Quantifying Coordination between Agonist and Antagonist Elbow Muscles during Backhand Crosscourt Shots in Adult Female Squash Players

The purpose of this study was to quantify the coordination between agonist and antagonist elbow muscles during squash backhand crosscourt shots in adult female players. Ten right-handed, international-level, female squash players participated in the study. The electrical muscle activity of two right elbow agonist/antagonist muscles, the biceps brachii and triceps brachii, were recorded using a surface EMG system, and processed using the integrated EMG to calculate a co-activation index (CoI) for the preparation phase, the execution phase, and the follow-through phase. A significant effect of the phases on the CoI was observed. Co-activation was significantly different between the follow-through and the execution phase (45.93 ± 6.00% and 30.14 ± 4.11%, p < 0.001), and also between the preparation and the execution phase (44.74 ± 9.88% and 30.14 ± 4.11%, p < 0.01). No significant difference was found between the preparation and the follow-through phase (p = 0.953). In conclusion, the co-activation of the elbow muscles varies within the squash backhand crosscourt shots. The highest level of co-activation was observed in the preparation phase and the lowest level of co-activation was observed during the execution. The co-activation index could be a useful method for the interpretation of elbow muscle co-activity during a squash backhand crosscourt shot.

β-Hydroxy β-methylbutyrate supplementation to adult Thoroughbred geldings increases type IIA fiber content in the gluteus medius

Consumption of β-hydroxy β-methylbutyrate (HMB) alters muscle composition and metabolism leading to strength and agility improvements in human athletes. To determine if HMB affects athletic performance and muscle function in horses, Thoroughbred geldings were fed a control (CON; n = 5) or HMB (n = 6) supplement for 6 wk prior to completing a standardized exercise test (SET). Gluteus medius (GM) muscle biopsies were obtained before the SET for fiber typing. Heart rate, biceps femoris (BF) and semitendinosus (ST) surface electromyograms (EMG), and fore and hind limbs metacarpophalangeal joint angles were captured at the gallop of the SET. Results demonstrate that HMB supplementation increased (P &lt; 0.05) the percentage of type IIA and IIA/X muscle fibers in the GM with a corresponding decrease (P &lt; 0.05) in type IIX fibers. The percentage of type I fibers was unaffected by diet. Supplementation with HMB did not result in any measurable effects on performance or biomechanical properties by comparison to CON. Supplementation with HMB resulted in an increase (P &lt; 0.05) in ST median frequency at speeds of 10 m/s and greater. Increasing treadmill speed resulted in an increase (P &lt; 0.05) in stride length and the maximal proximal forelimb fetlock angle, and a decrease (P &lt; 0.05) in stance phase time of the gait cycle. Integrated EMG (iEMG) increased (P &lt; 0.05) with increasing treadmill speeds for both the BF and ST with the BF exhibiting greater (P &lt; 0.05) iEMG values than the ST. In summary, HMB increased the percentage of type IIA GM fibers, which did not translate into improved performance.

Antagonist Muscle Co-Activation during Kettlebell Single Arm Swing Exercise

The purpose of this study was to determine the muscle activation and co-activation of selected muscles during the kettlebell single arm swing exercise. To the best of our knowledge, this is the first study investigating the muscle co-activation of a kettlebell single arm swing exercise. Nine volunteers participated in the present study (age: 22.6 ± 3.8 years; body mass: 80.4 ± 9.2 kg; height: 175.6 ± 7.5 cm). The electrical muscle activity of eight right agonist/antagonist muscles (AD/PD, ESL/RA, ESI/EO, and GM/RF) were recorded using a surface EMG system (Myon m320RX; Myon, Switzerland) and processed using the integrated EMG to calculate a co-activation index (CoI) for the ascending and descending phases. A significant effect of the ascending and descending phases on the muscles’ CoI was observed. Post hoc analyses showed that the co-activation was significantly higher in the descending phase compared to that in the ascending phase of AD/PD CoI (34.25 ± 18.03% and 24.75 ± 13.03%, p < 0.001), ESL/RA CoI (34.97 ± 17.86% and 24.19 ± 10.32%, p < 0.001), ESI/EO CoI (41.14 ± 10.72% and 30.87 ± 11.26%, p < 0.001), and GM/RF CoI (27.49 ± 12.97% and 34.98 ± 14.97%, p < 0.001). In conclusion, the co-activation of the shoulder muscles varies within the kettlebell single arm swing. The highest level of co-activation was observed in the descending phase of AD/PD and GM/RF CoI, and the lowest level of co-activation was observed during the descending phase, ESL/RA and ESI/EO CoI. In addition, the highest level of co-activation was observed in the ascending phase of ESL/RA and ESI/EO CoI, and the lowest level of co-activation was observed during the ascending phase, AD/PD and GM/RF CoI. The co-activation index could be a useful method for the interpretation of the shoulder and core muscles’ co-activity during a kettlebell single arm swing.

Relationship Between Speed of Performing Leg Extension With 30 RM Load and the Selected EMG Variables of Selected Quadricep Muscles

The aim of the study was to assess the effects of speed of leg extension exercise with 30 RM load on the EMG activity of Vastus Medialis (VM) and Vastus Lateralis (VL). Seventeen healthy male subjects performed 30 repetition of leg extension exercise with 30 RM load in minimum time possible and EMG activity from VM and VL of right lower extremity was recorded simultaneously. Two new criteria, namely gross load speed of movement (GLSM) and relative load speed of movement (RLSM) were developed as the variables of speed of exercise. Selected variables of EMG activity were median frequency (MDF), mean frequency (MNF), root mean square (RMS), and integrated EMG (IEMG). Product moment and rank order correlation were calculated between the selected variables of EMG activity and selected variables of speed of exercise. The selected EMG variables, namely MDF and MNF, reported a negative significant relationship (p<0.05) with selected variables of speed of exercise whereas a selected EMG variables, namely RMS reported a positive significant relationship (p<0.05) with selected with the selected variables of speed of exercise.

Pengenalan Pola Sinyal Electromyography (EMG) pada Gerakan Jari Tangan Kanan

ABSTRAKSinyal EMG merupakan salah satu sinyal yang dapat digunakan untuk memberikan perintah pada kursi roda listrik. Sinyal EMG yang digunakan diambil dari sinyal otot fleksor dan ekstensor yang berada di tangan kanan. Sinyal tersebut diambil menggunakan sensor Myo Armband. Klasifikasi sinyal EMG diambil dari pergerakan jari yang mewakili perintah gerak yaitu jari kelingking untuk bergerak maju, jari manis untuk berhenti, jari tengah untuk belok kanan dan jari telunjuk untuk belok kiri. Setiap sinyal EMG diekstraksi fitur untuk menentukan karakteristik sinyal sehingga fitur yang diperoleh adalah Average Absolute Value, Root Mean Square, Simple Integral Square, EMG Simple Variant and Integrated EMG. Kemudian fitur tersebut digunakan sebagai input dari metode klasifikasi Artificial Neural Network Backpropagation. Jumlah data latih yang digunakan adalah 800 data sedangkan data uji yang digunakan adalah 200 data. Tingkat keberhasilan proses klasifikasi ini sebesar 93%.Kata kunci: electromyogram, artificial neural network, klasifikasi sinyal, tangan kanan, Myo Armband. ABSTRACTEMG signal is one of the signals that can be used to give orders to electric wheelchairs. The EMG signal used is taken from the flexor and extensor muscle signals in the right hand. The signal is taken using the Myo Armband sensor. The EMG signal classification is taken from the movement of the finger which represents the command of motion ie the little finger to move forward, ring finger to stop, middle finger to turn right and index finger to turn left. Each EMG signal is extracted features to determine the signal characteristics so that the features obtained are Average Absolute Value, Root Mean Square, Simple Integral Square, EMG Simple Variant and Integrated EMG. Then the feature is used as input from the Backpropagation classification method. The amount of training data used is 800 data while the test data used is 200 data. The success rate of this classification process is 93%.Keywords: electromyogram, artificial neural network, signal classification, right hand, Myo Armband.

EMG-driven exergaming in wheelchairs on a mobile platform: Bench and pilot testing of the WOW-Mobile fitness system (Preprint)

BACKGROUND Individuals who use wheelchairs face many barriers to regular exercise. Implementing exercises in the form of video games, otherwise known as exergaming, has gained recent attention as a way to increase physical activity and combat health issues resulting from sedentary lifestyles. However, these exergaming apps have not been developed for exercises that can be performed in wheelchairs, and they tend to rely on whole body movements. OBJECTIVE Our objectives were to: 1) develop a mobile phone application that implements EMG-driven exergaming; 2) test the feasibility of using this app to enable people in wheelchairs to perform exergames, used in circuit resistance training, independently and flexibly in their own home; and 3) assess perceived usefulness and useability of this mHealth system. METHODS We have developed a mobile phone application (WOW-Mobile) which senses upper limb muscle activity (EMG) from wireless body-worn sensors to drive 3 different video games which implement upper limb exercises that were designed for people in wheelchairs. The app was developed in Java on an Android platform with the EMG acquired by Flexdots (Dynofit, Inc.), Bluetooth-enabled sensors. EMG drove the game engines and was recorded during all exergaming sessions on our cloud server, in order to enable long-term monitoring and feedback as well as multiplayer gaming. Benchtesting of data transmission and power consumption were tested with Android Studio’s Profiler. Pilot testing was conducted on four individuals with spinal cord injury. Each had a WOW-Mobile system in their home for 8 weeks. By analyzing the session data acquired in real-time and stored on our cloud server, we measured minutes the app was used; minutes exergames were played; and integrated EMG as a measure of energy expended. We also conducted a perceived usefulness and useability questionnaire. RESULTS Benchtest results reveal that the app meets performance specifications to enable real-time gaming, cloud storage of data, and live cloud server transmission for multiplayer gaming. The EMG sampling rate of 64 samples/s, in combination with zero-loss data communication with the cloud server within a 10m range, provided seamless control over the app exergames and allowed for offline data analysis. The WOW-mobile system was pilot tested by four individuals with spinal cord injury. Each participant successfully utilized the WOW-mobile system at home for 8 weeks. They utilized the app for an average of 146 (89-267) minutes per week with the system, actively exergaming for an average of 53% of that time (39-59%). Energy expenditure, as measured by integrated EMG (iEMG) was found to be directly proportional to time spent on the app (Pearson correlation coefficient, r = 0.57-0.86, depending on the game). Two out of the four participants did not exercise regularly before the study; these two participants increased from reportedly exercising close to 0 minutes per week to exergaming 58 and 158 minutes on average, respectively, using the WOW-Mobile fitness system. The perceived usefulness of WOW-mobile in motivating participants to exercise averaged 4.5 on a 5-point Likert-scale, and averaged 5 for the 3 participants with thoracic-level injuries. The average overall ease of use score was 4.25 out of 5. CONCLUSIONS Mobile app exergames driven by EMG has promising potential for encouraging and facilitating fitness for individuals in wheelchairs who have maintained arm and hand mobility. CLINICALTRIAL

Forced Use of the Paretic Leg Induced by a Constraint Force Applied to the Nonparetic Leg in Individuals Poststroke During Walking

Background. Individuals with stroke usually show reduced muscle activities of the paretic leg and asymmetrical gait pattern during walking. Objective. To determine whether applying a resistance force to the nonparetic leg would enhance the muscle activities of the paretic leg and improve the symmetry of spatiotemporal gait parameters in individuals with poststroke hemiparesis. Methods. Fifteen individuals with chronic poststroke hemiparesis participated in this study. A controlled resistance force was applied to the nonparetic leg using a customized cable-driven robotic system while subjects walked on a treadmill. Subjects completed 2 test sections with the resistance force applied at different phases of gait (ie, early and late swing phases) and different magnitudes (10%, 20%, and 30% of maximum voluntary contraction [MVC] of nonparetic leg hip flexors). Electromyographic (EMG) activity of the muscles of the paretic leg and spatiotemporal gait parameters were collected. Results. Significant increases in integrated EMG of medial gastrocnemius, medial hamstrings, vastus medialis, and tibialis anterior of the paretic leg were observed when the resistance was applied during the early swing phase of the nonparetic leg, compared with baseline. Additionally, resistance with 30% of MVC induced the greatest level of muscle activity than that with 10% or 20% of MVC. The symmetry index of gait parameters also improved with resistance applied during the early swing phase. Conclusion. Applying a controlled resistance force to the nonparetic leg during early swing phase may induce forced use on the paretic leg and improve the spatiotemporal symmetry of gait in individuals with poststroke hemiparesis.

The effect of different decline angles on the biomechanics of double limb squats and the implications to clinical and training practice

Bilateral decline squatting has been well documented as a rehabilitation exercise, however, little information exists on the optimum angle of decline. The aim of this study was to determine the ankle and knee angle, moments, the patellofemoral joint load, patellar tendon load and associated muscle activity while performing a double limb squat at different decline angles and the implications to rehabilitation. Eighteen healthy subjects performed double limb squats at 6 angles of declination: 0, 5, 10, 15, 20 and 25 degrees. The range of motion of the knee and ankle joints, external moments, the patellofemoral/patellar tendon load and integrated EMG of gastrocnemius, tibialis anterior, rectus femoris and biceps femoris were evaluated. As the decline angle increased up to 20 degrees, the range of motion possible at the ankle and knee increased. The joint moments showed a decrease at the ankle up to 15 degrees and an increase at the knee up to 25 degrees, indicating a progressive reduction in loading around the ankle with a corresponding increase of the load in the patellar tendon and patellofemoral joint. These trends were supported by a decrease in tibialis anterior activity and an increase in the rectus femoris activity up to 15 degrees declination. However, gastrocnemius and biceps femoris activity increased as the decline angle increased above 15 degrees. The action of gastrocnemius and biceps femoris stabilises the knee against an anterior displacement of the femur on the tibia. These findings would suggest that there is little benefit in using a decline angle greater than 15-20 degrees unless the purpose is to offer an additional stability challenge to the knee joint.

No reserve in isokinetic cycling power at intolerance during ramp incremental exercise in endurance-trained men

During whole body exercise in health, maximal oxygen uptake (V̇o2max) is typically attained at or immediately before the limit of tolerance (LoT). At the V̇o2max and LoT of incremental exercise, a fundamental, but unresolved, question is whether maximal evocable power can be increased above the task requirement, i.e., whether there is a “power reserve” at the LoT. Using an instantaneous switch from cadence-independent (hyperbolic) to isokinetic cycle ergometry, we determined maximal evocable power at the limit of ramp-incremental exercise. We hypothesized that in endurance-trained men at LoT, maximal (4 s) isokinetic power would not differ from the power required by the task. Baseline isokinetic power at 80 rpm (Piso; measured at the pedals) and summed integrated EMG from five leg muscles (ΣiEMG) were measured in 12 endurance-trained men (V̇o2max = 4.2 ± 1.0 l/min). Participants then completed a ramp incremental exercise test (20-25 W/min), with instantaneous measurement of Piso and ΣiEMG at the LoT. Piso decreased from 788 ± 103 W at baseline to 391 ± 72 W at LoT, which was not different from the required ramp-incremental flywheel power (352 ± 58 W; P > 0.05). At LoT, the relative reduction in Piso was greater than the relative reduction in the isokinetic ΣiEMG (50 ± 9 vs. 63 ± 10% of baseline; P < 0.05). During maximal ramp incremental exercise in endurance-trained men, maximum voluntary power is not different from the power required by the task and is consequent to both central and peripheral limitations in evocable power. The absence of a power reserve suggests both the perceptual and physiological limits of maximum voluntary power production are not widely dissociated at LoT in this population.