 h were significantly lower than their respective B0 levels. Negative relationships existed between peak cortisol response (at time F30) versus total testosterone (at F90, r=-0.53, P<0.05; and at P24 h, r=-0.60, P<0.01). There were no significant relationships between prolactin and total or free testosterone. In conclusion, the present findings give credence to the hypothesis suggesting a linkage between the low resting testosterone found in endurance-trained runners and stress hormones, with respect to cortisol.

Adult↗
PubMed2000

Short-term recovery from prolonged constant pace running in a warm environment: the effectiveness of a carbohydrate-electrolyte solution.

Recovery from prolonged exercise involves both rehydration and replenishment of endogenous carbohydrate stores. This study examined the influence of drinking a carbohydrate-electrolyte solution on short-term recovery and subsequent exercise capacity in a warm environment. Thirteen healthy male volunteers completed two trials, at least 7 days apart. On each occasion subjects performed an initial treadmill run at 60% of maximal oxygen uptake (VO2max), for 90 min or until volitional fatigue (T1), in a warm environment (35 degrees C, 40% relative humidity, RH). Volitional ingestion of water was permitted during each of the exercise trials. During a subsequent 4-h recovery period (REC) subjects consumed either a 6.9% carbohydrate-electrolyte solution (CES) or a sweetened placebo (P), in a volume equivalent to 140% of body mass loss. Following REC, subjects ran to exhaustion at the same % VO2max in order to assess their endurance capacity (T2). Mean (SEM) run times during T1 did not differ between the CES [74.8 (4.6) min] and P [72.5 (5.2) min] trials. Body mass was reduced (P < 0.01) by 1.9 (0.2)% (CES) and 1.7 (0.2)% (P), and plasma volume (P < 0.01) by 6.0 (0.9)% (CES) and 5.4 (1.0)% (P) during the T1 trials. During REC 2006 (176) ml and 1830 (165) ml of fluid was ingested, providing 138 (12) g and 0 g of carbohydrate in the CES and P trials, respectively. Prior to T2, plasma volume and net fluid balance were similarly restored [CES +58 (26) g; P -4 (68) g] in both trials. During T2 the exercise duration was longer (P < 0.01) in the CES compared to the P trial [CES 60.9 (5.5) min; P 44.9 (3.0) min]. Thus, provided that an adequate hydration status is maintained, inclusion of carbohydrate within an oral rehydration solution will delay the onset of fatigue during a subsequent bout of prolonged submaximal running in a warm environment.

Adult↗
PubMed2000

Quadriceps-hamstring EMG activity during functional, closed kinetic chain exercise to fatigue.

It has been hypothesized that the ability of the neuromuscular system to co-contract muscles for joint stabilization may be impaired during the development of fatigue. The purpose of this study was to examine muscle activation of the quadriceps and hamstring muscles during a prolonged closed kinetic chain exercise, the forward lunge. Eight males and two females [mean (SD) age 26.0 (2.3) years, height 177.2 (13.6) cm, body mass 82.8 (17.1) kg] with no prior knee pathology volunteered for this study. Subjects performed repeated forward lunges onto their dominant leg at the cadence of one full lunge cycle every 2 s, until the point of volitional failure. Digital switches were positioned to record foot-strike and knee-strike of the lunge leg at the midpoint of the lunge, as well as heel-strike upon return to stance. During the lunge performance, surface electromyographic (EMG) signals of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles of the supporting leg were measured. Heart rate was also monitored every 30 s during the performance. All EMG data were full-wave rectified, partitioned into up and down phases, and integrated over the entire exercise period. The results demonstrated a significant increase in activation of the VL, VM, and BF during performance of the forward lunge to volitional failure (P < 0.05). No significant increase was shown for the ST. Heart rate increased significantly over the course of the lunge. These findings suggest that activation of the VL, VM, and BF muscles occurs as a unit during performance of the forward lunge during both concentric and eccentric lunge phases.

Adult↗
PubMed1986

Voluntary supraspinal suppression of spinal reflex activity in paralyzed muscles of spinal cord injury patients.

Having previously demonstrated that residual facilitatory brain influence on segmental structures occurs in paralyzed spinal cord injury patients, we sought evidence of suprasegmental suppression in such patients. By recording EMG activity from leg muscles, we studied changes in segmental excitability of the plantar reflex elicited by cutaneous stimulation of the plantar surface. Using surface EMG recordings, 50 paralyzed spinal cord injury patients were examined for their ability to volitionally suppress the plantar reflex on three repeated trials after three baseline trials. The patients, who had no voluntary EMG activity in the monitored muscles, were able to volitionally suppress the plantar reflex responses by 45% in the tibialis anterior, hamstring, and triceps surae muscles and to suppress the quadriceps response by 72%. In this patient group, 73 of 100 tibialis anterior muscle groups showed suppression of more than 20% compared with the control response. On reexamination, these findings were consistent during a period of 2 years in six patients. We conclude that suprasegmental suppression of segmental activity does occur in paralyzed spinal cord injury patients, and that in clinically complete patients, neurological evaluation should include assessment of the degree of preservation of suprasegmental neurocontrol on segmental activity below the lesion.

Adolescent↗
PubMed1991

Volume detection during voluntary and passive breathing.

The ability to detect small changes in tidal volume (VT) during either volitional or passive breathing was compared in seven normal subjects. Passive breathing was achieved with positive pressure applied at the mouth by a ventilator. Although baseline breathing pattern was similar for each subject during the two types of breathing, the ability of the subjects to detect changes in VT was at least as good, and in general better, during passive as compared to volitional breathing. This suggests that the generation of a motor cortical command to inspire and the resultant respiratory muscle contraction are not essential to the perception of a change in lung volume. An increase in information from receptors in the mouth, pharynx and extrathoracic airways sensitive to positive pressure may be responsible for the increased ability of most subjects to detect changes in VT during passive breathing.

Adult↗
PubMed1987

Contents of monoamines in forebrain regions of alcohol-preferring (P) and -nonpreferring (NP) lines of rats.

The contents of monoamine neurotransmitters and metabolites were assayed in the frontal cortex, nucleus accumbens and anterior striatum of rats from the selectively bred alcohol-preferring P and nonpreferring NP lines. Lower levels of serotonin (20-30%) in all three brain regions of P as compared with NP rats lends support to the hypothesis that a decreased metabolic activity and/or innervation by serotonin neurons is associated with the abnormally high volitional intake of ethanol. Of additional interest, however, were the approximately 25% lower contents of dopamine and its major metabolites in the nucleus accumbens of the P rats. This observation may indicate that P rats have a specific deficiency in the dopaminergic projections from the ventral tegmental area to the nucleus accumbens and, since the accumbens is an important structure in brain reward circuitry, it might also be an important determinant of the excessive volitional intake of alcohol by P rats.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Velocity percepts of apparent laser speckle motion modulated by voluntary changes of visual accommodation: real-time, in-vivo measurements of the accommodative response.

This study examined negative volitional accommodation under open-loop viewing conditions by means of a coherent laser light pattern (633 nm) whose direction and velocity of motion is determined by the refractive state of the eye. Using the direct scaling procedure of free magnitude estimation, the subjects were required to quantitatively judge velocities of speckles when the retinal image of the subjects' eye was minimally influenced and when the subject was instructed to exert voluntary negative accommodation. Real-time, in-vivo measures of accommodation indicated that the dioptric strength of the crystalline eye lens was reduced under the condition of mental effort, and that the volitional accommodation values ranged between -0.26 and -1.90 D. The amplitude of these responses were noticeably correlated with individual measures of dark focus, so that larger dark focus values were associated with higher amplitudes of the voluntary negative response, and vice versa. By converting the dioptric strength of added optical lenses and the in-vivo measures of the eye lens curvature into angular velocities of laser speckles whose speed changes with focus relative the plane of stationarity, a specification of the proximal stimulus flow was obtained. The psychophysical functions describing the relationship between subjective speed and angular velocity generated either by placing lenses in front of the eye or by voluntary changes in accommodation had approximately the same appearance suggesting that the percepts reported by the subjects were valid and veridical estimates of the velocity of speckle movement.

Acceleration↗
PubMed1989

The nature of voluntary action.

This paper extends the microgenetic theory of action to the problem of volition and the nature of free will and responsibility. Volition is interpreted as an elaboration of the action structure without causal or agentive status in relation to the action. The implications of this approach for philosophy of mind are explored.

Attention↗
PubMed1994

The psychology of perserverative and stereotyped behaviour.

Many forms of psychopathology in higher animals and humans include the production of maladaptive, repetitive behaviour. Behaviour which is both repetitive and excessive in amount can be described as stereotyped whereas behaviour which represents a restriction of behavioural possibilities without excessive production can be described as perseverative. Both types of repetition can result from pathology in the neural mechanisms which control either the production of motor output or the organisation of behaviour at a higher level. A number of forms of repetitive behaviour can be induced environmentally. Confinement in adulthood results in a functional disorder which rapidly dissipates when normal conditions are restored but confinement in infancy may have a permanent effect on the organism's ability to interact in a flexible and creative way with its environment. The permanence of these disorders suggests that the environment can affect the way in which the nervous system develops. Repetitive behaviour is also a feature of mental illness including schizophrenia, autism, OCD, addiction and some neurological disorders including frontal lobe lesions, Tourette's syndrome and PD. In experimental studies in animals, stereotyped behaviour seems to be related mainly to excess dopaminergic activity in the basal ganglia while perserverative behaviour can be produced by lesions of the frontal lobes. It is supposed that the level of dopamine activity in the basal ganglia affects the baseline level of behavioural activation such that excess activation results in the excessive execution of the most probable response to the environment to the exclusion of other possibilities (i.e. stereotypy) while deficient activation results in the production of only a few responses which can exceed the necessary activation level (i.e. perseveration). In either case behaviour is 'stimulus-bound', being driven by only the most salient feature of the environment. The symptoms of PD result from inadequate levels of dopamine in the basal ganglia while the stimulant psychoses result from excessive availability of dopamine. The frontal lobes have a modulating effect on (i) the activation of motor activity by the basal ganglia, (ii) in the generation of self-initiated behaviour, i.e. volition, and (iii) in the neural mechanisms which permit different modes of neural function (e.g. perceiving, remembering or thinking) to be identified. Failures in these three functions could result in excessive and repetitive motor activity, stimulus-bound behaviour, the paucity of volitional and creative behaviour, and the perceptual and experiential symptoms of psychosis.

Animals↗
PubMedDate not supplied

Age dependent development of ethanol drinking in rats after inhibition of aldehyde dehydrogenase.

The purpose of this experiment was to determine the temporal characteristics associated with the age-related development of volitional consumption of ethanol induced by the pharmacological inhibition of aldehyde dehydrogenase (AlDH). To induce preference for ethanol, the AlDH inhibitor, cyanamide, was administered to male Sprague-Dawley rats which were 30 days of age. Cyanamide (n = 8) was injected subcutaneously twice daily in a dose of 10 mg/kg over a period of 3 days while the control group (n = 6) received the saline vehicle solution according to the same schedule. Then at 50, 70, 90, and 110 days of age, both groups of rats were given a standard 11-day test of preference for water versus ethanol offered in concentrations ranging from 3% through 30%. The results showed that at 70 days of age the preference for ethanol increased above the level of the 50-day test in terms of absolute g/kg intakes and proportion of ethanol to water consumed over the lower range of 3% through 15% concentrations. During the tests at 90 and 110 days of age, the cyanamide-treated rats further increased their preference for ethanol significantly over the levels at the 70-day test in terms of both g/kg and proportional intakes. The pattern of drinking of ethanol offered in the higher concentrations of 25% and 30% was unrelated to the age of the rats and the overall intakes were significantly higher than those of the lower concentrations. These findings demonstrate that the enzymatic inhibition of AlDH systematically acts in a delayed fashion to shift the pattern of preference for ethanol which is contingent on the maturation of the animal. In this instance, the volitional intake of ethanol in the cyanamide-treated rats reached its maximal level by 90-110 days of age. It is proposed that an endocrine mechanism involved in gonadal maturation may function in the intense shift in alcohol drinking.

Age Factors↗