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Results for “Neuromuscular adaptability”

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At least 109 records · Page 6Linked to original sources

PubMed2000

Electromyogram changes during sustained contraction after resistance training in women in their 3rd and 8th decades.

The present study aimed at investigating the neuromuscular adaptations to 6 weeks of resistance training in women in their third (6 experimental, 8 controls) and eighth decades (8 experimental, 8 controls). The surface electromyogram (sEMG) was measured from the biceps brachii muscle during constant-force isometric contractions lasting 12 s at 80% of maximal voluntary contraction (MVC). All the signals were analysed adopting in the time domain the root mean square (RMS) as a measure of amplitude and in the frequency domain the median frequency (MDF) of the power spectrum. Quantitative analysis was performed from the 3rd to the 6th second, to describe the early phase of the contraction ("Early"), starting from point at which 80% of the MVC was reached, and from the 9th to the 12th second, to describe the last part of the constant-force sustained contraction ("Late"). After training, the MVC increased by 22.4% in the young (P < 0.0001) and by 13.4% in the older (P < 0.05) women. The "Early" RMS increased by 60.4% with respect to the pre-training condition in the young (P < 0.01) but not in the older women. In contrast, the "Late" RMS increased by 46.7% in the older (P < 0.05) but not in the young women. The MDF remained unchanged in both groups. These results indicate that young and older women showed different training-induced adaptation of the motor unit (MU) activation pattern, in order to keep a constant level of force during a sustained isometric contraction at 80% of MVC.

Adolescent↗

PubMed1978

Myoelectric frequency changes in children during static force production.

Neuromuscular adaptations to a submaximal static contraction for a period of 2 min were investigated using children as subjects to detect changes in the contributing frequency components of the electromyogram (EMG) recorded from surface electrodes. The purpose of this study was to determine the similarity between EMG response patterns of children and published data for adult subjects under similar conditions. Spectral analysis of the EMG signal revealed a shift to lower frequency components and a concurrent increase in total variance of the signal as a response to fatigue. The frequency shift and increase amplitude for the EMG signal were discussed in light of evidence for recruitment and synchronization of motor units and changes in muscle fiber conduction velocity as possible mechanisms.

Adolescent↗

PubMed1975

Postinsertion changes in complete dentures.

The influence of denture changes, occurring during a period of use ranging from one to 15 years, was studied in a group of 35 complete denture subjects. Clinical and electromyographic data were collected. N0 correlation was found between denture serviceability on the one hand and masticatory performance and muscular coordination during chewing of test food on the other. However, a significant correlation was found between a subject's satisfaction and his masticatory performance, as well as his muscular coordination during chewing of test food. It appears that, as soon as the time-linked and insidious imperfections of complete dentures are compensated for by feedback-controlled neuromuscular adaptation, the subject's adjusted pattern of function does not affect his performance and comfort and consequently his satisfaction. Despite the obvious differences among the respective subjects, the number of masticatory strokes in the same individual was rather constant. Obviously, a subject's satisfaction may easily camouflage lack of denture fit, including its potential concomitant pathologic sequelae. Therefore, periodic examinations and adequate corrections are essential to successful complete denture treatment.

Adult↗

PubMed2026

Molecular mechanisms of neuroendocrine regulation of molting in the Chinese mitten crab (Eriocheir sinensis): A transcriptomic analysis based on eyestalk ablation model.

Molting disability severely restricts the sustainable aquaculture of the Chinese mitten crab, yet the neuroendocrine mechanisms coordinating physiological responses remain poorly understood. Using unilateral eyestalk ablation to remove the primary source of molt-inhibiting hormone (MIH), we performed time-resolved transcriptomic profiling of the thoracic ganglion at 24 h (early premolt) and 48 h (ecdysis) post-ablation. We identified 2825 differentially expressed genes and uncovered a biphasic molecular response. At 24 h, the thoracic ganglion activates pathways associated with neuromuscular adaptation, oxidative stress, and cardiac muscle contraction. Notably, the arachidonic acid metabolism pathway is selectively rewired: cytochrome P450 ω-hydroxylases (CYP2J2, CYP4V2) are upregulated, while competing branches (epoxide hydrolase, cyclooxygenase) are suppressed, promoting local synthesis of the potent vasoconstrictor 20-HETE within the thoracic ganglion. This enzymatic switch provides a mechanistic link between MIH withdrawal and the local generation of elevated hemolymph pressure required for molting. By 48 h, the transcriptional program shifts toward chitin-based extracellular matrix remodeling, glycosphingolipid biosynthesis, and synaptic reorganization. Collectively, our findings redefine the thoracic ganglion as an active neuroendocrine integrator that translates reduced MIH signaling into phased physiological outputs, revealing a "neuro-endocrine-hemolymph pressure" regulatory axis. This study provides novel molecular targets (e.g., CYP2J2, CHS1, UGCG) for mitigating molting disability in E. sinensis aquaculture.

Animals↗

PubMed2004

The role of selected extrinsic foot muscles during running.

OBJECTIVE: To determine the kinematic, kinetic and EMG responses to perturbations of the foot by running in varus, neutral, and valgus-wedged shoes. DESIGN: Within-subjects study comparing kinematics, kinetics and EMG while running in three different shoe conditions. BACKGROUND: Excessive pronation has been cited as a key contributor to many types of running injuries. However, the roles of the extrinsic foot muscles (those that control motion of the foot) during the stance phase of running have not been adequately identified, which is critical to determining the relationship between pronation and injury. METHODS: Ten males ran in varus, valgus, and neutral-wedged shoes while three-dimensional kinematic and kinetic data and EMG data were collected. Surface EMG data were collected from the tibialis anterior, peroneus longus, medial and lateral gastrocnemius, and soleus. Indwelling EMG was obtained from the tibialis posterior. The net joint moment, power, and total positive and negative work was calculated in the frontal plane. EMG onset, offset, and integrated values were reported. RESULTS: The maximum eversion angle, maximum inversion moment and total negative work done in the frontal plane were greatest while running in the valgus shoe and least in the varus shoe. The greater joint moment was not accompanied by changes in muscle activation patterns, although the tibialis posterior data were inconclusive in this respect. CONCLUSIONS: Greater pronation leads to greater energy absorption in the foot invertor muscles and tendons. While not conclusive, the EMG data suggest that for these muscles there was not a neuromuscular adaptation to the perturbation.

Adult↗

PubMed1989

Factors influencing the stability of the sagittal split osteotomy for mandibular advancement.

Relapse continues to be a potential problem with use of the sagittal split osteotomy to advance the mandible. In an effort to isolate predictive factors, the records of 235 patients were analyzed to determine the pretreatment facial morphology, the amount of advancement, the amount of relapse, and the duration of relapse. No relationship was found between any of the measures of facial morphology and relapse. However, the amount of advancement, the amount of relapse, and the duration of relapse all were found to be strongly related. It was found that all patients shared a similar facial morphology, and thus no influence of facial form on relapse would be expected from this group. The relationships between advancement and relapse could be attributed to neuromuscular adaptation, which would be more prolonged and more extensive in instances of greater advancement, and thus give rise to relapse of greater extent and duration. It is therefore suggested that mandibular advancements of greater than 10 mm be fixed more rigidly and for a greater length of time than those of lesser magnitude.

Adolescent↗

PubMed2001

EMG activities and plantar pressures during ski jumping take-off on three different sized hills.

Different profiles of ski jumping hills have been assumed to make the initiation of take-off difficult especially when moving from one hill to another. Neuromuscular adaptation of ski jumpers to the different jumping hills was examined by measuring muscle activation and plantar pressure of the primary take-off muscles on three different sized hills. Two young ski jumpers volunteered as subjects and they performed several trials from each hill (K-35 m, K-65 m and K-90 m) with the same electromyographic (EMG) electrode and insole pressure transducer set-up. The results showed that the differences in plantar pressure and EMGs between the jumping hills were smaller than expected for both jumpers. The small changes in EMG amplitudes between the hills support the assumption that the take-off was performed with the same intensity on different jumping hills and the timing of the gluteus EMG demonstrates well the similarity of the muscle activation on different hills. On the basis of the results obtained it seems that ski jumping training on small hills does not disturb the movement patterns for bigger hills and can also be helpful for special take-off training with low speed.

Electromyography↗

PubMed2004

Training volume and strength and power development.

The purpose of this study was to determine if three training loads equated by volume differed in terms of the temporal, kinematic and kinetic characteristics of each set. Twelve experienced weightlifters (30.2+/-10.6 years old and 75.8+/-13.0 kg) performed three sets (6 x 30% 1RM, 3 x 60% 1RM and 2 x 90% 1RM) of ballistic squats on an instrumented supine squat machine. Repeated measures ANOVA and Tukey HSD post hoc comparisons were used to distinguish significant differences between the three training loads on a variety of temporal, kinematic and kinetic variables. Significantly (p< 0.05) greater total time under tension during the eccentric (41-53%) and concentric phases (27-31%) was observed for the 30% 1RM condition compared to the other two conditions. Similarly, the lighter loading intensity resulted in significantly greater total eccentric (9-19%) and concentric (14-24%) force output compared to the other two conditions. Greater total power output was associated with the 30% 1RM condition for both the eccentric (25-48%) and concentric (40-69%) phases. Greater total work (9-24%) was also associated with the 30% 1RM condition. The 60% 1RM condition produced significantly greater total work, force and power compared to the 90% 1RM condition. However, greater concentric impulse (29-42%) was associated with the 90% 1RM condition. It is suggested that strength and power research needs to adopt a set kinematic and kinetic analysis approach within the research designs so that a better understanding of the nature of the neuromuscular adaptations elicited by different loading parameters is achieved.

Adaptation, Physiological↗

PubMed1998

Physiological differences between professional and elite road cyclists.

The purpose of this study was to compare the physiological responses of professional and elite road cyclists during an incremental cycle ergometer test. Twenty-five elite cyclists (EC; 23+/-1 yr) and 25 professional cyclists (PC; 25+/-2yr) performed a ramp protocol (increases of 25 W x min(-1)) during which the following parameters were measured: oxygen consumption (VO2), pulmonary ventilation (VE), ventilatory equivalents for oxygen and carbon dioxide (VE x VO2(-1) and VE x VCO2(-1), respectively), respiratory exchange ratio (RER), ventilatory thresholds 1 and 2 (VT1 and VT2, respectively), blood lactate, and electromyographic activity (EMG) of the vastus lateralis. Significant differences existed between the two groups mainly at submaximal intensities, since both VT1 and VT2 occurred at a higher exercise intensity (p<0.001) in PC than in EC (VT2: 80.4+/-6.6 vs 87.0+/- 5.9% VO2max in EC and PC, respectively). Lactate levels showed a similar response in both groups at low-to-moderate intensities (< 300 W), and thereafter blood lactate was significantly higher in EC. Finally, the "electromyographic threshold" (EMGT) occurred at a significantly higher intensity (p < 0.05) in PC when compared to EC (64.7+/-14.2 vs 56.0+/-14.9% VO2max, respectively). It was concluded that, in comparison with EC, PC exhibit some remarkable physiological characteristics such as a high VT2, an important reliance on fat metabolism even at high power outputs, and several neuromuscular adaptations.

Adaptation, Physiological↗

PubMed2002

Ambulatory efficiency in persons with acquired brain injury after a rehabilitation intervention.

OBJECTIVE: the purpose was to assess changes in cardiorespiratory responses to treadmill ambulation in a sample of patients with acquired brain injury. RESEARCH DESIGN: a repeated measures, pre-test post-test design examined differences between submaximal and peak responses at admission and discharge. METHODS AND PROCEDURES: forty individuals (29 male, 11 female) were studied. Subjects performed an ambulatory treadmill test during which heart rate (EKG) and oxygen consumption (VO(2)) were monitored continuously. Total ambulation time (TAT) was also recorded. RESULTS: TAT increased from 10.3 (SD 3.1) minutes to 13.6 (SD 3.5) minutes (p < 0.01). Peak HR did not change (168 (SD 20) bpm vs. 167 (SD 21 bpm)) nor did peak VO(2) (23.5 (SD 6.6)ml/min/kg vs. 24.3 (SD 6.4)ml/min/kg; p = 0.09). However, both sub-maximal HR and VO(2) decreased (p < 0.05) between 2-12 minutes when most subjects were still capable of ambulating. CONCLUSIONS: the results suggest an improvement in both aerobic capacity and movement efficiency. Further controlled studies will be necessary to distinguish between cardiorespiratory and neuromuscular adaptations. The changes observed should allow for greater community participation and functional independence after discharge.

Adolescent↗

PubMed2004

Neuromuscular control and coordination during cycling.

The neuromuscular control aspect of cycling has been investigated through the effects of modifying posture and cadence. These studies show that changing posture has a more profound influence on neuromuscular coordination than does changing slope. Most of the changes with standing posture occur late in the downstroke: increased ankle and knee joint moment, reduced hip joint moment and greater activity in specific muscles. Due to the influence of lower extremity inertial properties, higher pedaling frequency induces more neuromuscular changes at the hip than at the knee or ankle joints. These neuromuscular adaptations to environmental and task constraints are discussed with regard to the contributions of the central nervous system and the solution provided by peripheral anatomical structure--mono- and biarticular muscles. The results indicate that training and related movement analysis should be specific to the motion, supporting the notion of task-specific training.

Bicycling↗

PubMedDate not supplied

Motor skill learning of concentric and eccentric isokinetic movements in older adults.

Neuromuscular adaptation at the onset of resisted exercise can be observed as increases in torque and surface electromyography. The effect of learning the motor task has been hypothesized to contribute to these early increases, especially for older people. Thus, the purpose of this study was to investigate the facilitatory effects of practice on motor performance in older adults during short-term isokinetic training of the ankle dorsiflexors (DF). Twenty-eight men and women (M = 76.3 +/- 4.6 years) volunteered for a 2-week, 3-days/week strength training program. They were tested in a sitting position on a KinCom isokinetic dynamometer at 30, 90, and 180 degrees s-1 through 40 degrees of DF movement (concentric and eccentric contractions). Criterion curves of lever arm angle patterns were cross-correlated with subject-generated angle patterns, showing significantly better correlations on posttest versus baseline. Smoothness and proficiency of muscle contraction improved with practice by fewer hesitations in movement and increased ability to change between concentric and eccentric muscle contractions. Increased agonist electromyography and torque were hypothesized to be secondary to greater neural drive and/or synchronization of motor unit firing rate and/or recruitment during maximal voluntary contraction, improved coordination, and adapted neural control of concentric and eccentric muscle contraction.

Aged↗

PubMedDate not supplied

Midsole material-related force control during heel-toe running.

The impact maximum and rearfoot eversion have been used as indicators of load on internal structures in running. The midsole hardness of a typical running shoe was varied systematically to determine the relationship between external ground reaction force (GRF), in-shoe force, and kinematic variables. Eight subjects were tested during overground running at 4 m/s. Rearfoot movement as well as in-shoe forces and external GRF varied nonsystematically with midsole hardness. Kinematic parameters such as knee flexion and foot velocity at touchdown (TD), also varied nonsystematically with altered midsole hardness. Results demonstrate that considerable variations of in-shoe loading occur that were not depicted by external GRF measurements alone. Individuals apparently use different strategies of mechanical and neuromuscular adaptation in response to footwear modifications. In conclusion, shoe design effects on impact forces or other factors relating to injuries depend on the individual and therefore cannot be generalized.

Adult↗

PubMed2005

Age-related differences in peak joint torques during the support phase of single-step recovery from a forward fall.

BACKGROUND: Previous studies have reported that older adults have a reduced ability to recover balance with a single step after a forward-induced fall. To better understand the reasons for this reduced ability, this study investigated any age-related differences in peak joint torques during the support phase of a single-step balance recovery from a forward fall. METHODS: Ten young (19-23 years old) and 10 older (65-83 years old) men were released from forward-leaning positions and attempted to recover their balance with a single step. Lean was increased until they failed to recover their balance with a single step. Peak extensor torques were calculated for the support phase of balance recovery and were compared across age groups. RESULTS: A consistent pattern of joint torques emerged during the support phase of balance recovery, suggesting a similar strategy across young and older participants. Despite this similarity, older participants exhibited smaller peak knee extensor torques during the support phase of single-step balance recoveries, and trends toward larger peak extensor torques at the hip and ankle. CONCLUSIONS: The age-related differences found are believed to be the combined result of an age-related reduction in muscle strength and an age-related neuromuscular adaptation to mitigate the effects of muscle strength loss on physical performance capabilities.

Accidental Falls↗

PubMed1997

Resistance exercise prevents plantar flexor deconditioning during bed rest.

Because resistance exercise (REX) and unloading induce opposing neuromuscular adaptations, we tested the efficacy of REX against the effects of 14 d of bed rest unloading (BRU) on the plantar flexor muscle group. Sixteen men were randomly assigned to no exercise (NOE, N = 8) or REX (N = 8). REX performed 5 sets x 6-10 repetitions to failure of constant resistance concentric/eccentric plantar flexion every other day during BRU. One-repetition maximum (1RM) strength was tested on the training device. The angle-specific torque-velocity relationship across 5 velocities (0, 0.52, 1.05, 1.75, and 2.97 rad.s-1) and the full range-of-motion power-velocity relationship were assessed on a dynamometer. Torque-position analyses identified strength changes at shortened, neutral, and stretched muscle lengths. Concentric and eccentric contractile work were measured across ten repetitions at 1.05 rad.s-1. Maximal neural activation was measured by surface electromyography (EMG). 1RM decreased 9% in NOE and improved 11% in REX (P < 0.05). Concentric (0.52 and 1.05 rad.s-1), eccentric (0.52 and 2.97 rad.s-1), and isometric angle-specific torques decreased (P < 0.05) in NOE, averaging 18%, 17%, and 13%, respectively. Power dropped (P < 0.05) in NOE at three eccentric (21%) and two concentric (14%) velocities. REX protected angle-specific torque and average power at all velocities. Concentric and eccentric strength decreased at stretched (16%) and neutral (17%) muscle lengths (P < 0.05) in NOE while REX maintained or improved strength at all joint positions. Concentric (15%) and eccentric (11%) contractile work fell in NOE (P < 0.05) but not in REX. Maximal plantar flexor EMG did not change in either group. In summary, constant resistance concentric/eccentric REX completely prevented plantar flexor performance deconditioning induced by BRU. The reported benefits of REX should prove useful in prescribing exercise for astronauts in microgravity and for patients susceptible to functional decline during bed- or chair-bound hospital stays.

Adult↗

PubMed2002

Effect of four-month vertical whole body vibration on performance and balance.

PURPOSE: This randomized controlled study was designed to investigate the effects of a 4-month whole body vibration-intervention on muscle performance and body balance in young, healthy, nonathletic adults. METHODS: Fifty-six volunteers (21 men and 35 women, aged 19-38 yr) were randomized to either the vibration group or control group. The vibration-intervention consisted of a 4-month whole body vibration training (4 min.d(-1), 3-5 times a week) employed by standing on a vertically vibrating platform. Five performance tests (vertical jump, isometric extension strength of the lower extremities, grip strength, shuttle run, and postural sway on a stability platform) were performed initially and at 2 and 4 months. RESULTS: Four-month vibration intervention induced an 8.5% (95% CI, 3.7-13.5%, P=0.001) net improvement in the jump height. Lower-limb extension strength increased after the 2-month vibration-intervention resulting in a 3.7% (95% CI, 0.3-7.2%, P=0.034) net benefit for the vibration. This benefit, however, diminished by the end of the 4-month intervention. In the grip strength, shuttle run, or balance tests, the vibration-intervention showed no effect. CONCLUSION: The 4-month whole body vibration-intervention enhanced jumping power in young adults, suggesting neuromuscular adaptation to the vibration stimulus. On the other hand, the vibration-intervention showed no effect on dynamic or static balance of the subjects. Future studies should focus on comparing the performance-enhancing effects of a whole body vibration to those of conventional resistance training and, as a broader objective, on investigating the possible effects of vibration on structure and strength of bones, and perhaps, incidence of falls of elderly people.

Adult↗

PubMed1995

Effect of oral corticosterone administration on locomotor development of neonatal and juvenile rats.

In order to simulate the elevated corticosteroid levels to which offspring of stressed women may be subjected, rat pups were treated daily with two levels of oral corticosterone from the 2nd to the 15th postnatal day. The rat pups were subjected to swimming tests from their 8th postnatal day to examine their neuromuscular development and learning abilities. The locomotor performance of corticosterone-treated groups was similar to that of controls but its development was delayed, which demonstrates that even relatively low levels of corticosterone have a significant negative influence on the maturation and learning ability of neonatal rat pups. This indicates that the glucocorticoid levels to which suckling neonates (for example, children of women suffering from stress) might be exposed could modify the complex integrated neuromuscular adaptive mechanisms involved in normal locomotor development.

Animals↗

PubMed2006

Age-related differences in muscle power during single-step balance recovery.

The purpose of this study was to investigate age-related differences in muscle power during a surrogate task of trip recovery. Participants included 10 healthy young men (19-23 years old) and 10 healthy older men (65-83). The task involved releasing participants from a forward-leaning posture. After release, participants attempted to recover their balance using a single step of the right foot. Muscle power at the hip, knee, and ankle of the stepping limb were determined from the product of joint angular velocity and joint torque. Muscle powers during balance recovery followed a relatively consistent pattern in both young and older men, and showed effects of both lean and age. Interestingly, the effects of age did not always involve smaller peak power values in the older men as expected from the well-documented loss of muscle power with aging. Older men exhibited smaller peak muscle power at the knee and larger peak muscle power at the ankle and hip compared to young men. The increases in muscle power at the ankle and hip may result from a neuromuscular adaptation aimed at improving balance recovery ability by compensating for the age-related loss of muscle function.

Adult↗