fascia. Specifically, the existence of a continuity between the myofascial oblique muscles and the SA is described. 15 Recently, de Araújo et al 16 verified the existence of a positive correlation between the electromyographic (EMG) activity of the SA and EO during the execution of push-up on different
Rodrigo Cappato de Araújo, Vinícius Yan Santos Nascimento, Rafaela Joyce Barbosa Torres, Francis Trombini-Souza, David Behm and Ana Carolina Rodarti Pitangui
Gilbert M. Willett, Gregory M. Karst, Ellen M. Canney, Derrick Gallant and Jodene M. Wees
The purpose of this study was to investigate the electromyographic (EMG) activity of selected lower limb muscles during forward- and backward-facing stair-stepping exercises using a hydraulic step ergometer and during step aerobics using a standard 8 in. high step. Surface electrodes recorded EMG data from the vastus lateralis (VL), vastus medialis obliquus (VMO), and biceps femoris (BF) muscles on the right lower limbs of 13 healthy subjects under each of the four exercise conditions. Normalized mean EMG amplitude data were used to test for activity-dependent differences. Results indicated that (a) the VL and VMO were significantly (p < .05) more active during step ergometry than during step aerobics, (b) the BF was significantly (p < .05) more active during step aerobics than during step ergometry, and (c) when forward- versus backward-facing positions were compared, there were no statistically significant differences in mean EMG activity for either of the activities. These findings provide information relevant to the use and progression of stepping exercises commonly used for knee muscle strengthening and knee injury rehabilitation programs.
Frank C. Bakker, Marc S.J. Boschker and Tjuling Chung
Investigating emotional imagery, Lang (1977, 1979) proposed a dichotomy between stimulus and response propositions. In this study, Lang’s model is applied to movement images of lifting of 4.5 and 9 kg weights. Twenty-two male and 17 female students participated in the study. During the imaginary lifting of the weights, the electromyographical activity (EMG) of both biceps brachii muscles were assessed. Imagery ability was measured with the Movement Imagery Questionnaire (MIQ) and another self-report rating scale. When response propositions were emphasized in the script, imaginary weight lifting resulted in greater muscle activity than when stimulus propositions were emphasized. During imagined lifting, EMG activity of the active arm was greater than that of the passive arm. In addition, in the active arm, a significant difference in EMG activity was found between 9 kg and 4.5 kg. It was concluded that Lang’s model is also applicable to emotionally neutral movement imagery.
Peter A. Schaub and Teddy W. Worrell
During knee rehabilitation, squats are a commonly used closed kinetic chain exercise. We have been unable to locate data reporting electromyographic (EMG) activity of lower extremity musculature during maximal effort squats and the contribution of gastrocnemius and gluteus maximus muscles. Therefore, the purposes of this study were (a) to quantify EMG activity of selected lower extremity muscles during a maximal isometric squat and during a maximal voluntary isometric contraction (MVIC), and (b) to determine ratios between the vastus medialis oblique (VMO) and vastus lateralis (VL) during maximal isometric squat and MVIC testing. Twenty-three subjects participated in a single testing session. Results are as follows: intraclass correlations for MVIC testing and squat testing ranged from .60 to .80 and .70 to .90, respectively. Percentage MVIC during the squat was as follows: rectus femoris 40 ± 30%, VMO 90 ± 70%, VL 70 ±40%, hamstrings 10 ± 10%, gluteus maximus 20 ± 10%, and gastrocnemius 30 ± 20%. No statistical difference existed in VMO:VL ratios during MVIC or squat testing. We conclude that large variations in muscle recruitment patterns occur between individuals during isometric squats.
Mark L. McMulkin, Jeffrey C. Woldstad and Richard E. Hughes
Biomechanical optimization models are often used to estimate muscular and intervertebral disc forces during physical exertions. The purpose of this study was to determine whether an optimization-based biomechanical model predicts torso muscular activity of males and females equally well. The Minimum Intensity Compression (MIC) model, which has been extensively applied in industrial ergonomic task analysis, was used to estimate muscle forces for 3D moments. Participants (6 M, 6 F) performed 18 isometric exertions resisting 3D L3/L4 moments while electromyographic (EMG) activity was recorded for 8 muscles. Overall, model force estimates correlated better with male EMG activity (R 2 = 0.43) than with female EMG activity (R 2 = 0.33). Model force estimates of 4 muscles (LRA, RRA, REO, and RES) correlated better with male EMG activity than with female EMG. We conclude that trunk muscle forces estimated by current biomechanical modeling do not correlate equally well to male and female EMG activity. Future research needs to address validation or improvement of biomechanical trunk models for females.
Dorothy V. Harris and William J. Robinson
This study was designed to determine if muscular innervation during imagery was specific to muscles needed for actual performance and if individuals of different skill levels utilizing two imagery perspectives demonstrated differing amounts of muscular activity. A final purpose was to assess the effectiveness of the meditation-relaxation approach used in karate training to reduce tonic activity in muscles. Beginning and advanced (N = 36) karate students were randomly assigned to counterbalanced conditions of imagery perspective (internal/external) x skill level (beginning/advanced) x side (right/left) in a factorial design. EMG data were collected from both deltoid muscles before and after a relaxation session, during and between performances of imaginary arm lifts and between imagery perspectives. Following testing, a questionnaire involving the subject's perception of success at imagery was completed. The results of this investigation suggest that skill level does influence muscle innervation during imagery and that this innervation appears specific to the muscle group necessary to execute the task. Internal imagery produces more EMG activity than external imagery. The meditation-relaxation techniques used in karate do significantly reduce tonic muscle activity.
John P. Miller, Kerriann Catlaw and Robert Confessore
The purpose of this study was to examine the effect of ankle position on the electromyographic (EMG) activity, peak torque, and peak knee flexion to extension torque ratio during isokinetic testing of the knee. Twelve healthy female athletes performed six maximal knee extension and flexion repetitions with their dominant legs at 60 and 180°/s with the ankle in a plantar flexed position and again in a dorsiflexed position. Root mean square EMG (rmsEMG) activity was determined by placing bipolar surface electrodes on the quadriceps and the hamstrings. Ankle position had no effect on the rmsEMG activity of the quadriceps or the hamstrings at either 60 or 180°/s. Significant differences were noted for peak flexor torque at 607s (p < .001) and 180°/s (p <.01) and for peak torque flexor/extensor ratio (p < .01), with higher values observed with ankle dorsiflexion. This suggests that ankle position affects knee flexor torque and flexor/extensor ratio but not hamstring activity during isokinetic testing of the knee.
Christos Papadopoulos, Vasilios I. Kalapotharakos, Georgios Noussios, Konstantinos Meliggas and Evangelia Gantiraga
To examine the effect of static stretching on maximal voluntary contraction (MVC) and isometric force-time curve characteristics of leg extensor muscles and EMG activity of rectus femoris (RF), biceps femoris (BF), and gastrocnemius (GA).
A within subjects experimental design.
Ten healthy students were tested after a jogging and a jogging/stretch protocol.
The stretching protocol involved a 10 min jog and seven static stretching exercises.
Measurements included MVC, time achieved to MVC (TMVC), force at 100ms (F100), index of relative force (IRF), index of rate of force development (IRFD), and average integrated EMG activity (AEMG).
There were slight but no significant changes in MVC (1%), TMVC (4.8%), F100 (7.8%), IRF (1%), and IRFD (3.5%) between measurement. A significant difference (21%; P < 0.05) in AEMG of RF was found.
The present study indicated that a moderate volume of static stretching did not alter significantly the MVC and the isometric force-time curve characteristics. Neural inhibition, as it is reflected from AEMG of RF, did not alter MVC and isometric force-time curve characteristics.
Angie Selseth, Marilyn Dayton, Mitchell L. Cordova, Christopher D. Ingersoll and Mark A. Merrick
To analyze vastus medialis obliquus (VMO) and vastus lateralis (VL) muscle activity during the concentric and eccentric phases of a lateral step-up exercise.
Repeated-measures. Dependent variable: the integrated electromyogram measured as a percentage of the maximal voluntary isometric contraction of the VMO and VL muscles. Independent variable: muscle contraction with 2 levels (concentric and eccentric).
Twenty-three volunteers with no previous history of knee surgery or anterior knee pain.
Surface electrodes were positioned over the VMO and VL, and electromyographic data were collected during the exercise.
The 2 muscle phases of contraction were different when both dependent variables were considered simultaneously (F 2,7 = 33.2, P < .001). Concentric contractions produced greater muscle activity for VL (P < .05) and VMO (P < .05).
Because concentric contractions produce greater activity than eccentric contractions do during the lateral step-up exercise, they provide a stronger stimulus for muscle activation, which might result in greater muscle strength gains.
Jeffrey A. Bauer, Thomas S. Thomas and Daniel P. Connaughton
Lower back discomfort is common among users of standard vertical stair-climbing machines. A partially reclined stair-climbing machine (PRSC) has been designed to provide more comfort and protection to the lower back while providing the same exercise benefits. Ten individuals were recruited to exercise on both machines while their erector spinae electromyographic activity and heart rates were recorded. There was no significant difference (p < .05) in erector spinae muscle activity during exercise on either machine. Workout intensity levels necessary to achieve target heart rates were established during a familiarization session and tracked during exercise. The mean heart rates for both groups remained within the target zones throughout the exercise sessions, but a nonsignificant (p > .05) trend toward increased heart rate on both machines was observed in the women participants. Because of the high incidence of low back pain and injury, we need exercise modalities that provide both cardiovascular and muscular fitness development without placing additional stress on this region.