Biceps Femoris Activity Research Articles

Amplitude of Biceps Femoris Activation and Triaxial Acceleration in a 50-Meter Test in Sprinters: Pilot Study

Objective: To describe the relationship between bilateral electrical activity in the biceps femoris and the variation of triaxial acceleration in three 50 m sprints. Methods: Biceps femoris muscle activation and acceleration in the anterior–posterior, mediolateral, and superior–inferior axes were measured in three 50 m sprints in nine national-level sprinters. Results: There was significant asymmetry between both legs, and the variations between axes were significant between the anterior–posterior with respect to the lateral and superior–inferior, and between the lateral and superior–inferior (p < 0.05). Conclusions: Increased biceps femoris activation during running increases speed regardless of asymmetry in force application. In the maintenance of horizontal velocity, acceleration of the anterior–posterior axis is the most relevant and depends on the flexion-extension muscle actions contained in the lateral axis.

Exploring the use of wearable sensors for assessing risk factors during orthopedic surgeries: A protocol for data collection

During orthopedic surgeries, surgeons are generally exposed to prolonged periods of standing, awkward and sustained body postures, and forceful movements, which can increase the likelihood of developing work-related musculoskeletal disorders (WRMSD). Therefore, this study proposes a protocol to measure parameters related to physical risk factors contributing to lower limb WRMSD, during orthopedic surgery procedures. The protocol development was preceded by an initial phase of understanding and specifying the context of use, followed by pre-tests in laboratory environment. It integrates a motion capture system, using inertial measurement units (IMU) to collect posture data from hip, knee, and ankle, and electromyography system (EMG) to measure and record data from muscle activity of biceps femoris, rectus femoris, and gastrocnemius lateralis. Pre-tests provided insights for protocol optimization, estimating a 3-hour data collection session per surgery due to sensor battery limitations, streamlining the process by placing EMG sensors before IMU and refining thigh sensor placement strategies. The protocol presents an opportunity for a real-time and quantitative approach to monitor surgeon's exposure to risk factors contributing to lower limb WRMSD while performing surgical procedures. Two months after pre-tests, the protocol implementation began in a real work context. The study's final outcomes fall outside the paper's scope.

Amplitude of Lower Limb Muscle Activation in Different Phases of the Illinois Test in Parkinson's Disease Patients: A Pilot Study.

Background: Parkinson's disease (PD) is a neurodegenerative disorder with high prevalence in men and is characterized by symptoms such as tremors and gait difficulties. This study aimed to determine muscle activation in patients with PD by considering sex differences. Methods: This pilot study used analytical, quantitative, observational, and case-control methods. Surface electromyography was used to assess muscle activity during a variant of the Illinois agility test. The study population comprised an experimental group of patients with PD (N = 30) and a control group of healthy individuals without the disease (N = 10). Results: The Illinois agility test revealed significant differences in completion times between the groups. The Parkinson's disease group took longer overall (p = 0.004), especially for standing up (p < 0.001) and sitting down (p = 0.002), than the control group. In the control group, sex influenced gastrocnemius muscle activation, with women showing higher activation (rs = -0.87). Women also had greater rectus femoris activation during standing and sitting, with higher activation on the right side when standing (rs = -0.66) and the left side when sitting (rs = -0.87). In the control group, men exhibited greater activation of the right biceps femoris (rs = 0.87). However, in the Parkinson's disease group, sex did not affect muscle activation. Conclusions: Patients with Parkinson's showed lower muscle activation than healthy individuals while standing up, sitting down, and walking.

Enhancing lower limb and core muscle activation with blood flow restriction training: a randomized crossover study on high-intensity squat exercises.

The primary objective of this study was to assess the impact of high-intensity deep squat training integrated with various blood flow restriction (BFR) modalities on the activation of lower limb and core muscles. A randomized, self-controlled crossover experimental design was employed with 12 participants. The exercise protocol consisted of squat training at 75% of one-repetition maximum (1RM), performed in 3 sets of 8 repetitions with a 2-min inter-set rest period. This was conducted under four distinct BFR conditions: continuous low BFR (T1), intermittent medium BFR (T2), intermittent high BFR (T3), and a non-restricted control (C). Surface electromyography (EMG) was utilized to collect EMG signals from the target muscles during the BFR and squat training sessions. The root mean square (RMS) amplitude standard values were calculated for each squat set to quantify muscle activation levels, with these values expressed as a percentage of the maximum voluntary contraction (%MVC). Rating of Perceived Exertion was evaluated after each squat set, and leg circumference measurements were taken. 1) During the first two sets of deep squats, the %MVC of the vastus lateralis and vastus medialis in all compression groups was significantly higher than that in the control group (p < 0.05). Furthermore, in the first set, the %MVC of the vastus lateralis in Group T3 was significantly higher than in Group T2 (p < 0.05). In the third set, the %MVC of the vastus medialis in Groups T1 and T3 was significantly lower than in the first two sets (p < 0.05). 2) Group T1 showed an increased activation of the biceps femoris and semitendinosus muscles in the second and third sets, with %MVC values significantly greater than in the first set (p < 0.05). Group T2 only showed an increase in biceps femoris activation in the third set (p < 0.05). Group T3 significantly increased the activation of the biceps femoris and semitendinosus muscles only in the first set (p < 0.05). 3) No significant differences were observed in the changes of rectus abdominis %MVC among the groups (p > 0.05). In the first set, Group T3's erector spinae %MVC was significantly higher than the control group's; in the second set, it was significantly higher than both Group T2 and the control group's (p < 0.05). 4) After training, a significant increase in thigh circumference was observed in all groups compared to before training (p < 0.05). 5) For RPE values, Group T2's post-squat values were significantly higher than the control group's after all three sets (p < 0.05). Group T1's RPE values were also significantly higher than the control group's after the third set (p < 0.05). Groups T1, T2, and C all had significantly higher RPE values in the second and third sets compared to the first set (p < 0.05). All BFR modalities significantly enhanced the activation level of the anterior thigh muscles, with the continuous low BFR mode demonstrating a more stable effect. No significant differences were found in the activation level of the rectus abdominis among the groups. However, the intermittent high BFR mode was the most effective in increasing the activation level of the erector spinae muscles. While BFR did not further augment leg circumference changes, it did elevate subjective fatigue levels. The RPE was lowest during squatting under the intermittent high BFR condition.

Differential Back Muscle Flexion-Relaxation Phenomenon in Constrained versus Unconstrained Leg Postures.

Previous studies examining the flexion-relaxation phenomenon (FRP) in back muscles through trunk forward flexion tests have yielded inconsistent findings, primarily due to variations in leg posture control. This study aimed to explore the influence of leg posture control and individual flexibility on FRP in back and low limb muscles. Thirty-two male participants, evenly distributed into high- and low-flexibility groups, were recruited. Activities of the erector spinae, biceps femoris, and gastrocnemius muscles, alongside the lumbosacral angle (LSA), were recorded as participants executed trunk flexion from 0° to 90° in 15° increments, enabling an analysis of FRP and its correlation with the investigated variables. The findings highlighted significant effects of all examined factors on the measured responses. At a trunk flexion angle of 60°, the influence of leg posture and flexibility on erector spinae activities was particularly pronounced. Participants with limited flexibility exhibited the most prominent FRP under constrained leg posture, while those with greater flexibility and unconstrained leg posture displayed the least FRP, indicated by their relatively larger LSAs. Under constrained leg posture conditions, participants experienced an approximate 1/3 to 1/2 increase in gastrocnemius activity throughout trunk flexion from 30° to 90°, while biceps femoris activity remained relatively constant. Using an inappropriate leg posture during back muscle FRP assessments can overestimate FRP. These findings offer guidance for designing future FRP research protocols.

No difference in laxity, proprioception and neuromuscular control after suture-tape augmented ACL repair of acute proximal avulsions versus ACL reconstruction using hamstring autografts in young, active population.

The purpose of this study is to compare results of suture-tape augmented anterior cruciate ligament (ACL) repair (internal bracing [IB]) and ACL reconstruction (ACLR) with hamstring autograft in terms of laxity, proprioception and neuromuscular control. The hypothesis was that with strict indications IB may provide better results in proprioception and neuromuscular control. Patients with unilateral ACL injury treated with IB or ACLR with hamstring autograft were enroled in this retrospective study. Anterior tibial translation (ATT) in 30° and 90° of flexion was measured with Rolimeter. The joint position sense (JPS) test was performed in 30° and 60° of flexion using Biodex System 4Pro. The time-synchronized motion capture system and surface electromyography set were used during dynamic tasks to assess knee valgus and semitendinosus (ST) and biceps femoris (BF) activities. Comparisons between both techniques and operated versus contralateral healthy knees were performed. The study groups involved 28 patients after ACLR (21.8 ± 4.8 years) and 20 patients after IB (25.8 ± 10.5 years) with the average follow-up 30 ± 18 and 28 ± 15 months, respectively. The ATT did not differ significantly between operated groups. In 30° of flexion ATT for ACLR was significantly higher in operated than in contralateral knee (5.8 ± 2.4 mm vs. 4.3 ± 1.3 mm, p < 0.001). The JPS test and dynamic knee valgus presented no significant differences. The ACLR group presented significantly higher ST (p = 0.048) and BF (p = 0.012) activity comparing operated to contralateral knee in dynamic tasks. Suture-tape augmented ACL repair and ACLR with hamstring autograft yield similar results in terms of laxity, proprioception and neuromuscular control. Level III: Retrospective comparative study.

The effect of the conventional deadlift and Romanian deadlift on muscle activation and joint angles at submaximal intensity

For fitness professionals delivering strength and conditioning programmes and recreational athletes designing their own programmes, exercise selection and an appropriate loading stimulus over time are the cornerstones of an effective resistance training programme. The conventional deadlift (CD), a compound, closed-chain movement, is prescribed to increase the strength of the posterior chain and the quadriceps. The Romanian Deadlift (RDL) is an isolated knee variation of the CD, whereby the knee angle is stable throughout the movement (Lee et al., 2018, J Exer Sci Fit, 16, 87-93). The RDL is a key movement in weightlifting training and is a commonly used developer of posterior chain muscles (Weaver and Kerksick, 2017, Strength Cond J, 39, 85-90). Studies comparing the CD and RDL are limited. Using surface EMG 2D motion analysis of the lower limb, we aim to determine if (i) biceps femoris activation is greater than the vastus lateralis during the RDL, (ii) there is a higher activation of both vastus lateralis and biceps femoris during the CD, and (ii) whether an injury is more likely to occur during a CD or RDL using the angles and range of motion (ROM) of the hip, knee, and ankle. 15 recreationally active adults with experience with the CD and RDL were recruited. Surface EMG sensors were placed on the vastus lateralis and biceps femoris, and markers were placed for 2D motion analysis in the sagittal plane. MVC data were collected for three repetitions of both lifts at 70% RDL 1RM. Five repetitions at 50% RDL 1RM were used for analysis. Statistical analysis was conducted using a paired t-test and Wilcoxon signed-rank test. The results show greater activation of the vastus lateralis in the CD than the RDL (P &lt; 0.05) but no difference in the biceps femoris. No differences were found in hip angles during ascent or descent at mid-thigh and knee height (P = 0.343), but there were differences at the bottom position. Knee angles during ascent and descent at the mid-thigh were different (P = 0.027) but not at knee height. No differences at the ankle joint were found at the mid-thigh (P = 0.12), but differences were found at knee height and bottom position. Finally, ROM at the hip, knee, and ankle during ascent and descent were significantly different (P = 0.002). The findings may help fitness professionals and recreational athletes make decisions such as exercise selection, load management, and injury prevention strategies based on the comparative effectiveness and risks of the CD and RDL.

BORS/BJR TRAVELLING FELLOWSHIP ABSTRACT: MOTION CAPTURE OF NEONATAL INFANT KICKING MOVEMENTS CAN PROVIDE AN EARLY PREDICTION OF CEREBRAL PALSY

AbstractObjectivesNeonatal motor development transitions from initially spontaneous to later increasingly complex voluntary movements. A delay in transitioning may indicate cerebral palsy (CP). The general movement optimality score (GMOS) evaluates infant movement variety and is used to diagnose CP, but depends on specialized physiotherapists, is time-consuming, and is subject to inter-observer differences. We hypothesised that an objective means of quantifying movements in young infants using motion tracking data may provide a more consistent early diagnosis of CP and reduce the burden on healthcare systems. This study assessed lower limb kinematic and muscle force variances during neonatal infant kicking movements, and determined that movement variances were associated with GMOS scores, and therefore CP.MethodsElectromagnetic motion tracking data (Polhemus) was collected from neonatal infants performing kicking movements (min 50° knee extension-flexion, &lt;2 seconds) in the supine position over 7 minutes. Tracking data from lower limb anatomical landmarks (midfoot inferior, lateral malleolus, lateral knee epicondyle, ASIS, sacrum) were applied to subject-scaled musculoskeletal models (Gait2354_simbody, OpenSim). Inverse kinematics and static optimisation were applied to estimate lower limb kinematics (knee flexion, hip flexion, hip adduction) and muscle forces (quadriceps femoris, biceps femoris) for isolated kicks. Functional principal component analysis (fPCA) was carried out to reduce kicking kinematic and muscle force waveforms to PC scores capturing ‘modes’ of variance. GMOS scores (lower scores = reduced variety of movement) were collected in parallel with motion capture by a trained operator and specialised physiotherapist. Pearson's correlations were performed to assess if the standard deviation (SD) of kinematic and muscle force waveform PC scores, representing the intra-subject variance of movement or muscle activation, were associated with the GMOS scores.ResultsThe study compared GMOS scores, kinematics, and muscle force variances from a total of 26 infants with a mean corrected gestational age of 39.7 (±3.34) weeks and GMOS scores between 21 and 40. There was a significant association between the SD of the PC scores for knee flexion and the GMOS scores (PC1: R = 0.59, p = 0.002; PC2: R = 0.49, p = 0.011; PC3: R = 0.56, p = 0.003). The three PCs captured variances of the overall flexion magnitude (66% variance explained), early-to-late kick knee extension (20%), and continual to biphasic kicking (6%). For hip flexion, only the SD of PC1 correlated with GMOS scores (PC1: R = 0.52, p = 0.0068), which captured the variance of the overall flexion magnitude (81%). For the biceps femoris, the SD of PC1 and PC3 associated with GMOS scores (PC1: R = 0.50, p = 0.002; PC3: R = 0.45, p = 0.03), which captured the variance of the overall bicep force magnitude (79%) and early-to-late kick bicep activation (8%).ConclusionsInfants with reduced motor development as scored in the GMOS displayed reduced variances of knee and hip flexion and biceps femoris activation across kicking cycles. These findings suggest that combining objectively measured movement variances with existing classification methods could facilitate the development of more consistent and accurate diagnostic tools for early detection of CP.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Effects of Neurodynamics Versus Neurodynamic Sustained Natural Apophyseal Glide in Lumbosacral Radiculopathy

Lumbosacral radiculopathy is a frequently reported health issue in middle-aged people, with a prevalence varying fromabout 2.2% to 8%. Neurodynamic mobilization (NM) and Neurodynamic sustained natural apophyseal glide (N-SNAG) techniqueswere proven effective for Lumbosacral radiculopathy. But controversies are prevalent regarding the effectiveness of their treatmentin previous studies. N-SNAG is also a comparatively new technique that is clinically being used around, but more literature is neededto analyze its effectiveness. Hence, we aimed to evaluate the efficacy of N-SNAG in comparison with NM and conventional generalexercises in treating lumbosacral radiculopathy on pain, mobility, disability, muscle activation, and health-related quality of life(HRQL). One hundred and twenty-seven patients aged between 30 and 50 years were randomly allocated into 3 different treatmentgroups, where the first and second groups received N-SNAG and NM with general exercises, and the third (control) group receivedgeneral exercises only. Range of motion of lumbar and hip flexion, active straight leg raising, low back pain, radiculopathy pain, muscleactivation of biceps femoris and gastrocnemius muscles, disability, and HRQL were evaluated at baseline, and the end of 1st week, 2ndweek, 7th week and 18th week for all the groups. Two-way repeated measure ANOVA with Bonferroni’s t-test revealed significant(p&lt;0.05) improvement in the range of lumbar and hip flexion, LBP, radiculopathy pain, active SLR, disability, and HRQL in both withingroups and between groups. Muscle activation of biceps femoris and gastrocnemius also improved significantly (p&lt;0.05) in all threegroups, but no significant (p&gt;0.05) differences were seen between groups. The study concludes that N-SNAG is more efficient thanNM and general exercise in improving pain, lumbar and hip flexion range, SLR, disability, Muscle activation, and HRQL in Lumbosacralradiculopathy patients.

Muscle activity during crouched walking.

Muscle activity during crouched walking has been previously studied in the context of the evolution of hominin bipedalism and human movement disorders. However, crouched walking could also be used in approach hunting where postural height (actual height of the body from the ground to the top of the head during locomotion) is the limiting factor. Here, we aim to analyze the relationship between relative postural height (%stature), kinematics, and muscle activity during crouched walking. Adult males (n = 19) walked with extended limbs and at three degrees of crouch while their 3D motion capture kinematics and lower limb muscle electromyography were recorded. We measured activation of tibialis anterior, soleus, gastrocnemius medialis, gastrocnemius lateralis, vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus. We analyzed the effects of postural height on kinematics and muscle activation using linear mixed effects model. Flexion angles, individual muscle activation (except for medial gastrocnemius), and total muscle activation were negatively related to relative postural height, that is, were greater at more crouched postures. Relative postural height had a stronger effect on the activation of the thigh and gluteal muscles compared to shank muscles. General increase in lower limb muscle activation at lower postural heights suggests a negative relationship between relative postural height and fatigue, and may indicate a possible mechanism by which short stature could benefit the hunter in approach hunting. Greater activation of thigh and gluteal muscles relative to shank muscles may help to identify crouched walking in past human populations.

Effects of Mobile Phone Use on Gait and Balance Control in Young Adults: A Hip–Ankle Strategy

Background: This study aimed to derive the effects of walking while using a mobile phone on balance perturbation and joint movement among young adults. Methods: Sixteen healthy college students with no history of brain injury were tested. The participants were asked to walk under four different conditions: (1) walking, (2) browsing, (3) dialing, and (4) texting. Indicators related to balance control and lower limb kinematic/kinetic parameters were analyzed using the continuous relative phase and statistical nonparametric mapping methods. Results: Walking while using a mobile phone slowed participants’ gait speed and reduced the cadence, stride length, and step length. The posterior tilt angle (0–14%, 57–99%), torque of the hip flexion (0–15%, 30–35%, 75–100%), and angle of the hip flexion (0–28%, 44–100%) decreased significantly. The activation of biceps femoris and gastrocnemius, hip stiffness, and ankle stiffness increased significantly. This impact on gait significantly differed among three dual tasks: texting &gt; browsing &gt; dialing. Conclusion: Che overlap of walking and mobile phone use affects the gait significantly. The “hip–ankle strategy” may result in a “smooth” but slower gait, while this strategy was deliberate and tense. In addition, this adjustment also increases the stiffness of the hip and ankle, increasing the risk of fatigue. Findings regarding this effect may prove that even for young healthy adults, walking with mobile phone use induces measurable adjustment of the motor pattern. These results suggest the importance of simplifying the control of the movement.

Comparing the Effects of Lumbar-pelvic and Pelvic Belts on the Activity of Pelvic Muscles in Pregnant Women With Back and Pelvic Pain

Objective The physical and hormonal changes occur in pregnant women, which may cause skeletal and muscular discomforts and back and pelvic pain. If the pelvic muscles mechanism is damaged, pelvic joints may have less stability, and the joint is more exposed to shearing force. As a result of this condition, the activity pattern of these muscles of the lumbar region may change, increased muscle activity compensates for the anterior forces, and bending moments may occur, especially when the abdomen volume is increased. In previous studies, the activity of pelvic muscles in the test of active straight leg raise (ASLR) was evaluated in pregnant women without using a pelvic belt. These belts are strapped at the level of the pelvic ring and do not fully support the lumbar region. The lumbar-pelvic belt can extend below the lower angle of the scapula, completely covering the lumbar region and supporting the waist and pelvis simultaneously. As a result, the whole body acts as a unit compared to a pelvic belt. The present study aims to compare the effect of the lumbar-pelvic belt with the pelvic belt in the activity of the pelvic muscles during the ASLR test of the lower limb in pregnant women with back and pelvic pain. Materials &amp; Methods This was a clinical trial study on 48 pregnant women with pregnancy-related back and pelvic pain referred to the Kawsar Specialized and Subspecialty Clinic in Arak City, Iran. The sampling method was convenience sampling based on inclusion and exclusion. All participants completed the written consent form, and then they were randomly divided into three groups: lumbar-pelvic belt (14 women), pelvic belt (14 women), and control (20 women). First, a demographic questionnaire was completed by the participants. Then the pelvic muscles’ muscle activity was evaluated using surface electromyography during the ASLR test at the beginning of the study and then three weeks later. Covariance analysis was used in SPSS version 26 software for data analysis, and the significance level was considered 0.05. Results After three weeks of using the devices, the activity of the right rectus femoris, left rectus femoris, right biceps femoris, and left biceps femoris muscles decreased in both groups who used the belts and increased in the control group during the ASLR test. The activity of the right biceps femoris and left biceps femoris muscles in the lumbar-pelvic belt group was significantly reduced compared to the pelvic belt group (P&lt;0.001). Although the activity level of the right rectus femoris and left rectus femoris muscles in the lumbar-pelvic belt group decreased more than the pelvic belt group, this decrease was not statistically significant. Conclusion The activity of the rectus femoris and biceps femoris muscles during the ASLR test decreased in both groups using the pelvic belts and increased in the control group after three weeks. This finding shows the effect of both pelvic belts on improving pelvic muscle activity. However, the lumbar-pelvic belt had a greater impact on improving the activity of the biceps femoris muscles than the pelvic belt during the ASLR test.

A pilot study investigating motor adaptations when learning to walk with a whole-body powered exoskeleton

Evidence is emerging on how whole-body powered exoskeleton (EXO) use impacts users in basic occupational work scenarios, yet our understanding of how users learn to use this complex technology is limited. We explored how novice users adapted to using an EXO during gait. Six novices and five experienced users completed the study. Novices completed an initial training/familiarization gait session, followed by three subsequent gait sessions using the EXO, while experienced users completed one gait session with the EXO. Spatiotemporal gait measures, pelvis and lower limb joint kinematics, muscle activities, EXO torques, and human-EXO interaction forces were measured. Adaptations among novices were most pronounced in spatiotemporal gait measures, followed by joint kinematics, with smaller changes evident in muscle activity and EXO joint torques. Compared to the experienced users, novices exhibited a shorter step length and walked with significantly greater anterior pelvic tilt and less hip extension. Novices also used lower joint torques from the EXO at the hip and knee, and they had greater biceps femoris activity. Overall, our results may suggest that novices exhibited clear progress in learning, but they had not yet adopted motor strategies similar to those of experienced users after the three sessions. We suggest potential future directions to enhance motor adaptations to powered EXO in terms of both training protocols and human-EXO interfaces.

Effects of Six Weeks of Modified and Standard Nordic Hamstring Exercises on Electromyography of Hamstring, Hip And Trunk Muscles and Sprint Performance in Young Male Football Players

Background and Aims hamstring injury is the most common injury in football. Nordic hamstring exercise (NHE) is one of the best hamstring injury prevention strategies. This study was aims to compare the effect of six weeks of standard NHE and modified NHE on electromyography of hamstring, hip and trunk muscles and sprint performance in young male football players Methods In this study, participants were 26 male football players in Kerman, Iran who were selected using purposeful and convenience sampling methods and randomly divided into two groups of NHE (Age: 16.31±0.51 years, Height: 173.08±5.15 cm, weight: 59.85±5.71 kg) and modified NHE (Age: 16.41±0.54 years, Height: 173±6.84 cm, weigh: 64.20±8.76 kg). Sprint performance was measured by the 20-meter sprint test, and muscles activity was measured by electromyography. Repeated-measure analysis of variance was used for data analysis. Results In the modified NHE group, there was a significant difference between the pretest and posttest phases in the electrical activity of biceps femoris (P=0.001), semitendinosus (P=0.001), gluteus maximus (P=0.016) and erector spinae muscles (P=0.001). In the NHE group, although the activity of muscles increased by 13% in the biceps femoris, 11% in the Semitendinosus, 9% in the gluteus maximus and 4% in erector spinae muscles, the difference was significant only in the biceps femoris (P=0.001) and Semitendinosus (P=0.024). The results also showed a significant difference between the two groups in electrical activity of biceps femoris (P=0.021), semitendinosus (P=0.046) and erector spinae muscles (P=0.039). Conclusion Both standard and modified NHE are effective in preventing hamstring injury by increasing the electrical activity of the Biceps femoris and Semitendinosus, but the modified NHE is more effective in prevention of injury by changing the parameters of NHE and increasing the training load.

Weight-Bearing Exercises on Slideboard Increase Quadriceps and Hamstring Activation Levels and Improve Hip- and Knee-Flexion Angles in Physically Active Individuals.

Slideboards are commonly used in exercise programs, but there is limited information about how they affect muscle activities during exercise. We aim to compare the activation levels of quadriceps and hamstring muscles and hip- and knee-flexion angles during lunge and single-leg squat exercises between normal ground and slideboard in physically active individuals. Cross-sectional study. Thirty healthy individuals (age: 23.83 [2.84]y, body mass index: 21.75 [1.72]kg/m2) were included in the study. Surface electromyography was used to measure vastus medialis, vastus lateralis, biceps femoris, and semitendinosus activation levels during reaching and returning phases of the forward, lateral, and back lunges and squats that were performed on the normal ground and slideboard. Exercises were performed at a slow pace (60 beats/min). Hip- and knee-flexion angles during the exercises were evaluated by using 2-dimensional motion analysis. Repeated measures of analysis of variance were used for statistical analysis. Vastus medialis and vastus lateralis activation levels were greater during reaching and returning phases of the exercises on slideboard compared with normal ground (P < .05). However, semitendinosus and biceps femoris activity were greater only during the returning phase of the forward lunge (P < .001) and the returning phase of the back squat (P = .002, P = .009, respectively). Hip-to-knee flexion ratios were closer to 1 when the forward lunge (P < .001), back lunge (P = .004), and forward squat (P = .001) exercises were performed on a slideboard. In exercise programs that target the quadriceps and hamstring muscles, slideboards can be effectively used in exercise progressions as they can increase muscle activity. Moreover, squat and lunge exercises on slideboard with a slow pace may also be helpful for improving the balance between hip- and knee-flexion angles.

Relationships between Body Weight Support and Gait Speed Parameters and Muscle Activity and Torque during Robot-Assisted Gait Training in Non-Neurological Adults: A Preliminary Investigation

Robot-assisted gait training (RAGT) is a promising therapeutic vehicle to maximize active participation and enhance functional neuroplasticity in patients with central nervous system pathology by adequately adjusting gait speed, body weight support (BWS) level, and impedance provided by the exoskeleton. The aim of the present study was to determine the relationship between RAGT training parameters (BWS and speed) and electromyography (EMG) muscle activity torques in the knee and hip joint during RAGT. To analyze the correlation between the joint torques measured in the Walkbot gait rehabilitation system and the EMG signal of the lower limbs (vastus lateralis oblique, biceps femoris, tibialis anterior, and gastrocnemius) and understand the real-time state of the lower limb an experiment involving 20 subjects was conducted. The EMG–torque relationship was evaluated in a general rehabilitation training setting to overcome the limitations of in vivo settings. Pearson correlation coefficient analysis was performed at p &lt; 0.05. Moderate relationships between biceps femoris activation data and hip and knee torques were statistically significant, ranging from r = 0.412 to −0.590, p &lt; 0.05). Importantly, inverse relationships existed between hip torques and vastus lateralis oblique, biceps femoris, and tibialis anterior activation, respectively. The present results demonstrated the association between EMG locomotor control patterns and torque generation in the hip and knee joints during RAGT-treadmill under the different BWS and walking speed settings while adjusting the impedance mode parameters in non-neurological adults. Additionally, the EMG locomotor control patterns, concurrent torque generation in the hip and knee joints, and application of different BWS and walking speed parameters in the RAGT were linked to the gait speed and BWS. The outcomes also showed that the amount of BWS supplied had an impact on the effects of treadmill speed on muscle activity and temporal step control. It is essential to adjust RAGT parameters precisely in order to maximize training session efficiency and quality. The results of this study nevertheless call for more investigation into the relationship between muscle activity and torque outcomes in diseased populations with gait impairment.

Effect of Load on Muscle Activity, Kinematics, and Force Production During the Reverse Hyperextension Exercise.

The reverse hyperextension exercise is used to strengthen posterior chain musculature without axially loading the spine; however, there are no suggestions for loading. Twenty recreationally active individuals (13 males and 7 females; aged 25.4 [2.5]y; height 1.76 [0.09]m; mass 79.3 [15.8]kg) performed 2 sets of 10 repetitions with 50%, 100%, and 150% of bodyweight. Surface electromyography measured erector spinae, gluteus maximus, and biceps femoris activity. Motions of the trunk, lower extremities, and reverse hyperextension exercise pendulum were tracked. A 1-way repeated-measures analysis of variance was used to analyze differences. Few differences were found between 100% and 150% loads; however, heavier loads resulted in increased hip (5.0°) and trunk (4.0°) flexion compared with the 50% load. Similar patterns emerged for peak and integrated muscle activity, with erector spinae and gluteus maximus activity greater in the 100% and 150% loads than in the 50% load, and biceps femoris activation increasing as load increased. Peak force significantly (P < .001) increased with 100% (28% [31%]) and 150% (34% [40%]) loads compared with the 50% load. Findings suggest the reverse hyperextension exercise targets posterior chain musculature, but increasing loads does not linearly increase force and muscle activation.

Lower-Limb Muscle Activity During Aquatic Treadmill Running in Individuals With Anterior Cruciate Ligament Reconstruction

While anterior cruciate ligament (ACL) tears are commonly managed with ACL reconstruction (ACL-R), 35% of ACL-R individuals fail to return to the preinjury elite sport level. Persistent neuromuscular deficits in the hamstrings and quadriceps have been observed. It has been proposed that aquatic therapy can be used to optimize neuromuscular control after ACL-R. (1)To compare muscle activity in ACL-R individuals during aquatic treadmill (ATM) running at different water depths and (2)to compare muscle activity during ATM running between ACL-R and healthy individuals. A total of 38 participants, including 18 ACL-R individuals (mean postoperative time [SD] = 25.8 [25.0] mo) and 20 healthy individuals were recruited. Muscle activity of biceps femoris (BF), rectus femoris (RF), tibialis anterior, and medial gastrocnemius during land treadmill and ATM running at mid-shin, mid-thigh, and waist levels were recorded using surface electromyography (sEMG). The sEMG signals of the selected muscles were normalized and expressed in % Maximal Voluntary Contraction (%MVC). Muscle activity of the ACL-R, ACL-contralateral, and healthy control limbs at different water depths was compared. Among the 3 groups, the ACL-R group demonstrated the most prominent percentage increase of 101.97% (P = .001) at mid-shin level, 139.66% (P = .001) at mid-thigh level, and 141.97% (P < .001) at waist level, respectively, in %MVC when compared to land. In the ACL-R group, muscle activity of BF in the stance phase (BFSt) was significantly higher than the control group on land at all water depths. Muscle activity of RF in the swing phase (RFSw) in the ACL-R group significantly increased in all water depths immersion when compared to land, respectively. This study showed an increasing trend in muscle activity of BFSt and RFSw in ACL-R individuals during ATM running at increased water depths. ATM running could be implemented as neuromuscular training in rehabilitation after ACL-R.

Effect of Initial Knee angle and Arm Facilitation on biomechanics of the Sit-to-Stand movement.

Spinal cord injuries cause loss of muscle function and subsequently reduce independence. Therapeutic interventions such as transcutaneous spinal cord stimulation are increasingly being used to help improve motor functioning however, a comprehensive understanding of the biomechanical elements of movement may help optimize stimulation protocols. Twenty healthy participants completed five sit-to-stand (STS) transitions while initial knee angle and arm facilitation were altered. Electromyography (EMG) activation of four lower limb muscles and centre of pressure dynamics were recorded. Acute initial knee angles resulted in a change in duration of phases within the STS, and restrictive arm positioning caused the time to completion to increase (p=0.04). Muscle activation patterns across phases were compared and showed significant differences between phases in both the Tibialis Anterior and Rectus Femoris (p<0.006). Acute initial knee angles were also found to significantly increase Biceps Femoris activation across multiple phases (p=0.034). Altering the starting position and limb movement result in vastly different temporal and muscular strategies to complete the STS. Thus, joint angle and upper limb facilitation should be considered when designing rehabilitative interventions for clinical cohorts.

Evidence for the use of dynamic maximum normalization method of muscle activation during weighted back squats

Electromyography (EMG) is a popular technique for analyzing muscle activation profiles during athletic maneuvers such as the back squat. Two methods are commonly implemented for normalizing EMG: a maximum voluntary isometric contraction (MVIC) and a dynamic maximum during the task being performed (DMVC). Although recent literature suggests DMVC may be superior, these suggestions havent been examined for weighted exercises. This study examined the influence of normalization method on rectus femoris, vastus medialis, and biceps femoris activations during back squats. Muscle activations were collected on twenty-seven participants (13 females, 14 males) performing one-repetition maximum (DMVC) and submaximum (80%) back squats. Data from submaximum squats were normalized to MVICs and DMVC. Data were compared using intra-class correlations over two testing days, variance ratio, and coefficients of variation. Mixed-model ANOVAs were used to elucidate the influence on intra-participant (method) and inter-participant (sex) variability. Reliability was “good” or “excellent” for MVIC and “excellent” for DMVC. Inter-subject variability was greater for MVIC compared to DMVC for all muscles. A significant normalization by sex interaction for both peak and mean biceps femoris activation was found. Based on our findings and current literature, normalization to DMVC is the superior method for weighted exercises.