Increased deltoid and abdominal muscle activity during Swiss ball bench press

The swiss is widely used in the recreational training environment as a supplement to conventional resistance training. One such application is to use the swiss ball as a bench support for bench press exercise. There is no evidence to indicate that the use of a swiss ball is beneficial for resistance training exercise. This study investigated muscle activity using surface electromyography of upper-body and abdominal muscles during the concentric and eccentric phases of the bench press on and off a swiss ball. Volunteers for this study were 14 resistance-trained subjects who performed isolated concentric and eccentric bench press repetitions using the 2 test surfaces with a 2-second cadence at a load equivalent to 60% maximum force output. The average root mean square of the muscle activity was calculated for each movement, and perceived exertion during the tasks was collected using a Borg Scale. The results of the study showed that deltoid and abdominal muscle activity was increased for repetitions performed using the swiss ball. Increased deltoid muscle activity supports previous findings for increased activity when greater instability is introduced to the bench press movement. Abdominal muscle activity increases were not hypothesized, but this finding provides scientific evidence for anecdotal reasoning behind swiss ball use as a potential core stability training device.     

Replacing a Swiss ball for an exercise bench causes variable changes in trunk muscle activity during upper limb strength exercises

Background

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.

Methods

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.

Conclusion

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.

     

Trunk muscle activity during stability ball and free weight exercises

The purpose of this investigation was to compare trunk muscle activity during stability ball and free weight exercises. Nine resistance-trained men participated in one testing session in which squats (SQ) and deadlifts (DL) were completed with loads of approximately 50, 70, 90, and 100% of one-repetition maximum (1RM). Isometric contractions during 3 stability ball exercises (quadruped (QP), pelvic thrust (PT), ball back extension (BE)) were also completed. During all exercises, average integrated electromyography (IEMG) from the rectus abdominus (RA), external oblique (EO), longissimus (L1) and multifidus (L5) was collected and analyzed. Results demonstrate that when expressed relative to 100% DL 1RM, muscle activity was 19.5 +/- 14.8% for L1 and 30.2 +/- 19.3% for L5 during QP, 31.4 +/- 13.4% for L1 and 37.6 +/- 12.4% for L5 during PT, and 44.2 +/- 22.8% for L1 and 45.5 +/- 21.6% for L5 during BE. IEMG of L1 during SQ and DL at 90 and 100% 1RM, and relative muscle activity of L5 during SQ and DL at 100% 1RM was significantly greater (P < or = 0.05) than in the stability ball exercises. Furthermore, relative muscle activity of L1 during DL at 50 and 70% 1RM was significantly greater than in QP and PT. No significant differences were observed in RA and EO during any of the exercises. In conclusion, activity of the trunk muscles during SQs and DLs is greater or equal to that which is produced during the stability ball exercises. It appears that stability ball exercises may not provide a sufficient stimulus for increasing muscular strength or hypertrophy; consequently, the role of stability ball exercises in strength and conditioning programs is questioned. SQs and DLs are recommended for increasing strength and hypertrophy of the back extensors.     

Validation of a portable EMG device to assess muscle activity during free-living situations

Portable amplifiers that record electromyograms (EMGs) for longer than four hours are commonly priced over $20,000 USD. This cost, and the technical challenges associated with recording EMGs during free-living situations, typically restrict EMG use to laboratory settings. A low-cost system (μEMG; OT Bioelecttronica, 100€), using specialized concentric bipolar electrodes, has been developed specifically for free-living situations. The purpose of this study was to validate the μEMG system by comparing EMGs from μEMG with a laboratory-based alternative (Telemyo 900; Noraxon USA, Inc.). Surface EMGs from biceps brachii (BB) and tibialis anterior (TA) of ten subjects were recorded simultaneously with both systems as subjects performed maximal voluntary contractions (MVCs), submaximal contractions at 25%, 50%, and 75% MVC, seven simulated activities of daily living (ADLs), and >60 min of simulated free-living inside the laboratory. In general, EMG parameters (e.g., average full-wave rectified EMG amplitude) derived from both systems were not significantly different for all outcome variables, except there were small differences across systems in baseline noise and absolute EMG amplitudes during MVCs. These results suggest that μEMG is a valid approach to the long-term recording of EMG.     

Surface EMG recorded by branched electrodes during sustained muscle activity.

The purpose of the present investigation is to use surface interference EMG recorded by branched electrodes for assessment of muscle fatigue during sustained voluntary isometric contractions at different levels. Level-trigger averaging and turn/amplitude analysis have been applied. The conduction velocity (CV) of excitation was calculated from the time shift of the negative peaks of the averaged potentials (AvPs) derived from the EMG recorded by two electrodes placed along the muscle fibers. The recruitment of new motor units affects the negative amplitude (NA) of AvPs, the number of turns per second and the mean amplitude of turns in a different way depending on the level of sustained contractions. In contrast, the CV declined at all levels of sustained contractions and was the most appropriate parameter for the muscle fatigue assessment. There was a good correlation between CV decrease and torque reduction during sustained maximal efforts. The level-trigger averaging technique of the interference EMG recorded by surface branched electrodes is easy and non-invasive, thus being very convenient for routine application.     

Shoulder muscle activity during pushing, pulling, elevation and overhead throw.

PURPOSE: The aim of this study was to compare the muscle activity of recreational athletes and professional javelin throwers during pull, push, and elevation of upper extremities and during overhead throw. SCOPE: Nine professional javelin throwers and 16 recreational athletes without shoulder problems were studied. Signals were recorded by surface EMG from eight different muscles. The results obtained from the muscles of upper extremities of throwers were compared with those of recreational athletes. CONCLUSION: The different neuromuscular control of professional throwers caused a more profitable muscle activity. Differences during the overhead throw were more significant. The deltoid muscle and rotator cuff of recreational athletes showed stronger activity than those of throwers during pull, push and elevation. The deltoid muscle and the rotator cuff of professional throwers showed stronger activity during overhead throw. Studying the detailed characteristics of muscle activity pattern (differences in length of activity periods, MVC% of muscles and time broadness among peak muscle activities in percent of total time of a movement cycle) may provide a basis for better understanding improved performance and help in planning proper rehabilitation protocol.     

Patterns of EMG activity of rat plantaris muscle during swimming and other locomotor activities

The purpose of the study was to examine the patterns of electromyographic (EMG) activity of the rat plantaris during loaded swimming in comparison with other locomotor activities. Five female Sprague-Dawley rats were implanted with chronic bipolar electrodes in the plantaris muscle of the left hindlimb under pentobarbital anesthesia. Characteristics of EMG bursts recorded while the conscious rat was performing treadmill walking (0.24 m/s) were stable and reproducible 10-14 days postsurgery. Following this stabilization period, records of EMG activity were obtained during walking, loaded swimming (6.5 g attached to tail), and several other locomotor tasks. Compared to walking, EMG bursts during loaded swimming were significantly higher (67%) in maximum amplitude, one-third as long in duration, and occurred at a greater rate (4.4 vs. 1.7 bursts/s, P less than 0.05). Swimming bursts were of higher amplitudes than those of all other activities examined and reached 65% of the EMG amplitude recorded following stimulation of the sciatic nerve with supramaximal voltage. The addition of a mass to the animal's tail during swimming did not increase the EMG burst amplitudes but resulted in a higher frequency of bursts. Compared with treadmill walking, loaded swimming elicited burst of high variability in amplitude. Swimming in the rat involves rapid, extensive activation of plantaris, thus providing an exercise model to study the adaptability of the neuromuscular system to prolonged activity of this type.     

Shoulder and elbow muscle activity during fully supported trajectory tracking in people who have had a stroke

An inability to perform tasks involving reaching is a common problem for stroke patients. This paper provides an insight into mechanisms associated with recovery of upper limb function by examining how stroke participants’ upper limb muscle activation patterns differ from those of neurologically intact participants, and how they change in response to an intervention.In this study, five chronic stroke participants undertook nine tracking tasks in which trajectory (orientation and length), speed and resistance to movement were varied. During these tasks, EMG signals were recorded from triceps, biceps, anterior deltoid, upper, middle and lower trapezius and pectoralis major. Data collection was performed in sessions both before, and after, an intervention in which participants performed a similar range of tracking tasks with the addition of responsive electrical stimulation applied to their triceps muscle. The intervention consisted of eighteen one hour treatment sessions, with two participants attending an additional seven sessions. During all sessions, each participant’s arm was supported by a hinged arm-holder which constrained their hand to move in a two dimensional plane.Analysis of the pre intervention EMG data showed that timing and amplitude of peak EMG activity for all stroke participants differed from neurologically intact participants. Analysis of post intervention EMG data revealed that statistically significant changes in these quantities had occurred towards those of neurologically intact participants.     

Shoulder and elbow muscle activity during fully supported trajectory tracking in neurologically intact older people

An inability to perform tasks involving reaching is a common problem for stroke patients. Knowledge of normal muscle activation patterns during these tasks is essential to the identification of abnormal patterns in post-stroke hemiplegia. Findings will provide insight into changes in muscle activation patterns associated with recovery of upper limb function.In this study with neurologically intact participants the co-ordination of shoulder and elbow muscle activity during two dimensional reaching tasks is explored. Eight participants undertook nine tracking tasks in which trajectory (orientation and length), duration, speed and resistance to movement were varied. The participants’ forearm was supported using a hinged arm-holder, which constrained their hand to move in a two dimensional plane. EMG signals were recorded from triceps, biceps, anterior deltoid, upper, middle and lower trapezius and pectoralis major.A wide variation in muscle activation patterns, in terms of timing and amplitude, was observed between participants performing the same task. EMG amplitude increased significantly with length, duration and resistance of the task for all muscles except anterior deltoid. Co-activation between biceps and triceps was significantly dependent on both task and trajectory orientation. Activation pattern of pectoralis major was dependent on trajectory. Neither trajectory orientation nor task condition affected the activation pattern of anterior deltoid. Normal ranges of timing of muscle activity during the tasks were identified.     

Shoulder muscle recruitment patterns during a kayak stroke performed on a paddling ergometer.

Precise muscle co-ordination is required to maintain normal shoulder function and alterations in synchrony between shoulder muscles can result in loss of full range of movement and pain. Although shoulder pain in kayakers is high with 53% of elite international paddlers reporting shoulder injuries, little information is available regarding the pattern of shoulder muscle recruitment during paddling. The aim of this study was to investigate the normal recruitment pattern of shoulder muscles during the kayak stroke. Nine recreational paddlers without shoulder pain were examined. EMG data from eight shoulder muscles of the dominant arm were collected simultaneously with video data during simulated paddling on an ergometer. EMG data was normalized to time and peak amplitude. Intersubject consistency was evaluated using Pearson correlation analysis. The results of this study indicated a fair to high correlation in at least one phase of the kayak stroke in five of the muscles examined: upper trapezius, supraspinatus, latissimus dorsi, serratus anterior and rhomboid major. This normative data will enable comparisons with the shoulder muscle recruitment patterns in kayakers with shoulder pain in order to determine the role of altered motor control in the painful kayaking shoulder.     

Masseter EMG activity during sleep and sleep bruxism

The masseter muscle is involved in the complex and coordinated oromotor behaviors such as mastication during wakefulness. The masseter electromyographic (EMG) activity decreases but does not disappear completely during sleep: the EMG activity is generally of low level and inhomogeneous for the duration, amplitude and intervals. The decreased excitability of the masseter motoneurons can be determined by neural substrates for NREM and REM sleep. The masseter EMG activity is increased in association with the level of arousal fluctuations within either sleep state. In addition, there are some motor events such as REM twitches, swallowing and rhythmic masticatory muscle activity (RMMA), whose generation might involve the additional activation of specific neural circuits. Sleep bruxism (SB) is characterized by exaggerated occurrence of RMMA. In SB, the rhythmic activation of the masseter muscle can reflect the rhythmic motor inputs to motoneurons through, at least in part, common neural circuits for generating masticatory rhythm under the facilitatory influences of transient arousals. However, it remains elusive as to which neural circuits determine the genesis of sleep bruxism. Based on the available knowledge on the masseter EMG activity during sleep, this review presents that the variety of the masseter EMG phenotypes during sleep can result from the combinations of the quantitative, spatial and temporal neural factors eventually sending net facilitatory inputs to trigeminal motoneurons under sleep regulatory systems.     

Relationship between muscle length and moment arm on EMG activity of human triceps surae muscle.

PURPOSE: The purpose of this experiment was to evaluate the effects of both muscle length and moment arm (MA) on the electromyographic (EMG) and force output of the triceps surae (TS) muscle. RELEVANCE: It is well recognized that changes in muscle length affect both the muscle's force generating capacity as well as its twitch speed. This relationship is well established in animal preparations. Contrary to animal experiments where length can be directly manipulated in isolated muscles, human experiments require that all muscle length changes be secondary to changes in a joint angle. Such experimental manipulations therefore produce changes in not only muscle length, but also in the muscle's MA. The relative effect of muscle length and MA changes on muscle EMG has not been determined in previous experiments. METHODS: This study was executed in two phases. First, using fresh human cadaver lower limbs, data were gathered describing the relationship between knee and ankle angle changes for maintenance of a constant TS muscle length, while its MA at the ankle joint has been changed. In the second phase of the study, results obtained from phase one were applied to 10 healthy adult human subjects to measure the EMG (surface and fine wire) activity of TS at three different conditions: when both length and MA were shortened, when muscle length was decreased given a constant MA and when MA was shortened given a constant muscle length. RESULTS: A significant increase in muscle activity was found as both the length and MA of TS muscle were shortened. A similar pattern of increased muscle activity was observed when the MA was shortened given a constant muscle length. No significant change in TS activity was found when muscle length was shortened, given a constant MA at the ankle joint. CONCLUSIONS: The findings of this study indicate that changes in the Achilles tendon MA predominate over the muscle length variations in determining the level of TS activity when generating plantar flexion torque.     

EMG spectral indices and muscle power fatigue during dynamic contractions

The purpose of this study was to examine acute exercise-induced changes on muscle power output and surface electromyography (sEMG) parameters (amplitude and spectral indices of muscle fatigue) during a dynamic fatiguing protocol. Fifteen trained subjects performed five sets consisting of 10 leg presses (10RM), with 2 min rest between sets. Surface electromyography was recorded from vastus medialis (VM) and lateralis (VL) and biceps femoris (BF) muscles. A number of EMG-based parameters were compared for estimation accuracy and sensitivity to detect peripheral muscle fatigue. These were: Mean Average Voltage, median spectral frequency, Dimitrov spectral index of muscle fatigue (FI_nsm5), as well as other parameters obtained from a time–frequency analysis (Choi–Williams distributions) such as mean and variance of the instantaneous frequency and frequency variance. The log FI_nsm5 as a single parameter predictor accounted for 37% of the performance variance of changes in muscle power and the log FI_nsm5 and MFM as a two factor combination predictor accounted for 44%. Peripheral impairments assessed by sEMG spectral index FI_nsm5 may be a relevant factor involved in the loss of power output after dynamic high-loading fatiguing task.     

Individual muscle contributions to push and recovery subtasks during wheelchair propulsion

Manual wheelchair propulsion places considerable physical demand on the upper extremity and is one of the primary activities associated with the high prevalence of upper extremity overuse injuries and pain among wheelchair users. As a result, recent effort has focused on determining how various propulsion techniques influence upper extremity demand during wheelchair propulsion. However, an important prerequisite for identifying the relationships between propulsion techniques and upper extremity demand is to understand how individual muscles contribute to the mechanical energetics of wheelchair propulsion. The purpose of this study was to use a forward dynamics simulation of wheelchair propulsion to quantify how individual muscles deliver, absorb and/or transfer mechanical power during propulsion. The analysis showed that muscles contribute to either push (i.e., deliver mechanical power to the handrim) or recovery (i.e., reposition the arm) subtasks, with the shoulder flexors being the primary contributors to the push and the shoulder extensors being the primary contributors to the recovery. In addition, significant activity from the shoulder muscles was required during the transition between push and recovery, which resulted in increased co-contraction and upper extremity demand. Thus, strengthening the shoulder flexors and promoting propulsion techniques that improve transition mechanics have much potential to reduce upper extremity demand and improve rehabilitation outcomes.     

Effect of stimulation of cold receptors with menthol on EMG activity of quadriceps muscle during low load contraction

Purpose: Facilitatory and inhibitory responses of spinal motor neurons are influenced by somatosensory input from the skin. The purpose of this study, employing electromyography, was to examine the neuromuscular changes that occur with menthol applied to the skin over the quadriceps muscle.

Methods: Forty-two healthy volunteers performed isometric knee extensions at 35% maximum voluntary contraction (MVC) in three groups (Adult Placebo, Adult Menthol, Older Adult Menthol). Stimulation used was application of 5% menthol gel to the skin. Surface electromyography (sEMG) from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) was recorded using miniature pair electrodes.

Results: Root mean square electromyography (rmsEMG) in VL and VM significantly increased with menthol stimulation both in Adult and Older Adult, but no significant difference was observed between Adult Menthol and Older Adult Menthol. There was a significant decrease in mean power frequency (MPF) in VM with menthol stimulation in Older Adult, but no significant changes were observed in Adult Menthol.

Conclusion: Neuromuscular modulation was observed with the application of menthol gel at low loads in the present study. These findings could lead to a new method of muscular training that targets the recruitment of fast type muscle safe for older adults.     

Respiratory muscle activity measured with a noninvasive EMG technique: technical aspects and reproducibility.

A new method is being developed to investigate airway obstruction in young children by means of noninvasive electromyography (EMG) of diaphragmatic and intercostal muscles. The purpose of this study was to evaluate the reproducibility of the EMG measurements. Eleven adults, 39 school children (20 healthy, 19 asthmatic), and 16 preschool children were studied during tidal breathing on separate occasions: two for adults with a time interval of 3 wk and three for children with time intervals of 1 and 24 h. Single electrodes were placed on the second intercostal space left and right of the sternum and at the height of the frontal and the dorsal diaphragm. Bipolar electrode pairs were placed on the rectus abdominis muscle. A newly designed digital physiological amplifier without any analog filtering was used to measure the EMG signals. Except for the average dorsal diaphragm EMG derivation in healthy school children on the second occasion, a significant correlation between the mean peak-to-peak inspiratory activity of average diaphragmatic and intercostal EMG was found in the different age groups on the different measurement occasions (P < 0.05). To assess the repeatability, we described the agreement between the repeated measurements within the same subjects. No significant differences were found between the measurements on the separate occasions. Our observations indicate that the EMG signals derived from the diaphragm and intercostal muscles are, in different age groups with and without asthma, reproducible during tidal breathing.     

Multiphasic variations in sunshine and thyroid activity during a year

Fifty years of percentage possible sunshine data from US Weather Bureau stations in the midwestern states around Iowa were analyzed with a periodic regression technique employing the Fourier series. As in an earlier study of sunshine conditions in the southeastern US, multiphasic sunshine rhythms with a frequency of three or four cycles per year were found. Using an¹²⁵I tracer technique, thyroid activity in cats was measured for a year, and, as in a previous study done in North Carolina, a 3- to 4-month rhythm was found. Multiphasic thyroid rhythms of the same frequency have been reported for a variety of species. Comparison of the midwestern and southeastern sets of sunshine and thyroid data indicated similar regional differences in sunshine conditions and thyroid activity.

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Zusammenfassung Die Werte von 50 Jahren des prozentual möglichen Sonnenscheins von US Wetterdienst-Stationen in den Staaten des Mittelwestens um Iowa wurden nach der Methode der periodischen Regression unter Anwendung der Fourier Analyse untersucht. Wie in einer früheren Studie über die Sonnenschein Bedingungen im Süd-Osten der Vereinigten Staaten wurden mehrphasische Sonnenscheinrhythmen mit einer Frequenz von 3 bis 4 Zykeln pro Jahr gefunden. Unter Anwendung der¹²⁵Jod-Technik wurde die Schilddrüsenaktivität von Katzen gemessen und wie in einer früheren Studie in North Carolina, ergab sich ein 3–4 Monate Rhythmus. Multiphasische Schilddrüsenaktivitäts-Rhythmen gleicher Frequenz sind bei anderen Tierarten beobachtet worden. Der Vergleich der Sonnenschein-und Schilddrüsenaktivitätswerte im Mittelwesten und Süd-Osten der Vereinigten Staaten deutet auf ähnliche regionale Unterschiede hin.

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Resume On a analysé les valeurs de la durée d'insolation relative de 50 années d'observations aux stations du réseau du US Weather Bureau situées dans les Etats du centre des Etats-Unis, aux environs de Iowa. Pour ce faire, on s'est servi d'une technique de régressions périodiques basée sur les séries de Fourier. Dans une précédente étude se rapportant au sud-est des Etats-Unis, on avait déjà pu isoler des rythmes de l'insolation à plusieurs phases, rythmes présentant des fréquences de trois à quatre cycles par an. En utilisant¹²⁵I comme traceur, on a mesuré durant une année l'activité de la glande thyroïde de chats. On a trouvé, comme d'ailleurs lors d'une recherche précédente faite en Caroline du Nord, un rythme de trois à quatre mois. Des rythmes à plusieurs phases de l'activité de la thyroïde et de la même fréquence ont été isolés chez d'autres espèces d'animaux. En comparant les valeurs de l'insolation et de l'activité thyroïdienne obtenues dans le sud-est et le "midwest" des Etats-Unis, on trouve des différences régionales semblables entre les deux phénomènes.

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This research was supported by Grant MH15402 from the National Institute of Mental Health, United States Public Health Service. We wish to express our thanks and appreciation to Dr John Fix for his consultation on the astronomical aspects of this study.     

Distribution of muscle fiber types and EMG activity in cat intercostal muscles

The electromyogram (EMG) activity and histochemical properties of intercostal muscles in the anesthetized cat were studied. The parasternal muscles were consistently active during inspiration. The external intercostals in the rostral spaces and the ventral portions of the midthoracic spaces were also recruited during inspiration. The remaining external intercostals were typically silent, regardless of the level of respiratory drive. The internal intercostal muscles located in the caudal spaces were occasionally recruited during expiration. There was a clear correlation between recruitment patterns of the intercostals and the histochemically defined fiber type properties of the muscles. Intercostal muscles that were routinely recruited during inspiration had a significantly higher proportion of slow-oxidative muscle fibers.