The purpose of this study was to examine activations of selected scapular stabilizing musculature while performing an overhead throw with a hold (not releasing the ball) in two different throwing positions—standing with a crow hop and kneeling on the ipsilateral knee. Surface electromyography was used to examine activations of throwing side lower trapezius (LT), middle trapezius (MT), serratus anterior (SA), and upper trapezius (UT). Muscle activations were recorded while performing the overhead throw with holds while in two throwing positions. MANOVA results revealed no significant differences between the two throwing conditions and muscle activations of LT, MT, SA, and UT: F(8,124) = .804, p = .600; Wilks’s Λ = .904, partial η2 = .049. Although no significant differences were observed in the scapular stabilizers between the two conditions, moderate (21–50% MVIC) to high (> 50% MVIC) activations of each muscle were present, indicating that nonrelease throws may be beneficial for scapular stabilization in throwers.
Gretchen Oliver, Lisa Henning and Hillary Plummer
Kristi Edgar, Aimee Appel, Nicholas Clay, Adam Engelsgjerd, Lauren Hill, Eric Leeseberg, Allison Lyle and Erika Nelson-Wong
-tolerant). These differences can be identified during standing a priori to LBP onset and include muscle activation patterns. 5 – 7 , 11 Individuals classified as standing-intolerant demonstrated a reversal of the typical muscle activation sequence during return-to-stand from forward flexion and atypical flexion
Chad Van Ramshorst and Woochol Joseph Choi
1 ). In each trial, vertical contact forces (ground reaction forces) were recorded through a force plate (NC-4060; Bertec). Muscle activation of the rectus femoris and gluteus medius muscles was also acquired by a wireless electromyography (EMG) system (EMG DTS system; Noraxon, Scottsdale, AZ
S. Jayne Garland, Vicki L. Gray and Svetlana Knorr
Many stroke survivors have residual sensorimotor deficits that impact negatively on balance and quality of life. The purpose of this review is to provide an overview of the impairments in motor control following stroke and the impact of those impairments on muscle activation patterns during postural control in stroke. Motor control impairments following stroke result in force production that is slow, weak and lacking in precision making it difficult to produce a fast rate of force development with sufficient magnitude to be effective for postural responses. Whether postural perturbations require feedback or feedforward responses, there is impairment to the timing, magnitude and sequencing of muscle activation following stroke. The impairment in muscle activation is dependent on the extent of the motor control impairments and strategies used by the individuals following stroke to compensate for the impairments. The central nervous system uses a variety of mechanisms to improve the muscle activation patterns needed for the recovery of postural responses following stroke.
Alyssa Muething, Shellie Acocello, Kimberly A. Pritchard, Stephen F. Brockmeier, Susan A. Saliba and Joseph M. Hart
Understanding how muscles activate in a population with a previous glenohumeral-joint (GH) injury may help clinicians understand how to build a conservative treatment plan to strengthen or activate the specific muscles in an attempt to reduce recurrent shoulder injury and development of GH laxity.
To investigate muscle-activation differences between the previously injured limb of individuals with a history of GH-joint injury and healthy matched controls during functional isometric contractions.
University research laboratory.
17 individuals (8 women, 9 men; age 22.3 ± 2.6 y, height 172.4 ± 8.8 cm, mass 75.4 ± 16.5 kg) with previous unilateral shoulder pain and 17 (8 women, 9 men; age 22.9 ± 3.9 y, height 170.9 ± 11.3 cm, mass 73.6 ± 22.9 kg) with no history of shoulder pain or injury.
Diagnostic ultrasound measurements of the supraspinatus were completed in both resting and contracted states to assess changes in muscle thickness. Manual muscle tests (anterior deltoid, upper trapezius, infraspinatus, lower trapezius, serratus anterior) and functional isometric contractions (forward flexion, scaption, abduction) were measured using electromyography.
Main Outcome Measures:
Peak, normalized activation of each muscle and supraspinatus thickness activation ratio were compared between groups and bilaterally within groups using separate ANOVAs.
The anterior deltoid was significantly less activated during all functional isometric tasks in previously injured subjects than in healthy subjects (P = .024). In previously injured subjects, the involved limb-lower trapezius was significantly less activated during scaption and abduction tasks than the contralateral side (P = .022 and P = .031, respectively).
There were decreases in muscle activation in the anterior deltoid between previously injured and healthy people, as well as in the lower trapezius, in previously injured subjects. Understanding the source of muscle-activation deficits can help clinicians focus rehabilitation exercises on specific muscles.
Cameron Mitchell, Rotem Cohen, Raffy Dotan, David Gabriel, Panagiota Klentrou and Bareket Falk
Previous studies in adults have demonstrated power athletes as having greater muscle force and muscle activation than nonathletes. Findings on endurance athletes are scarce and inconsistent. No comparable data on child athletes exist.
This study compared peak torque (Tq), peak rate of torque development (RTD), and rate of muscle activation (EMG rise, Q30), in isometric knee extension (KE) and fexion (KF), in pre- and early-pubertal power- and endurance-trained boys vs minimally active nonathletes.
Nine gymnasts, 12 swimmers, and 18 nonathletes (7–12 y), performed fast, maximal isometric KE and KF. Values for Tq, RTD, electromechanical delay (EMD), and Q30 were calculated from averaged torque and surface EMG traces.
No group differences were observed in Tq, normalized for muscle cross-sectional area. The Tq-normalized KE RTD was highest in power athletes (6.2 ± 1.9, 4.7 ± 1.2, 5.0 ± 1.5 N·m·s–1, for power, endurance, and nonathletes, respectively), whereas no group differences were observed for KF. The KE Q30 was significantly greater in power athletes, both in absolute terms and relative to peak EMG amplitude (9.8 ± 7.0, 5.9 ± 4.2, 4.4 ± 2.2 mV·ms and 1.7 ± 0.8, 1.1 ± 0.6, 0.9 ± 0.5 (mV·ms)/(mV) for power, endurance, and nonathletes, respectively), with no group differences in KF. The KE EMD tended to be shorter (P = .07) in power athletes during KE (71.0 ± 24.1, 87.8 ± 18.0, 88.4 ± 27.8 ms, for power, endurance, and nonathletes), with no group differences in KF.
Pre- and early-pubertal power athletes have enhanced rate of muscle activation in specifically trained muscles compared with controls or endurance athletes, suggesting that specific training can result in muscle activation-pattern changes before the onset of puberty.
Kerry E. Costello, Janie L. Astephen Wilson, William D. Stanish, Nathan Urquhart and Cheryl L. Hubley-Kozey
gastrocnemius, quadriceps, and hamstrings muscle activation and prolonged quadriceps and hamstrings activation through mid-stance were found at baseline in those who progressed. 23 Higher peak KFM, thought to indicate greater compressive loads on the joint, has been associated with progression of a structural
Eleni Bassa, Dimitrios Patikas, Konstantinos Hatzikotoulas and Christos Kotzamanidis
We would like to comment on the paper by Dotan et al. (8) entitled “Child-adult differences in muscle activation—a review.” Dotan et al.’s review (8) in conjunction with the commentary of O’Brien et al. (20) constitutes an important contribution to the question “who are stronger: children or adults?” based on specific force comparisons between children and adults and not on absolute values. For simplification reasons, we would like to limit the context of this question to single-joint isometric and isokinetic contractions only. Hence, we will not discuss multi-joint dynamic actions.
Lukas D. Linde, Jessica Archibald, Eve C. Lampert and John Z. Srbely
abdominal activation on trunk control or verify the level of abdominal muscle activation. 13 Consequently, a key gap remains in our understanding of the association between trunk control through increased abdominal activation and the immediate effect on lower limb mechanics related to ACL injury risk. The
Se-yeon Park, Won-gyu Yoo, Hun Kwon, Dong-hyun Kim, Si-eun Lee and Mi-jin Park
Activation of the upper trapezius, lower trapezius, serratus anterior, and triceps brachii muscles was measured, while center of pressure excursion beneath the hands was simultaneously monitored, during the performance of a push-up exercise on both a stable and an unstable base of support. The activation levels of all muscles were significantly greater for the unstable support surface when compared to those for a stable support surface (p < 0.05). A negative correlation was found between activation of the serriatus anterior muscle and center of pressure excursion (r = -0.64, p < 0.05). Performance of the push-up exercise on an unstable support surface appears to elicit greater muscle activation than a standard push-up exercise performed on a stable support surface.