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At least 127 records · Page 7Linked to original sources

PubMed2003

Peroneus longus stretch reflex amplitude increases after ankle brace application.

BACKGROUND: The use of external ankle support is widespread throughout sports medicine. However, the application of ankle bracing to a healthy ankle over a long period has been scrutinised because of possible neuromuscular adaptations resulting in diminished dynamic support offered by the peroneus longus. OBJECTIVE: To investigate the immediate and chronic effects of ankle brace application on the amplitude of peroneus longus stretch reflex. METHODS: Twenty physically active college students (mean (SD) age 23.6 (1.7) years, height 168.7 (8.4) cm, and mass 69.9 (12.0) kg) who had been free from lower extremity pathology for the 12 months preceding the study served as subjects. None had been involved in a strength training or conditioning programme in the six months preceding the study. A 3 x 3 x 2 (test condition x treatment condition x time) design with repeated measures on the first and third factor was used. The peroneus longus stretch reflex (% of maximum amplitude) during sudden foot inversion was evaluated under three ankle brace conditions (control, lace up, and semi-rigid) before and after eight weeks of ankle brace use. RESULTS: A 3 x 3 x 2 repeated measures analysis of variance showed that peroneus longus stretch reflex amplitude increased immediately after application of a lace up brace (67.1 (4.4)) compared with the semi-rigid (57.9 (4.3)) and control (59.0 (5.2)) conditions (p<0.05). Peroneus longus stretch reflex also increased after eight weeks of use of the semi-rigid brace compared with the lace up and control conditions (p<0.05). CONCLUSIONS: Initial application of a lace up style ankle brace and chronic use of a semi-rigid brace facilitates the amplitude of the peroneus longus stretch reflex. It appears that initial and long term ankle brace use does not diminish the magnitude of this stretch reflex in the healthy ankle.

Adaptation, Physiological↗

PubMed2000

Age causes a redistribution of joint torques and powers during gait.

At self-selected walking speeds, elderly compared with young adults generate decreased joint torques and powers in the lower extremity. These differences may be actual gait-limiting factors and neuromuscular adaptations with age or simply a consciously selected motor pattern to produce a slower gait. The purpose of the study was to compare joint torques and powers of young and elderly adults walking at the same speed. Twelve elderly and fourteen young adults (ages 69 and 21 yr) walked at 1.48 m/s over a force platform while being videotaped. Hip, knee, and ankle torques and powers were calculated from the reaction force and kinematic data. A support torque was calculated as the sum of the three joint torques. Extensor angular impulse during stance and positive work at each joint were derived from the torques and powers. Step length was 4% shorter and cadence was 4% higher in elderly adults (both P < 0.05) compared with young adults. Support angular impulse was nearly identical between groups, but elderly adults had 58% greater angular impulse and 279% more work at the hip, 50% less angular impulse and 39% less work at the knee, and 23% less angular impulse and 29% less work at the ankle compared with young adults (t-test, all P < 0.05). Age caused a redistribution of joint torques and powers, with the elderly using their hip extensors more and their knee extensors and ankle plantar flexors less than young adults when walking at the same speed. Along with a reduction in motor and sensory functions, the natural history of aging causes a shift in the locus of function in motor performance.

Adult↗

PubMed2002

Activation of human plantar flexor muscles increases after electromyostimulation training.

Neuromuscular adaptations of the plantar flexor muscles were assessed before and subsequent to short-term electromyostimulation (EMS) training. Eight subjects underwent 16 sessions of isometric EMS training over 4 wk. Surface electromyographic (EMG) activity and torque obtained under maximal voluntary and electrically evoked contractions were analyzed to distinguish neural adaptations from contractile changes. After training, plantar flexor voluntary torque significantly increased under isometric conditions at the training angle (+8.1%, P < 0.05) and at the two eccentric velocities considered (+10.8 and +13.1%, P < 0.05). Torque gains were accompanied by higher normalized soleus EMG activity and, in the case of eccentric contractions, also by higher gastrocnemii EMG (P < 0.05). There was an 11.9% significant increase in both plantar flexor maximal voluntary activation (P < 0.01) and postactivation potentiation (P < 0.05), whereas contractile properties did not change after training. In the absence of a change in the control group, it was concluded that an increase in neural activation likely mediates the voluntary torque gains observed after short-term EMS training.

Adult↗

PubMed2004

Training-induced changes in muscle CSA, muscle strength, EMG, and rate of force development in elderly subjects after long-term unilateral disuse.

The ability to develop muscle force rapidly may be a very important factor to prevent a fall and to perform other tasks of daily life. However, information is still lacking on the range of training-induced neuromuscular adaptations in elderly humans recovering from a period of disuse. Therefore, the present study examined the effect of three types of training regimes after unilateral prolonged disuse and subsequent hip-replacement surgery on maximal muscle strength, rapid muscle force [rate of force development (RFD)], muscle activation, and muscle size. Thirty-six subjects (60-86 yr) were randomized to a 12-wk rehabilitation program consisting of either 1) strength training (3 times/wk for 12 wk), 2) electrical muscle stimulation (1 h/day for 12 wk), or 3) standard rehabilitation (1 h/day for 12 wk). The nonoperated side did not receive any intervention and thereby served as a within-subject control. Thirty subjects completed the trial. In the strength-training group, significant increases were observed in maximal isometric muscle strength (24%, P < 0.01), contractile RFD (26-45%, P < 0.05), and contractile impulse (27-32%, P < 0.05). No significant changes were seen in the two other training groups or in the nontrained legs of all three groups. Mean electromyogram signal amplitude of vastus lateralis was larger in the strength-training than in the standard-rehabilitation group at 5 and 12 wk (P < 0.05). In contrast to traditional physiotherapy and electrical stimulation, strength training increased muscle mass, maximal isometric strength, RFD, and muscle activation in elderly men and women recovering from long-term muscle disuse and subsequent hip surgery. The improvement in both muscle mass and neural function is likely to have important functional implications for elderly individuals.

Aged↗

PubMedDate not supplied

Functional knee brace effects during walking in patients with anterior cruciate ligament reconstruction.

The purpose of this study was to compare lower extremity joint kinematics and kinetics during walking with and without a functional knee brace in patients with recent anterior cruciate ligament reconstructions. Seven volunteers walked at 1.26 m/s with and without one of two functional knee braces 3 weeks after surgery. Eleven uninjured subjects were also tested as a control group. Video and ground-reaction data were collected and combined with inverse dynamics to estimate the joint positions, moments, and powers during the stance phase. Patients with ligament reconstructions were more erect with the brace, using 19% less knee flexion compared with walking without the brace. Areas under the internal extensor moment curve (angular impulse) and power curve (work) at the hip increased 40% and 44%, respectively, while walking with the brace. Extensor angular impulse decreased 41% at the knee while using the brace, and plantar flexor angular impulse and work increased 21% and 30%, respectively, at the ankle. While walking with the brace, the patients still had different kinematics, moments, and powers than the control subjects. The reduced extensor moment at the knee in the braced condition indicated that the load on the recently reconstructed ligament was reduced and that the brace protected the ligament during the stance phase of walking. We concluded that functional knee braces may be one means of developing neuromuscular adaptations during gait after anterior cruciate ligament reconstruction surgery.

Adolescent↗

PubMed2004

The effect of short-duration sub-maximal cycling on balance in single-limb stance in patients with anterior cruciate ligament injury: a cross-sectional study.

BACKGROUND: It has previously been shown that an anterior cruciate ligament (ACL) injury may lead to impaired postural control, and that the ability to maintain postural control is decreased by fatigue in healthy subjects. To our knowledge, no studies have reported the effect of fatigue on postural control in subjects with ACL injury. This study was aimed at examining the effect of fatigue on balance in single-limb stance in subjects with ACL injury, and to compare the effects, and the ability to maintain balance, with that of a control group of uninjured subjects. METHODS: Thirty-six patients with unilateral, non-operated, non-acute ACL injury, and 24 uninjured subjects were examined with stabilometry before (pre-exercise) and immediately after (post-exercise) short-duration, sub-maximal cycling. In addition, the post-exercise measurements were compared, to evaluate the instantaneous ability to maintain balance and any possible recovery. The amplitude and average speed of center of pressure movements were registered in the frontal and sagittal planes. The paired t-test was used for the intra-group comparisons, and the independent t-test for the inter-group comparisons, with Bonferroni correction for multiple comparisons. RESULTS: No differences were found in the effects of exercise between the patients and the controls. Analysis of the post-exercise measurements revealed greater effects or a tendency towards greater effects on the injured leg than in the control group. The average speed was lower among the patients than in the control group. CONCLUSIONS: The results of the present study showed no differences in the effects of exercise between the patients and the controls. However, the patients seemed to react differently regarding ability to maintain balance in single-limb stance directly after exercise than the control group. The lower average speed among the patients may be an expression of different neuromuscular adaptive strategies than in uninjured subjects.

Adolescent↗

PubMed2005

Task-oriented aerobic exercise in chronic hemiparetic stroke: training protocols and treatment effects.

Stroke is the leading cause of disability in older Americans. Each year 750,000 Americans suffer a stroke, two thirds of whom are left with neurological deficits that persistently impair function. Principal among them is hemiparetic gait that limits mobility and increases fall risk, promoting a sedentary lifestyle. These events propagate disability by physical deconditioning and "learned non-use," with further functional declines accelerated by the sarcopenia and fitness decrements of advancing age. Conventional rehabilitation care typically provides little or no structured therapeutic exercise beyond the subacute stroke recovery period, based on natural history studies showing little or no further functional motor recovery beyond 6 months after stroke. Emerging evidence suggests that new models of task-oriented exercise have the potential to improve motor function even years after stroke. This article presents treadmill as a task-oriented training paradigm to optimize locomotor relearning while eliciting cardiovascular conditioning in chronic stroke patients. Protocols for exercise testing and longitudinal aerobic training progression are presented that provide fundamental formulas that safely approach the complex task of customizing aerobic training to gait deficit severity in the high CVD risk stroke population. The beneficial effects of 6 months task-oriented treadmill exercise on cardiovascular-metabolic fitness, energy cost of hemiparetic gait, ADL mobility task performance, and leg strength are discussed with respect to the central and peripheral neuromuscular adaptations targeted by the training. Collectively, these findings constitute one initial experience in a much broader neuroscience and exercise rehabilitation development of task-oriented training paradigms that offer a multisystems approach to improving both neurological and cardiovascular health outcomes in the chronic stroke population.

Adaptation, Physiological↗

PubMed2001

Skeletal advancement for the treatment of obstructive sleep apnea in children.

OBJECTIVE: Maxillomandibular advancement is curative for some adult patients with obstructive sleep apnea (OSA). Little is known, however, about the efficacy of this treatment in children. The purpose of this retrospective analysis is to assess the clinical outcomes of children with medically refractory OSA who were treated with a variety of procedures to advance the maxillofacial skeleton. METHODS: The records of eight children with OSA (five boys and three girls; mean age, 8.6 years; range, 2 to 17 years) were reviewed. Six children had identifiable syndromes associated with micrognathia, one child had mandibular ankylosis, and one child was nonsyndromic. In five of the children, conventional medical and surgical treatment of OSA had failed; therefore, these children were considered tracheostomy candidates. The remaining three children had had tracheostomies placed in infancy. Specific signs and symptoms with regard to each patient's OSA were identified and recorded. Bronchoscopy was performed preoperatively to evaluate the airway and localize the site of obstruction and again postoperatively if the patient's signs and symptoms recurred. Oxygen saturation and sleep patterns were monitored overnight in the five patients without tracheostomies, revealing a mean apnea index of 25.3 (range, 2.0 to 60.0) and mean lowest desaturation of 73% (range, 62% to 77%). All patients underwent a variety of skeletal procedures to advance the mandible, maxilla, and/or chin. OUTCOME MEASURES: Criteria for success after treatment were twofold: (1) decannulation and (2) cessation or improvement in symptoms facilitating avoidance of tracheostomy. Criteria for failure, likewise, were (1) inability to decannulate and (2) recurrence or nonimprovement in symptoms necessitating tracheostomy. RESULTS: To date, with a mean follow-up time of 7.2 years (range, 19 months to 19 years), the treatment of four of the eight children in our population can be considered a success. Two of the three children with previously placed tracheostomies were able to be decannulated within days of surgery and experienced no further signs or symptoms of OSA. Two other children experienced complete cessation of clinical signs and symptoms and elimination of previous oxygen requirements. Of the four patients in whom treatment failed, three had transient improvement (mean, 6 months) and, despite skeletal stability, eventually experienced relapse of symptoms: one patient with Down syndrome and tracheobronchomalacia required subsequent tracheostomy; the second had a central obstructive component and underwent a ventriculoperitoneal shunt for treatment of a Chiara I malformation; and the third experienced relapse of symptoms due to lack of mandibular growth. The fourth child could not be decannulated because of accompanying tracheal and laryngeal malacia. CONCLUSIONS: Skeletal advancement can be an effective treatment for medically refractory OSA in children. Success, however, is dependent not only on skeletal position but also on neuromuscular adaptation. Bronchoscopy is the most valuable diagnostic and predictive tool.

Adolescent↗

PubMed2005

Post-activation potentiation: underlying physiology and implications for motor performance.

The response of muscle to volitional or electrically induced stimuli is affected by its contractile history. Fatigue is the most obvious effect of contractile history reflected by the inability of a muscle to generate an expected level of force. However, fatigue can coexist with post-activation potentiation (PAP), which serves to improve muscular performance, especially in endurance exercise and activities involving speed and power. The measured response of muscular performance following some form of contractile activity is the net balance between processes that cause fatigue and the simultaneous processes that result in potentiation. Optimal performance occurs when fatigue has subsided but the potentiated effect still exists. PAP has been demonstrated using electrically induced twitch contractions and attributed to phosphorylation of myosin regulatory light chains, which makes actin and myosin more sensitive to Ca(2+). The potentiated state has also been attributed to an increase in alpha-motoneuron excitability as reflected by changes in the H-reflex. However, the significance of PAP to functional performance has not been well established. A number of recent studies have applied the principles of PAP to short-term motor performance as well as using it as a rationale for producing long-term neuromuscular changes through complex training. Complex training is a training strategy that involves the execution of a heavy resistance exercise (HRE) prior to performing an explosive movement with similar biomechanical characteristics, referred to as a complex pair. The complex pair is then repeated for a number of sets and postulated that over time will produce long-term changes in the ability of a muscle to generate power. The results of these studies are equivocal at this time and, in fact, no training studies have actually been undertaken. The discrepancies among the results of the various studies is due in part to differences in methodology and design, with particular reference to the mode and intensity of the HRE, the length of the rest interval within and between the complex pairs, the type of explosive activity, the training history of the participants, and the nature of the dependent variables. In addition, few of the applied studies have actually included measures of twitch response or H-reflex to determine if the muscles of interest are potentiated. There is clearly more research required in order to clarify the functional significance of PAP and, in particular, the efficacy of complex training in producing long-term neuromuscular adaptations.

Fatigue↗

PubMed2007

Power athletes and distance training: physiological and biomechanical rationale for change.

The development of power lies at the foundation of all movement, especially athletic performance. Unfortunately, training programmes of athletes often seek to improve cardiovascular endurance through activities such as distance training that are detrimental for the performance of power athletes, rather than using other means of exercise. Performance decrements from continuous aerobic training can be a result of inappropriate neuromuscular adaptations, a catabolic hormonal profile, an increased risk for overtraining and an ineffective motor learning environment. However, long, sustained exercise continues to be employed at all levels of competition to obtain benefits that could be achieved more effectively through other forms of conditioning. While some advantageous effects of endurance training may occur, there are unequivocal drawbacks to distance training in the power athlete. There are many other types of conditioning that are more relevant to all anaerobic sports and will also avoid the negative consequences associated with distance training.

Biomechanical Phenomena↗

PubMed2002

Effect of mandibular setback surgery on the posterior airway size.

Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy, and therefore, mandibular setback surgery has the potential to diminish airway size. The purpose of this study was to evaluate the long-term effect of mandibular setback surgery on the airway size. The material consisted of pre- and postoperative (minimum 1 year) lateral radiograms of 22 individuals (18 females and 4 males) with a mean age of 30 years, who had undergone mandibular setback surgery to correct skeletal Class III discrepancies. Hard and soft tissue points were digitized with a Numonics Accugrid digitizer and analyzed with Xmetrix software. A paired t test was used to evaluate the difference between pre- and postoperative measurements. In addition, Pearson's coefficient correlation was calculated to reveal the possible association between the skeletal change in relation to the change in airway size. The mean value for the initial SNA was 81.3 degrees, 85.4 degrees for SNB, 36.9 degrees for S-Na/MP, and for the posterior airway, 10.5 mm and 12.0 mm retropalatinally and retrolingually, respectively. At the postoperative evaluation, SNB was 80.7 degrees, S-Na/MP 41.0 degrees, and the posterior airway retropalatinally 8.3 mm and retrolingually 9.8 mm. Statistical analysis revealed a highly significant correlation between the change in the ANB angle and in the S-Na/MP angle versus the change in the upper airway size, both retropalatinally and retrolingually. Mandibular setback surgery with posterior rotation may gradually result in increased upper airway resistance in cases where neuromuscular adaptation is insufficient to compensate for the reduction in the airway size. Therefore, large anteroposterior discrepancies should be corrected by combined maxillary and mandibular osteotomies.

Adolescent↗

PubMedDate not supplied

[Effects of orthodontic treatment on the masseter muscle inhibitory reflex].

OBJECTIVE: The aim of this study was to identify the effect of the orthodontic treatment on inhibitory masseteric reflex. METHODS: Twenty-three patients with any type of malocclusion and without any temporomandibular joint dysfunction were studied and treated under arch wire technique with Roth's brackets prescription (0.22" x 0.28"). Electromyographic record of the inhibitory masseteric reflex was obtained before and after orthodontic treatment. RESULTS: ANOVA test identified not reflex differences between molar relation types; using Student t test for paired data it was identified that with orthodontic treatment (14.65 +/- 2.40 months), the left reflex latency was increased from 6.17 +/- 9.29 ms to 37.00 +/- 66.33 ms (p < 0.05). However the left inhibition duration was decreased from 57.78 +/- 30.70 ms to 35.31 +/- 25.72 ms (p < 0.05), the right inhibition amplitude was decreased from 48.40 +/- 34.44 mV to 28.59 +/- 17.26 mV (p < 0.05) and the left inhibition amplitude was decreased from 40.72 +/- 29.75 mV to 18.73 +/- 17.68 mV (p < 0.05). CONCLUSIONS: Orthodontic treatment produced constraint of the masseter inhibitory capacity, which could be a transitory neuromuscular adaptation signal in the presence of sensorial scheme modifications. It is necessary to wait for a longer period of time before a new register to clarify the reflex morphology tendency.

Adolescent↗

PubMed2000

Long-term ankle brace use does not affect peroneus longus muscle latency during sudden inversion in normal subjects.

OBJECTIVE: External ankle supports are widely used in sports medicine. However, ankle bracing in a healthy ankle over a sustained period has been scrutinized due to possible neuromuscular adaptations resulting in diminished dynamic support offered by the peroneus longus muscle. Although this claim is anecdotal in nature, we sought to investigate the effects of long-term ankle bracing using 2 commonly available appliances on peroneus longus latency in normal subjects. Our second purpose was to evaluate the effects of ankle bracing on peroneus longus latency before a period of extended use. DESIGN AND SETTING: A 3 x 3 x 2 design with repeated measures on the first and third factors was used in this study. All data were collected in the Sports Injury Research Laboratory. SUBJECTS: Twenty (12 men and 8 women) physically active college students (age = 23.6 +/- 1.7 years; height = 168.7 +/- 8.4 cm; weight = 69.9 +/- 12.0 kg) free of ankle or lower extremity injury in the 12 months before the study and not involved in a strength-training or conditioning program in the 6 months before the study. MEASUREMENTS: We evaluated peroneus longus latency by studying the electromyogram of the muscle after sudden foot inversion. RESULTS: Application of a lace-up or semirigid brace did not affect peroneus longus latency. Additionally, 8 weeks of longterm ankle appliance use had no effect on peroneus longus latency. CONCLUSIONS: The duration of the peroneus longus stretch reflex (latency) is neither facilitated nor inhibited with extended use of an external ankle support. Proprioceptive input provided by the muscle spindles within the peroneus longus does not appear to be compromised with the long-term use of ankle braces.

Journal Article↗

PubMed1983

Effects of strength training on G tolerance.

The G tolerance of pilots flying modern, high-performance fighter aircraft is crucial. Therefore, methods to increase G tolerance are of vital importance. In this study, G tolerance was studied in a human centrifuge using simulated aerial combat maneuvers (ACM)--consisting of 15-s periods of 4.5 and 7 G until exhaustion--before and after 11 weeks of muscle strength training. The ACM-time in 11 fighter pilots was increased after this training by 39%. Gains were observed in knee extensor muscle strength during slow contractions by 17% and in anaerobic power by 14%. Aerobic performance and various muscle histochemical indices, as assessed from muscle biopsy samples obtained from m. vastus lateralis, were unchanged. Neuromuscular adaptation seems to be responsible for the increased muscle strength, as well as for the improved performance of the M-1 straining maneuver. This might explain the enhanced G tolerance.

Adult↗

PubMed1980

Postoperative results of posterior maxillary osteotomy after long-term immobilization.

We have treated 22 patients for correction of open bite, using a one-stage posterior maxillary osteotomy, by two different techniques. Relapse was the most significant postoperative complication after this procedure. To avoid the high incidence and, particularly, the severity of this complication, we used long-term (11 to 12 weeks) maxillomandibular fixation to provide for neuromuscular adaptation to the newly derived rest position in the mandible.

Adolescent↗

PubMed1994

Knee extensor fatigability and strength after bicycle ergometer training.

The objective of this research was to study the effect of a 10-week bicycle-ergometer training program on the strength of knee extension and vastii muscles fatigability in male subjects with no knee pathology. Subjects performed maximum effort isometric knee extension at 60 degrees of knee flexion. Fatigue rates of vastii muscles were evaluated by quantifying myoelectric power density spectrum changes during a 1-minute dynamic (concentric/eccentric) knee exercise. Maximal oxygen uptake as well as muscle efficiency increased (p < .01), indicating positive changes in physical fitness and neuromuscular adaptation in muscles. The endurance of knee extensors increased (p < .001-.05) whereas their maximal short-term force decreased (p < .01-.05). Training response was greater (p < .01-.05) in vastus medialis than in vastus lateralis muscle. This effect encourages to use bicycle ergometer in knee rehabilitation programs.

Adaptation, Physiological↗

PubMed1996

[Clinical study of a mivacurium-propofol combination for laparoscopic surgery in children].

Coelioscopic surgery in children is today in constant progress and requires pharmacological agents which provide excellent surgical conditions for variable and unpredictable durations. The mivacurium-propofol association was clinically studied in this context in 30 ASA I patients aged from 6 to 16 years and appeared safe, efficient and easy to use. The orbicularis oculi and pollicis adductor stimulation allows simple and adapted neuromuscular blockade monitoring. Double-burst stimulation at the ulnar nerve improves the detection of a residual curarization.

Age Factors↗

PubMed1990

Axotomy-induced temporal dissociation of long-term adaptive changes at neuromuscular synapses of a crayfish phasic motoneuron.

Periodic in situ stimulation of an identified crayfish phasic extensor motoneuron for 3 consecutive days (2 h/day) at 2.5 Hz leads to long-term adaptation (LTA) of its neuromuscular synapses. LTA is characterized by reductions in both initial excitatory postsynaptic potential (EPSP) amplitudes and synaptic depression during repeated stimulation. These adaptive changes were evident 1 day following periodic stimulation. Axotomy of the motoneuron before or after the first day of stimulation of its distal surviving axon abolished both adaptive changes. Axotomy between the second and third stimulation periods abolished only the resistance to synaptic depression. Both adaptive changes were expressed following axotomy after the third day of stimulation. Axotomy alone did not affect neuromuscular transmission in control, unstimulated animals. These results show that axonal continuity between the phasic extensor motoneuron's cell body and its neuromuscular synapses is required at specific times during periodic stimulation for the expression of each of these long-term adaptive changes in neuromuscular transmission. Furthermore, the two adaptive changes in transmission are temporally separable, with the resistance to depression requiring more periodic stimulation to emerge than the reduction in initial EPSP amplitudes. The results also suggest that the molecular components responsible for the expression of these adaptive changes are synthesized in the soma and transported down the axon in response to periodic stimulation of the phasic axon.

Adaptation, Physiological↗