Differential activation of parts of the latissimus dorsi with various isometric shoulder exercises

As no study has examined whether the branches of the latissimus dorsi are activated differently in different exercises, we investigated intramuscular differences of components of the latissimus dorsi during various shoulder isometric exercises. Seventeen male subjects performed four isometric exercises: shoulder extension, adduction, internal rotation, and shoulder depression. Surface electromyography (sEMG) was used to collect data from the medial and lateral components of the latissimus dorsi during the isometric exercises. Two-way repeated analysis of variance with two within-subject factors (exercise condition and muscle branch) was used to determine the significance of differences between the branches, and which branch was activated more with the exercise variation. The root mean squared sEMG values for the muscles were normalized using the modified isolation equation (%Isolation) and maximum voluntary isometric contraction (%MVIC). Neither the %MVIC nor %Isolation data differed significantly between muscle branches, while there was a significant difference with exercise. %MVIC was significantly higher with shoulder extension, compared to the other isometric exercises. There was a significant correlation between exercise condition and muscle branch in the %Isolation data. Shoulder extension and adduction and internal rotation increased %Isolation of the medial latissimus dorsi more than shoulder depression. Shoulder depression had the highest value of %Isolation of the lateral latissimus dorsi compared to the other isometric exercises. Comparing the medial and lateral latissimus dorsi, the medial component was predominantly activated with shoulder extension, adduction, and internal rotation, and the lateral component with shoulder depression. Shoulder extension is effective for activating the latissimus dorsi regardless of the intramuscular branch.     

Standardised surface electromyography allows effective submental muscles assessment

The aims of this pilot study were to evaluate: (i) the reproducibility and variability of an electromyographical protocol developed for the assessment of submental muscles (SM) (ii) to apply the new protocol to maximal teeth clenching, a simple and largely studied static task in order to quantify the relative contribution of submental muscles. In 20 healthy subjects, aged 19–35 years, surface electromyography of SM, masseter (MM) and anterior temporalis (TA) muscles was performed during maximal voluntary clenching (MVC) with and without cotton rolls and the pushing of the tongue against the palate. Clenching on cotton rolls and pushing the tongue against the palate were used to standardise respectively MM and TA, and SM muscular potentials. The exercises were repeated in two appointments (T1–T2); submental muscles standardisation was also repeated twice (A-B) in each session to assess repeatability. Symmetry and activity were calculated for each couple of muscles. A two-way analysis of variance was computed for SM: no Factor 1 (T1 vs T2) or Factor 2 (A vs B) or F1 × F2 significant effects were found. SM recruitment was 31% of the maximal activity, with symmetry values larger than 80%. In conclusion, standardised electromyography allows a reliable assessment of Submental muscles activity.     

No difference in 1RM strength and muscle activation during the barbell chest press on a stable and unstable surface

Exercise or Swiss balls are increasingly being used with conventional resistance exercises. There is little evidence supporting the efficacy of this approach compared to traditional resistance training on a stable surface. Previous studies have shown that force output may be reduced with no change in muscle electromyography (EMG) activity while others have shown increased muscle EMG activity when performing resistance exercises on an unstable surface. This study compared 1RM strength, and upper body and trunk muscle EMG activity during the barbell chest press exercise on a stable (flat bench) and unstable surface (exercise ball). After familiarization, 13 subjects underwent testing for 1RM strength for the barbell chest press on both a stable bench and an exercise ball, each separated by at least 7 days. Surface EMG was recorded for 5 upper body muscles and one trunk muscle from which average root mean square of the muscle activity was calculated for the whole 1RM lift and the concentric and eccentric phases. Elbow angle during each lift was recorded to examine any range-of-motion differences between the two surfaces. The results show that there was no difference in 1RM strength or muscle EMG activity for the stable and unstable surfaces. In addition, there was no difference in elbow range-of-motion between the two surfaces. Taken together, these results indicate that there is no reduction in 1RM strength or any differences in muscle EMG activity for the barbell chest press exercise on an unstable exercise ball when compared to a stable flat surface. Moreover, these results do not support the notion that resistance exercises performed on an exercise ball are more efficacious than traditional stable exercises.     

Effects of a tongue training program in Parkinson's disease: Analysis of electrical activity and strength of suprahyoid muscles

ObjectiveTo assess the electrical activity of the suprahyoid muscle and the tongue pressure in a two-wing program of tongue strengthening in individuals with Parkinson's disease (PD).MethodsA pre-post-detraining design study included sixty PD patients assigned to two groups randomly. The experimental group (EG) performed tongue isometric pressure exercises using the Iowa Oral Performance Instrument with an increasing scheme of 5% load weekly and traditional tongue therapy for 8 weeks. The control group (CG) performed only traditional therapy. The electrical activity of suprahyoids was measured using surface electromyography (sEMG) during tongue-to-palate pressure. Four selected domains of the Swallowing Quality of Life Questionnaire (SWAL-QOL) mostly related to tongue strength were considered.ResultsThe experimental group showed increased sEMG values of suprahyoid muscles reaching statistically significant difference at the fourth week of tongue training, while the control did it at the eighth week. Experimental group showed significant improvements in tongue strength (d = 2.128; p = 0.000). Only controls showed detraining effect. Statistically significant difference within groups were found in one and three dimensions of the SWAL-QOL in the CG and EG, respectively.ConclusionAnalysis of electrical activity on suprahyoids muscles provided a better understanding of the changes underlying the outcomes of tongue strength gains obtained through a combined tongue strengthening exercises protocol in PD. Such protocol led not only to increased tongue strength but also to a better perceived swallowing function in PD subjects.     

No sex differences in evoked contractile properties after fatiguing isometric and isotonic exercise for the plantar flexors

Objectives:Females tend to fatigue less than males after isometric exercise, but less is clear for isotonic exercise. Further, there have been relatively few sex comparisons for fatigability of the plantar flexors (PFs). We sought to investigate potential sex differences in contractile properties after a sustained maximal voluntary isometric contraction (MVIC) and isotonic contractions.Methods:Twenty-seven physically active males (n=14; 22±2 yrs) and females (n=13; 21±2 yrs) randomly performed a 2 min MVIC and 120 concentric isotonic (30% MVIC) contractions for the PFs on separate visits. Before and after each fatiguing task, muscle activation was obtained from brief MVICs, which was followed (~2 sec) by tibial nerve stimulation at rest. Contractile properties including peak twitch, absolute and normalized time to peak twitch, and half relaxation time were calculated.Results:No sex differences existed for fatigue-induced changes in muscle activation (p=0.09-0.41; d=0.33-0.69) or contractile properties (p=0.19-0.96; d=0.06-0.94).Conclusions:Peripheral fatigue, as indicated by contractile parameters, did not differ between sexes after isometric or isotonic exercise. The PFs similar fiber type proportions between sexes or greater fiber type heterogeneity may explain why sex differences in fatigability, though common in other muscle groups (e.g., knee extensors), were not expressed in this muscle group.     

An electromyographical comparison of trunk muscle activity during isometric trunk and dynamic strengthening exercises

The purpose of this study was to compare rectus abdominis and erector spinae muscle activity during isometric (prone bridge [PB] and superman [SM]) and dynamic strengthening exercises (back squat, front squat [FS], and military press). Participants (n = 10, age 21.8 ± 2.6 years; body mass 82.65 ± 10.80 kg, 174.5± 7.2 cm), performed each exercise in a randomized order, using a repeated-measures design. Electromyographical (EMG) activity (sampling at 2,000 Hz) of the rectus abdominis (RA) and the erector spinae (ES) muscles was recorded throughout the duration of the exercises. Intraclass correlations demonstrated the highest levels of reliability for muscle activity during the isometric exercises; however, all exercises demonstrated high level of reliability (r = 0.764-0.998, p ≤ 0.01). The PB demonstrated significantly greater (p < 0.01) RA activity compared to all other exercises. The ES activity was significantly (p < 0.01) greater during the FS (1.010 ± 0.308 root mean square value [RMS (V)]) and SM (0.951 ± 0.217 RMS[V]) and compared to all other exercises, although there was no significant difference (p > 0.05) between the FS and the SM exercise. The PB may be the most suitable exercise for strengthening the RA, compared to dynamic exercises at a low to moderate load, because of a higher level of muscle activity. The FS may be a useful alternative to isometric exercises when strengthening the ES, because it results in slightly higher muscle activity levels when using only a light to moderate load. Because of the dynamic nature of the FS, this may also be more beneficial in transferring to activities of daily living and sporting environments.     

Comparison of surface electromyography and myotonometric measurements during voluntary isometric contractions

Objectives: Muscle stiffness increases during muscle contraction. The purpose of this study was to determine the strength of the correlation between myotonometric measurements of muscle stiffness and surface electromyography (sEMG) measurements during various levels of voluntary isometric contractions of the biceps brachii muscle. Subjects: Eight subjects (four female; four male), with mean age of 30.6±8.23 years, volunteered to participate in this study. Methods: Myotonometer and sEMG measurements were taken simultaneously from the right biceps brachii muscle. Data were obtained: (1) at rest, (2) while the subject held a 15 lb (6.8 kg) weight isometrically and, (3) during a maximal voluntary isometric contraction. Myotonometer force–displacement curves (amount of tissue displacement to a given unit of force applied perpendicular to the muscle) were compared with sEMG measurements using Pearson’s product–moment correlation coefficients. Results: Myotonometer and sEMG measurement correlations ranged from −0.70 to −0.90. The strongest correlations to sEMG were from Myotonometer force measurements between 1.00 and 2.00 kg. Conclusions: Myotonometer and sEMG measurements were highly correlated. Tissue stiffness, as measured by the Myotonometer, appears capable of assessing changes in muscle activation levels.     

Immediate effects and short-term retention of multi-modal instruction compared to written only on muscle activity during the prone horizontal abduction exercise in individuals with shoulder pain

In rehabilitation, exercise instructions are multi-modal and can include a focus of increasing mean activity of a target muscle and inhibiting aberrant synergistic muscle activity, particularly during shoulder exercises, such as the prone horizontal abduction (PHA). The objective was to compare the immediate effects and short-term retention of multi-modal exercise instruction by a physical therapist written only instruction on normalized mean upper and lower trapezius muscle activity during three phases (concentric/isometric/eccentric) versus of an isotonic PHA exercise between participants with and without shoulder pain. Surface electromyography (EMG) was recorded from fourteen healthy participants and twelve participants with shoulder pain during the PHA exercise under two conditions: (1) written only instructions and (2) multi-modal instruction. Retention of multi-modal instruction on muscle activity was assessed one week later. Results demonstrate 12.8–16.0% increase in lower trapezius muscle activity during the concentric and isometric phases with multi-modal instructions in both groups. Inhibition of the upper trapezius did not occur in either group. Facilitation effects were maintained in short-term follow-up. Findings suggest that regardless of shoulder pain, multi-modal instruction by a physical therapist facilitates greater neuromuscular activity of a targeted muscle compared to written instructions alone and these effects are retained.     

Surface electromyograph activity of submental muscles during swallowing and expiratory muscle training tasks in Huntington’s disease patients

IntroductionHuntington’s disease (HD) patients have difficulty in swallowing, leading to aspiration pneumonia, which is a major cause of death. It seems possible that submental muscles that are crucial for preventing an escape of a bolus into the airway, are affected by HD, but no previous studies have investigated this.ObjectiveTo assess surface electromyograph (sEMG) activity of submental muscles during swallowing and expiratory muscle training (EMT) tasks in HD patients in comparison to healthy volunteers.MethodssEMG activities of submental muscles during saliva, water swallowing, EMT tasks performed at 25% and 75% of maximum expiratory pressure were recorded and normalised by the sEMG activity during an effortful swallow in 17 early to mid stage HD patients and 17 healthy volunteers.ResultssEMG activity was greater (p < 0.05) during EMT tasks than saliva and water swallowing, but was not significantly different between groups for saliva, water swallowing and EMT at 25%. HD patients had lower sEMG activity for EMT at 75% (p < 0.05).ConclusionDecreases in submental muscle activity were not evident in HD patients except during EMT at 75%. This suggests that relative submental muscle weakness is observed only during a high intensity task in early to mid stage HD patients.     

Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans

The effects of dynamic and intermittent isometric knee extension exercises on skeletal muscle blood flow and flow heterogeneity were studied in seven healthy endurance-trained men. Regional muscle blood flow was measured using positron emission tomography (PET) and an [(15)O]H(2)O tracer, and electromyographic (EMG) activity was recorded in the quadriceps femoris (QF) muscle during submaximal intermittent isometric and dynamic exercises. QF blood flow was 61% (P = 0.002) higher during dynamic exercise. Interestingly, flow heterogeneity was 13% (P = 0.024) lower during dynamic compared with intermittent isometric exercise. EMG activity was significantly higher (P < 0.001) during dynamic exercise, and the change in EMG activity from isometric to dynamic exercise was tightly related to the change in blood flow in the vastus lateralis muscle (r = 0.98, P < 0.001) but not in the rectus femoris muscle (r = -0.09, P = 0.942). In conclusion, dynamic exercise causes higher and less heterogeneous blood flow than intermittent isometric exercise at the same exercise intensity. These responses are, at least partly, related to the increased EMG activity.     

Non-uniform excitation of pectoralis major induced by changes in bench press inclination leads to uneven variations in the cross-sectional area measured by panoramic ultrasonography

This study combined surface electromyography with panoramic ultrasound imaging to investigate whether non-uniform excitation could lead to acute localized variations in cross-sectional area and muscle thickness of the clavicular and sternocostal heads of pectoralis major (PM). Bipolar surface electromyograms (EMGs) were acquired from both PM heads, while 13 men performed four sets of the flat and 45° inclined bench press exercises. Before and immediately after exercise, panoramic ultrasound images were collected transversely to the fibers. Normalized root mean square (RMS) amplitude and variations in the cross-sectional area and muscle thickness were calculated separately for each PM head. For all sets of the inclined bench press, the normalized RMS amplitude was greater for the clavicular head than the sternocostal head (P < 0.001), and the opposite was observed during the flat bench press (P < 0.001). Similarly, while greater increases in cross-sectional area were observed in the clavicular than in the sternocostal head after the inclined bench press (P < 0.001), greater increases were quantified in the sternocostal than in the clavicular head after the flat bench press exercise (P = 0.046). Therefore, our results suggest that the PM regional excitation induced by changes in bench press inclination leads to acute, uneven responses of muscle architecture following the exercise.     

Electromyographic analysis of the superior belly of the omohyoid muscle and anterior belly of the digastric muscle in tongue and head movements.

The participation of the superior belly of the omohyoid muscle and anterior belly of the digastric muscle in tongue and head movements was studied eletromyographically in 20 normal young volunteers. A pair of monopolar electrodes was used in each muscle for simultaneous recording of their actions. The muscles act in the following tongue movements: protrusion, right and left lateral movements, placement of the tip of the tongue on soft and hard palates and on the floor of the mouth. The strongest levels of activity of the superior belly of the omohyoid muscle were observed in the placement of the tip of the tongue on the soft palate, coincidentally with a greater dislocation of hyoid bone. Both of the muscles studied did not participate in the head's kinesiology.     

静态负荷诱发肌肉疲劳后恢复期sEMG信号变化规律

目的:探讨肌肉疲劳过程中sEMG功率谱变化与H 的关系以及可能存在的其它影响因素.方法:利用肌肉进行疲劳收缩结束后,短时间内肌肉pH值尚无明显改变的特性,观察恢复期30 s内s EMG功率谱的变化规律.八名男性受试者,以肱二头肌为目标肌肉,负荷强度为60%MVC,静态持续负荷至疲劳点后,在恢复期以同样负荷分别观察2 s、4 s、6 s、8 s、10 s、20 s、30 s时的sEMG信号特征.结果:肱二头肌在以60%MVC静态疲劳负荷过程中MPF呈线性下降.在疲劳负荷后的恢复期,MPF恢复极其迅速,运动结束后仅2 s,MPF已恢复到整个下降范围的26.5%;至30 s,MPF已恢复到整个下降范围的87.7%.结论:由[H ]增加引起的肌纤维动作电位传导速度下降不是决定sEMG功率谱左移的唯一因素,提示sEMG功率谱左移可能与神经源性的中枢机制的作用有关.     

Exercise induced muscle damage and recovery assessed by means of linear and non-linear sEMG analysis and ultrasonography.

This study was aimed at investigating the time-course and recovery from eccentric (EC) exercise induced muscle damage by means of surface electromyography (sEMG), ultrasonography (US), and blood enzymes. Five subjects (EC Group) performed two bouts of 35 EC maximum contractions with the biceps brachii of their non dominant arm, five subjects were tested without performing EC (Control Group: CNT). The maximal isometric force (MVC) was measured. Force and sEMG signals were recorded during 80% MVC isometric contractions. In EC and CNT subjects US assessment on non-dominant biceps brachii was performed; creatin kinase (CK) and lactic dehydrogenasis (LDH) plasma levels were also assessed. Force, sEMG and CK-LDH measurements were performed before EC and after it periodically for 4 weeks. The sEMG was analysed in time and frequency domains; a non-linear analysis (Lyapunov 1st exponent, L1) of sEMG was also performed. After EC, the MVC was reduced by 40% on average with respect to the pre-EC values. A significant decrease in the initial frequency content, and in the MDF and L1 decay (13-42% less than the pre-EC values, respectively) was also observed. The sEMG amplitude (Root Mean Square, RMS) was unchanged after EC. The US revealed an increase in muscle belly thickness and in local muscle blood flow after EC. A complete recovery of all the considered parameters was achieved in two weeks. In conclusion sEMG analysis was confirmed as an early indicator of muscle damage. Muscle recovery from damage is followed by both sEMG and US and this may have useful clinical implications. Non linear analysis (L1) was revealed to be sensitive to early sEMG modifications induced by EC as well as able to follow the post EC changes in the sEMG.     

Assessing the validity of surface electromyography for recording muscle activation patterns from serratus anterior

PurposeNo direct evidence exists to support the validity of using surface electrodes to record muscle activity from serratus anterior, an important and commonly investigated shoulder muscle. The aims of this study were to determine the validity of examining muscle activation patterns in serratus anterior using surface electromyography and to determine whether intramuscular electromyography is representative of serratus anterior muscle activity.MethodsSeven asymptomatic subjects performed dynamic and isometric shoulder flexion, extension, abduction, adduction and dynamic bench press plus tests. Surface electrodes were placed over serratus anterior and around intramuscular electrodes in serratus anterior. Load was ramped during isometric tests from 0% to 100% maximum load and dynamic tests were performed at 70% maximum load. EMG signals were normalised using five standard maximum voluntary contraction tests.ResultsSurface electrodes significantly underestimated serratus anterior muscle activity compared with the intramuscular electrodes during dynamic flexion, dynamic abduction, isometric flexion, isometric abduction and bench press plus tests. All other test conditions showed no significant differences including the flexion normalisation test where maximum activation was recorded from both electrode types. Low correlation between signals was recorded using surface and intramuscular electrodes during concentric phases of dynamic abduction and flexion.ConclusionsIt is not valid to use surface electromyography to assess muscle activation levels in serratus anterior during isometric exercises where the electrodes are not placed at the angle of testing and dynamic exercises. Intramuscular electrodes are as representative of the serratus anterior muscle activity as surface electrodes.     

Trunk muscle electromyographic activity with unstable and unilateral exercises

The purpose of this cross-sectional study was to evaluate the effect of unstable and unilateral resistance exercises on trunk muscle activation. Eleven subjects (6 men and 5 women) between 20 and 45 years of age participated. Six trunk exercises, as well as unilateral and bilateral shoulder and chest presses against resistance, were performed on stable (bench) and unstable (Swiss ball) bases. Electromyographic activity of the upper lumbar, lumbosacral erector spinae, and lower-abdominal muscles were monitored. Instability generated greater activation of the lower-abdominal stabilizer musculature (27.9%) with the trunk exercises and all trunk stabilizers (37.7-54.3%) with the chest press. There was no effect of instability on the shoulder press. Unilateral shoulder press produced greater activation of the back stabilizers, and unilateral chest press resulted in higher activation of all trunk stabilizers, when compared with bilateral presses. Regardless of stability, the superman exercise was the most effective trunk-stabilizer exercise for back-stabilizer activation, whereas the side bridge was the optimal exercise for lower-abdominal muscle activation. Thus, the most effective means for trunk strengthening should involve back or abdominal exercises with unstable bases. Furthermore, trunk strengthening can also occur when performing resistance exercises for the limbs, if the exercises are performed unilaterally.     

Direction-specific recruitment of rotator cuff muscles during bench press and row

Recent studies indicate that rotator cuff (RC) muscles are recruited in a reciprocal, direction-specific pattern during shoulder flexion and extension exercises. The main purpose of this study was to determine if similar reciprocal RC recruitment occurs during bench press (flexion-like) and row (extension-like) exercises. In addition, shoulder muscle activity was comprehensively compared between bench press and flexion; row and extension; and bench press and row exercises. Electromyographic (EMG) activity was recorded from 9 shoulder muscles sites in 15 normal volunteers. All exercises were performed at 20, 50 and 70% of subjects’ maximal load. EMG data were normalized to standard maximal voluntary contractions. Infraspinatus activity was significantly higher than subscapularis during bench press, with the converse pattern during the row exercise. Significant differences in activity levels were found in pectoralis major, deltoid and trapezius between the bench press and flexion exercises and in lower trapezius between the row and extension exercises. During bench press and row exercises, the recruitment pattern in each active muscle did not vary with load. During bench press and row exercises, RC muscles contract in a reciprocal direction-specific manner in their role as shoulder joint dynamic stabilizers to counterbalance antero-posterior translation forces.     

Analysis on the activation of the VMO and VLL muscles during semisquat exercises with and without hip adduction in individuals with patellofemoral pain syndrome

Objective: The purpose of this study was to investigate the effect of hip adduction on the activity of the Vastus Medialis Obliquus (VMO) and Vastus Lateralis Longus (VLL) muscles during semisquat exercises.

Methods: Twenty female subjects, divided into two groups comprising healthy and patellofemoral pain syndrome (PFPS) subjects (ten volunteers for each group), performed three double-leg semisquat exercise trials with maximum hip adduction isometric contraction (DLSS-HA) and three double-leg semisquat exercise trials without hip adduction (DLSS). The normalized electromyographic muscle data were analysed using Repeated Measure ANOVA (p  0.05).

Results: The electrical activity of both VMO and VLL muscles was significantly greater during DLSS-HA exercise than during DLSS (p = 0.0002) for both groups. Additionally, an independent Repeated Measure ANOVA revealed that the electric activity of the VLL muscle was significantly greater (p = 0.0149) than that of the VMO muscle during DLSS exercises only for the PFPS group. However, no differences were found during DLSS-HA exercises.

Conclusions: Although there was no preferential VMO muscle activation, the association of hip adduction with squat exercise promoted a greater balance between the medial and lateral portions of the quadriceps femoris muscle and could be indicated for the conservatory treatment of PFPS patients. The association of isometric hip adduction with isometric semisquat exercises produced a more overall quadriceps activity and could be indicated for clinical rehabilitation or muscle strengthening programs.     

Specificity of resistance training responses in neck muscle size and strength

This study examined hypertrophy after head extension resistance training to assess which muscles of the complicated cervical neuromuscular system were used in this activity. We also determined if conventional resistance exercises, which are likely to evoke isometric action of the neck, induce generalized hypertrophy of the cervical muscle. Twenty-two active college students were studied. [mean (SE) age, weight and height: 21 (1) years, 71 (4) kg and 173 (3) cm, respectively]. Subjects were assigned to one of three groups: RESX (head extension exercise and other resistance exercises), RES (resistance exercises without specific neck exercise), or CON (no training). Groups RESX (n = 8) and RES (n = 6) trained 3 days/week for 12 weeks with large-muscle mass exercises (squat, deadlift, push press, bent row and mid-thigh pull). Group RESX also performed three sets of ten repetitions of a head extension exercise 3 days/week with a load equal to the 3 × 10 repetition maximum (RM). Group CON (n = 8) was a control group. The cross-sectional area (CSA) of nine individual muscles or muscle groups was determined by magnetic resonance imaging (MRI) of the cervical region. The CSA data were averaged over four contiguous transaxial slices in which all muscles of interest were visible. The 3 × 10 RM for the head extension exercise increased for RESX after training [from 17.9 (1.0) to 23.9 (1.4) kg, P < 0.05] but not for RES [from 17.6 (1.4) to 17.7 (1.9)␣kg] or CON [from 10.1 (2.2) to 10.3 (2.1) kg]. RESX showed an increase in total neck muscle CSA after training [from 19.5 (3.0) to 22.0 (3.6) cm², P < 0.05], but RES and CON did not [from 19.6 (2.9) to 19.7 (2.9)␣cm² and 17.0 (2.5) to 17.0 (2.4) cm², respectively]. This hypertrophy for RESX was due mainly to increases in CSA of 23.9 (3.2), 24.0 (5.8), and 24.9 (5.3)% for the splenius capitis, and semispinalis capitis and cervicis muscles, respectively. The lack of generalized neck muscle hypertrophy in RES was not due to insufficient training. For example, the CSA of their quadriceps femoris muscle group, as assessed by MRI, increased by 7 (1)% after this short-term training (P < 0.05). The results suggest that: (1) the splenius capitis, and semispinalis capitis and cervicis muscles are mainly responsible for head extension; (2) short-term resistance training does not provide a sufficient stimulus to evoke neck muscle hypertrophy unless specific neck exercises are performed; and (3) the postural role of head extensors provides modest loading in bipeds. Accepted: 15 October 1996     

A comparison of muscle activity of the dominant and non-dominant side of the body during low versus high loaded bench press exercise performed to muscular failure

The main aim of the study was to compare the peak surface electromyography (sEMG) amplitude of muscles during low and high loaded bench press exercises performed to muscular failure on the dominant and non-dominant body side. Ten resistance-trained healthy males with at least six-year experience in resistance training (27.7 ± 5.6 years, 81.1 ± 5.8 kg and 175.3 ± 5.2 cm, bench press one-repetition maximum [1RM] = 98.9 ± 7.1 kg) performed the bench press at 50% and at 90%1RM. The differences in peak sEMG amplitude between body-sides and the external loads were recorded for the pectoralis major (PM), anterior deltoid (AD), and the long head of the triceps brachii (TB) during each attempt. A two-way repeated-measures ANOVAs revealed statistically significant main effect of side for AD (p < 0.001) and TB (p < 0.001) but not for PM (p = 0.168) and a significant main effect of load for TB (p < 0.001) but not for AD and PM (p = 0.229; p = 0.072; respectively). The post-hoc analysis for the main effect of side showed significantly higher peak sEMG amplitude for the dominant side compared to the non-dominant side for AD and TB at 50%1RM and 90%1RM (p < 0.001; all) with no statistically significant differences for PM (p = 0.187; p = 0.155; both loads). The post-hoc analysis for the main effect of load for TB revealed a significantly higher peak sEMG amplitude at 90%1RM compared to the 50%1RM (p = 0.009). The obtained results indicate that regardless of the external load, the peak sEMG activity of the AD, PM, and TB during the bench press exercise performed to muscular failure was higher on the dominant body-side.