Neuromuscular Activity Research Articles

Characteristics of Lower Extremity Muscle Activation in Response to Change in Inclination while Walking on a Treadmill

Treadmill walking is a popular form of exercise that offers many benefits to its users, such as improvements in cardiovascular health and gait patterns. Few research studies have explored muscle activation of various lower extremity joints at different levels of inclination on a treadmill. Therefore, this study aims to further characterize muscle activation during gait in healthy individuals in response to changes in treadmill inclination at a constant speed. Twenty healthy participants (24.5 ± 4.3 years of age) were recruited for this study. Participants were instructed to walk on a treadmill at six different inclines (0%, 3%, 6%, 9%, 12%, and 15%) while maintaining a constant speed of 3.4 mph. Muscle activation of the tibialis anterior (TA), gastrocnemius (GA), gluteus maximus (GMAX), gluteus medius (GMED), vastus medialis (QUADS), and biceps femoris (HS) were collected using surface EMG. There were slight differences in muscle activation between the muscle groups during the various intervals. However, there were no significant differences between muscle groups. The results revealed that the extensor muscles (GA, HS, and GMAX) of the lower extremity showed trends of longer activation periods with an increase in inclination. This study found that as inclination increases, activation of the extensor muscles of the lower extremity also increases while walking on a treadmill. The findings of this study will serve as a baseline for research to compare populations with known gait impairments, such as individuals with HIV, post-stroke, or the elderly, to better understand EMG analysis leading to gait deviations or abnormalities with neuromuscular activation.

Exoskeleton Device For Left Hemiplegia Patients With Electromyograph

Loss of motion is a condition in which muscle activity in a part of the body is lost; it is also known as paralysis. Loss of motion is most commonly caused by a severe stroke, in which the blood supply to a portion of the cerebrum is cut off. Hemiplegia is a sort of loss of motion which influences half of the body, i.e., one arm and one leg of same side of the body will not be functioning. Normally, left hemiplegia is a severe disease caused by a lack of blood supply to the cerebrum’s right hemisphere. Fixed frameworks, such as Lokomat, are used in rehabilitation centres to assist patients in resuming their normal activities. However, the results provided by those frameworks are extremely time-consuming and will only benefit patients who can walk on a treadmill. However, these frameworks are not portable and cannot be used for home or day-to-day exercises. To overcome these disadvantages, this paper presents the ergonomic framework, which includes an exoskeleton that guides and assists in the development process of the left upper arm. The entire framework is powered by a compatible and miniaturized motor via a microcontroller, which aids in the development of patient flexion and augmentation. Meanwhile, EMG acquisition would be done by putting flexible pre-gelled electrodes to know the recuperation of physiological neuro-muscular activities of the subject.

A Review of the Relationships Between Knee Pain and Movement Neuromechanics.

Knee injury and disease are common, debilitating, and expensive. Pain is a chief symptom of knee injury and disease and likely contributes to arthrogenic muscle inhibition. Joint pain alters isolated motor function, muscular strength, and movement biomechanics. Because knee pain influences biomechanics, it likely also influences long-term knee joint health. The purpose of this article is 2-fold: (1)review effects of knee pain on lower-extremity muscular activation and corresponding biomechanics and (2)consider potential implications of neuromechanical alterations associated with knee pain for long-term knee joint health. Experimental knee pain is emphasized because it has been used to mimic clinical knee pain and clarify independent effects of knee pain. Three common sources of clinical knee pain are also discussed: patellofemoral pain, anterior cruciate ligament injury and reconstruction, and knee osteoarthritis. The PubMed, Web of Science, and SPORTDiscus databases were searched for articles relating to the purpose of this article. Researchers have consistently reported that knee pain alters neuromuscular activation, often in the form of inhibition that likely occurs via voluntary and involuntary neural pathways. The effects of knee pain on quadriceps activation have been studied extensively. Knee pain decreases voluntary and involuntary quadriceps activation and strength and alters the biomechanics of various movement tasks. If allowed to persist, these neuromechanical alterations might change the response of articular cartilage to joint loads during movement and detrimentally affect long-term knee joint health. Physical rehabilitation professionals should consider neuromechanical effects of knee pain when treating knee injury and disease. Resolution of joint pain can likely help to restore normal movement neuromechanics and potentially improve long-term knee joint health and should be a top priority.

Distinct Kinematic and Neuromuscular Activation Strategies During Quiet Stance and in Response to Postural Perturbations in Healthy Individuals Fitted With and Without a Lower-Limb Exoskeleton.

Many individuals with disabling conditions have difficulty with gait and balance control that may result in a fall. Exoskeletons are becoming an increasingly popular technology to aid in walking. Despite being a significant aid in increasing mobility, little attention has been paid to exoskeleton features to mitigate falls. To develop improved exoskeleton stability, quantitative information regarding how a user reacts to postural challenges while wearing the exoskeleton is needed. Assessing the unique responses of individuals to postural perturbations while wearing an exoskeleton provides critical information necessary to effectively accommodate a variety of individual response patterns. This report provides kinematic and neuromuscular data obtained from seven healthy, college-aged individuals during posterior support surface translations with and without wearing a lower limb exoskeleton. A 2-min, static baseline standing trial was also obtained. Outcome measures included a variety of 0 dimensional (OD) measures such as center of pressure (COP) RMS, peak amplitude, velocities, pathlength, and electromyographic (EMG) RMS, and peak amplitudes. These measures were obtained during epochs associated with the response to the perturbations: baseline, response, and recovery. T-tests were used to explore potential statistical differences between the exoskeleton and no exoskeleton conditions. Time series waveforms (1D) of the COP and EMG data were also analyzed. Statistical parametric mapping (SPM) was used to evaluate the 1D COP and EMG waveforms obtained during the epochs with and without wearing the exoskeleton. The results indicated that during quiet stance, COP velocity was increased while wearing the exoskeleton, but the magnitude of sway was unchanged. The OD COP measures revealed that wearing the exoskeleton significantly reduced the sway magnitude and velocity in response to the perturbations. There were no systematic effects of wearing the exoskeleton on EMG. SPM analysis revealed that there was a range of individual responses; both behaviorally (COP) and among neuromuscular activation patterns (EMG). Using both the OD and 1D measures provided a more comprehensive representation of how wearing the exoskeleton impacts the responses to posterior perturbations. This study supports a growing body of evidence that exoskeletons must be personalized to meet the specific capabilities and needs of each individual end-user.

Changes in Muscle Activation During and After a Shoulder-Fatiguing Task: A Comparison of Elite Female Swimmers and Water Polo Players.

This study compared female athletes with different aquatic sports expertise in their neuromuscular activation before, during, and after a shoulder internal rotation fatigue protocol. Eleven water polo players, 12 swimmers, and 14 controls completed concentric maximal voluntary external and internal shoulder rotations before and after a fatigue protocol consisting of concentric internal rotations at 50% of maximal voluntary contraction for at least 3 min or until reporting a rating of perceived effort RPE of 8/10 or higher. Muscle activation was measured for the maximal voluntary contractions, as well as for the first (T1), middle (T2), and third (T3) minute of the fatigue protocol using surface electromyography (EMG) on pectoralis major, anterior and posterior deltoid, upper and middle trapezius, and latissimus dorsi. Intramuscular EMG was used for supraspinatus, infraspinatus, and subscapularis. Pre-fatigue internal rotation torque was significantly correlated with shorter task duration (r = −0.39, p = 0.02), with water polo players producing significantly greater torque than controls but having significantly lower endurance. Swimmers demonstrated decreased latissimus dorsi activation at T3 compared to T2 (p = 0.020, g = 0.44) and T1 (p = 0.029, g = 0.74), differing from water polo players and controls who exhibited increased agonist activation and decreased activation of stabilizers. Comparing the pre-fatigue to the post-fatigue maximal shoulder rotations, water polo players had decreased activation in subscapularis (p = 0.018, g = 0.67); all groups had decreased activation in latissimus dorsi (p < 0.001), though swimmers demonstrated a large effect (g = 0.97); and controls had decreased activation in supraspinatus (p = 0.005, g = 0.71). Together, these results suggest that sports expertise may be associated with different muscle activation both while and after fatigue is induced. Further research should continue to explore sports-specific patterns of muscle recruitment and fatigue adaptations, as well as if certain strategies are adaptive or maladaptive. This may have important consequences for injury prevention among athletes who perform repetitive overhead movements in their sports and who are susceptible to overuse injuries.

Analysis of Trunk Neuromuscular Activation During Equine-Assisted Therapy in Older Adults.

The three-dimensional movement of the horse in physical therapy is a valuable kinesio-therapeutic phenomenon that simultaneously affects several body systems, including particularly the neuromuscular system. However, the effects of equine-assisted services (EAS) on neuromuscular activation patterns in older adults have not been thoroughly investigated. In this study, we evaluated the impact of a 10-weeks EAS program on trunk muscles in older adults who used a saddle and placed their feet in stirrups for the first 15 minutes and out of stirrups for the remaining 15 minutes of 30-minute EAS sessions. We gathered electromyographic (EMG) data of the trunk muscles five times each on the first, fifth, and 10th sessions: pre-EAS and post-EAS on a stationary horse and at 1-minute, 15-minutes, and 30-minutes on a horse in motion. Participants were 20 adults, aged 60-79 years. We analyzed normalized EMG data with 5 (session time) by 3 (session number) analyses of variance (ANOVAs) with repeated measures and with Bonferroni's testing (p ≤ .05). There was a significant difference over the number of interventions for the right thoracic paravertebral muscle (p = .025) and session time effect for the left trapezius (p = .042), right thoracic paravertebral (p < .001), right and left multifidus (p < .001), and right and left rectus abdominis muscles (p < .001). Thus, trunk muscles in older adults showed complex neuromuscular activation synchronized with the horse's movement, which was influenced by session time and number of interventions. The practical implication of these findings is that EAS can reduce fall risk among elderly adults of both sexes.

Application of suspension systems with rigid elastic elements in the physical rehabilitation of patients with amputation defects of the lower extremities

BACKGROUND: Exercise on suspension systems (gravitational neuromuscular activation) is a highly effective means of physical rehabilitation for patients with various pathologies. Modernization of these products through the use of rigid elastic slings or equipping standard simulators with elastic elements expands the capabilities of this type of equipment, allows you to master new types of exercises, positively affecting the strength, tone and endurance of muscle groups.&#x0D; AIMS: to study the impact of the inclusion of suspension systems with rigid elastic elements (slings) in physical rehabilitation programs for patients with amputation stumps at the hip level.&#x0D; MATERIAL AND METHODS: Twelve patients were tested before and after repeated prosthetics in the conditions of the FB MSE Clinic, which, due to the use of suspension systems, including elastic elements, not only increased strength, endurance and coordination relationships of muscles, but also changed the structure of their walking. The active part of the course of physical rehabilitation with the inclusion of suspension systems with elastic elements was less than two weeks. Setting the patient the task of increasing the speed of movement on the prosthesis in the long term, in the near future we focused exclusively on the correctness of the step structure and subjective sensations.&#x0D; RESULTS: The technical improvement of suspension systems due to elastic elements increases the convenience of their use, the speed of mastering by patients and the degree of efficiency, determining a high percentage of achieving the planned result. Inclusion in the course of training on the simulator with the use of elastic slings allows the patient to master and confidently perform various complexly coordinated movements, including squats, to participate in new types of game activities, which contributes to an increase in his adaptation and socialization in society. Subjectively, patients note greater strength of muscle groups that have undergone additional stress on these systems, improved coordination of movements and endurance when walking on a prosthesis as a whole, as well as a sense of "correctness" of walking, which is confirmed by clinical examination methods and the results of biomechanical tests (increased pace and speed of walking with a decrease in the duration of the step cycle).&#x0D; CONCLUSIONS: Suspension systems are most useful for the prevention and elimination of atrophy of the muscles that support the movement of the pelvic girdle, in comparison with conventional dynamic training and walking on a prosthesis. Modifications of suspension systems by including elastic elements in them allow functional training not only using static, but also dynamic exercises, expanding their application possibilities in medical and complex rehabilitation, adaptive physical culture and adaptive sports.

Sequence-to-Sequence Voice Reconstruction for Silent Speech in a Tonal Language.

Silent speech decoding (SSD), based on articulatory neuromuscular activities, has become a prevalent task of brain–computer interfaces (BCIs) in recent years. Many works have been devoted to decoding surface electromyography (sEMG) from articulatory neuromuscular activities. However, restoring silent speech in tonal languages such as Mandarin Chinese is still difficult. This paper proposes an optimized sequence-to-sequence (Seq2Seq) approach to synthesize voice from the sEMG-based silent speech. We extract duration information to regulate the sEMG-based silent speech using the audio length. Then, we provide a deep-learning model with an encoder–decoder structure and a state-of-the-art vocoder to generate the audio waveform. Experiments based on six Mandarin Chinese speakers demonstrate that the proposed model can successfully decode silent speech in Mandarin Chinese and achieve a character error rate (CER) of 6.41% on average with human evaluation.

May a Nonlocalized Postactivation Performance Enhancement Exist Between the Upper and Lower Body in Trained Men?

Bartolomei, S, De Luca, R, and Marcora, SM. May a nonlocalized postactivation performance enhancement exist between the upper and lower body in trained men? J Strength Cond Res 37(1): 68-73, 2023-The aim of this study was to establish whether a resistance exercise for the upper body may generate a postactivation performance enhancement (PAPE) in the lower body. Thirteen resistance-trained men (age = 26.4 ± 3.3 years, body mass = 76.9 ± 6.3 kg, and height = 177.6 ± 5.2 cm) participated in the present investigation and were tested for upper-body and lower-body power (bench press throw and countermovement jump power [CMJP] tests). Subjects were also tested for maximum force and electromyographic (EMG) activation of quadriceps muscles while performing an isometric leg extension. All assessments were performed before and 8 minutes after a high-intensity (HI: 5 sets of 1 rep at 90% of 1 repetition maximum [1RM]) bench press protocol, a high-power protocol (POW: 5 sets of 1 rep at 30% of 1RM with maximum explosive intent), and a control trial (CON). Subjects performed all trials in a randomized order and on different days. A significant trial × time interaction was detected for CMJP ( p = 0.049). This parameter was significantly increased following the HI protocol only ( p = 0.024). A significant interaction was also noted for EMG with a significant improvement following the HI protocol ( p = 0.032) and a significant decrease following the POW protocol ( p = 0.020). No other significant effects were detected ( p > 0.05). The results of this investigation indicate that a HI bench press protocol may produce a PAPE in the lower-body power and increase the neuromuscular activation of leg extensor muscles. The POW bench press protocol did not show any positive effects on lower-body performance. Athletes and practitioners may take advantage from the inclusion of upper-body HI resistance exercises throughout complex resistance workouts to improve lower-body power output.

Whole Body Vibration on the Neuromuscular Performance of Elderls: Randomized Controlled Trial

Objective The main purpose of this study was to evaluate the effects of exercising on a vibratory platform on older adults’ lower limb performance, muscle activation and balance. Design A total of 44 volunteers exercised on a vibratory platform. For half of them (random assignment), the platform vibrated at 40 Hz with 4 mm displacements and for the other half, the platform was off. Lower limb isokinetic performance, neuromuscular activity and balance were assessed before and after exercise protocol. Results A significant increase was observed in 3 of the 4 dynamometric variables evaluated along with increased soleus muscle activation, with no difference between the groups. Conclusion Squatting exercises had immediate effects on neuromuscular performance, muscle activation and balance. However, whole body vibration did not magnify the effects of squatting exercises on older adults. Clinical Trials NCT03356418.

Floating EMG sensors and stimulators wirelessly powered and operated by volume conduction for networked neuroprosthetics

BackgroundImplantable neuroprostheses consisting of a central electronic unit wired to electrodes benefit thousands of patients worldwide. However, they present limitations that restrict their use. Those limitations, which are more adverse in motor neuroprostheses, mostly arise from their bulkiness and the need to perform complex surgical implantation procedures. Alternatively, it has been proposed the development of distributed networks of intramuscular wireless microsensors and microstimulators that communicate with external systems for analyzing neuromuscular activity and performing stimulation or controlling external devices. This paradigm requires the development of miniaturized implants that can be wirelessly powered and operated by an external system. To accomplish this, we propose a wireless power transfer (WPT) and communications approach based on volume conduction of innocuous high frequency (HF) current bursts. The currents are applied through external textile electrodes and are collected by the wireless devices through two electrodes for powering and bidirectional digital communications. As these devices do not require bulky components for obtaining power, they may have a flexible threadlike conformation, facilitating deep implantation by injection.MethodsWe report the design and evaluation of advanced prototypes based on the above approach. The system consists of an external unit, floating semi-implantable devices for sensing and stimulation, and a bidirectional communications protocol. The devices are intended for their future use in acute human trials to demonstrate the distributed paradigm. The technology is assayed in vitro using an agar phantom, and in vivo in hindlimbs of anesthetized rabbits.ResultsThe semi-implantable devices were able to power and bidirectionally communicate with the external unit. Using 13 commands modulated in innocuous 3 MHz HF current bursts, the external unit configured the sensing and stimulation parameters, and controlled their execution. Raw EMG was successfully acquired by the wireless devices at 1 ksps.ConclusionsThe demonstrated approach overcomes key limitations of existing neuroprostheses, paving the way to the development of distributed flexible threadlike sensors and stimulators. To the best of our knowledge, these devices are the first based on WPT by volume conduction that can work as EMG sensors and as electrical stimulators in a network of wireless devices.

Differences in the recruitment properties of the corticospinal pathway between the biceps femoris and rectus femoris muscles

The neuromuscular activity in the hamstring and quadriceps muscles is vital for rapid force control during athletic movements. This study aimed to investigate the recruitment properties of the corticospinal pathway of the biceps femoris long head (BFlh) and rectus femoris (RF) muscles. Thirty-two male subjects were participated in this study. Corticospinal excitability was investigated for BFlh and RF during the isometric knee flexion and extension tasks, respectively, using transcranial magnetic stimulation. A sigmoidal relationship was observed between the stimulus intensity and amplitude of motor-evoked potentials and characterized by a plateau value, maximum slope, and threshold. Compared with RF, BFlh had a significantly lower plateau value (P < 0.001, d = 1.17), maximum slope (P < 0.001, r = 0.79), and threshold (P = 0.003, d = 0.62). The results showed that the recruitment properties of the corticospinal pathway significantly differ between BFlh and RF. These results reveal that when a sudden large force is required during athletic movements, the RF can produce force through a rapid increase in the recruitment of motor units. The BFlh, on the other hand, requires larger or more synchronized motor commands for enabling the proper motor unit behavior to exert large forces. These differences in the neurophysiological factors between the hamstrings and quadriceps can have a substantial effect on the balance of force generation during athletic activities.

Effects of wearable resistance load placement on neuromuscular activity and stride kinematics: A preliminary study.

Wearable resistance (WR) training is a modality that allows athletes to perform loaded sport-specific movements to develop force and power outputs. The acute responses by which WR works is still relatively unknown, and the effects of WR load and location of the load has not yet been examined. To investigate the acute neuromuscular and stride characteristic responses to different wearable resistance (WR) loads and placements on the calf muscles during high-speed running. Ten well-trained subjects completed a workout of ten sets of three 10s runs at 18km.h-1 (20s of rest between runs and one min between sets). Five conditions were tested: (1) unloaded control, (2) bilateral 0.75 vs. 1.5% body mass (BM) loading on the distal posterior calf, (3) bilateral proximal vs. distal loading of 1.5% BM positioned posteriorly, (4) bilateral anterior vs. posterior loading of 1.5% BM positioned distally, (5) unilateral loading of 1.5% BM on the distal posterior calf. Data were collected using Electromyography (EMG) and back-mounted GPS-embedded accelerometers. Magnitude of differences of within athlete and between muscle comparisons were calculated using effect sizes (ES) ± 90% confidence limits (CL). No substantial differences in accelerometry data were observed between any of the loaded conditions and the control. EMG activity was lower for proximal loading compared to the control for the gluteus maximus (ES±90%CL; -0.72±0.41), vastus lateralis (-0.89±0.47) and vastus medialis (VM) (-0.97±0.46). Anterior loading induced substantially lower EMG activity for the semitendinosus (-0.70±0.48) and VM (-0.64±0.39) muscles compared with the control. EMG activity of the VM (-0.73±0.46) muscle was also substantially lower for posterior loading compared to the control. Unilateral loading induced no substantial differences in EMG activity between the loaded and unloaded legs. This preliminary study has provided a rationale for the performance of further investigations into the effects of WR lower limb loading on stride characteristics and EMG activity from a chronic standpoint using a larger population.

3D Reconstruction of Phonatory Glottal Shape and Volume: Effects of Neuromuscular Activation.

Although phonatory glottal posture and airflow pulse shape affect voice quality, studies to date have been limited by visualization of vocal fold (VF) vibration from a superior view. We performed a 3D reconstruction of VF vibratory motion during phonation from a medial view and assessed the glottal volume waveform and resulting acoustics as a function of neuromuscular stimulation. In vivo canine hemilarynx phonation. Across 121 unique combinations of the superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN) stimulation, the hemilarynx was excited to the oscillation with airflow. VF medial surface reference points were tracked on high-speed video, mapped into 3D space, and surface shape was restored using cubic spline interpolation. Glottal surface shape, reconstruction-based parameters, and glottal volume waveform were calculated. Fundamental frequency (F0), cepstral peak prominence (CPP), and harmonic amplitude (H1-H2) were measured from high-quality audio samples. The glottis was convergent during opening and divergent during closing. Neuromuscular activation changed phonatory glottal shape and reduced glottal volume. Significant reduction in glottal volume and closing quotient were present with SLN stimulation. RLN stimulation significantly increased F0 and CPP and decreased H1-H2 (constricted glottis), while SLN effects were similar and synergistic with concurrent RLN stimulation. 3D reconstruction of in vivo medial surface vibration revealed effects of laryngeal nerve stimulation on glottal vibratory pattern and acoustic correlates of voice quality. SLN activation resulted in significantly quicker glottal closure per cycle, decreased glottal volume, and higher-pitched, less breathy, and less noisy voice. RLN had a similar effect on acoustic measures. NA, Basic Science Laryngoscope, 133:357-365, 2023.

Effect of the phospholipase A2 inhibitor Varespladib, and its synergism with crotalic antivenom, on the neuromuscular blockade induced by Crotalus durissus terrificus venom (with and without crotamine) in mouse neuromuscular preparations

The venom of the South American rattlesnake Crotalus durissus terrificus causes an irreversible neuromuscular blockade in isolated preparations due to action of the presynaptically-acting heterodimeric phospholipase A2 (PLA2) crotoxin. Some populations of this subspecies contain, in addition to crotoxin, the toxin crotamine, which acts directly on muscle fibers. In this study we used C. d. terrificus venoms with (crot+) or without (crot-) crotamine to test whether Varespladib, a PLA2 inhibitor, is able to abrogate the neuromuscular blockade induced by these venoms comparatively with crotalic antivenom. Mouse phrenic nerve-diaphragm preparations were exposed to venoms previously incubated with two different concentrations of Varepladib or antivenom, or with a mixture of these two agents, before addition to the bath. In another experimental setting, venoms were initially added to the system, followed by the addition of Varespladib or antivenom 10, 30, or 60 min after venom. At the highest concentrations tested, Varespladib and antivenom inhibited the action of the venom >80% and >70%, respectively. With lower concentrations the inhibition of neuromuscular blockade decreased, but when low doses of the two agents were incubated together with the venom, the inhibitory effect improved, underscoring a synergistic phenomenon. When added after venom, Varespladib was able to halt the progression of the neuromuscular blockade even when added at 60 min. Antivenom exhibited a lower ability to inhibit the toxic effect of the venoms in these conditions. In conclusion, the PLA2 inhibitor Varespladib is highly effective at abrogating the neuromuscular blocking activity of crotamine-positive and crotamine-negative C. d. terrificus venoms and seems to act synergistically with antivenom.

Surgical management of concurrent lateral ankle instability and osteochondral lesions of the talus increases dynamic sagittal ankle range of motion.

A biomechanical study, in which imaging modalities are used to strictly include patients with concurrent lateral ankle instability (LAI) and osteochondral lesions of the talus (OLT), is needed to demonstrate the static and dynamic ankle range of motion (ROM) restriction in these patients, and determine whether ankle ROM restriction can be corrected postoperatively. Eight patients with concurrent LAI and OLT treated with the arthroscopic modified Broström procedure and microfracture were recruited from June 2019 to January 2020. Patients were assessed using outcome scales, static ankle ROM, and a stair descent gait analysis for dynamic ankle ROM, a day prior to surgery and one year postoperatively. Eight healthy subjects were assessed using the same modalities upon recruitment. Operative outcomes and variables during stair descent were documented and compared among the preoperative, postoperative, and healthy groups. A curve analysis, one-dimensional statistical parametric mapping, was performed to compare the dynamic ankle kinematics and muscle activation curves over the entire normalised time series. The functional outcomes of patients with concurrent LAI and OLT were significantly worse than those of healthy subjects preoperatively, but were partially improved postoperatively. Patients had decreased static and dynamic ROM preoperatively, and static ROM did not significantly increase postoperatively (preoperative, 39.6 ± 11.3; postoperative, 44.9 ± 7.1; healthy, 52.0 ± 4.6; p = 0.021). Patients showed increased dynamic ankle flexion ROM (preoperative, 41.2 ± 11.6; postoperative, 53.6 ± 9.0; healthy, 53.9 ± 3.4; p = 0.012) postoperatively, as well as increased peroneus longus activation (preoperative, 35.8 ± 12.0; postoperative, 55.4 ± 25.1; healthy, 71.9 ± 13.4; p = 0.002) and muscle co-contraction of the tibialis anterior and peroneus longus (preoperative, 69.4 ± 23.4; postoperative, 88.4 ± 9.3; healthy, 66.2 ± 18.1; p = 0.045). Patients with concurrent LAI and OLT had decreased static and dynamic sagittal ankle ROM and altered neuromuscular activation patterns. The arthroscopic modified Broström procedure and microfracture did not significantly increase the static sagittal ankle ROM. However, the dynamic sagittal ankle ROM, peroneus longus activation and muscle co-contraction of the tibialis anterior and peroneus longus increased postoperatively. IV.

Efficacy of Different Cold-Water Immersion Temperatures on Neuromotor Performance in Young Athletes.

Cold-Water-Immersion (CWI) has been frequently used to accelerate muscle recovery and to improve performance after fatigue onset. In the present study, the aim was to investigate the effects of different CWI temperatures on neuromuscular activity on quadriceps after acute fatigue protocol. Thirty-six young athletes (16.9 ± 1.4 years-old; 72.1 ± 13.8 kg; 178.4 ± 7.2 cm) were divided into three groups: passive recovery group (PRG); CWI at 5 °C group (5G); and CWI at 10 °C group (10G). All participants performed a fatigue exercise protocol; afterwards, PRG performed a passive recovery (rest), while 5G and 10G were submitted to CWI by means of 5 °C and 10 °C temperatures during 10 min, respectively. Fatigue protocol was performed by knee extension at 40% of isometric peak force from maximal isometric voluntary contraction. Electromyography was used to evaluate neuromuscular performance. The passive recovery and CWI at 5 °C were associated with normalized isometric force and quadriceps activation amplitude from 15 until 120 min after exercise-induced fatigue (F = 7.169, p < 0.001). CWI at 5 °C and 10 °C showed higher muscle activation (F = 6.850, p < 0.001) and lower median frequency (MF) than passive recovery after 15 and 30 min of fatigue (F = 5.386, p < 0.001). For neuromuscular efficiency (NME) recovery, while PRG normalized NME values after 15 min, 5G and 10G exhibited these responses after 60 and 30 min (F = 4.330, p < 0.01), respectively. Passive recovery and CWI at 5 °C and 10 °C revealed similar effects in terms of recovery of muscle strength and NME, but ice interventions resulted in higher quadriceps activation recovery.

Characterisation of the transient mechanical response and the electromyographical activation of lower leg muscles in whole body vibration training

The aim of this study is to characterise the transient mechanical response and the neuromuscular activation of lower limb muscles in subjects undergoing Whole Body Vibration (WBV) at different frequencies while holding two static postures, with focus on muscles involved in shaping postural responses. Twenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while in hack squat or on fore feet. Surface electromyography and soft tissue accelerations were collected from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles. Estimated displacement at muscle bellies revealed a pattern never highlighted before that differed across frequencies and postures (p < 0.001). After stimulation starts, muscle oscillation peaks, drops and further stabilises, suggesting the occurrence of a neuromuscular activation to reduce the vibration-induced oscillation. The oscillation attenuation at the SOL muscle correlated with its increased activation (rho = 0.29, p < 0.001). Furthermore, only specific WBV settings led to a significant increase in muscle contraction: WBV-induced activation of SOL and GL was maximal in fore-feet (p < 0.05) and in response to higher frequencies (30 Hz vs 15 Hz, p < 0.001). The analysis of the mechanical dynamics of lower leg muscles highlights a resonant response to WBVs, that for the SOL correlates to the increased muscle activation. Despite differing across frequencies and postures, this resonant behaviour seems to discourage the use of dynamic exercises on vibrating platforms. As for the most efficient WBV combination, calf muscle response to WBVs is maximised if those muscles are already pre-contracted and the stimulation frequencies are in the 25–30 Hz range.

Analysis of vibratory mode changes in symmetric and asymmetric activation of the canine larynx.

Investigations of neuromuscular control of voice production have primarily focused on the roles of muscle activation levels, posture, and stiffness at phonation onset. However, little work has been done investigating the stability of the phonation process in regards to spontaneous changes in vibratory mode of vocal fold oscillation as a function of neuromuscular activation. We evaluated 320 phonatory conditions representing combinations of superior and recurrent laryngeal nerve (SLN and RLN) activations in an in vivo canine model of phonation. At each combination of neuromuscular input, airflow was increased linearly to reach phonation onset and beyond from 300 to 1400 mL/s. High-speed video and acoustic data were recorded during phonation, and spectrograms and glottal-area-based parameters were calculated. Vibratory mode changes were detected based on sudden increases or drops of local fundamental frequency. Mode changes occurred only when SLNs were concurrently stimulated and were more frequent for higher, less asymmetric RLN stimulation. A slight increase in amplitude and cycle length perturbation usually preceded the changes in the vibratory mode. However, no inherent differences between signals with mode changes and signals without were found.

Neuromuscular activation of quadriceps bellies during tasks performed in the same biomechanical condition in patients undergoing total knee arthroplasty

ObjectiveTo investigate neuromuscular activation of quadriceps bellies during different tasks in patients before and after total knee arthroplasty (TKA). MethodsTwenty-six patients scheduled for TKA and 16 control subjects performed three isometric tasks: knee extension (KE), hip flexion (HF), hip flexion with contralateral hip extension (HFE). Surface electromyography signals of rectus femoris, vastus medialis and vastus lateralis were collected the day before (T0), at one (T1) and three (T2) days after surgery, whereas control subjects underwent a single evaluation. The Root Mean Square peak normalized for its highest value during the three tasks (nRMS-peak) was used as index of maximum neuromuscular activation for each belly. Sixteen patients performed the postoperative assessment, due to the placement of an elastomeric pump aimed at reducing pain in 10 patients. ResultsPatients showed lower rectus femoris nRMS-peak during KE compared to HF and HFE before and after surgery (p < 0.001), as occurred in control subjects. Differently from control subjects, patients showed higher vastus medialis and vastus lateralis nRMS-peak during HF compared to KE at T1 (p = 0.008) and T2 (p = 0.039). ConclusionTKA modified quadriceps neuromuscular activation during different tasks performed the same biomechanical condition. These findings may be considered in planning physiotherapy interventions after TKA.