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1.  Electromyographic Analysis of Four Popular Abdominal Exercises 
Journal of Athletic Training  1993;28(2):120-126.
This study was designed to evaluate the effects of four specific sit-up exercises on muscular activity of the rectus abdominis. Pairs of surface electrodes were placed unilaterally on four quadrants of the rectus abdominis, delimited by tendinous inscriptions, in four male subjects. Electromyographic (EMG) recordings were taken while the subjects performed four different abdominal exercises. Each abdominal exercise was hypothesized to have a specific effect on one of the four quadrants of the rectus abdominis. The four exercises analyzed were: 1) long lying crunch, 2) bent knee crunch, 3) leg raise, and 4) vertical leg crunch. Analysis of the standardized EMG recordings demonstrated no significant differences in the mean muscle activity between the four different quadrants, in the mean muscle activity between the four different exercises, and in interactions between the exercises and the quadrants of the rectus abdominis. We conclude that none of the four abdominal exercises studied are specific for strengthening individual muscle quadrants of the rectus abdominis.
PMCID: PMC1317695  PMID: 16558218
While elastic resistance training, targeting the upper body is effective for strength training, the effect of elastic resistance training on lower body muscle activity remains questionable. The purpose of this study was to evaluate the EMG‐angle relationship of the quadriceps muscle during 10‐RM knee‐extensions performed with elastic tubing and an isotonic strength training machine.
7 women and 9 men aged 28‐67 years (mean age 44 and 41 years, respectively) participated. Electromyographic (EMG) activity was recorded in 10 muscles during the concentric and eccentric contraction phase of a knee extension exercise performed with elastic tubing and in training machine and normalized to maximal voluntary isometric contraction (MVC) EMG (nEMG). Knee joint angle was measured during the exercises using electronic inclinometers (range of motion 0‐90°).
When comparing the machine and elastic resistance exercises there were no significant differences in peak EMG of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM) during the concentric contraction phase. However, during the eccentric phase, peak EMG was significantly higher (p<0.01) in RF and VM when performing knee extensions using the training machine. In VL and VM the EMG‐angle pattern was different between the two training modalities (significant angle by exercise interaction). When using elastic resistance, the EMG‐angle pattern peaked towards full knee extension (0°), whereas angle at peak EMG occurred closer to knee flexion position (90°) during the machine exercise. Perceived loading (Borg CR10) was similar during knee extensions performed with elastic tubing (5.7±0.6) compared with knee extensions performed in training machine (5.9±0.5).
Knee extensions performed with elastic tubing induces similar high (>70% nEMG) quadriceps muscle activity during the concentric contraction phase, but slightly lower during the eccentric contraction phase, as knee extensions performed using an isotonic training machine. During the concentric contraction phase the two different conditions displayed reciprocal EMG‐angle patterns during the range of motion.
Level of Evidence:
PMCID: PMC3537465  PMID: 23316424
Electromyography; strength training; quadriceps; perceived exertion
Decreased hip muscle strength is frequently reported in patients with hip injury or pathology. Furthermore, soccer players suffering from groin injury show decreased strength of hip muscles. Estimating 10‐repetition maximum can be time‐consuming and difficult, thus, using the Borg category rating 10 scale (Borg CR10 scale) can be a useful tool for estimating the intensity of exercise. The aims of this study were 1) to investigate the feasibility of the use of the Borg CR10 scale for rating strength training intensity of the hip abductor and hip adductor muscles, and 2) to compare hip muscle activity during hip abduction and hip adduction exercises using elastic resistance and isotonic machines, using electromyography (EMG).
EMG activity was recorded from 11 muscles at the hip, thigh and trunk during hip adduction and hip abduction exercises in 16 untrained women, using elastic resistance and isotonic exercise machines. These recordings were normalized to maximal voluntary contraction (MVC) EMG (nEMG). The exercises were performed at four levels of perceived loading reported using the Borg CR10: light (Borg ≤2), moderate (Borg >2–<5), heavy (Borg ≥5–<7) and near maximum (Borg ≥7).
Moderate to strong associations were observed between perceived loading and nEMG obtained during the adduction exercise with elastic resistance (r=0.8±0.3) as well as in machine (r=0.69±0.55) and the abduction exercise with elastic resistance (r=0.66±0.29) as well as in machine (r =0.62±0.54). The abduction exercise performed with elastic resistance displayed significantly higher gluteus medius nEMG recruitment than the in machine exercise.
The results of this study show that the Borg CR10 scale can be a useful tool for estimating intensity levels during resistance training of the hip adductor and hip abductor muscles. Although elastic resistance and exercise machine seem equally effective for recruiting muscle activity of the hip adductors, the elastic resistance condition was able to demonstrate greater muscle recruitment than the exercise machine during hip abduction.
PMCID: PMC3867074  PMID: 24377067
Elastic resistance; hip adduction; hip abduction; strength training
4.  EMG Activity in the Abdominal Muscles and the Kinematics of the Lumbar Spine during Unilateral Upper-limb Resistance Exercises under Stable and Unstable Conditions 
[Purpose] We investigated the effects of unstable conditions on the electromyographic (EMG) activity of the rectus abdominis (RA) and the transverse abdominis–internal oblique (TrA-IO) muscles, and lumbar kinematics during unilateral upper-limb resistance exercises using elastic tubing bands. [Subjects] Twelve healthy males were recruited. [Methods] The subjects performed isometric left shoulder abduction using an elastic tubing band in a sitting position on a chair, and on a Swiss ball. During this exercise, EMG activities of the RA and TrA-IO were recorded using a wireless EMG system, and a three-dimensional motion analysis system monitored lumbar kinematics. Differences in EMG activities of the RA and TrA-IO, the ratio of TrA-IO to RA activity, and lumbar kinematics were compared between the stable and unstable conditions using the paired t-test. [Results] Under the unstable condition, the EMG activities of both muscles were significantly greater than that under the stable condition; however the ratio of TrA-IO to RA activity did not significantly differ between the conditions. The lumbar angle significantly differed only in the coronal plane. [Conclusions] These findings indicate that trunk posture should be considered when performing exercises under unstable conditions.
PMCID: PMC4085211  PMID: 25013286
Swiss ball; Abdominal muscles; Electromyography
5.  Selective Activation of the Rectus Abdominis Muscle During Low-Intensity and Fatiguing Tasks 
In order to understand the potential selective activation of the rectus abdominis muscle, we conducted two experiments. In the first, subjects performed two controlled isometric exercises: the curl up (supine trunk raise) and the leg raise (supine bent leg raise) at low intensity (in which only a few motor units are recruited). In the second experiment, subjects performed the same exercises, but they were required to maintain a certain force level in order to induce fatigue. We recorded the electromyographic (EMG) activities of the lower and upper portions of the rectus abdominis muscle during the exercises and used spatial-temporal and frequency analyses to describe muscle activation patterns. At low-intensity contractions, the ratio between the EMG intensities of the upper and lower portions during the curl up exercise was significantly larger than during the leg raise exercise (p = 0.02). A cross-correlation analysis indicated that the signals of the abdominal portions were related to each other and this relation did not differ between the tasks (p = 0.12). In the fatiguing condition, fatigue for the upper portion was higher than for the lower portion during the curl up exercise (p = 0.008). We conclude that different exercises evoked, to a certain degree, individualized activation of each part of the rectus abdominis muscle, but different portions of the rectus abdominis muscle contributed to the same task, acting like a functional unit. These results corroborate the relevance of varying exercise to modify activation patterns of the rectus abdominis muscle.
Key pointsSelective activation of the rectus abdominis muscle is possible because this muscle has different portions (which can have different motor fibers in series) which can be innervated by different nerves as well as by a common nerve branch.Changes in body position and exercise intensity cre-ate different demands for the different portions of the rectus abdominis muscle.Exercise variation seems to be valid to modify the activation patterns of the rectus abdominis muscle.
PMCID: PMC3761871  PMID: 24149878
Motor control; electromyography; biomechanics; exercise
6.  Surface Electromyographic Amplitude-to-Work Ratios During Isokinetic and Isotonic Muscle Actions 
Journal of Athletic Training  2006;41(3):314-320.
Context: Isokinetic and isotonic resistance training exercises are commonly used to increase strength during musculoskeletal rehabilitation programs. Our study was designed to examine the efficacy of isokinetic and isotonic muscle actions using surface electromyographic (EMG) amplitude-to-work ratios (EMG/WK) and to extend previous findings to include a range of isokinetic velocities and isotonic loads.
Objective: To examine work (WK), surface EMG amplitude, and EMG/WK during concentric-only maximal isokinetic muscle actions at 60, 120, 180, 240, and 300°/s and isotonic muscle actions at 10%, 20%, 30%, 40%, and 50% of the maximal voluntary isometric contraction (MVIC) torque during leg extension exercises.
Design: A randomized, counterbalanced, cross-sectional, repeated-measures design.
Setting: A university-based human muscle physiology research laboratory.
Patients or Other Participants: Ten women (mean age = 22.0 ± 2.6 years) and 10 men (mean age = 20.8 ± 1.7 years) who were apparently healthy and recreationally active.
Intervention(s): Using the dominant leg, each participant performed 5 maximal voluntary concentric isokinetic leg extension exercises at randomly ordered angular velocities of 60, 120, 180, 240, and 300°/s and 5 concentric isotonic leg extension exercises at randomly ordered loads of 10%, 20%, 30%, 40%, and 50% of the isometric MVIC.
Main Outcome Measure(s): Work was recorded by a Biodex System 3 dynamometer, and surface EMG was recorded from the superficial quadriceps femoris muscles (vastus lateralis, rectus femoris, and vastus medialis) during the testing and was normalized to the MVIC. The EMG/WK ratios were calculated as the quotient of EMG amplitude (μVrms) and WK (J) during the concentric phase of each exercise.
Results: Isotonic EMG/WK remained unchanged ( P > .05) from 10% to 50% MVIC, but isokinetic EMG/WK increased ( P < .05) from 60 to 300°/s. Isotonic EMG/WK was greater ( P < .05) than isokinetic EMG/WK for 50% MVIC versus 60°/s, 40% MVIC versus 120°/s, and 30% MVIC versus 180°/s; however, no differences were noted ( P > .05) between 20% MVIC versus 240°/s or 10% MVIC versus 300°/s. An 18% decrease in active range of motion was seen for the isotonic muscle actions, from 10% to 50% MVIC, and a 3% increase in range of motion for the isokinetic muscle actions from 60 to 300°/s was also observed. Furthermore, the peak angular velocities for the isotonic muscle actions ranged from 272.9 to 483.0°/s for 50% and 10% MVIC, respectively.
Conclusions: When considering EMG/WK, peak angular velocity, and range of motion together, our data indicate that maximal isokinetic muscle actions at 240°/s or controlled-velocity isotonic muscle actions at 10%, 20%, or 30% MVIC may maximize the amount of muscle activation per unit of WK done during the early stages of musculoskeletal rehabilitation. These results may be useful to allied health professionals who incorporate open-chain resistance training exercises during the early phases of rehabilitation and researchers who use isotonic or isokinetic modes of resistance exercise to examine muscle function.
PMCID: PMC1569550  PMID: 17043700
range of motion; angular velocity; muscle activation; leg extension; rehabilitation
7.  Trunk muscle activity during bridging exercises on and off a Swissball 
A Swiss ball is often incorporated into trunk strengthening programs for injury rehabilitation and performance conditioning. It is often assumed that the use of a Swiss ball increases trunk muscle activity. The aim of this study was to determine whether the addition of a Swiss ball to trunk bridging exercises influences trunk muscle activity.
Surface electrodes recorded the myoelectric activity of trunk muscles during bridging exercises. Bridging exercises were performed on the floor as well as on a labile surface (Swiss ball).
Results and Discussion
During the prone bridge the addition of an exercise ball resulted in increased myoelectric activity in the rectus abdominis and external oblique. The internal oblique and erector spinae were not influenced. The addition of a swiss ball during supine bridging did not influence trunk muscle activity for any muscles studied.
The addition of a Swiss ball is capable of influencing trunk muscle activity in the rectus abdominis and external oblique musculature during prone bridge exercises. Modifying common bridging exercises can influence the amount of trunk muscle activity, suggesting that exercise routines can be designed to maximize or minimize trunk muscle exertion depending on the needs of the exercise population.
PMCID: PMC1187901  PMID: 16053529
EMG; trunk stability; exercise; swiss ball; rehabilitation
8.  Abdominal Muscle Activity While Performing Trunk-Flexion Exercises Using the Ab Roller, ABslide, FitBall, and Conventionally Performed Trunk Curls 
Journal of Athletic Training  2004;39(1):37-43.
To compare the surface electromyographic activity of the abdominal musculature and rectus femoris (RF) muscle during trunk-flexion exercises using 3 abdominal exercise devices (Ab Roller, ABslide, and FitBall) and the traditional trunk curl.
Design and Setting:
Each subject performed approximately 15 repetitions for each exercise condition. A repeated-measures, one-way multivariate analysis of variance was used to compare the mean integrated electric activity value for each muscle during each exercise condition.
A total of 10 male and 13 female collegiate undergraduate students.
Surface electromyographic activity was recorded for the upper rectus abdominis (URA), lower rectus abdominis (LRA), external oblique (EO), and RF during 5 consecutive repetitions of each exercise bout. The signal was amplified by a factor of 1000, rectified, and integrated. These integrated values were then divided by the time value for each exercise to give the mean integrated electromyography value.
A significant difference existed among exercise conditions for the RF (P < .0001), with the ABslide and the FitBall having greater electric activity than the other exercise conditions. Activity was significantly different (P < .0009) for the URA, with the ABslide having the least electric activity. For the EO, exercising with the ABslide produced significantly greater electric activity (P < .0001) than all other exercise conditions. No significant difference was found across exercise conditions for the LRA (P < .051).
Performing abdominal exercises with the Ab Roller, ABslide, and FitBall did not elicit greater activity of the URA and LRA than performing traditional trunk curls. Use of the ABslide elicited greater EO activity and significantly less URA activity than the other 3 modes. Both the ABslide and FitBall resulted in greater involvement of the hip flexors, an undesirable feature of abdominal exercises.
PMCID: PMC385260  PMID: 15085210
electromyography; fitness; rehabilitation; sit-ups; abdominal crunches
9.  Comparison of Trunk Muscle Activity During Bridging Exercises Using a Sling in Patients with Low Back Pain 
The aims of this study were to compare the activation of global and local muscles of the trunk during bridging with sling exercise (BSE), bridging with ball exercise (BBE), and normal bridging exercise (NBE) and to conduct and analyze these exercises in supine and prone positions to prove the effectiveness of sling exercises. Thirty patients with current low back pain (LBP) were recruited. In the supine and prone bridging exercise, each subject lifted their pelvis with their legs and feet in contact with the sling, ball, or normal surface. The electrical activities of the inferior oblique (IO), rectus abdominis (RA), multifidus (MF), and erector spinae (ES) muscles during the bridging exercises on the 3 surfaces were measured using surface electromyography (sEMG). For normalization, maximum sEMG signals were evaluated during each maximum voluntary isometric contraction (MVIC) maneuver. The root mean square during the exercise was normalized as a percentage of the MVIC (%MVIC). In the supine and prone positions, %MVIC of the IO, RA, MF, and ES during BSE was significantly higher than those during BBE and NBE (p < 0.05). In the supine position, %MVIC of the RA and ES during BBE was significantly higher than that during NBE (p < 0.05). In the prone position, all %MVIC during BBE were significantly higher than NBE (p < 0.05). These results verify the theory that the use of an unstable surface increases the activation of global and local trunk muscles during bridging exercises in the supine and prone positions. In conclusion, the use of BSE in a rehabilitation program may have therapeutic effects for patients with LBP by increasing trunk muscle activation.
Key pointsCompared with the BBE and NBE, the BSE increased the %MVIC values of the IO, RA, MF, and ES muscles in the supine and prone positions in the patients with LBP.We verified that activation of the global and local trunk muscles was increased by the use of unstable surfaces during the bridging exercises in the supine and prone positions.The BSE was shown to be an effective exercise method for patients with LBP in a rehabilitation program by increasing trunk muscle activation.
PMCID: PMC3737950  PMID: 24149361
Sling; bridging exercise; sEMG; local trunk muscle; global trunk muscle
10.  Shoulder muscle EMG activity during push up variations on and off a Swiss ball 
Dynamic Medicine  2006;5:7.
Surface instability is a common addition to traditional rehabilitation and strength exercises with the aim of increasing muscle activity, increasing exercise difficulty and improving joint proprioception. The aim of the current study was to determine if performing upper body closed kinetic chain exercises on a labile surface (Swiss ball) influences myoelectric amplitude when compared with a stable surface.
Thirteen males were recruited from a convenience sample of college students. Surface electromyograms were recorded from the triceps, pectoralis major, latissimus dorsi, rectus abdominis and external oblique while performing push up exercises with the feet or hands placed on a bench and separately on a Swiss ball. A push up plus exercise was also evaluated with hands on the support surface.
Results and discussion
Not all muscles responded with an increase in muscle activity. The pectoralis major muscle was not influenced by surface stability. The triceps and rectus abdominis muscles showed increases in muscle activity only when the hands were on the unstable surface. The external oblique muscle was only influenced by surface stability during the performance of the push up plus exercise. No muscle showed a change in activation level when the legs were supported by the Swiss ball instead of the bench.
Muscle activity can be influenced by the addition of surface instability however an increase in muscle activity does not influence all muscles in all conditions. The relationship between the participant's center of mass, the location of the unstable surface and the body part contacting the Swiss ball may be important factors in determining the muscle activation changes following changes in surface stability.
PMCID: PMC1508143  PMID: 16762080
11.  Surface Electromyographic Analysis of Core Trunk and Hip Muscles During Selected Rehabilitation Exercises in the Side-Bridge to Neutral Spine Position 
Sports Health  2014;6(5):416-421.
Strengthening of core hip, trunk, and abdominal muscles has been utilized with injury prevention and low back pain and has the potential to improve athletic performance.
During a side-bridge, trunk and thigh muscles on the ipsilateral weightbearing side would produce greater activation than their counterparts on the contralateral nonweightbearing side.
Study Design:
Descriptive laboratory study.
Twelve females and 13 males participated. Electromyography (EMG) signals were gathered for 5 right-sided muscles (rectus abdominis [RA], external oblique [EO], longissimus thoracis [LT], lumbar multifidus [LM], and gluteus medius [GM]) during 3 repetitions of 4 side-bridging exercises (trunk-elevated side support [TESS], foot-elevated side support [FESS], clamshell, and rotational side-bridge [RSB]) performed bilaterally in random order using surface electrodes. EMG signals were normalized to peak activity in maximum voluntary isometric contraction (MVIC) trials and expressed as a percentage. Descriptive EMG data were calculated for EMG recruitment (% MVIC) and compared between right side up and right side down conditions and between exercises with 2-way repeated-measures analyses of variance at α = 0.05.
RSB created the most muscle activation in 3 of 4 recorded trunk muscles (RA, 43.9% MVIC; EO, 62.8 % MVIC; and LT, 41.3% MVIC). Activation of the GM exceeded 69% MVIC for TESS, FESS, and RSB. With the exception of the RA in RSB and LT in TESS, recruitment within muscles of the ipsilateral weightbearing trunk and thigh (% MVIC) was significantly greater than their counterparts on the nonweightbearing trunk and thigh for all muscles during the side-bridge exercise conditions.
Muscle recruitment was greater within muscles of the ipsilateral weightbearing trunk and thigh for all examined muscles except RA during RSB and LT during TESS. Activation at or above 50% MVIC is needed for strengthening. Activation of the GM and EO meets these requirements.
Clinical Relevance:
Side-bridge exercises appear to provide strengthening benefits to core hip, trunk, and abdominal muscles on the ipsilateral weightbearing side.
PMCID: PMC4137676  PMID: 25177418
side plank; core musculature; therapeutic exercises; electromyography
12.  Neuromuscular Evaluation of Trunk-Training Exercises 
Journal of Athletic Training  2001;36(2):109-118.
To evaluate the neuromuscular activation profiles of trunk muscles in commonly used gymnastic strength exercises with a polymyographic set-up and to describe the training effects of each exercise.
Design and Setting:
Subjects performed 9 repetitions of each of 12 gymnastic exercises. Variations of 5 trunk flexions, 5 extensions, and 2 lateral-flexion movements were performed under standardized test conditions.
Ten healthy subjects (men and women) who were familiar with the exercises participated in the study.
We recorded surface electromyograms (EMGs) from the rectus abdominis, external oblique, rectus femoris, middle trapezius, erector spinae at T12 and L3, gluteus maximus, and semitendinosus and semimembranosus muscles. Recording of each repetition cycle was triggered by a flexible electronic goniometer attached to the trunk. The raw EMG signals were rectified, smoothed, amplitude normalized to maximal voluntary contraction (MVC), and averaged for the last 8 repetitions.
Pure spine-flexion exercises, such as a curl-up, produced sufficient and isolated activation (greater than 50% MVC) of the abdominal muscles. When flexion of the spine was combined with hip flexion (sit-up), the peak activation was increased. Lateral-flexion tasks targeted primarily the external oblique muscle, which demonstrated high activity in side-lying flexion tasks. Back- and hip-extension exercises, such as bridging and diagonal hip and shoulder extension, produced only moderate mean activities (less than 35% MVC) in the trunk-extensor muscles. Trunk-extension exercises with combined hip extension increased the EMG activity to 50% MVC but only at the end of the extension.
Individual responses to each exercise varied markedly, which complicated the classification of exercise effects. However, within the limitations of the study, we found that the chosen abdominal exercises provided an effective training stimulus for the trunk-flexor muscles, whereas in the back- and hip-extension exercises, the neuromuscular activation tended to be too low or unspecific to qualify as muscle-specific training.
PMCID: PMC155519  PMID: 12937449
electromyography; activation profiles; EMG normalization; EMG variability; movement standardization; back muscles; abdominal muscles; hip muscles; training effectiveness
13.  Replacing a Swiss ball for an exercise bench causes variable changes in trunk muscle activity during upper limb strength exercises 
The addition of Swiss balls to conventional exercise programs has recently been adopted. Swiss balls are an unstable surface which may result in an increased need for force output from trunk muscles to provide adequate spinal stability or balance. The aim of the study was to determine whether the addition of a Swiss ball to upper body strength exercises results in consistent increases in trunk muscle activation levels.
The myoelectric activity of four trunk muscles was quantified during the performance of upper body resistance exercises while seated on both a stable (exercise bench) and labile (swiss ball) surface. Participants performed the supine chest press, shoulder press, lateral raise, biceps curl and overhead triceps extension. A repeated measures ANOVA with post-hoc Tukey test was used to determine the influence of seated surface type on muscle activity for each muscle.
Results & Discussion
There was no statistically significant (p < .05) difference in muscle activity between surface conditions. However, there was large degree of variability across subjects suggesting that some individuals respond differently to surface stability. These findings suggest that the incorporation of swiss balls instead of an exercise bench into upper body strength training regimes may not be justified based only on the belief that an increase spinal stabilizing musculature activity is inherent. Biomechanically justified ground based exercises have been researched and should form the basis for spinal stability training as preventative and therapeutic exercise training regimes.
Selected trunk muscle activity during certain upper limb strength training exercises is not consistently influenced by the replacement of an exercise bench with a swiss ball.
PMCID: PMC1177975  PMID: 15935097
EMG; exercise; spine stability; swiss balls; rehabilitation; low back pain
14.  Core Muscle Activity during TRX Suspension Exercises with and without Kinesiology Taping in Adults with Chronic Low Back Pain: Implications for Rehabilitation 
This study aimed to examine the effects of kinesiology taping (KT) and different TRX suspension workouts on the amplitude of electromyographic (EMG) activity in the core muscles among people with chronic low back pain (LBP). Each participant (total n = 21) was exposed to two KT conditions: no taping and taping, while performing four TRX suspension exercises: (1) hamstring curl, (2) hip abduction in plank, (3) chest press, and (4) 45-degree row. Right transversus abdominis/internal oblique (TrAIO), rectus abdominis (RA), external oblique (EO), and superficial lumbar multifidus (LMF) activity was recorded with surface EMG and expressed as a percentage of the EMG amplitude recorded during a maximal voluntary isometric contraction of the respective muscles. Hip abduction in plank increased TrAIO, RA, and LMF EMG amplitude compared with other TRX positions (P < 0.008). Only the hamstring curl was effective in inducing a high EMG amplitude of LMF (P < 0.001). No significant difference in EMG magnitude was found between the taping and no taping conditions overall (P > 0.05). Hip abduction in plank most effectively activated abdominal muscles, whereas the hamstring curl most effectively activated the paraspinal muscles. Applying KT conferred no immediate benefits in improving the core muscle activation during TRX training in adults with chronic LBP.
PMCID: PMC4491390  PMID: 26185520
15.  Reliability of ultrasound in combination with surface electromyogram for evaluating the activity of abdominal muscles in individuals with and without low back pain 
This study investigated the reliability of ultrasound in combination with surface electromyogram (EMG) for evaluating the activity of the abdominal muscles in individuals with and without low back pain during the abdominal drawing-in maneuver (ADIM). The study recruited ten individuals with or without low back pain, respectively. While the participants were performing the ADIM, the activities of the transversus abdominis (TrA) and the internal oblique (IO) were measured using ultra-sound, while the activities of the external oblique (EO) and the rectus abdominis (RA) were measured using surface EMG. Intra-class correlation coefficients (ICC) were used to verify the inter-rater reliability of ultrasound in combination with surface EMG at rest and during the ADIM, and Bland-Altman plots were used to verify intra-rater reliability. The inter-rater reliability for the two groups at rest and during the ADIM was excellent (ICC2,1 = 0.77–0.95). In the Bland-Altman plots, the mean differences and 95% limits of agreement in the abdominal muscles of the two groups at rest were −0.03∼0.03 mm (−0.66 to 0.60 mm) and −0.12∼ −0.05 (−0.58 to 0.48% MVIC), respectively. The mean differences and 95% limits of agreement in the abdominal muscles of the two groups during the ADIM were −0.04∼0.02 mm (−0.73 to 0.65 mm) and −0.19∼0.05% MVIC (−1.24 to 1.34% MVIC), respectively. The ultrasound in combination with surface EMG showed excellent inter-rater and intra-rater reliability at rest and during the ADIM.
PMCID: PMC4157930  PMID: 25210698
Ultrasound; Surface EMG; Reliability; Abdominal drawing-in maneuver
16.  Neuromuscular Activity of Upper and Lower Limbs during two Backstroke Swimming Start Variants 
A proficient start is decisive in sprint competitive swimming events and requires swimmers’ to exert maximal forces in a short period to complete the task successfully. The aim of this study was to compare the electromyographic (EMG) activity in-between the backstroke start with feet positioned parallel and partially emerged performed with the hands on the highest horizontal and on the vertical handgrip at hands-off, take-off, flight and entry start phases. EMG comparisons between starting variants were supported by upper and lower limb joint angles at starting position and 15 m start time data. Following a four-week start training to familiarize participants with each start variant, 10 male competitive backstroke swimmers performed randomly six 15 m maximal trials, being three of each start variant. Surface EMG of Biceps Brachii, Triceps Brachii, Rectus Femoris, Biceps Femoris, Gastrocnemius Medialis and Tibialis Anterior was recorded and processed using the time integral EMG (iEMG). Eight video cameras (four surface and four underwater) were used to determine backstroke start phases and joint angles at starting position. EMG, joint angles and temporal parameters have not evidenced changes due to the different handgrips. Nevertheless, clear differences were observed in both variants for upper and lower limb muscles activity among starting phases (e.g. Biceps Brachii at take-off vs. flight phase, 15.17% ± 2.76% and 22.38% ± 4.25%; 14.24% ± 7.11% and 25.90% ± 8.65%, for variant with hands horizontal and vertically positioned, respectively). It was concluded that different handgrips did not affect EMG, kinematics and temporal profile in backstroke start. Despite coaches might plan similar strength training for both start variants, further attention should be given on the selection of proper exercises to maximize the contribution of relevant muscles at different starting phases.
Key pointsAn effective swim start component (from the starting signal until the swimmers’ vertex reaches the 15 m mark) is decisive in short distance events.In 2008, FINA approved the Omega OSB11 starting block (Swiss Timing Ltd., Switzerland) with two horizontal and one vertical backstroke start handgrip and currently swimmers can adopt different starting variants.The start performance is related to the exertion of maximal force in the shortest time, as other high-velocity movements; thus, the study of the current variants in-between them from a neuromuscular standpoint is indispensable for training support.The use of different handgrips did not affect upper and lower limb electromyographic activity; angular kinematics and overall 15 m backstroke start profile.Independent of the start variant selected, the role played by each upper and lower limb muscles at different starting phases should be considered in specific resistance training program to optimize backstroke start performance.
PMCID: PMC4541124  PMID: 26336346
Biomechanics; surface electromyography; starting technique; backstroke events
17.  Trunk muscle activity in healthy subjects during bridging stabilization exercises 
Trunk bridging exercises are often used as therapeutic exercises for lumbopelvic stabilization. These exercises focus on the retraining of muscle coordination patterns in which optimal ratios between local segmental stabilizing and global torque producing muscle activity are assumed to be essential. However, a description of such ratios is lacking. The purpose of this study was to investigate both relative (as a percentage of maximal voluntary isometric contraction) muscle activity levels and ratios of local to global muscle activity, during bridging stabilization exercises.
Thirty healthy university students (15 men, 15 women) with a mean age of 19.6 year volunteered to perform 3 bridging exercises (single bridging, ball bridge and unilateral bridging). The surface electromyographic activity of different trunk muscles was evaluated on both sides.
During all bridging exercises, the ratio of the internal oblique to the rectus abdominis was very high due to minimal relative activity of the rectus abdominis. In general, the ratio of the internal/external abdominal oblique activity was about 1. However, during the unilateral bridging exercise, the ipsilateral internal/external abdominal oblique activity ratio was 2.79 as a consequence of the significant higher relative activity of the internal oblique compared to the external oblique. The relative muscle activity and the ratios of the back muscles demonstrated similar activity levels for all back muscles, resulting in ratios about 1.
Both the minimal relative activity of the rectus abdominis and the high internal oblique to the rectus abdominis activity ratio reported in the present study are in accordance with results of other trunk stabilization exercises. The relative muscle activity and the ratio of the abdominal obliques seem to alter depending on the task and the presumable need for stability. The findings concerning the relative muscle activity and the ratios of the back muscles support the assumption that during these bridging exercises, all back muscles contribute in a similar way to control spine positions and movements in a healthy population.
PMCID: PMC1599724  PMID: 16987410
The RAZOR curl has been introduced as a hamstring exercise. However, modifications to the exercise have been developed which are proposed to utilize some of the muscles of the lumbo-pelvic-hip complex. Thus, it was the purpose of this study to quantitatively examine the modified RAZOR curl using surface electromyography (sEMG), as an exercise that may recruit the trunk muscles of the lumbo-pelvic-hip complex.
Twenty-eight active male and female graduate students (24.2±1.3 years; 174.8±9.9 cm; 74.9±14.9 kg), consented to participate. Dependent variables were muscle activation of trunk musculature (dominant side gluteus medius, gluteus maximus, multifidus, longissimus, lower rectus abdominis, upper rectus abdominis, external obliques) reported as percent of maximum voluntary isometric contraction (%MVIC) during the exercise while the independent variable was the muscle selected.
The multifidus and longissimus demonstrated moderately strong activation (35-50%MVIC) while the upper rectus abdominis demonstrated strong activation (20-35%MVIC) and the gluteus medius, gluteus maximus, lower rectus abdominis, and external obliques had minimal activation.
These findings allow the practitioner to utilize an exercise that provides a functional training stimulus that activates not only the hamstrings but also some musculature of the trunk muscles of the lumbopelvic-hip complex at strong to moderately strong levels.
Level of Evidence:
PMCID: PMC3273882  PMID: 22319680
core control; core stabilization; functional exercises; sEMG
19.  A study of passive weight-bearing lower limb exercise effects on local muscles and whole body oxidative metabolism: a comparison with simulated horse riding, bicycle, and walking exercise 
We have developed an exercise machine prototype for increasing exercise intensity by means of passively exercising lower limb muscles. The purpose of the present study was to compare the passive exercise intensity of our newly-developed machine with the intensities of different types of exercises. We also attempted to measure muscle activity to study how these forms of exercise affected individual parts of the body.
Subjects were 14 healthy men with the following demographics: age 30 years, height 171.5 cm, weight 68.3 kg. They performed 4 types of exercise: Passive weight-bearing lower limb exercise (PWLLE), Simulated horse riding exercise (SHRE), Bicycle exercise, and Walking exercise, as described below at an interval of one week or longer. Oxygen uptake, blood pressure, heart rate, and electromyogram (EMG) were measured or recorded during exercise. At rest prior to exercise and immediately after the end of each exercise intensity, the oxygenated hemoglobin levels of the lower limb muscles were measured by near-infrared spectroscopy to calculate the rate of decline. This rate of decline was obtained immediately after exercise as well as at rest to calculate oxygen consumption of the lower limb muscles as expressed as a ratio of a post-exercise rate of decline to a resting one.
The heart rate and oxygen uptake observed in PWLLE during maximal intensity were comparable to that of a 20-watt bicycle exercise or 2 km/hr walking exercise. Maximal intensity PWLLE was found to provoke muscle activity comparable to an 80-watt bicycle or 6 km/hr walking exercise. As was the case with the EMG results, during maximal intensity PWLLE, the rectus femoris muscle consumed oxygen in amounts identical to that of an 80-watt bicycle or a 6 km/hr walking exercise.
Passive weight-bearing lower limb exercise using our trial machine could provide approximately 3 MET of exercise and the thigh exhibited muscle activity equivalent to that of 80-watt bicycle or 6 km/hr walking exercise. Namely, given the same oxygen uptake, PWLLE exceeded bicycle or walking exercise in muscle activity, thus PWLLE is believed to strengthen muscle power while reducing the load imposed on the cardiopulmonary system.
PMCID: PMC2780382  PMID: 19900292
20.  The Effect of Trunk Stabilization Exercises with a Swiss Ball on Core Muscle Activation in the Elderly 
Journal of Physical Therapy Science  2014;26(9):1473-1474.
[Purpose] The purpose of this study was to investigate the effects of trunk stabilization exercise on the muscle EMG activations related to core stability. [Subjects and Methods] Fifteen elderly people in a geriatric hospital performed trunk stabilization exercises with a Swiss ball for 20 minutes five times per week for 8 weeks. Trunk muscle activations were measured using electromyography before and after the intervention. [Results] After the intervention, the muscle activations of the rectus abdominis, erector spinae, lateral low-back (quadratus lumborum and external oblique), and gluteus medius muscles increased significantly. [Conclusion] The trunk stabilization exercise with a Swiss ball significantly increased the muscle activities of the elderly.
PMCID: PMC4175260  PMID: 25276039
Elderly; Electromyography; Core stability
21.  Cocontraction of Ankle Dorsiflexors and Transversus Abdominis Function in Patients With Low Back Pain 
Journal of Athletic Training  2012;47(4):379-389.
The abdominal draw-in maneuver (ADIM) with cocontraction has been shown to be a more effective method of activating the transversus abdominis (TrA) in healthy adults than the ADIM alone. Whether such an augmented core stabilization exercise is effective in managing low back pain (LBP) remains uncertain.
To determine the effect of 2 weeks of ADIM and cocontraction training on abdominal muscle thickness and activation timing and to monitor pain and function in patients with LBP.
Case-control study.
Local orthopaedic clinic and research laboratory.
Patients or Other Participants
Twenty patients with mechanical LBP (age = 27.20 ± 6.46 years, height = 166.25 ± 8.70 cm, mass = 58.10 ± 11.81 kg) and 20 healthy, age-matched people (age = 24.25 ± 1.59 years, height = 168.00 ± 8.89 cm, mass = 60.65 ± 11.99 kg) volunteered for the study.
Both the LBP and control groups received ten 30-minute sessions of ADIM and cocontraction training of the tibialis anterior (TA) and rectus femoris (RF) muscles over a 2-week period.
Main Outcome Measure(s)
A separate, mixed-model analysis of variance was computed for the thicknesses of the TrA, internal oblique (IO), and external oblique muscles. The differences in mean and peak electromyographic (EMG) amplitudes, onset time, and latency were compared between the groups. The visual analog pain scale, Pain Disability Index, and LBP rating scale were used to assess pain in the LBP group before and after the intervention.
We found an interaction between the LBP and control groups and a main effect from pretest to posttest for only TrA muscle thickness change (F1,38 = 6.57, P = .01). Reductions in all pain measures were observed after training (P < .05). Group differences in peak and mean EMG amplitudes and onset time values for TrA/IO and TA were achieved (P < .05). The RF peak (t38 = −3.12, P = .003) and mean (t38 = −4.12, P = .001) EMG amplitudes were different, but no group difference was observed in RF onset time (t38 = 1.63, P = .11) or the cocontracted TrA/IO peak (t38 = −1.90, P = .07) and mean (t38 = −1.81, P = .08). The test-retest reliability for the muscle thickness measure revealed excellent correlations (intraclass correlation coefficient range, 0.95–0.99).
We are the first to demonstrate that a cocontraction of the ankle dorsiflexors with ADIM training might result in a thickness change in the TrA muscle and associated pain management in patients with chronic LBP.
PMCID: PMC3396297  PMID: 22889653
core stability; electromyographic sequencing; ultrasound imaging
22.  The Impact of Ergometer Design on Hip and Trunk Muscle Activity Patterns in Elite Rowers: An Electromyographic Assessment 
This study used surface electromyography (sEMG) to examine whether there were differences in hip and trunk muscle activation during the rowing cycle on two of the most widely used air braked ergometers: the Concept 2C and the Rowperfect. sEMG methods were used to record the muscle activity patterns from the right: m. Erector spinae (ES), m. Rectus Abdominus (RA), m. Rectus Femoris (RF) and m. Biceps Femoris (BF) for their contributions as agonist-antagonist pairs underlying hip and trunk extension/flexion. The sEMG activity patterns of these muscles were examined in six young male elite rowers completing a 2 minute set at a moderate training intensity (23 stroke·min-1 and 1:47.500 m-1 split time, 300W). The rowers closely maintained the required target pace through visual inspection of the standard LCD display of each ergometer. The measurements of duration of each rowing cycle and onset of each stroke during the test were recorded simultaneously with the sEMG activity through the additional instrumentation of a foot-pressure switch and handle accelerometry. There were no significant differences between the two ergometer designs in group means for: work rate (i.e., rowing speed and stroke rate), metabolic load as measured by mean heart rate, rowing cycle duration, or timing of the stroke in the cycle. 2-D motion analysis of hip and knee motion for the rowing cycle from the video footage taken during the test also revealed no significant differences in the joint range of motion between the ergometers. Ensemble average sEMG activity profiles based on 30+ strokes were obtained for each participant and normalised per 10% intervals of the cycle duration as well as for peak mean sEMG amplitude for each muscle. A repeated measures ANOVA on the sEMG activity per 10% interval for the four muscles contributing to hip and trunk motion during the rowing cycle revealed no significant differences between the Concept 2C and Rowperfect (F = 0.070, df = 1,5, p = 0.802). The outcome of this study suggests that the two different ergometer designs are equally useful for dry land training.
Key PointsThe effects of endurance training on HR recovery after exercise and cardiac ANS modulation were investigated in female marathon runners by comparing with untrained controls.Time and frequency domain analysis of HRV was used to investigate cardiac ANS modulation.As compared with untrained controls, the female marathon runners showed faster HR recovery after exercise, which should result from their higher levels of HRV, higher aerobic capacity and exaggerated blood pressure response to exercise.
PMCID: PMC3880080  PMID: 24431957
Flexion; extension; land-based training
23.  Comparison of Abdominal Muscle Activity During a Single-Legged Hold in the Hook-Lying Position on the Floor and on a Round Foam Roll 
Journal of Athletic Training  2011;46(4):403-408.
To improve trunk stability or trunk muscle strength, many athletic trainers and physiotherapists use various types of unstable equipment for training. The round foam roll is one of those unstable pieces of equipment and may be useful for improving trunk stability.
To assess the effect of the supporting surface (floor versus round foam roll) on the activity of abdominal muscles during a single-legged hold exercise performed in the hook-lying position on the floor and on a round foam roll.
Crossover study.
University research laboratory.
Patients or Other Participants:
Nineteen healthy volunteers (11 men, 8 women) from a university population.
Interventions :
The participants were instructed to perform a single-legged hold exercise while in the hook-lying position on the floor (stable surface) and on a round foam roll (unstable surface).
Main Outcome Measure(s):
Surface electromyography (EMG) signals were recorded from the bilateral rectus abdominis, internal oblique, and external oblique muscles. Dependent variables were examined with a paired t test.
The EMG activities in all abdominal muscles were greater during the single-legged hold exercise performed on the round foam roll than on the stable surface.
The single-legged hold exercise in the hook-lying position on an unstable supporting surface induced greater abdominal muscle EMG amplitude than the same exercise performed on a stable supporting surface. These results suggest that performing the single-legged hold exercise while in the hook-lying position on a round foam roll is useful for activating the abdominal muscles.
PMCID: PMC3419152  PMID: 21944072
trunk stability; low back pain; electromyography; injury prevention
Ergometers are used during rehabilitation and fitness to restore range of motion, muscular strength, and cardiovascular fitness. The primary difference between upright and recumbent ergometers is that the seat and crank spindle are aligned nearly vertically on upright bicycles and nearly horizontally on recumbent ergometers. In addition, recumbent ergometers are characterized by large seats with backrests to provide support for the upper body and are low to the ground, permitting easier access for wheelchair users and individuals with mobility impairments. Despite the great utility of the recumbent bike, it has not been studied with regard to energy costs or muscular output. This is the first study to investigate the differences between two commercial ergometers by analyzing of lower limb EMG in participants who are not habitual cyclers.
Ten non‐cyclist males with no history of musculoskeletal lower limb injury pedaled on standard recumbent and upright ergometers. EMG data were recorded from the volunteers’ lower limb muscles (rectus femoris, semitendinosus, tibialis anterior, and medial gastrocnemius muscles). EMG signals were normalized to the highest EMG signals recorded for the maximum voluntary isometric contractions (MVIC). The peak normalized EMG value of the studied muscles over the average of the 10 pedal cycles was analyzed.
The differences in average peak muscle activity were not statistically significant for any of the four muscles tested. Pedaling a recumbent ergometer resulted in greater activity in two (semitendinosus and tibialis anterior) of the four muscles studied. Only the rectus femoris muscle demonstrated greater activity during upright pedaling.
There were no differences in the EMG activity of the muscles studied during pedaling on a standard recumbent and an upright stationary exercise ergometer at moderate workload. This increased understanding of muscle activity during pedaling may be useful in the development of new exercise protocols and therapeutic approaches.
Level of Evidence:
PMCID: PMC3924611  PMID: 24567858
Bicycling; electromyography; ergometry; lower extremity; pedaling
25.  Effects of performing an abdominal hollowing exercise on trunk muscle activity during curl-up exercise on an unstable surface 
[Purpose] The purpose of this study was to investigate the effects of the abdominal hollowing exercise on trunk muscle activity during the curl-up exercise on an unstable surface by measuring electromyography (EMG) activity. [Subjects] Fourteen young healthy adults (nine male, five female) voluntarily participated in this study. [Methods] Each subject was asked to perform a curl-up exercise on two supporting surfaces (stable and unstable surfaces) combined with the abdominal hollowing exercise on an unstable surface. The muscle activities of the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) were measured using surface EMG during performance of the curl-up exercise. [Results] The EMG activity of the RA and EO was significantly higher on an unstable surface than on a stable surface during the curl-up exercise. The EMG activities of the TrA and IO were greater in combination with the abdominal hollowing exercise on an unstable surface than during the curl-up exercise on both a stable and unstable surface. [Conclusion] These findings suggest that the local trunk muscle activity during the curl-up exercise is more strongly affected by combination with the abdominal hollowing exercise than by performance on an unstable supporting surface.
PMCID: PMC4339172  PMID: 25729202
Abdominal hollowing exercise; Curl-up exercise; Unstable surface

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