Surface Electromyographic Activity Research Articles

Surface electromyographic activity of the erector spinae and multifidus during arm- and leg-ergometer exercises in young healthy men.

Objectives: Ergometer exercise was considered a new loading method that can be used for participants who are unable to assume the core strengthening exercise posture commonly used to strengthen the erector spinae and multifidus. This study aimed to investigate with healthy participants whether arm and leg ergometers could be used for core strengthening exercises and whether different exercise sites would affect the results. Methods: The study was conducted with 15 healthy adult male participants aged 20-35 years. The intervention consisted of arm- and leg-ergometer exercises performed by the participants. The exercise protocol consisted of three 1-min sessions (rest, 50W, and 100W), which were measured consecutively. Surface electromyography (sEMG) was measured during the sessions. Maximal voluntary contraction (MVC) of the erector spinae and multifidus was also measured, during which sEMG was measured. The sEMG during ergometer exercise was calculated as a percentage of the MVC (calculated as % MVC). The root mean square (RMS) was recorded from the sEMG activity. Muscle activity of the erector spinae and multifidus was compared between ergometer exercises and between intensity levels. Heart rate (HR) was recorded by electrocardiogram. Results: In the arm-ergometer exercise, the % MVC values of the erector spinae were 6.3 ± 3.1, 10.9 ± 5.4, and 16.9 ± 8.3% at rest, 50W, and 100W conditions, respectively. The multifidus was 4.6 ± 2.9, 9.2 ± 5.6, and 12.6 ± 7.6% at rest, 50W, and 100W conditions, respectively. The respective % MVC values during the leg-ergometer exercise were 3.8 ± 1.7, 7.2 ± 3.8, and 10.4 ± 4.0% at rest, 50W, and 100W conditions, respectively. Leg-ergometer exercises were 2.6 ± 2.1, 6.9 ± 5.7, and 10.3 ± 6.8% at rest, 50W, and 100W conditions, respectively. The activities of the two muscles increased at comparable levels with increased workload in both types of exercises (p < 0.01, each). HR increased with the increased workload and the increase was larger during arm-than leg-ergometer exercises. Conclusion: These results demonstrate that both arm- and leg-ergometer exercises are potentially alternative methods for erector spinae and multifidus training for healthy participants. Further research is needed to target elderly.

Quadriceps Electromyographic Activity in Closed and Open Kinetic-Chain Exercises with Hip-Adductor Co-Contraction in Sedentary Women.

Background: Different closed and open kinetic-chain exercises with hip-adductor co-contraction have different effects on quadriceps activity. The aim of this study was to investigate the difference in quadriceps activity during the squat (SQ) and knee extension (KE) and straight leg raise (SLR) exercises with and without hip adduction in sedentary women. Methods: Twenty-eight sedentary women aged 44.5 ± 8.5 years were recruited. They performed three exercises with and without hip adduction. Surface electromyography (sEMG) activity was measured on the rectus femoris (RF), vastus medialis oblique (VMO) and vastus lateralis (VL) muscles. The levels of sEMG activities of the three muscles were compared among the six exercises using a repeated-measures ANOVA. Results: The findings showed that RF activity was lowest during the SQ alone and highest during the SLR exercise (p < 0.05 to 0.001). The VMO activity was significantly greater in the SQH than in the five types of exercises (p < 0.05 to 0.001), which led to a significant VMO/VL ratio as well. VL activity increased while the squat with hip adduction and knee extension with hip adduction exercise compared with SQ alone. Conclusion: This study indicates that a closed-chain squat with hip co-contraction can produce the VMO and VMO/VL ratio activity, while an open chain of SLR better activates the RF activity. The findings support the understanding of quadriceps activity in different exercises to be an alternative home-based exercise for physical therapy in women facing muscle weakness.

Kinematic, Electromyographic Activity and Muscular Architecture Description in Patients Operated with Pars-Dresden Technique

Category: Sports; Ankle; Basic Sciences/Biologics Introduction/Purpose: Kinematic, muscular architecture and myoelectric activity are altered during the healing process after Achilles tendon surgery. Currently, there are minimally invasive surgical techniques (PARS-Dresden) which have accelerated rehabilitation processes. However, evidence that compares kinematic, architecture and myoelectric activity between operated vs. non-operated leg is limited. The aim of this study is to describe the kinematic changes, muscular architecture and electromyographic (EMG) activity of the lower limb between operated vs. non-operated legs after Achilles tendon surgery. Methods: After obtaining IRB approval, patients undergoing the PARS-Dresden technique for acute Achilles tendon ruptures were invited to participate. We excluded patients with previous injuries or surgery in lower limbs that affect gait, muscular activity, or architecture. Eleven patients met the inclusion/exclusion criteria. Patients were evaluated at three time-frames: 8, 12, and 24 weeks. Evaluations were performed walking on a treadmill at self-selected speed, while kinematic and surface EMG activity was measured in stance and swing phases of the gait. Kinematic variables were captured using a 3D motion analysis system with eight infrared cameras and twenty reflective markers over the lower limbs. Muscle architecture was evaluated using ultrasonography. A descriptive analysis was performed comparing operated versus non-operated legs. Results: Median age 36 years, 3 females. Kinematic evaluation shows sagittal plane asymmetry between operated versus non- operated legs at 8 and 12w. However, the 24w evaluation shows symmetry between both lower limbs. The EMG shows lower activity in the stance phase for the medial gastrocnemius, lateral gastrocnemius, and soleus for operated legs at 8w and 12w, but at the 24w evaluation the activity was symmetric for these muscles evaluated in both legs. The muscular architecture shows less thickness in gastrocnemius muscles in the operated leg at 8w (median 11.2% operated vs 35.4% no-operated), reaching a symmetric thickness at 24w (median 34.2% operated vs 35.7% no-operated). Achilles tendon present asymmetric transversal area between both legs at three time-frames (median 1.88 cm2 versus 0.59 cm2). The pennation angles showed no difference between both legs in the three evaluation periods (median 22.0° versus 24.3° for MG, and 15.0° versus 13.5° for LG). Conclusion: We described kinematic, electromyographic and architectonic asymmetries between operated versus non-operated legs at 8 and 12 weeks postoperative of patients who underwent PARS-Dresden surgery for acute Achilles tendon ruptures. All patients achieved symmetric results at 24 weeks evaluation.

Neuromuscular Control During Stair Descent and Artificial Tibial Translation After Acute ACL Rupture.

Background:Anterior cruciate ligament (ACL) rupture has direct effect on passive and active knee stability and, specifically, stretch-reflex excitability.Purpose/Hypothesis:The purpose of this study was to investigate neuromuscular activity in patients with an acute ACL deficit (ACL-D group) compared with a matched control group with an intact ACL (ACL-I group) during stair descent and artificially induced anterior tibial translation. It was hypothesized that neuromuscular control would be impaired in the ACL-D group.Study Design:Cross-sectional study; Level of evidence, 3.Methods:Surface electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST) muscles was recorded bilaterally in 15 patients with ACL-D (mean, 13.8 days [range, 7-21 days] since injury) and 15 controls with ACL-I during stair descent and artificially induced anterior tibial translation. The movements of stair descent were divided into preactivity, weight acceptance, and push-off phases. Reflex activity during anterior tibial translation was split into preactivity and short, medium, and late latency responses. Walking on a treadmill was used for submaximal EMG normalization. Kruskal-Wallis test and post hoc analyses with Dunn-Bonferroni correction were used to compare normalized root mean square values for each muscle, limb, movement, and reflex phase between the ACL-D and ACL-I groups.Results:During the preactivity phase of stair descent, the hamstrings of the involved leg of the ACL-D group showed 33% to 51% less activity compared with the matched leg and contralateral leg of the ACL-I group (P < .05). During the weight acceptance and push-off phases, the VL revealed a significant reduction (approximately 40%) in the involved leg of the ACL-D group compared with the ACL-I group. At short latency, the BF and ST of the involved leg of the ACL-D group showed a significant increase in EMG activity compared with the uninvolved leg of the ACL-I group, by a factor of 2.2 to 4.6.Conclusion:In the acute phase after an ACL rupture, neuromuscular alterations were found mainly in the hamstrings of both limbs during stair descent and reflex activity. The potential role of prehabilitation needs to be further studied.

Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks.

The firing properties of the motor units are usually affected by the motor task. However, it has not been clarified whether the firing properties of the motor units of a specific muscle are different between postural and voluntary tasks. Therefore, this study investigated whether the recruitment and rate coding of the motor units differ between these two motor tasks. Thirteen healthy volunteers performed trapezoidal muscle contraction with a target value of 15% maximum electromyography (EMG) activity by voluntary left knee extension in the sitting position (voluntary task) and postural maintenance in the semi-squatting position (postural task) with a knee flexion angle of 30°. We obtained four channels of surface EMG activity during each task from left vastus lateralis muscle. We extracted the firing properties of individual motor units using the EMG decomposition algorithm. The recruitment threshold and motor unit action potential amplitude were significantly lower in the postural task than in the voluntary task, and conversely, the mean firing rate was significantly higher. These results were explained by the preferential recruitment of motor units with higher recruitment threshold and amplitude in the voluntary task, while motor units with lower recruitment threshold and higher firing rate were preferentially recruited in the postural task. Preferential activation of fatigue-resistant motor units in the postural task is a reasonable strategy as it allows for sustained postural maintenance. We provide the first evidence that motor unit firing properties are clearly different between postural and voluntary tasks, even at the same muscle activity level.

A Comparison of Electromyographic Inter-Limb Asymmetry During a Standard Versus a Sling Shot Assisted Bench Press Exercise.

The objective of this study was to compare peak surface electromyography (sEMG) activity of selected muscles along with inter-limb asymmetries between a control (CONT) and a Sling shot assisted (SS) bench press exercise. Ten resistance-trained males with at least three-year experience in resistance training (22.2 ± 1.9 years, 88.7 ± 11.2 kg, 179.5 ± 4.1 cm, bench press one-repetition maximum (1RM) = 127.3 ± 25.9 kg) performed the flat bench press exercise under two conditions at selected loads (85% and 100% of 1RM assessed without the SS). Peak sEMG amplitude of triceps brachii, pectoralis major, and anterior deltoid was recorded for the dominant and the non-dominant side of the body during each attempt. The comparison between the dominant and the non-dominant side was carried out using the limb symmetry index (LSI(%) = (2*(XR - XL)/(XR + XL))*100%) where XR = values of the right side and XL = values of the left side. There was a main effect of condition (p = 0.004; η2 = 0.64) and the load (p = 0.004; η2 = 0.63) for the triceps brachii LSI in parallel with a main effect of condition (p = 0.003; η2 = 0.42) for the anterior deltoid LSI. Post hoc analysis for the main effect of condition showed significant differences in the LSI between the CONT and SS conditions for the triceps brachii (p = 0.003; 1.10% vs. -8.78%) as well as for the anterior deltoid muscles (p = 0.03; 12.91% vs. 9.23%). The results indicate that the assistance of the Sling shot significantly affects the sEMG activity pattern on both the dominant and non-dominant sides of the body while influencing inter-limb asymmetries.

People with chronic low back pain display spatial alterations in high-density surface EMG-torque oscillations

We quantified the relationship between spatial oscillations in surface electromyographic (sEMG) activity and trunk-extension torque in individuals with and without chronic low back pain (CLBP), during two submaximal isometric lumbar extension tasks at 20% and 50% of their maximal voluntary torque. High-density sEMG (HDsEMG) signals were recorded from the lumbar erector spinae (ES) with a 64-electrode grid, and torque signals were recorded with an isokinetic dynamometer. Coherence and cross-correlation analyses were applied between the filtered interference HDsEMG and torque signals for each submaximal contraction. Principal component analysis was used to reduce dimensionality of HDsEMG data and improve the HDsEMG-based torque estimation. sEMG-torque coherence was quantified in the δ(0–5 Hz) frequency bandwidth. Regional differences in sEMG-torque coherence were also evaluated by creating topographical coherence maps. sEMG-torque coherence in the δ band and sEMG-torque cross-correlation increased with the increase in torque in the controls but not in the CLBP group (p = 0.018, p = 0.030 respectively). As torque increased, the CLBP group increased sEMG-torque coherence in more cranial ES regions, while the opposite was observed for the controls (p = 0.043). Individuals with CLBP show reductions in sEMG-torque relationships possibly due to the use of compensatory strategies and regional adjustments of ES-sEMG oscillatory activity.

Surface Electromyographic Activity of the Rectus Abdominis and External Oblique during Isometric and Dynamic Exercises.

Exercises for the abdominal muscles are widely used in athletic activities for strength training and prevention of low back disorders. The timing and volume of muscle activation for various movements have not yet been clarified. The purpose of this research was to evaluate the surface electromyographic activity from the upper (RAU) and lower part (RAL) of the rectus abdominis and the external oblique (EO) muscles during eleven abdominal muscle strength training exercises. Thirty-five healthy male university students with a subspecialty in soccer participated in the study. They performed exercises involving isometric, concentric, and eccentric muscle contractions. The electromyographic recordings were amplified by a factor of 1000, rectified, and integrated. Mean integrated values were calculated by dividing the elapsed time for the five repetitions, to provide the mean integrated electromyographic values for each exercise. Leg movements from a long lying position showed higher activity of the rectus abdominis, compared to the EO (p < 0.001). The dynamic sit-ups showed an obvious dominant activity of the EO, compared to the rectus abdominis (p < 0.001). During eccentric exercise, higher activity was found in the RAU, compared to the RAL (p < 0.001). The results could serve as a basis for improving the design and specification of training exercises. Pre-exercises should be performed before testing abdominal muscle strength.

Effects of Preceding Transcranial Direct Current Stimulation on Movement Velocity and EMG Signal during the Back Squat Exercise.

This study aimed to evaluate the effects of preceding anodal transcranial direct stimulation (a-tDCS) over the dorsolateral prefrontal cortex (DLPFC) during the back squat exercise on movement velocity and surface electromyographic (sEMG) activity. Thirteen healthy, well-trained, male firefighters (34.72 ± 3.33 years; 178 ± 7.61 cm; 76.85 ± 11.21 kg; 26.8 ± 4.2 kg·m−2; back squat 1-repetition maximum 141.5 ± 16.3 kg) completed this randomised double-blinded sham-controlled crossover study. After familiarisation and basal measurements, participants attended the laboratory on two occasions separated by 72 h to receive either Sham or a-tDCS (current intensity of 2 mA for 20 min). Immediately after stimulation, participants completed three sets of 12 repetitions (70% of 1-RM) with three minutes of recovery between sets monitored with a linear position transducer. The sEMG of the rectus femoris (RF) and vastus lateralis (VL) of both legs were recorded. No significant differences were observed between a-tDCS and Sham interventions on mean concentric velocity at any set (p > 0.05). Velocity loss and effort index were significantly higher (p < 0.05) in set 3 compared to set 1 only in the a-tDCS group. The right-leg RM and right-leg VL elicited the greatest muscle activation during set 1 after a-tDCS and Sham, respectively (p < 0.05). Our results revealed that a-tDCS over the DLPFC might impact movement velocity or fatigue tolerance in well-trained individuals. Notwithstanding, significant differences in dominant-leg muscle activity were found both in a-tDCS and Sham.

Backstroke-to-Breaststroke Turns Muscular Activity. A Study Conducted in Age Group Swimmers.

The aims of this study were to compare surface electromyographic (EMG) activity and kinematic variables among open, somersault, bucket and crossover backstroke-to-breaststroke turning techniques, and identify relationships between the integrated electromyography (iEMG) and kinematics profile focusing on the rotation and push-off efficacy. Following a four-week of systematically increasing contextual interference intervention program, eight 12.38 ± 0.55 years old male swimmers randomly performed twelve repetitions (three in each technique) turns in and out of the wall at maximum speed until the 7.5 m reference mark. Surface EMG values of the right vastus lateralis, biceps femoris, tibialis anterior, gastrocnemius medialis, rectus abdominis, external oblique, erector spinae and latissimus dorsi were recorded and processed using the integrated electromyography (iEMG) and the total integrated electromyography (TiEMG) that was expressed as a percentage of iEMGmax to normalize per unit of time for each rotation and push-off phase. Complementarily, 2D sagittal views from an underwater video camera were digitized to determine rotation and push-off efficacy. The crossover turn presented the highest rotation and push-off iEMG values. Erector spinae and gastrocnemius medialis had the highest activity in the rotation and push-off phases (89 ± 10 and 98 ± 69%, respectively). TiEMG depicted a very high activity of lower limb muscles during push-off activity (222 ± 17 to 247 ± 16%). However, there were no relation between TiEMG and rotation and push-off time, tuck index and final push-off velocity during the rotation and the push-off phases across all the studied turning techniques. The rotation efficacy in age-group swimmers were dependent on rotation time (p = 0.04). The different turning techniques were not distinguishable regarding iEMG activity as a possible determinant of rotation and push-off efficacy. Our study has direct implications for selecting appropriate exercises and designing training programs for optimizing the rotation and push-off phases of backstroke-to-breaststroke turning at young ages.

Effects of Relative Inertial Load on Quadriceps Electromyography during Maximal Effort Flywheel-based Iso-Inertial Training (FIT) Squats

The effects of inertial load on quadriceps electromyography (EMG) during flywheel-based iso-inertial training (FIT) squats is unclear. Healthy, resistance-trained males (n=8) and females (n=8) completed five sets of five maximal-effort squats with varying inertial loads in a randomized order. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL) were measured. Average knee angular velocity, but not peak knee flexion or total excursion, decreased during both the concentric and eccentric phases with increasing inertial load (p&lt;0.001) in both sexes. Integrated EMG (iEMG) activity increased with increasing inertial load for all muscles (p&lt;0.001). VL iEMG and peak amplitude were significantly greater in females. However, peak EMG amplitude was not significantly different among inertial loads for either sex. Mean EMG amplitude during the concentric phase and eccentric phases of the VL tended to be greater in females. Increasing relative inertial load increases quadriceps iEMG activity due to greater exercise duration, but has minimal effects on EMG amplitude.

Surface electromyographic activity of trunk muscles during trunk control exercises for people after stroke; effect of a mobile and stable seat for rehabilitation.

The aim of this study was to explore differences in trunk muscle activity on a stable and mobile seat for people after stroke and healthy participants. Trunk control exercises are known to have a beneficial effect on trunk control, balance, and mobility after stroke. The effect of such exercises could be enhanced by the use of a mobile seat to provide further training stimuli. However, little research on the musculoskeletal effects of trunk training on mobile seats has been carried out. On a stable and a mobile seat, thirteen people after stroke and fifteen healthy participants performed two selective trunk control exercises, which were lateral flexion initiated by the pelvis and the thorax. The maximal surface electromyography relative to static sitting of the muscles multifidus, erector spinae, and obliquus externus was recorded bilaterally. The effects of group, seat condition, trunk control exercise, and muscle side were investigated employing within-subject linear-mixed-models. Compared to the stable seat, the maximal muscle activity of people after stroke on the mobile seat was higher during the thorax-initiated exercise and lower during the pelvis-initiated exercise. Healthy participants showed opposite results with higher muscle activity on the mobile seat during the pelvis-initiated exercise. For trunk control training on a mobile seat with high muscle activation people after stroke should perform trunk control exercises initiated by the thorax, for training with lower muscle activity people after stroke should initiate selective trunk movements by the pelvis. The results can support the planning of progressive trunk control rehabilitation programs.

Within-Subject Changes in Shoulder Girdle Muscle Activation After Soft Tissue Mobilization of the Upper Trapezius

ObjectiveThe purpose of this study was to investigate the effect of the integrated neuromuscular inhibition technique (INIT) of the upper trapezius (UT) on shoulder muscle activity in chronic shoulder pain. MethodsTwenty-two patients (mean age 42.5 ± 16.07) with chronic unilateral shoulder pain with UT myofascial trigger points (MTrPs) (n = 27) and scapular dyskinesis received a single session of INIT (∼15 minutes for each MTrP). The pain on the visual analog scale, along with surface electromyographic activity, maximum voluntary contraction in % (in arm raising and lowering in scapular plane), and pressure pain threshold (PPT) of 5 girdle muscles UT, lower trapezius, serratus anterior, middle deltoid, and infraspinatus were measured before and immediately after treatment. Wilcoxon signed-rank test was used for analysis (at α ≤ 0.05). ResultsMuscle activity of all the muscles, especially the lower trapezius, was reduced during arm raising in the scapular plane (76.69%-71.14% [p = 0.003]). UT activity decreased during arm lowering also (56.70%-45.99% [p ˂ 0.001]). The intensity of shoulder pain reduced (50.50 mm to 22 mm, [p ˂ 0.001]), and PPT values of all 5 muscles improved post-treatment. ConclusionThe findings of this study provide preliminary evidence for the application of a single session of INIT on UT MTrPs in reducing activity in the scapular muscles, improving shoulder pain, and PPT in chronic unilateral shoulder pain.

How does multi-set high-load resistance exercise impact neuromuscular function in normoxia and hypoxia?

ABSTRACT This study examined whether hypoxia during multi-set, high-load resistance exercise alters neuromuscular responses. Using a single-blinded (participants), randomised crossover design, eight resistance-trained males completed five sets of five repetitions of bench press at 80% of one repetition maximum in moderate normobaric hypoxia (inspiratory oxygen fraction = 0.145) and normoxia. Maximal isometric bench press trials were performed following the warm-up, after 10 min of altitude priming and 5 min post-session (outside, inside and outside the chamber, respectively). Force during pre-/post-session maximal voluntary isometric contractions and bar velocity during exercise sets were measured along with surface electromyographic (EMG) activity of the pectoralis major, anterior deltoid and lateral and medial triceps muscles. Two-way repeated measures ANOVA (condition×time) were used. A significant time effect (p = 0.048) was found for mean bar velocity, independent of condition (p = 0.423). During sets of the bench press exercise, surface EMG amplitude of all studied muscles remained unchanged (p > 0.187). During maximal isometric trials, there were no main effects of condition (p > 0.666) or time (p > 0.119), nor were there any significant condition×time interactions for peak or mean forces and surface EMG amplitudes (p > 0.297). Lower end-exercise blood oxygen saturation (90.9 ± 1.8 vs. 98.6 ± 0.6%; p < 0.001) and higher blood lactate concentration (5.8 ± 1.4 vs. 4.4 ± 1.6 mmol/L; p = 0.007) values occurred in hypoxia. Acute delivery of systemic normobaric hypoxia during multi-set, high-load resistance exercise increased metabolic stress. However, only subtle neuromuscular function adjustments occurred with and without hypoxic exposure either during maximal isometric bench press trials before versus after the session or during actual exercise sets. Highlights Performing multi-set, high-load bench press resistance exercise in hypoxia accentuates metabolic stress, as evidenced by lower arterial oxygen saturation and higher blood lactate concentration, compared to normoxia. Acute hypoxic exposure doesn’t alter neuromuscular responses during the execution of the sets since mean bar velocity dropped similarly in both conditions from set 2 to set 5 with no difference in peak velocity and surface EMG amplitude of the prime movers during the bench press. Only subtle adjustments in peak or mean force and accompanying surface EMG activity occur with and without hypoxic exposure during maximal isometric bench press trials after a 10-min hypoxic priming period and 5 min after the session in reference to post-warm-up.

Functional Role of Suprahyoid Muscles in Bolus Formation During Mastication.

It still remains unclear how the suprahyoid muscles function in bolus formation during mastication. This study aimed to investigate the contributory role of the suprahyoid muscles during mastication. A total of 20 healthy young volunteers were asked to perform tongue pressure generation tasks and unilateral mastication tasks using peanuts and two different types of rice crackers. Surface electromyographic (EMG) activity of the masseter and suprahyoid muscles and mandibular kinematics were recorded. Suprahyoid activity increased with increasing tongue pressure. Masticatory duration until the first deglutition differed significantly among the different foods; the harder the food, the longer the duration. This was also the case in masseter activity per masticatory cycle. Masticatory rate and suprahyoid activity per masticatory cycle were significantly higher during soft rice cracker mastication. Masseter activity was higher on the masticatory side than on the non-masticatory side, however, there was no difference in suprahyoid activity between the sides. Suprahyoid activity and jaw gape showed significant positive correlation in the early stage on both the masticatory and non-masticatory sides. The suprahyoid muscles functioned dominantly for jaw-opening during peanut mastication, and for bolus formation, especially in the late stage during soft rice cracker mastication. Bolus formation was performed dominantly on the masticatory side during rice cracker mastication. These findings clearly demonstrate a functional role of the suprahyoid muscles during mastication of solid foods from assessments using both EMG activity and mandibular kinematic recordings.

Sex influence on muscle synergies in a ballistic force-velocity test during the delayed recovery phase after a graded endurance run

The acute and delayed phases of the functional recovery pattern after running exercise have been studied mainly in men. However, it seems that women are less fatigable and/or recover faster than men, at least when tested in isometric condition. After a 20 km graded running race, the influence of sex on the delayed phase of recovery at 2–4 days was studied using a horizontal ballistic force-velocity test. Nine female and height male recreational runners performed maximal concentric push-offs at four load levels a week before the race (PRE), 2 and 4 days (D2 and D4) later. Ground reaction forces and surface electromyographic (EMG) activity from 8 major lower limb muscles were recorded. For each session, the mechanical force-velocity-power profile (i.e. theoretical maximal values of force (F¯ 0), velocity (V¯ 0), and power (P¯ max)) was computed. Mean EMG activity of each recorded muscle and muscle synergies (three for both men and women) were extracted. Independently of the testing sessions, men and women differed regarding the solicitation of the bi-articular thigh muscles (medial hamstring muscles and rectus femoris). At mid-push-off, female made use of more evenly distributed lower limb muscle activities than men. No fatigue effect was found for both sexes when looking at the mean ground reaction forces. However, the force-velocity profile varied by sex throughout the recovery: only men showed a decrease of both V¯ 0 (p < 0.05) and P¯ max (p < 0.01) at D2 compared to PRE. Vastus medialis activity was reduced for both men and women up to D4, but only male synergies were impacted at D2: the center of activity of the first and second synergies was reached later. This study suggests that women could recover earlier in a dynamic multi-joint task and that sex-specific organization of muscle synergies may have contributed to their different recovery times after such a race.

Quadriceps electromyography during flywheel-based inertial training (FIT) and dynamic constant external resistance (DCER) squats at similar tempo

ABSTRACT Flywheel-based iso-inertial training (FIT) has been purported to provide enhanced adaptations to muscle overload compared to dynamic constant external resistance (DCER), but previous studies have not controlled for exercise intensity. We compared quadriceps electromyography (EMG) amplitude between FIT- and DCER-squats with similar tempo. Eleven (5 M and 6F) resistance-trained participants completed sets of five maximal velocity FIT (0.025 kg∙m2) and DCER (55 ± 15 %1RM) squats. Sagittal plane knee joint angles and surface EMG activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were measured. Repetition time and peak knee angles were similar between FIT and DCER squats. Mean knee angular velocity during the concentric (122.2 ± 23.6 vs. 108.9 ± 22.9, p = 0.022, Cohen’s D: 0.820), but not eccentric, phase was significantly greater during FIT. Peak VM (210.4 ± 49.3 vs. 177.5 ± 56.3 %MVIC, p = 0.001; Cohen’s D: 1.416), but not VL or RF, EMG amplitude was significantly greater in FIT compared to DCER. Mean EMG amplitude was significantly (p < 0.001) greater during the concentric than the eccentric phase for the VL and VM but not RF. Mean EMG amplitude was not significantly different between modes during either the concentric or eccentric phase. Quadriceps EMG amplitude is largely similar between FIT and DCER squats when matched for movement velocity.

Verification of surface electromyographic activity of the oblique externus abdominis using ultrasound shear wave elastography.

This study used ultrasound shear wave elastography (SWE) to revalidate whether surface electromyographic (EMG) electrodes placed on the oblique externus abdominis (OE) can detect only the OE activity without the confounding activity of the underlying oblique internus abdominis (OI). During left and right trunk rotations, the EMG activity was acquired using surface EMG electrodes placed on the right OE. Shear wave velocity (Vs) values of the right OE and OI were acquired using SWE. The EMG activity during the left and right trunk rotations significantly increased as the level of exertion increased (25%, 50%, 75%, and 100% of the one‐repetition maximum [1RM]). The Vs of the right OE was significantly different only between 25% and 75% 1RM in the right trunk rotation, but significantly increased from 25% to 75% 1RM during the left trunk rotation. The Vs of the right OI during the right trunk rotation significantly increased with increased levels of exertion, except between 50% and 75% 1RM. The results for the Vs of the OE and OI in the right trunk rotation suggest that surface EMG electrodes placed on the OE would detect not only the antagonistic OE activity but also the agonistic OI activity.

Electromyographic Activity of Masseter Muscles After Complete Denture Rehabilitation in Edentulous Participants.

To evaluate the electromyographic (EMG) activity of masseter muscles (MMs) after the provision of new complete dentures (CDs) and to assess the possible correlations between clinical behavior and the EMG findings. The sample included 78 edentulous participants (56 women, 22 men; mean age: 65.59 ± 10.47 years). Prior to provision of the new CDs, surface EMG activity of the masseter muscles was recorded during rest, maximum voluntary contraction, and mastication (MAST) using a wax artifact (WA). The tests were repeated using the new CDs, followed by the WA, at 7 days, 14 days, 21 days, and 10 months. At each assessment after placement of the CDs, the participants were questioned regarding five parameters (comfort, esthetics, retention, mastication, and speech). There was an initial decline in the EMG activity of the masseter muscles after the provision of new CDs during MAST, followed by a gradual increase in this activity over time (P > .05). There was a significant improvement in MAST reported by participants at 10 months (3.59 ± 1.141) compared to 7 days (2.50 ± 1.058) (P = .011). There was no significant correlation between the EMG findings and the clinical parameters (P > .05). Although there was no significant difference in EMG activity of the MMs over time, an improvement in MAST reported by the participants was observed.

Investigation of Flexion-Relaxation Ratio Symmetry in Subjects with and without Non-Specific Chronic Neck Pain

Introduction: Neuromuscular imbalance between right and left sides of Cervical Erector Spinae (CES) muscles can induce pain by applying the asymmetric loads on the spine incorrectly. This study evaluated the symmetry of the right and left cervical flexion-relaxation ratio (FRR) in patients with Non-Specific Chronic Neck Pain (NSCNP) and healthy subjects.We aimed to investigate the symmetry of FRR on the right and left sides of the CES muscles in individuals with and without NSCNP.Materials and Methods: A total of 25 patients with NSCNP and 25 healthy subjects participated in this study. The surface electromyography activity of CES muscles during four phases of flexion and extension tasks were measured and recorded. Unilateral FRR in the right and left sides of CES muscles was calculated and compared in each group.Results: Only in NSCNP patients, FRR in the right CES muscle was significantly higher than that in the left one (P&lt;0.05). Also, FRR for bilateral CES muscles was significantly higher in healthy subjects than in NSCNP patients (P&lt;0.001).Conclusion: The study results indicated a greater FRR asymmetry in CES muscles in NSCNP patients than in healthy subjects. This asymmetry is probably due to the dominance of the limb. Moreover, asymmetric FRR as a kind of neuromuscular imbalance may cause pain due to imposing asymmetric loads on spine structures.