Effect of fatigue on intermuscular EMG-EMG coupling during bench press exercise at 60% 1RM workload in males

Objective

To explore the neuromuscular control mechanism and quantifying the fatigue response during bench press exercise is important references to prescribe an appropriate exercise program. However, current literature struggles to provide a concrete conclusion on the changes of intermuscular EMG-EMG coupling between synergistic and antagonist muscles during the exercise. Thus, the current study was designed to reveal fatigue-related changes of intermuscular EMG-EMG coupling during bench press exercise.

Methods

Thirty-one healthy male participants performed a bench press exercise on the Smith machine at 60% One Repetition Maximum (1RM) workload to exhaustion, while surface electromyographic signals (sEMG) were collected from triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD), posterior deltoid (PD), and pectoralis major (PM). Surface EMG signals were divided into the first half and second half of the bench press exercise. Phase synchronization index (PSI) was calculated between sEMG of synergistic muscle pairs AD-TB, AD-PM and antagonist muscle pairs BB-TB, AD-PD.

Results

EMG power of TB, AD, PD, PM muscles in alpha (8-12 Hz) frequency band and EMG power of each muscle in beta (15-35 Hz), and gamma (35-60 Hz) frequency bands were all increased during the second half of contraction compared with the first half of contraction. PSI of gamma frequency band was significantly decreased in BB-TB muscle pair while EMG-EMG coupling of AD-TB in gamma frequency band was significantly increased during the second half of contraction compared to the first half of contraction.

Conclusions

The results indicated a decrease of interconnection between synchronized cortical neurons and the motoneuron pool of BB and TB, and an increase of interconnection between AD-TB muscles during fatiguing bench press exercise at 60% 1RM workload. The changes of intermuscular coupling may be related to the supraspinal modulations to compensate for the decrease of muscle force as well as a result of unbalanced changes of agonist and antagonist muscle contractility.

Preliminary feasibility and acute physiological effects of a single session of upper limb vibration training for persons with spinal cord injury

CONTEXT

Strong upper limb musculature is essential for persons with spinal cord injury (SCI) to operate a manual wheelchair and live independently. Targeted upper limb vibration may be a viable exercise modality to build muscle efficiently while eliminating some of the barriers associated with exercise for persons with SCI.

OBJECTIVE

The purpose of this study was to assess preliminary feasibility of completing a single exercise session of upper limb vibration and compare the acute physiological effects to a single session of standard dumbbell resistance exercise.

METHODS

Individuals with SCI performed seven upper limb exercises (1) isometrically using a vibrating dumbbell at 30 Hz for 60 s (n = 22) and (2) using a standard isotonic resistance protocol (n = 15).

RESULTS

Nineteen (86.4%) of 22 participants were able to perform all vibration exercises at 30 Hz but hold time success rates varied from 33% (side flies and front raises) to 95% (internal rotation). No significant differences were found between vibration exercise and standard resistance protocol for blood lactate, power output, and heart rate (P > 0.05). Perceptions of the training were positive, with most participants (>70%) expressing interest to train with vibration in the future.

CONCLUSIONS

Vibration training was not feasible for all participants, suggesting an individualized approach to starting weight and progression may be necessary. Similar acute physiological changes were seen between vibration exercise and standard resistance protocol, suggesting they could have similar benefits. Additional research is needed to determine if vibration exercise is feasible and beneficial to incorporate into a long-term training program.

Superimposed vibration on suspended push-ups

Background

Superimposition of vibration has been proposed in sports training using several devices and methods to enhance muscle activation and strength adaptations. Due to the popularity of suspension training, vibration systems have recently been developed to increase the effects of this training method. The present cross-sectional study aims to examine the effects of superimposing vibration on one of the most popular exercises in strength and conditioning programs: push-ups.

Methods

Twenty-eight physically active men and women executed push-ups in three suspended conditions (non-vibration, vibration at 25 Hz, and vibration at 40 Hz). OMNI-Res scale was registered, and surface electromyographic signals were measured for the activity of the right and left external oblique, anterior deltoid, triceps brachii, sternal, and clavicular heads of the pectoralis major.

Results

A linear mixed model indicated a significant fixed effect for vibration at 25 Hz and 40 Hz on muscle activity. Suspended push-ups with superimposed vibration (25 Hz and 40 Hz) showed a significant higher activity on left (25 Hz: p = 0.036, d = 0.34; 40 Hz: p = 0.003, d = 0.48) and right external oblique (25 Hz: p = 0.004, d = 0.36; 40 Hz: p = 0.000, d = 0.59), anterior deltoid (25 Hz: p = 0.032, d = 0.44; 40 Hz: p = 0.003, d = 0.64), and global activity (25 Hz: p = 0.000, d = 0.55; 40 Hz: p = 0.000, d = 0.83) compared to non-vibration condition. Moreover, OMNI-Res significant differences were found at 25 Hz (6.04 ± 0.32, p = 0.000 d = 4.03 CI = 3.27, 4.79) and 40 Hz (6.21 ± 0.36 p = 0.00 d = 4.29 CI = 3.49, 5.08) compared to the non-vibration condition (4.75 ± 0.32).

Conclusion

Superimposing vibration is a feasible strategy to enhance the muscle activity of suspended push-ups.

sEMG Activity in Superimposed Vibration on Suspended Supine Bridge and Hamstring Curl

Traditionally in strength and conditioning environments, vibration has been transmitted using platforms, barbells, dumbbells, or cables but not suspension devices. This study aimed to examine the effects on the lower limb of applying superimposed vibration on a suspension device. Twenty-one physically active men and women performed supine bridge and hamstring curl exercises in three suspended conditions (non-vibration, vibration at 25 Hz, and vibration at 40 Hz). In each exercise condition, the perceived exertion scale for resistance exercise (OMNI-Res) was registered, and the electromyographic signal was assessed for gastrocnemius (medialis and lateralis), biceps femoris, semitendinosus, gluteus maximus, and rectus femoris. A linear mixed model indicated a significant fixed effect for vibration at 25 Hz and 40 Hz on muscle activity in suspended supine bridge (p < 0.05), but no effect for suspended hamstring curl (p > 0.05). Likewise, the Friedman test showed a significant main effect for vibration at 25 Hz and 40 Hz in suspended supine bridge (p < 0.05) but not for suspended hamstring curl (p > 0.05) on OMNI-Res. Post hoc analysis for suspended supine bridge with vibration at 25 Hz showed a significant activation increase in gastrocnemius lateralis (p = 0.008), gastrocnemius medialis (p = 0.000), semitendinosus (p = 0.003) activity, and for semitendinosus under 40 Hz condition (p = 0.001) compared to the non-vibration condition. Furthermore, OMNI-Res was significantly higher for the suspended supine bridge at 25 Hz (p = 0.003) and 40 Hz (p = 0.000) than for the non-vibration condition. Superimposed vibration at 25 Hz elicits a higher neuromuscular response during the suspended supine bridge, and the increase in vibration frequency also raises the OMNI-Res value.

Effects of vibratory massage therapy on grip strength, endurance time and forearm muscle performance

BACKGROUND

Vibration therapy (VT) causes an increase in motor unit activation tendency, an involuntary recruitment of earlier sedentary motor units, which increases the muscle fiber force generating capacity and muscle performance.

OBJECTIVE

To evaluate the effect of vibratory massage therapy at 23 Hz and 35 Hz on grip strength, endurance, and forearm muscle performance (in terms of EMG activity).

METHODS

Ten healthy and right-handed men participated voluntarily in this study. The experiment was characterized by the measurement of MVC (maximal voluntary contraction) grip strength and grip endurance time at 50%MVC, accompanied by the corresponding measurement of the EMG signals of the muscles viz., flexor digitorum superficialis (FDS); flexor carpi ulnaris (FCU); extensor carpi radialis brevis (ECRB); and extensor carpi ulnaris (ECU) in supine posture.

RESULTS

MANCOVA results showed significant effects of VT frequency on endurance time (p < 0.001); but no significant effect on the grip strength (p = 0.161) and muscle performance (in terms of EMG activities of the forearm muscles). However, VT improves the MVC grip strength and grip endurance time (better at 35 Hz). The Pearson correlation was significant between: weight, palm length, palm circumference, and forearm length with MVC grip strength; and the palm length with the endurance time. In addition, the palm length, palm circumference, and forearm circumference generally serve to better predict MVC grip strength and grip endurance time.

CONCLUSIONS

Vibration therapy at 35 Hz for 10 minutes on the forearms had a significant positive effect on the neuromuscular performance to enhance muscle performance of upper extermitites and can be used as the optimal range to study the effect of VT. Findings may be used to prepare guidelines for VT in rehabilitation, healthcare, sports, and medical for therapists.

The effect of targeted resistance training on bench press performance and the alternation of prime mover muscle activation patterns

Targeted muscle strengthening might improve performance or help overcome training stagnation; therefore, the aim of the present study was to investigate changes in muscle activity patterns before and after six weeks of targeted resistance training. Twenty-seven resistance-trained men were divided into three groups according to their prime mover activity, as measured by surface electromyography during a bench press (BP). Each group underwent a six-week block of targeted exercises for one of the following muscles: anterior deltoid (AD), pectoralis major (PM) or triceps brachii (TB). ANOVA showed that each group increased their 1 repetition maximum (1RM) (p < 0.05) and the activity of the exercised muscle group during an isometric bench press (p < 0.01) and during a dynamic bench press (p < 0.01) at 85% of the 1RM. During the isometric BP, the TB training group had an increase in TB activity in comparison to the other groups. Targeted muscle training is a useful method for muscle activity increase and increasing the maximum strength in complex exercise, when applied in activity-deficient muscle groups. Strengthening the TB elicits changes in all prime movers and results in TB activity domination during a bench press.

A systematic review of surface electromyography analyses of the bench press movement task

BACKGROUND

The bench press exercise (BP) plays an important role in recreational and professional training, in which muscle activity is an important multifactorial phenomenon. The objective of this paper is to systematically review electromyography (EMG) studies performed on the barbell BP exercise to answer the following research questions: Which muscles show the greatest activity during the flat BP? Which changes in muscle activity are related to specific conditions under which the BP movement is performed?

STRATEGY

PubMed, Scopus, Web of Science and Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library were searched through June 10, 2016. A combination of the following search terms was used: bench press, chest press, board press, test, measure, assessment, dynamometer, kinematics and biomechanics. Only original, full-text articles were considered.

RESULTS

The search process resulted in 14 relevant studies that were included in the discussion. The triceps brachii (TB) and pectoralis major (PM) muscles were found to have similar activity during the BP, which was significantly higher than the activity of the anterior deltoid. During the BP movement, muscle activity changes with exercise intensity, velocity of movement, fatigue, mental focus, movement phase and stability conditions, such as bar vibration or unstable surfaces. Under these circumstances, TB is the most common object of activity change.

CONCLUSIONS

PM and TB EMG activity is more dominant and shows greater EMG amplitude than anterior deltoid during the BP. There are six factors that can influence muscle activity during the BP; however, the most important factor is exercise intensity, which interacts with all other factors. The research on muscle activity in the BP has several unresolved areas, such as clearly and strongly defined guidelines to perform EMG measurements (e.g., how to elaborate with surface EMG limits) or guidelines for the use of exact muscle models.

Effect of vibration frequency on agonist and antagonist arm muscle activity

PURPOSE

This study aimed to assess the effect of vibration frequency (f out) on the electromyographic (EMG) activity of the biceps brachii (BB) and triceps brachii (TB) muscles when acting as agonist and antagonist during static exercises with different loads.

METHODS

Fourteen healthy men were asked to hold a vibratory bar as steadily as possible for 10 s during lying row (pulling) and bench press (pushing) exercise at f out of 0 (non-vibration condition), 18, 31 and 42 Hz with loads of 20, 50, and 80 % of the maximum sustainable load (MSL). The root mean square of the EMG activity (EMGRMS) of the BB and TB muscles was expressed as a function of the maximal EMGRMS for respective muscles to characterize agonist activation and antagonist coactivation.

RESULTS

We found that (1) agonist activation was greater during vibration (42 Hz) compared to non-vibration exercise for the TB but not for the BB muscle (p < 0.05); (2) antagonist activation was greater during vibration compared to non-vibration exercise for both BB (p < 0.01) and TB (p < 0.05) muscles; (3) the vibration-induced increase in antagonist coactivation was proportional to vibration f out in the range 18-42 Hz and (4) the vibration-induced increase in TB agonist activation and antagonist coactivation occurred at all loading conditions in the range 20-80 % MSL.

CONCLUSION

The use of high vibration frequencies within the range of 18-42 Hz can maximize TB agonist activation and antagonist activation of both BB and TB muscles during upper limb vibration exercise.

The influence of preset frequency, loading condition, and exercise type on the mechanical behavior of a novel vibratory bar

This study aimed to analyze the influence of different vibration frequencies, loading conditions, and exercise types on the mechanical behavior of a novel vibratory bar (VB). Fourteen healthy men were asked to hold the VB during lying row (pulling) and bench press (pushing) static exercise as steadily as possible for 10 seconds with loads of 20, 50, and 80% of the maximum sustained load (MSL) and at preset vibration frequencies (f(in)) of 20, 35, and 50 Hz. Root mean square vibration acceleration (a(RMS)), peak-to-peak displacement (D), and frequency (f(out)) were gained from a 3-dimensional accelerometer fixed to the VB. Increasing vibration frequency (from 20 to 50 Hz) resulted in a progressive and sizeable increase in VB a(RMS) and f(out) (both p ≤ 0.001) with smaller variations of D (≤5.9%, p ≤ 0.001). Adding weight to the VB (progressive overload from 20 to 80% MSL) did not affect D and minimally altered a(RMS) (<4.2%, p = 0.014) and f(out) (<1.7%, p = 0.002). Altering the type of exercise (pulling vs. pushing) did not affect VB a(RMS), D, and f(out). In conclusion, this study establishes the validity of a novel VB and legitimates its use for effective and safe upper-body static exercise with a wide range of vibration frequencies and loading conditions in the context of physical training or rehabilitation.