Comparison Of Muscle Activity Research Articles

The Influence of Ankle Inversion Angle on Trunk Muscle Activity during Squat Exercise

Objectives: To see the trunk muscle activation during squat exercise in accordance with the inversion angle. Methods/Statistical Analysis: After previous research, we recruited healthy adult of 12 males and 12 females (The mean age 20.7±1.66, a total of 24 adults) who agreed to participate in this study. This study measured External Oblique abdominis (EO), Transverse Abdominis (TrA), Eractor Spinae (ES), Multifidus (MF) muscle activation during the squat exercise according to four inversion angles (0°, 10°, 15°, 20°). In order to calculate the subject characteristics, the mean value and the standard deviation of all the variables of the subjects, descriptive statistics were employed. One-way repeated ANOVA was used to compare muscle activities of EO, TrA, ES and MF depending on the four inversion angles. Bonferroni’s correction was used as post-hoc comparison and statistical significance level was set at α = .05. Findings: In EO, there was significant difference on four inversion angles (p<.001). Post-hoc test result showed significant difference (p<.001) on four inversion angles between 0°-10°, 0°-15°, 0°-20°, 10°-15° and 15°-20°. In TrA, there was significant difference on four inversion angles (p<.001) as well. Post-hoc test result indicated significant difference(p<.001) on four inversion angles between 0°-15°, 0°-20°, 10°-15° and 10°-20°. In ES and MF, they did not show significant difference in every inversion angle. Also, post-hoc test result did not reveal significant difference between every intervention. This study has been conducted to see the change of trunk muscle activation in accordance with inversion angle during squat exercise. In order to investigate the changes, we compared global and local muscles of trunk by applying the four inversion angles (0°, 10°, 15°, 20°). Since lower extremity or trunk global muscle activation has been studied a lot already, we put difference by measuring local muscle additionally during squat exercise. There were lots of studies about lower extremity and trunk muscle activation using squat exercise. In this research, however, the back muscle did not show a significant difference during squat exercise. These results mean that back muscle is not that significant in the squat exercise with altering inversion angles. Also, we experimented with the traditional squat exercise and added an intervention of changing the inversion angle. However, we presume that if we provide a variety of intervention on the trunk position, or require a trunk flexion or extension, there would be another result on the back muscle. Thus, more research, related with trunk position as well as ankle position, needs to be carried out continuously. Application/Improvements: In conclusion, squat exercise with inversion angle is an effective exercise method in that it can cause the activation of both global and local muscle of the abdomen. Also, the inversion angle of 15° is the most ideal one to activate the trunk muscle with effectiveness without ankle inversion injury. Therefore, the squat exercise with the varying inversion angles will be helpful to maintain trunk stability for the position through time effectiveness.

Comparison of muscle activity between subjects with or without lip competence: Electromyographic activity of lips, supra- and infrahyoid muscles

Aim: This study compares the electromyographic (EMG) activity of the muscles from the lips and hyoid bone in subjects with or without lip competence.Methodology: Two groups of 20 subjects each, with or without lip competence were studied. EMG activity of the superior orbicularis oris (SOO), inferior orbicularis oris (IOO), suprahyoid (SH) and infrahyoid (IH) muscles was recorded with the subject seated in the upright position during the following tasks: (1) at rest; (2) speaking; (3) swallowing; (4) forced deep breathing; (5) maximal voluntary clenching; and (6) chewing.Results: EMG activity was significantly higher in subjects without competent lips than with competent lips in the SOO and IOO muscles during tasks 3 and 4, SOO during task 2 and IOO during task 6. EMG activity was similar in the SOO and IOO muscles during tasks 1 and 5, SOO during task 6 and IOO during task 2. Activity of the SH and IH muscles was similar in both groups for all tasks.Conclusions: Higher activity in subjects without competent lips implies a higher muscular effort due to the requirement of lip sealing during functional activities. Hyoid muscular activity was not modified by the presence or absence of lip competence.

Difference in muscle activation patterns during high-speed versus standard-speed yoga: A randomized sequence crossover study

ObjectivesTo compare the difference in muscle activation between high-speed yoga and standard-speed yoga and to compare muscle activation of the transitions between poses and the held phases of a yoga pose. DesignRandomized sequence crossover trial SettingA laboratory of neuromuscular research and active aging Interventions: Eight minutes of continuous Sun Salutation B was performed, at a high speed versus a standard-speed, separately. Electromyography was used to quantify normalized muscle activation patterns of eight upper and lower body muscles (pectoralis major, medial deltoids, lateral head of the triceps, middle fibers of the trapezius, vastus medialis, medial gastrocnemius, thoracic extensor spinae, and external obliques) during the high-speed and standard-speed yoga protocols. Main Outcome Measures: Difference in normalized muscle activation between high-speed yoga and standard-speed yoga. ResultsNormalized muscle activity signals were significantly higher in all eight muscles during the transition phases of poses compared to the held phases (p<0.01). There was no significant interaction between speed×phase; however, greater normalized muscle activity was seen for highspeed yoga across the entire session. ConclusionsOur results show that transitions from one held phase of a pose to another produces higher normalized muscle activity than the held phases of the poses and that overall activity is greater during highspeed yoga than standard-speed yoga. Therefore, the transition speed and associated number of poses should be considered when targeting specific improvements in performance.

어깨관절의 이마면과 어깨면에서 벌림각도에 따른 중간 등세모근과 아래 등세모근의 근 활성도 비교

Purpose: The purpose of this study was to compare muscle activities in the frontal plane and scapular plane of the middle fiber and lower fiber of the trapezius muscle at different shoulder abduction angles. Methods: Twenty male and female students in their 20s participated in this study. Each subject maintained shoulder abduction at <TEX>$75^{\circ}$</TEX>, <TEX>$90^{\circ}$</TEX>, <TEX>$125^{\circ}$</TEX>, and <TEX>$160^{\circ}$</TEX> in a standing position and repeated motions three times each in the frontal plane and the scapular plane. While maintaining the motions for 10 seconds in each posture, surface electromyography (EMG) was used to measure muscle activity of the middle fiber and lower fiber of the trapezius muscle. The collected EMG data were normalized using maximal voluntary isometric contraction (MVIC). Differences in muscle activity of the middle fiber and lower fiber of the trapezius muscles according to the angles at each plane were statistically processed using repeated measured analysis of variance, and an independent t-test was used to examine the differences between the two planes at each angle. Results: Muscle activity of the middle and lower trapezius during shoulder abduction in the frontal plane and scapular plane significantly increased as the angles increased (p<.05). However, muscle activity of the middle trapezius was significantly lower in the scapular plane than in the frontal plane for all shoulder abduction angles (p<.05). Conclusion: The results of this study suggest that during shoulder abduction, angles should be different according to the goals, and for training during an acute phase or early phase for functional recovery, it is more efficient to perform the training in the scapular plane than in the frontal plane.

Effect of Forefoot Strike on Lower Extremity Muscle Activity and Knee Joint Angle During Cutting in Female Team Handball Players.

BackgroundThe purpose of this study is to examine the effects of different strike forms, during cutting, on knee joint angle and lower limb muscle activity.MethodsSurface electromyography was used to measure muscle activity in individuals performing cutting manoeuvres involving either rearfoot strikes (RFS) or forefoot strikes (FFS). Three-dimensional motion analysis was used to calculate changes in knee angles, during cutting, and to determine the relationship between muscle activity and knee joint angle. Force plates were synchronized with electromyography measurements to compare muscle activity immediately before and after foot strike.ResultsThe valgus angle tends to be smaller during FFS cutting than during RFS cutting. Just prior to ground contact, biceps femoris, semitendinosus, and lateral head of the gastrocnemius muscle activities were significantly greater during FFS cutting than during RFS cutting; tibialis anterior muscle activity was greater during RFS cutting. Immediately after ground contact, biceps femoris and lateral head of the gastrocnemius muscle activities were significantly greater during FFS cutting than during RFS cutting; tibialis anterior muscle activity was significantly lower during FFS cutting.ConclusionsThe results of the present study suggest that the hamstrings demonstrate greater activity, immediately after foot strike, during FFS cutting than during RFS cutting. Thus, FFS cutting may involve a lower risk of anterior cruciate ligament injury than does RFS cutting.

Muscle Activation During Landing Before and After Fatigue in Individuals With or Without Chronic Ankle Instability.

Ankle instability is a common condition in physically active individuals. It often occurs during a jump landing or lateral motion, particularly when participants are fatigued. To compare muscle activation during a lateral hop prefatigue and postfatigue in individuals with or without chronic ankle instability (CAI). Cross-sectional study. Sports medicine research laboratory. A total of 32 physically active participants volunteered for the study. Sixteen participants with CAI (8 men, 8 women; age = 20.50 ± 2.00 years, height = 172.25 ± 10.87 cm, mass = 69.13 ± 13.31 kg) were matched with 16 control participants without CAI (8 men, 8 women; age = 22.00 ± 3.30 years, height = 170.50 ± 9.94 cm, mass = 69.63 ± 14.82 kg) by age, height, mass, sex, and affected side. Electromyography of the tibialis anterior, peroneus longus, gluteus medius, and gluteus maximus was measured before and after a functional fatigue protocol. Activation of 4 lower extremity muscles was measured 200 milliseconds before and after landing from a lateral hop. We observed no interactions. The group main effects for the peroneus longus demonstrated higher muscle activation in the CAI group (52.89% ± 11.36%) than in the control group (41.12% ± 11.36%) just before landing the lateral hop (F1,30 = 8.58, P = .01), with a strong effect size (d = 1.01). The gluteus maximus also demonstrated higher muscle activation in the CAI group (45.55% ± 12.08%) than in the control group (36.81% ± 12.08%) just before landing the lateral hop (F1,30 = 4.19, P = .049), with a moderate effect size (d = 0.71). We observed a main effect for fatigue for the tibialis anterior, with postfatigue activation higher than prefatigue activation (F1,30 = 7.45, P = .01). No differences were present between groups for the gluteus medius. Our results support the presence of a centralized feed-forward neuromuscular alteration in patients with CAI, not only in the ankle-joint muscles but also in the proximal hip muscles. These results may have implications for rehabilitation programs in these patients.

Comparison Of Muscle Activation Using A Nitrogen Piston-based Resistance Device With Free Weights

Resistance training is especially important for populations at risk of sarcopenia and osteopenia such as older adults or astronauts working in microgravity. A limitation of common forms of resistance training is that they are gravity-based and lack efficacy in microgravity. Therefore, to maintain muscle and bone mass in microgravity, an alternative solution must be sought. One alternative is the use of a gas-filled piston-based resistance training system. PURPOSE: The goal of the current study is to assess the effectiveness of a Nitrogen-filled piston-based resistance training system (NitroForce) compared to isotonic resistance training. METHODS: Thirty recreational athletes performed five repetitions of squat and toe-raise exercises, in two experimental conditions: NitroForce and Isotonic. The NitroForce condition was characterized by resistance of approximately 70% of the participant’s one repetition maximum (1RM) while resistance was supplied using the NitroForce system. Isotonic condition was characterized by participants performing each exercise with resistance equal to 70% of 1RM provided by free weights. Surface electromyography (sEMG, 1928 Hz, Delsys) was recorded from the vastus medialis (VM), vastus lateralis (VL), and the lateral (LG) and medial heads of the gastrocnemius (MG). Mean sEMG amplitude was quantified using the RMS (20 ms smoothing window) and normalized to MVC for each muscle in each condition. Paired samples t-tests were used to compare mean sEMG values. Significance was set at p < 0.05. RESULTS: In the squat exercise, VM activation was significantly greater in the NitroForce compared to isotonic condition (p = 0.039), but no differences were observed in the VL (p = 0.367). No significant differences were observed between the NitroForce and isotonic conditions for the LG (p = 0.400) or MG (p = 0.442) in the toe-raise exercise. CONCLUSIONS: These data demonstrate that muscle activation intensity as measured by sEMG is not significantly different in the NitroForce compared to isotonic conditions. Therefore, the NitroForce provides a similar level of resistance and overload to standard isotonic resistance training loads. However, due to the non-gravity-based nature of the NitroForce, it may provide a better resistance training solution in microgravity environments.

Muscle Activity of the Lower Limb During Single-Legged Hopping

Running can be described as a series of bilateral single-legged jumps and landings; however, single-legged locomotion (SLL) is anecdotally more difficult than bi-lateral locomotion (BLL). Muscle activity may play a role in this increased difficulty; it is not known how active different muscles are during SLL vs. BLL, or whether providing body weight support during SLL would elicit more similar activity levels compared with BLL. PURPOSE: To compare muscle activity during single-legged locomotion at different levels of effective body weight (BW). METHODS: Subjects (n=12; 25.00±7.74 years, 1.67±0.09 m, 63.28±11.42 kg) performed running at 100% BW in addition to single-legged hopping at 80%, 70%, 60%, 50%, and 40% BW. Muscle activity of the Rectus Femoris, Semitendinosus, Tibialis Anterior, and Medial Gastrocnemius was measured. Average muscle activity was calculated over 15 seconds (zero offset removed, full-wave rectified). Activity from each muscle was analyzed using a one-way repeated measures analysis of variance (α=0.05). RESULTS: Muscle activity of the Semitendinosus and Tibialis Anterior was not affected by varying levels of effective BW (p>0.05). Muscle activity of the Rectus Femoris and Medial Gastrocnemius was influenced by varying levels of effective BW (p<0.05). For the Rectus Femoris, hopping at 80% BW and 70% BW elicited higher average muscle activity than running (92.4%; 70.8% increase, respectively), hopping at 60% BW (24.2%; 10.2%), hopping at 50% BW (39.9%; 24.2%), and hopping at 40% BW (62.5%; 44.3%). For the Gastrocnemius, hopping at 80% BW and 70% BW elicited higher average muscle activity than running (70.3%; 50.8% increase, respectively) and hopping at 40% BW (57.2%; 39.2%). CONCLUSIONS: It appears that increased knee flexor muscle activity is the primary mechanism that is responsible for why SLL is more difficult than BLL. Muscle activity between BLL and SLL at 50% BW were shown to be similar, which suggests the occurrence of a bilateral deficit. However, it is still unclear whether these increases are the result of the existence of a bilateral deficit, or a result of a change in the movement pattern.

Proprioceptive acuity predicts muscle co-contraction of the tibialis anterior and gastrocnemius medialis in older adults’ dynamic postural control

Older adults use a different muscle strategy to cope with postural instability, in which they ‘co-contract’ the muscles around the ankle joint. It has been suggested that this is a compensatory response to age-related proprioceptive decline however this view has never been assessed directly. The current study investigated the association between proprioceptive acuity and muscle co-contraction in older adults. We compared muscle activity, by recording surface electromyography (EMG) from the bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) muscles, in young (aged 18–34) and older adults (aged 65–82) during postural assessment on a fixed and sway-referenced surface at age-equivalent levels of sway. We performed correlations between muscle activity and proprioceptive acuity, which was assessed using an active contralateral matching task. Despite successfully inducing similar levels of sway in the two age groups, older adults still showed higher muscle co-contraction. A stepwise regression analysis showed that proprioceptive acuity measured using variable error was the best predictor of muscle co-contraction in older adults. However, despite suggestions from previous research, proprioceptive error and muscle co-contraction were negatively correlated in older adults, suggesting that better proprioceptive acuity predicts more co-contraction. Overall, these results suggest that although muscle co-contraction may be an age-specific strategy used by older adults, it is not to compensate for age-related proprioceptive deficits.

Gender Comparison of Muscle Activity and Strength in Gluteus Medius and Quadriceps and Knee Valgus Angle During Controlled Single-Leg Squat in Individuals With Patellar Femoral Pain Syndrome

Background: Investigation in gender differences of kinetics and kinematics for individuals with patellar femoral pain syndrome (PFPS) was not sufficiently performed. Objects: The purpose of this study is that whether there is a difference depending on gender from muscle activity and strength and knee valgus angle during controlled single-leg squat which is widely used as clinical movement test for the patient with PFPS. Methods: 20 young adults (10 men, years; 10 women, years) with PFPS were voluntarily recruited in this study. Muscle activity and strength and knee valgus angle were collected during single-leg squat. Independent t-test and Mann-Whitney test were used to compare the differences between groups of male and female. Results: Rectus femoris (t=-2.204, p=.041) and vastus medialis oblique (t=-2.151, p=.045) muscle activity of women were significantly higher than male group. Normalized muscle strength of hip and knee muscles showed a significant difference between men and women (p

An Acute Bout of Barefoot Running Alters Lower-limb Muscle Activation for Minimalist Shoe Users.

Despite the abundance of barefoot running-related research, there have been no electromyography studies evaluating the effects of this mode of exercise on habitual users of minimalist footwear. The present study investigated differences in muscle activation during acute bouts of barefoot and shod running, in minimalist shoe users. 8 male participants ran on a motorized treadmill for 10 min under both conditions, at 70% maximal aerobic speed. Electromyographic data were sampled from the biceps femoris, gluteus maximus, gastrocnemius medialis, tibialis anterior, and vastus lateralis during both swing and stance. Root-mean-square analysis of electromyographic data was conducted to compare muscle activation between conditions. During stance, barefoot running resulted in greater muscle activity in gastrocnemius medialis and gluteus maximus, and lower muscle activity in tibialis anterior. During swing, barefoot running resulted in increased muscle activity in vastus lateralis and gastrocnemius medialus. These results indicate that, for minimalist shoe users, an acute bout of barefoot running results in significantly different lower-limb muscle activity. Increased activation in the above muscles presents a possible mechanism for injury, which should be considered during exercise prescription.

Thermal sensitivity of motor control of muscle-powered versus elastically powered tongue projection in salamanders

Elastic-recoil mechanisms can improve organismal performance and circumvent the thermal limitations of muscle contraction, yet they require the appropriate motor control to operate. We compare muscle activity during tongue projection in salamanders with elastically powered, ballistic projection with activity of those with muscle-powered, non-ballistic projection across a range of temperatures to understand how motor control is integrated with elastically powered movements, and how this integration contributes to reduced thermal sensitivity. Species with ballistic tongue projection activated and deactivated their projector muscles significantly earlier than non-ballistic species, in a pattern consistent with a mechanism in which the muscle strains elastic tissue that subsequently recoils to power projection. Tongue projection was more thermally robust in ballistic species, but in both ballistic and non-ballistic species the projector muscles were activated earlier and for longer as temperature decreased. The retractor muscles showed a pattern similar to that of the projector muscles, but declined in a similar manner in the two groups. Muscle activity intensity also decreased at low temperatures in both groups, revealing that compensatory muscle activation does not account for the improved thermal robustness in ballistic species. Thus, relatively minor shifts in motor patterns accompanying morphological changes such as increased elastic tissue are sufficient to improve performance and decrease its thermal sensitivity without specialization of muscle contractile physiology.

Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise.

The purpose of this study was to compare muscle activation of the lower limb muscles when performing a maximal isometric back squat exercise over three different positions. Fifteen young, healthy, resistance-trained men performed an isometric back squat at three knee joint angles (20°, 90°, and 140°) in a randomized, counterbalanced fashion. Surface electromyography was used to measure muscle activation of the vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF), biceps femoris (BF), semitendinosus (ST), and gluteus maximus (GM). In general, muscle activity was the highest at 90° for the three quadriceps muscles, yet differences in muscle activation between knee angles were muscle specific. Activity of the GM was significantly greater at 20° and 90° compared to 140°. The BF and ST displayed similar activation at all joint angles. In conclusion, knee position alters muscles activation of the quadriceps and gluteus maximus muscles. An isometric back squat at 90° generates the highest overall muscle activation, yet an isometric back squat at 140° generates the lowest overall muscle activation of the VL and GM only.

The effect of bilateral trainings on upper extremities muscle activation on level of motor function in stroke patients.

[Purpose] This study was conducted in order to compare muscle activation level on the affected and unaffected limb according to the recovery level of upper limb between bilateral activity with hands clasped and bilateral activity with pilates ring. [Subjects and Methods] Twenty inpatient who have had a stroke were recruited. Subjects were divided into two groups by the Fugl-Meyer Assessment of Motor Function score of moderately recovered group and well recovered group. The muscles activation of upper extremity and Co-Contraction Ratio (CCR) were analyzed. [Results] In the muscles activation of the well group, trapezius, anterior deltoid, and triceps muscles of affected side and biceps muscles of both sides were significantly higher when activity with pilates ring than activity with hands clasped. CCR of both side in the well group was significantly decreased during activity with pilates ring and in the moderate group, CCR of affected side was significantly decreased during activity with pilates ring. [Conclusion] Bilateral activity with a pilates ring is more effective than activity with hands clasped for the facilitation of muscle activation and coordination in stroke patients.

Muscle activity during daily life in the older people.

Daily muscle activity is important for functional independence. This study examined muscle activity patterns during normal daily life and simulated daily tasks and compared muscle activity and energy consumption during active and passive transport tasks in older adults. Nine volunteers (70±6years) were measured for quadriceps and hamstring muscle activity (EMG) during normal daily life, treadmill walking, and during passive and active transport tasks. EMG was normalized to that recorded during maximal voluntary contraction (MVC). Oxygen uptake (VO2) was measured during treadmill and transport tasks. During daily life the mean EMG amplitude was 5.9±2.4% of EMGMVC, activity time was 187±43min and the longest continuous inactivity periods were 20.9±10.0min. During stair ascend the peak EMG activity was 120% of EMGMVC and the peak VO2 values were only about 70% of VO2max. One kilometer walk consumed 3.5 times more energy than passive transport by bus, and using stairs consumed 11.7 times more energy than using an elevator. In daily life, older adults use only a small fraction of muscle's maximal capacity and have long continuous inactivity periods. Negotiating stairs produce significant load to neuromuscular, but not to cardiovascular system, thus providing an effective strength training stimulus.

Modifying the shoulder joint position during shrugging and retraction exercises alters the activation of the medial scapular muscles

BackgroundIn patients with shoulder or neck pain, often an imbalance of the activation in the scapular upward and downward rotators is present which can cause abnormalities in coordinated scapular rotation. Shrug exercises are often recommended to activate muscles that produce upward rotation, but little information is available on the activity of the downward rotators during shrugging exercises. The position used for the shrug exercise may affect the relative participation of the medial scapular rotators. ObjectivesTo compare muscle activity, using both surface and fine-wire electrodes, of the medial scapular muscles during different shoulder joint positions while performing shrug and retraction exercises. DesignControlled laboratory study. MethodTwenty-six subjects performed 3 different exercises: shrug with the arms at the side while holding a weight (“Shrug”), shrug with arms overhead and retraction with arms overhead. EMG data with surface and fine wire electrodes was collected from the Upper Trapezius (UT), Levator Scapulae (LS), Middle Trapezius (MT), Rhomboid Major (RM) and Lower Trapezius (LT). ResultsThe results showed that activity levels of the main medial scapular muscles depend upon the specific shoulder joint position when performing shrug and retraction exercises. High UT activity was found across all exercises, with no significant differences in UT activity between the exercises. The LS and RM activity was significantly lower during “ShrugOverhead” and the RM, MT and LT activity was significantly higher during “RetractionOverhead”. ConclusionsThis study has identified that all three exercises elicited similar UT activity. LS and RM activity is decreased with the “ShrugOverhead” exercise. The “RetractionOverhead” was the most effective exercise in activating the medial scapular muscles.

A comparison of muscle activity in using touchscreen smartphone among young people with and without chronic neck–shoulder pain

This study aimed to examine differences in muscle activity between young people with and without neck–shoulder pain (n = 20 in each group), when they performed texting on a smartphone. Texting was compared between using both hands (‘bilateral texting’) and with only one hand (‘unilateral texting’). Texting tasks were also compared with computer typing. Surface electromyography from three proximal postural muscles and four distal hand/thumb muscles on the right side was recorded. Compared with healthy controls, young people with neck–shoulder pain showed altered motor control consisting of higher muscle activity in the cervical erector spinae and upper trapezius when performing texting and typing tasks. Generally, unilateral texting was associated with higher muscle loading compared with bilateral texting especially in the forearm muscles. Compared with computer typing, smartphone texting was associated with higher activity in neck extensor and thumb muscles but lower activity in upper and lower trapezius as well as wrist extensors.

Identifying yoga-based knee strengthening exercises using the knee adduction moment

BackgroundThis study aimed to compare muscle activations, co-contraction indices, and the knee adduction moment between static standing yoga postures to identify appropriate exercises for knee osteoarthritis. MethodsHealthy young women (24.4 (5.4) years, 23.1 (3.7) kg/m2) participated. Primary outcome variables were electromyographic activations of the vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and semitendinosus; co-contraction between the biceps femoris and rectus femoris, and vastus lateralis and vastus medialis; and knee adduction moments of both legs during six static, standing yoga postures (two squatting postures, two lunging postures, a hamstring stretch, and a single-leg balance posture). A two-factor repeated measures analysis of variance was used to identify differences in muscle amplitudes, co-contractions, and knee adduction moment between postures and legs. FindingsQuadriceps activations were highest during squat and lunge postures (p≤0.001). Hamstring activations were highest during the hamstring stretch (p≤0.003). Squat and lunge postures produced higher co-contraction indices than other postures (p≤0.011). The wide legged squat (Goddess) and lunge with trunk upright (Warrior) produced the lowest knee adduction moments (p≤0.006), while the single-leg balance posture elicited a higher knee adduction moment than all other postures (p<0.05). InterpretationSquatting and lunging postures could improve leg strength while potentially minimizing exposure to high knee adduction moments. Future work should evaluate whether these exercises are useful in people with knee osteoarthritis.

Hamstring Tendon Grafts Result in Altered Muscle Activity 1-Year After ACL Reconstruction

The semitendinosus/gracilis graft (ST/G) is one of the most common grafts used for anterior cruciate ligament reconstruction (ALCR). While the ST/G tendon provides a stable graft and muscle morphology is not compromised, little is known about how harvesting the ST/G influences muscle activity. PURPOSE: The purpose of this study was to compare muscle activity of patients who received ST/G to those who received a bone-patellar tendon-bone (BPTB) autograft, and allograft (Allo). METHODS: One year after ACLR, 35 athletes (18 ST/G, 5 BPTB, 12 Allo) completed biomechanical analysis of gait with EMG recorded from the involved limb medial and lateral hamstrings (MH and LH), rectus femoris (RF), vastus medialis and lateralis (VM and VL). EMG were filtered and amplitude normalized, with the mean activity calculated for each phase of stance: weight acceptance (WA), mid-stance (MS), Terminal stance (TS). Repeated measures ANOVAs (Graft x Phase) were performed to compare muscle activity and co-activity of muscle pairs (MH-LH, MH-VM, VM-VL). Post-hoc tests were performed in the presence of interactions; alpha ≤ 05. RESULTS: A significant Graft x Phase interaction was observed for MH activity during WA (p=.022), with greater MH activity in the ST/G group (17.3±6.3%) compared to BPTB (8.3±5.4%; p=.021). A significant Graft x Phase interaction was also observed at WA for RF activity (p<.001), with less RF activity in the ST/G (6.8±4.9%) compared to BPTB (20.7±22.5%; p=.006) and during MS compared to Allo (ST/G: 2.9±3.8%; Allo: 7.6±7.0%; p=.032). There were significant Graft X Phase interactions for co-activity of the MH-LH (p=.003) and for MH-VM (p=.008). Post hoc analyses revealed greater MH-LH coactivity during WA in the ST/G (21.9±8.8%) compared to Allo (11.2±6.8%; p=.002), but not compared to BPTB (14.8 ±6.8%; p≥.106). The ST/G also exhibited less MH-VM coactivity (3.3±.2.8) during TS compared to Allo (17.6±17.7%; p=.003), but not compared to BPTB (14.3±16.6%; p=.083). CONCLUSIONS: Muscle activity differences were observed in the ST/G group compared to BPTB and Allo groups, one year after ACLR, suggesting the use of ST/G during ACLR may result in altered hamstring activity patterns and function. Further work is needed to examine the effects of these differences to knee function and the relation with to knee flexor strength.

Muscle Activation Patterns during TRX Suspension Training Exercises

Suspension training has been utilized to train multiple muscle groups, especially core musculature, under the assumption that increased muscle activation will occur as compared to similar exercises performed on a stable surface. PURPOSE: To determine whether suspension training with a TRX augments muscle activation compared to similar exercises performed on a stable surface. METHODS: 25 healthy adults (male: 16; women: 9; BMI: 23.50 ± 2.48 kg/m2) were instrumented with 16 pre-amplified wireless surface EMG electrodes bilaterally on the: pectoralis major, middle deltoid, serratus anterior, obliques, rectus abdominis, gluteus maximus, erector spinae, and middle trapezius/rhomboids. Each participant performed isometric exercises including the Sorensen test, push up, plank, and inverted row to establish a baseline muscle contraction. Muscle activation was assessed from all muscles during the following exercises performed in a randomized manner: TRX bridge, TRX push up, TRX inverted row, TRX plank, floor bridge, floor push up, floor row, and floor plank. Three minutes of rest time was given between exercises to ensure adequate muscle recovery. The root mean square (RMS) of each side for every muscle was averaged for data analysis. RESULTS: Four multivariate analysis of variance (MANOVA) with post-hoc comparisons as appropriate were performed to compare muscle activation between each TRX exercise and its stable surface counterpart. MANOVAs for all exercise comparison showed statistically significant greater muscle activation during the TRX condition. Post-hoc analyses revealed a statistically significant increase in muscle activation for the following exercises/muscle combinations: Plank: Obliques (p=0.021); Pushup: pectoralis (p=0.002), Rectus abdominus (p<0.0001), obliques (p=0.019), rhomboids (p<0.0001), and erector spinae (p=0.006); Row: deltoid (p=0.016), rectus abdominus (p=0.059), and obliques (p=0.027); Bridge: rectus abdominus (p=0.013) and erector spinae (p<0.0001). CONCLUSION: Performing exercises with the TRX exercise system elicits an increase in muscle activation of selected muscles when compared to similar exercises performed on a stable surface.