Rectus Femoris Muscle Activity Research Articles

One Session Effects of Knee Motion Visualization Using Immersive Virtual Reality in Patients with Hemophilic Arthropathy.

(1) Background: Hemophilic knee arthropathy is characterized by a loss of muscle mass and decreased strength of the quadriceps muscle. The visualization of movement aims to favor the recruitment of the motor system in the same premotor and parietal areas, as would happen with the active execution of the observed action. The aim was to evaluate changes in quadriceps activation in patients with hemophilic knee arthropathy following immersive VR visualization of knee extension movements. (2) Methods: We recruited 13 patients with severe hemophilia A and knee arthropathy. Patients underwent a 15 min session of immersive VR visualization of knee extension movements. The quadriceps muscle activation was evaluated by surface electromyography. (3) Results: After the intervention, there were no changes in the muscle activation of vastus medialis, vastus lateralis, or rectus femoris muscles. There was a large effect size of changes in rectus femoris muscle activation. Age and knee joint damage did not correlate with changes in quadriceps activation. Dominance, inhibitor development, and type of treatment were not related with post-intervention muscle activation. (4) Conclusions: A session of immersive VR visualization of knee extension movement does not modify quadriceps muscle activation. A specific protocol for patients with hemophilic knee arthropathy may be effective in improving the activation of the rectus femoris muscle.

Training Benefits and Injury Risks of Standing Yoga Applied in Musculoskeletal Problems: Lower Limb Biomechanical Analysis.

Standing yoga poses strengthen a person’s legs and helps to achieve the goal of musculoskeletal rehabilitation, but inadequate exercise planning can cause injuries. This study investigated changes in the electromyogram and joint moments of force (JMOFs) of lower extremities during common standing yoga poses in order to explore the feasibility and possible injury risk in dealing with musculoskeletal problems. Eleven yoga instructors were recruited to execute five yoga poses (Chair, Tree, Warrior 1, 2, and 3). The results revealed significant differences in hip, knee, and ankle JMOFs and varying degrees of muscle activation among the poses. Among these poses, rectus femoris muscle activation during the Chair pose was the highest, Warrior 2 produced the highest muscle activation in the vastus lateralis of the front limb, while Warrior 1 had the highest muscle activation in the vastus medialis of the back limb. Therefore, all three poses can possibly be suggested as a therapeutic intervention for quadriceps strengthening. Warrior 1 was possibly suggested as a therapeutic intervention in order to reduce excessive lateral overload of the patella, but the possible adverse effects of Warrior 2 with the highest knee adductor JMOF in the back limb could raise joint reaction forces across the medial condyles. In single-leg balance postures, Warrior 3 had unique training effects on the hamstring, and is therefore suggested as a part of hamstring rehabilitation exercises. The Tree pose induced low lower-extremity JMOFs and a low level of thigh muscle activations when it was performed by senior instructors with excellent balance control; however, for yoga beginners with insufficient stability, it will be a useful training mode for strengthening the muscles that help to keep one upright. This study quantified the physical demands of yoga poses using biomechanical data and elucidated the structures and principles underlying each yoga movement. This is crucial for yoga practitioners.

Analysis of Muscle Activity During Shooting Motion of Korean Traditional Archers

The past few decades has seen increasing kinematic studies using surface electoromyography (EMG) in archery, however there has been no such specific study in Korean traditional archery. The purpose of this study was to evaluate EMGs during archery shooting motion in Korean traditional archers. Ten men Korean traditional archers were participated, and divided into two groups according to the shooting stance; parallel stance group(PSG, n=5) and oblique stance group(OSG, n=5). The surface EMGs were measured 12 muscles during shooting motion of five events including Junbi(Set), Geogung(Set up), Manjak(Full draw), Balsi(Release), Machigi(Ending). At the result, muscle activity of posterior deltoid, trapezius, rhomboid major, latissimus dorsi, biceps brachii, forearm extensor bundle, triceps brachii, levator scapulae significantly increased at event of full draw and release, then significantly decreased again at event of ending, respectively(p<.01, p<.001). The muscle activity of erector spinae(ES) was also significantly increased at event of full draw and release(p<.01, p<.001), while no significant changes in muscles of rectus abdominis, rectus femoris(RF), gluteus maximus. As a result of comparing PSG and OSG, muscle activity of RF in OSG was higher than PSG at event of release(p<.05), it remained until event of ending(p<.05). On the other hand, the higher the tension of the bow, the higher the muscle activity of the draw arm at event of release(p<.05). These results suggest that when Korean traditional archery shooting, both side arm and back muscles are more activated than the abdomen, leg and hip muscles. The parallel stance might suppress the muscle activity of the lower extremities to twist the upper body. And the higher bowstring tension needs to increase of muscle strength in BB of draw arm.

Comparison of muscle activity during sit-to-stand movement at different chair heights between obese and normal-weight subjects.

The purpose of present study was to compare the tibialis anterior (TA), rectus femoris (RF), and erector spinae (ES) muscle activities at variety chair height during sit-to-stand (STS) on normal weight and obese subjects. Also, we compared the muscle activity difference between the normal weight and obese subjects. The study included 26 subjects (normal weight 13 and obese 13). Each subject performed STS at three chair heights (40 cm, 50 cm, 60 cm) and TA, RF, and ES muscle activities measured. According to the results of the measurement, muscle activation of TA showed significantly higher than RF and ES muscle activation during STS at all chair heights on obese subjects. The muscle activation of TA showed significantly higher than RF muscle activation during STS at all chair heights on normal weight subjects. The muscle activation of RF and ES showed significantly higher in normal weight subjects than obese subjects at 40 cm and 50 cm of chair heights. However, the TA muscle activation showed no significant difference between normal weight subjects and obese subjects. This study’s results suggested that obese subjects should practice the use of RF and ES muscles in a low-height chair during STS.

Feasibility, safety and muscle activity during flywheel vs traditional strength training in adult patients with severe haemophilia.

Eccentric training has been associated with several specific physiological adaptations. The flywheel machine is one of the easiest ways of performing eccentric overload training. However, no studies evaluated its feasibility, safety and muscle activity in patients with haemophilia (PWH). To evaluate feasibility and safety and compare muscle activity during flywheel vs weight machine knee extension exercise in severe PWH. Eleven severe PWH [mean age of 33.5 (8.1) years] participated in this cross-sectional study after receiving prophylactic treatment. Surface electromyography (EMG) signals were recorded for the rectus femoris during the knee extension exercise performed with 2 different conditions (flywheel and weight machine) with matched intensity (6 on the Borg CR10 scale). Kinesiophobia was assessed before and after the experimental session. Participants were asked to rate tolerability of each condition. Adverse effects were evaluated 24 and 48hours after the session. Kinesophobia did not increase after the experimental session, and no adverse effects were reported. At 60%-70% of the contraction cycle, the flywheel exercise showed higher (P=.024) eccentric rectus femoris muscle activity than the weight machine. In contrast, during the last 90%-100% of the contraction cycle, the traditional weight machine showed higher (P=.004) rectus femoris activity than the flywheel. The knee extension exercise performed with the flywheel at moderate intensity is safe and well tolerated among severe PWH under adequate factor coverage. Importantly, the flywheel variation provides higher eccentric rectus femoris activity at the breaking force moment, while it provides lower eccentric muscle activity at the end of the cycle.

Rectus femoris hyperreflexia contributes to Stiff-Knee gait after stroke

BackgroundStiff-Knee gait (SKG) after stroke is often accompanied by decreased knee flexion angle during the swing phase. The decreased knee flexion has been hypothesized to originate from excessive quadriceps activation. However, it is unclear whether hyperreflexia plays a role in this activation. The goal of this study was to establish the relationship between quadriceps hyperreflexia and knee flexion angle during walking in post-stroke SKG.MethodsThe rectus femoris (RF) H-reflex was recorded in 10 participants with post-stroke SKG and 10 healthy controls during standing and walking at the pre-swing phase. In order to attribute the pathological neuromodulation to quadriceps muscle hyperreflexia and activation, healthy individuals voluntarily increased quadriceps activity using electromyographic (EMG) feedback during standing and pre-swing upon RF H-reflex elicitation.ResultsWe observed a negative correlation (R = − 0.92, p = 0.001) between knee flexion angle and RF H-reflex amplitude in post-stroke SKG. In contrast, H-reflex amplitude in healthy individuals in presence (R = 0.47, p = 0.23) or absence (R = − 0.17, p = 0.46) of increased RF muscle activity was not correlated with knee flexion angle. We observed a body position-dependent RF H-reflex modulation between standing and walking in healthy individuals with voluntarily increased RF activity (d = 2.86, p = 0.007), but such modulation was absent post-stroke (d = 0.73, p = 0.296).ConclusionsRF reflex modulation is impaired in post-stroke SKG. The strong correlation between RF hyperreflexia and knee flexion angle indicates a possible regulatory role of spinal reflex excitability in post-stroke SKG. Interventions targeting quadriceps hyperreflexia could help elucidate the causal role of hyperreflexia on knee joint function in post-stroke SKG.

Earlier onsets in internal oblique and gluteus maximus muscles during leg raising in Functional Movement Screen score 3 than score 1.

Active straight leg raising (ASLR) is a fundamental test and used in the Functional Movement Screen (FMS). In the ASLR of the FMS, one subgroup performs the movement correctly without any compensation (ASLR-3), whereas another subgroup has limitations in ASLR but not the passive straight leg raising (ASLR-1-SMCD). We aimed to investigate whether abdominal muscle activities in ASLR are different between individuals with ASLR-1-SMCD and ASLR-3. The relative latency of the onset of the following muscles to the right rectus femoris muscle during the right ASLR and the amplitude of activity in the following muscles for 50 msec after the onset of rectus femoris muscle activity were compared: left rectus abdominal, bilateral external oblique, bilateral internal oblique, and left gluteus maximus muscles. Data of 17 participants with ASLR-3 and 34 participants with ASLR-1-SMCD, whose sex ratio was matched to the ASLR-3 group, were analyzed. Those with ASLR-1-SMCD had statistically significant delays in the relative latency of the right internal oblique muscle (46.32±70.83 msec) and left gluteus maximus muscle (100.36±75.40 msec) muscles compared with those with ASLR-3 (right internal oblique muscle=9.75±23.07 msec, left gluteus maximus muscle=57.50±36.89 msec). However, the difference in the amplitude of activity in any muscles was not significant. The ASLR-1-SMCD group had greater relative latency of the onset of right internal oblique muscle and left gluteus maximus muscle to the onset of the right rectus femoris muscle during the right ASLR compared with the ASLR-3 group.

Timing of Rectus Femoris and Biceps Femoris Muscle Activities in Both Legs at Maximal Running Speed.

ABSTRACTPurposeThe purpose of this study was to investigate the relationship between spatiotemporal variables of running and onset/offset timing of rectus femoris (RF) and biceps femoris (BF) muscle activities in both legs.MethodsEighteen male well-trained athletes (age = 20.7 ± 1.8 yr) were asked to run 50 m at maximal speed. The spatiotemporal variables (running speed, step frequency, and step length) over the distance from 30 to 50 m were measured. In addition, RF and BF muscle activities were obtained from both legs using wireless EMG sensors. To quantify the onset and offset timing of muscle activity, the band-pass filtered (20–450 Hz) EMG signal was processed using a Teager–Kaiser energy operator filter. We calculated RF and BF onset/offset timings (%) in both legs (e.g., ipsilateral leg RF [iRF] and contralateral leg BF [cBF]) during running cycle. Based on those timings, we obtained the EMG timing variables (%) as follows: “Switch1 (iBF-offset to iRF-onset),” “Switch2 (iRF-offset to iBF-onset),” “Scissors1 (cBF-onset to iRF-onset),” and “Scissors2 (iRF-offset to cBF-offset).ResultsWe found that “Switch2” had positive (r = 0.495, P = 0.037), “Scissors1” had negative (r = −0.469, P = 0.049), and “Scissors2” had positive (r = 0.574, P = 0.013) correlations with step frequency. However, these variables had no significant correlations with running speed or step length.ConclusionsThese results indicate that higher step frequency would be achieved by smoother switching of the agonist–antagonist muscle activities and earlier iRF activation relative to the cBF activity. To improve sprint performance, athletes and coaches should consider not only muscle activities in one leg but also coordination of muscle activities in both legs.

Does the Environment Cause Changes in Hemiparetic Lower Limb Muscle Activity and Gait Velocity During Walking in Stroke Survivors?

Stroke survivors often face difficulty in community ambulation though they attain steady-state walking in clinical setups. Compliance and unpredictability of the environment may alter the muscle activity and challenge the individual's gait. Successful reintegration into the community requires gait assessment and training in a real-life challenging environment. Little is known about the assessment and training of gait in the community environment under challenging mobility dimensions. Hence, we aimed to study the changes that real-life environmental dimensions have on the activity of selected muscles in hemiparetic lower limb and gait velocity in stroke survivors. Methods: An observational cross-sectional study was conducted on 16 ambulatory stroke survivors to assess the hemiparetic lower limb muscle activity during walking in real-life environmental dimensions. Participants were made to walk in the community on a walkway consisting of even surface, ramp, stairs, uneven terrain and obstacles. They were also made to manoeuvre through traffic and pick a load while walking for a distance in the walkway. Muscle activity of Rectus Femoris, Biceps Femoris, Gastrocnemius Medialis and Tibialis Anterior of the paretic lower limb were continuously recorded while walking using wireless surface electromyography. Gait velocity for the entire walkway and level of perceived difficulty while walking in different dimensions were also measured. Paired t-test was used to compare the percentage Maximum Voluntary Contraction (%MVC) of lower limb muscles between even surface and real-life environment dimensions while walking. One sample t-test was used to compare the gait velocity in real-life dimensions versus gait velocity in even surface measured in an earlier study. Results: There was a significant reduction (p < 0.01) in the activity of all four hemiparetic lower limb muscles while walking under the influence of real-life environmental dimensions compared to even surface. Gait velocity (0.33 ± 0.17 m/s) was significantly lower than that is essential to be a community ambulator. The level of perceived difficulty across all dimensions was reported qualitatively with the highest difficulty reported during stair and obstacle clearance. Conclusion: Real-life environmental dimensions lead to the reduction of paretic lower limb muscle activities and gait velocity during walking in community-dwelling stroke survivors. Stroke survivors perceived more difficulty while walking in real-life environment dimensions particularly while negotiating stairs and obstacles. Significance: Knowledge about the influence of real-life environmental dimensions will help the clinicians to target rehabilitation methods to improve walking adaptability.

Impact Of Vibration On Rectus Femoris During Bodyweight Squats In Female Collegiate Track Athletes

Whole-body vibration (WBV) exposes the entire body to mechanical oscillations when one is standing on a vibrating platform. In recent years, researchers have studied the extent to which these oscillations effect the body. Previous studies have investigated muscle activity in the general population during static exercises with WBV, but there has been little research that has focused on the effects of WBV during dynamic movements in athletes. PURPOSE: The purpose of the study was to investigate the effects of WBV on rectus femoris muscle activity during a whole-body squat (WBS) exercise in NCAA Division 1 female track and field athletes. METHODS: Fifteen NCAA Division 1 track and field female athletes (Height = 165.20+7.85 cm; Weight = 61.11+9.46 kg; BF% = 18.80+4.92 %; Age = 19.80+1.57 years) were assessed for adequate squat form using the FMS deep squat protocol. Subjects then completed a dynamic warm-up before a wired EMG sensor was placed over the rectus femoris muscle belly of the right leg. Subjects completed two trials consisting of 10 repetitions of WBS with and without WBV, in a counterbalanced order. Root mean squared (RMS) values were collected using the EMG sensor during WBS trials. RMS values for WBS during each trial were analyzed using a Dependent t-Test with an alpha level of p< 0.05. RESULTS: Mean values for RMS were 74.92+22.81 μV for WBV trials, and 53.11+24.46 μV for ground squat trials. The values for RMS were significantly (p < 0.001) greater for the WBV trials. CONCLUSIONS: Significantly higher RMS values occurred for the WBV trials which may indicate that more motor units were recruited in the rectus femoris when the athlete was performing WBS and experiencing WBV. Future research may be required to determine if the current study’s results may apply to collegiate male track and field athletes.

The effects of enhanced abdominal activation on quadriceps muscle activity levels during selected unilateral lower extremity exercises.

The purpose of this study was to investigate the effect of Abdominal Enhancement (AE) on the muscle activation of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) muscle activation levels during eccentric, isometric and concentric phases of single leg raise (SLR), single leg wall squat (SLWS) and forward lunge (FL) exercises. Sixteen healthy individuals (Age: 24.6±1.7years) were included in the study. Internal Obliques/Transversus Abdominis (IO/TA), VMO, RF and VL muscle activation levels were measured by surface EMG during the exercises in two conditions: with and without AE. The abdominal drawing-in technique was used for AE. Repeated-measures analysis of variance was performed for statistical analysis. With AE, the average of IO/TA muscle activation level was 28.9%. VMO and VL muscle activation levels were significantly greater with AE during SLR (p=.02), SLWS (p<.001) and FL (VMO, p=.008, VL, p=.04) exercises. The effect of AE on VMO muscle activation level ranged from 2.5% to 5% (Effect size range: 0.54 to 0.91) and VL muscle activation level ranged from 2.1% to 5.5% (Effect size range: 0.35-1.24). RF muscle activation level did not change with AE (p>.05). The results of this study showed that AE increased VMO and VL muscle activities during SLR, SLWS and FL exercises but the corresponding changes were small. Even if this is not enough for muscle strengthening, exercises with AE may be used to enhance knee joint stability while controlling lumbopelvic stability.

Influence of the trunk position on knee kinematics during the single-leg landing: implications for injury prevention

ABSTRACTThe purpose of the present study was to investigate the influence of the trunk position during the single-leg landing on the knee angle and muscle activity. Forty healthy university students (20 men and 20 women) performed right single-leg landings from a 40 cm-high platform with the trunk in neutral, flexion, extension, and right and left lateral flexion. Knee flexion and valgus angles were determined by two-dimensional video analysis, and rectus femoris (RF) and biceps femoris (BF) muscle activities were assessed. The knee flexion angle was significantly higher in the trunk-flexion position than in the other trunk positions. The knee valgus angle was significantly lower in the trunk-neutral and trunk-flexion positions than in the trunk-extension, trunk-right-lateral-flexion, and trunk-left-lateral flexion positions. Muscle activity of the RF was significantly lower in the trunk-flexion position than in the trunk-extension position and that of the BF was significantly higher in the trunk-flexion position than in the trunk-neutral, trunk-extension, and trunk-right-lateral-flexion positions. Single (right)-leg landing with the trunk in flexion may confer a low risk of anterior cruciate ligament injury compared to that with the trunk in extension or right lateral flexion.

Differences in Baseline Joint Moments and Muscle Activation Patterns Associated With Knee Osteoarthritis Progression When Defined Using a Clinical Versus a Structural Outcome.

Both structural and clinical changes can signify knee osteoarthritis progression; however, these changes are not always concurrent. A better understanding of mechanical factors associated with progression and whether they differ for structural versus clinical outcomes could lead to improved conservative management. This study examined baseline gait differences between progression and no progression groups defined at an average of 7-year follow-up using 2 different outcomes indicative of knee osteoarthritis progression: radiographic medial joint space narrowing and total knee arthroplasty. Of 49 individuals with knee osteoarthritis who underwent baseline gait analysis, 32 progressed and 17 did not progress using the radiographic outcome, while 13 progressed and 36 did not progress using the arthroplasty outcome. Key knee moment and electromyography waveform features were extracted using principal component analysis, and confidence intervals were used to examine between-group differences in these metrics. Those who progressed using the arthroplasty outcome had prolonged rectus femoris and lateral hamstrings muscle activation compared with the no arthroplasty group. Those with radiographic progression had greater mid-stance internal knee rotation moments compared with the no radiographic progression group. These results provide preliminary evidence for the role of prolonged muscle activation in total knee arthroplasty, while radiographic changes may be related to loading magnitude.

Effects of Whole Body Electromyostimulation on Muscle Activity and Muscle Thickness of Rectus Femoris, and Muscle Thickness of Abdominis Muscle in Healthy Adults

Background: Whole body-electromyostimulation (WB-EMS) is widely used for the rehabilitation and recovery of patients with various neuromusculoskeletal disorders.Objects: To objectively measure changes in lower extremity and abdominal muscles after sit-to-stand dynamic movement training using WB-EMS.Methods: A total of 46 healthy adults (23 experimental and 23 control subjects) performed sit-to-stand exercise; the experimental group with WB-EMS, and the control group without WB-EMS. The muscle activity of the lower extremity, and the muscle thickness of the lower extremity and abdominal muscles were measured before and after the intervention.Results: In terms of electromyographic activity, there was a significant interaction effect for the rectus femoris (RF) muscle (F=30.212, p=.000). With regards to ultrasonographic imaging, the muscle thickness of the RF muscle had a significant interaction effect at the muscle contraction ratio (F=8.071, p=.007). The deep abdominal muscles, such as the transverse abdominal (TrA) and internal oblique (IO) muscles, also showed significant interaction effects at the muscle contraction ratio (F=5.474, p=.024, F=24.151, p=.000, respectively)Conclusion: These findings suggest that WB-EMS may help to improve the muscular activity of the RF muscle, and the muscle thickness of the RF muscle and deep muscles such as the TrA and IO muscles.

Ergonomic Recommendation of Suitable Toilet Seat Height for Older Thai People

Objective: This study aimed to determine the main factors affecting older people as they rise from a toilet seat and to identify the suitable toilet seat height for this population.Material and Methods: Data from 342 older people both male and female aged 60 years and older were used to design a mock-up toilet with a specified seat width according to the 95th percentile of hip breadth. The data of lower leg length were used to design toilet seat height levels in the second phase in another 30 older participants at 100.0%, 110.0% and 120.0% of an individual’s lower leg length (LLL). Rectus femoris and gluteus maximus muscle activity, time taken while rising, pressure under the thighs and satisfaction of the older participants were compared across three toilet seat height levels; using the repeated analysis measurements of variance. These three potential factors were then analyzed together with the prioritized factor indicated by the specialists using the Analytic Hierarchy Process.Results: Rectus femoris muscle activity, time taken while rising, and satisfaction of the older participants in rising from toilet seat heights 100.0, 110.0 and 120.0% LLL were significantly different (p-value&lt;0.05).Conclusion: It was found that the suitable toilet seat height level for older people for industrial ergonomic purposes was at 110.0% LLL, which was also equivalent to the 95th percentile of male and female LLL.

Investigation the EMG Activities of Lower Limb Muscles When Doing Squatting Exercise in Water and on Land.

(1) Background: Squatting is one of the common closed-kinetic chain (CKC) exercises for knee rehabilitation. Some patients cannot perform squatting exercises on land occasionally due to knee pain. Several studies had suggested that lower limb muscle activities are lower in water than on land while performing CKC exercises. The purpose of this study is to investigate the surface electromyography (sEMG) activities of Rectus femoris (RF) and Biceps femoris (BF) muscles when doing a squatting exercise in water and on land. (2) Methods: This was a cross-sectional experimental study. A total of 20 healthy participants (10 males, 10 females) were recruited by convenience sampling. The sEMG of RF and BF muscles in water and on land were collected and the knee motions were videotaped. Participants were instructed to perform closed kinetic-chain back squatting exercises at a specific speed (30 beats per minute) in water and on land at angular speed of 45°/s. Eight repetitions of the squatting exercise (0–90° knee flexion) were performed. The mean percentage maximal voluntary contraction (%MVC) between two muscles was compared in two conditions. The %MVC of RF and BF muscles at different specific knee flexion angles (30°, 60° and 90° knee flexion) was also identified. (3) Result: Muscle activities of RF (p = 0.01) and BF (p < 0.01) muscles were significantly lower in water than on land. The %MVC of RF and BF muscles was found to be 15.01% and 10.68% lower in water than on land respectively. For different knee angle phases, the differences in %MVC between land and water had significant difference for both RF muscles and BF muscles. (4) Conclusion: This study found a difference of mean percentage MVC of RF and BF muscles between land and water in different phases of squatting. The water medium reduced the two muscles’ activities to a similar extent. The result showed that the aquatic environment allows an individual to perform squatting with less muscle activation which may serve as an alternative knee exercise option for patients who encounter difficulty in land squatting due to lower limb muscle weakness or a high level of knee pain.

Neuromuscular training for children with developmental coordination disorder: A randomized controlled trial.

Background:Adaptive balance control is often compromised in children with developmental coordination disorder (DCD). Neuromuscular training (NMT) is commonly used in clinical settings to improve neuromuscular control and hence balance performance in these children. However, its effectiveness has not been proven scientifically. This randomized controlled study aimed to explore the effectiveness of NMT for improving adaptive balance performance and the associated leg muscle activation times in children with DCD.Methods:Eighty-eight children with DCD were randomly assigned to the NMT or control group (44 per group). The NMT group received two 40-minute NMT sessions/week for 3 months, whereas the control group received no intervention. The outcomes were measured at baseline and 3 and 6 months. The primary outcome was the sway energy score (SES) in both the toes-up and toes-down conditions as derived using the Adaptation Test (ADT). Secondary outcomes included the medial gastrocnemius, medial hamstring, tibialis anterior and rectus femoris muscle activation onset latencies during ADT, measured using surface electromyography and accelerometry. Data were analyzed using a repeated measures analysis of covariance based on the intention-to-treat principle.Results:At 3 months, no significant within-group or between-group differences were noted in the SESs for either group. At 6 months, the toes-down SES decreased by 6.8% compared to the baseline value in exclusively the NMT group (P = .004). No significant time, group or group-by-time interaction effects were observed in any leg muscle activation outcomes.Conclusions:Short-term NMT failed to improve adaptive balance performance and leg muscle activation times in children with DCD. Further studies should explore the clinical applications of longer-term task-specific interventions intended to improve the adaptive balance performance of these children.

Loading in an Upright Tilting Hospital Bed Elicits Minimal Muscle Activation in Healthy Adults

Purpose: Upright tilting hospital beds (THB) are used during early rehabilitation of critically ill patients. Tilting patients in a THB to achieve weight-bearing or loading is purported to mitigate the response of prolonged immobility associated with critical illness. The primary aim of this study is to determine the level of muscle activation during loading in a THB and secondarily to assess whether safety straps influence the level of muscle activation. Methods: Quasi-experimental design in a musculoskeletal laboratory. Nineteen healthy community-dwelling adults with no prior neuromuscular disorder were included. Two groups, 10 subjects with straps-on and 9 subjects with straps-off, were tilted in a THB through 9 intervals of 10° (0°-80°). Muscle activation was recorded using surface electromyography in tibialis anterior, rectus femoris, gluteus medius, and lumbar erector spinae muscles. Raw and electromyography-normalized data were analyzed across angles and conditions. Loading (weight-bearing) was recorded using the THB footplate scale. Results: Electromyographic activity in the tibialis anterior, rectus femoris, gluteus medius, and lumbar erector spinae muscles was minimal as the angle of tilt and loading increased. No statistically significant increases compared with supine rest were observed, except rectus femoris muscle activation at 60° in the groups without straps (P = .023). Similarly, only muscle activation in the rectus femoris was higher in the group without straps from angles 40° to 80° than in the group with straps. Conclusion: Relaxed, gravity-facilitated loading in a THB elicits minimal muscle activation in healthy subjects and, therefore, passive loading's usefulness for enhancing muscle strength is questioned. Removal of safety straps did lead to increased muscle activation in the rectus femoris; this concept should be explored further to understand whether location of the straps, tightness of the straps, and/or the angle of the hip and knee joints during loading could hamper muscle activation.

Assisting Human Balance in Standing With a Robotic Exoskeleton

This letter presents an experimental study on balance recovery control with a lower limb exoskeleton robot. Four participants were subjected to a perturbation during standing, a forward force impulse applied to their pelvis that forced them to step forward with the right leg for balance recovery. Trials with and without exoskeleton assistance to move the stepping legs thigh were conducted to investigate the influence of the exoskeletons control assistance on balancing performance and a potential adaptation. Analysis of the body kinematics and muscle activation demonstrates that robotic assistance: first, was easy to use and did not require learning, nor inhibited the healthy stepping behavior; second, it modified the stepping leg trajectories by increasing hip and knee movement; third, increased reaction speed and decreased the step duration; and finally, generally increased biceps femoris and rectus femoris muscle activity.

Acute Effects of Different Stretching Techniques on Lower Limb Kinematics, Kinetics and Muscle Activities during Vertical Jump

The purpose of this study was to examine the acute effects of different stretching techniques on performance and lower limb kinematics, kinetics and muscle activities during vertical jump in female aerobics athletes. 10 female college aerobics athletes participated in this study. Three-dimensional kinematic and kinetic data, as well as electromyography of rectus femoris, biceps femoris and gastrocnemius medialis were collected using Vicon motion analysis system, Kistler force plate and Wireless surface electromyographic system respectively during the test. No significant differences in jump height had been determined among these 3 warm-up methods. Hip peak flexion and internal rotation angles decreased significantly after BSM and peak adduction angle decreased significantly after SSM and BSM during landing. Knee peak flexion and internal rotation angles increased significantly after SSM and BSM during take-off. Also, BSM showed significantly greater peak flexion compared with SSM. Ankle peak plantarflexion angle increased significantly after BSM. In addition, BSM showed significantly greater improvement in the variation range than SSM except for the ankle int-external rotation. Existence of no significant differences in the peak value of vertical ground reaction force during take-off and landing phase had been determined among these 3 warm-up methods, and muscle activities of rectus femoris, biceps femoris and gastrocnemius medialis were likewise not significantly different. The results of this study suggest that it would be suitable for female aerobics athletes to perform ballistic stretching in warm-up in order to improve flexibility without decreasing the following vertical jumping event and may also reduce the risk of ankle sprain injury.