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Norihide Sugisaki, Taku Wakahara, Koichiro Murata, Naokazu Miyamoto, Yasuo Kawakami, Hiroaki Kanehisa and Tetsuo Fukunaga

Although the moment arm of the triceps brachii muscle has been shown to be associated with the muscle’s anatomical crosssectional area, whether training-induced muscle hypertrophy alters the moment arm of the muscle remains unexplored. Therefore, the current study aimed to examine this. Eleven men underwent a 12-week resistance training program for the triceps brachii muscle. The maximum muscle anatomical cross-sectional area (ACSAmax), the moment arm of the triceps brachii muscle, and the anterior-posterior dimension of the olecranon were measured using a magnetic resonance imaging system before and after intervention. The ACSAmax (33.6 ± 11.9%, P < .001) and moment arm (5.5 ± 4.0%, P = .001) significantly increased after training, whereas the anterior-posterior dimension of the olecranon did not change (P > .05). The change in moment arm was smaller than that expected from the relationship between the ACSAmax and the moment arm before the intervention. The present results indicate that training-induced triceps brachii muscle hypertrophy could increase the muscle moment arm, but its impact can be small or negligible.

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Ryota Akagi, Tomofumi Shikiba, Jun Tanaka and Hideyuki Takahashi

We investigated the effect of a 6-week resistance training program on the shear modulus of the triceps brachii (TB). Twentythree young men were randomly assigned to either the training (n = 13) or control group (n = 10). Before and after conducting the resistance training program, the shear modulus of the long head of the TB was measured at the point 70% along the length of the upper arm from the acromial process of the scapula to the lateral epicondyle of the humerus using shear wave ultrasound elastography. Muscle thickness of the long head of the TB was also determined at the same site by ultrasonography used during both tests. A resistance exercise was performed 3 days a week for 6 weeks using a dumbbell mass-adjusted to 80% of the 1-repetition maximum (1RM). The training effect on the muscle thickness and 1RM was significant. Nevertheless, the muscle shear modulus was not significantly changed after the training program. From the perspective of muscle mechanical properties, the present results indicate that significant adaptation must occur to make the TB more resistant to subsequent damaging bouts during the 6-week training program to target the TB.

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Atsuki Fukutani and Toshiyuki Kurihara

Recent studies have reported that resistance training increases the cross-sectional areas (CSAs) of tendons; however, this finding has not been consistently observed across different studies. If tendon CSA increases through resistance training, resistance-trained individuals should have larger tendon CSAs as compared with untrained individuals. Therefore, in the current study, we aimed to investigate whether resistance training increases tendon CSAs by comparing resistance-trained and untrained individuals. Sixteen males, who were either body builders or rugby players, were recruited as the training group, and 11 males, who did not participate in regular resistance training, were recruited into the control group. Tendon CSAs and muscle volumes of the triceps brachii, quadriceps femoris, and triceps surae were calculated from images obtained by using magnetic resonance imaging. The volumes of the 3 muscles were significantly higher in the training group than in the control group (P < .001 for all muscles). However, a significant difference in tendon CSAs was found only for the distal portion of the triceps surae tendon (P = .041). These findings indicate that tendon CSA is not associated with muscle volume, suggesting that resistance training does not increase tendon CSA.

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Simon Gavanda, Stephan Geisler, Oliver Jan Quittmann and Thorsten Schiffer

], absolute and relative fat mass [relFM], FFM, MM, muscle thickness of rectus femoris [RF], vastus lateralis [VL], and triceps brachii [TB]). In addition, 40-yd sprint times were taken as a test for speed. Countermovement jump (CMJ) height, peak power (Wpeak) estimated from vertical jump performance, and

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Fabien Dal Maso, Mickaël Begon and Maxime Raison

One approach to increasing the confidence of muscle force estimation via musculoskeletal models is to minimize the root mean square error (RMSE) between joint torques estimated from electromyographic-driven musculoskeletal models and those computed using inverse dynamics. We propose a method that reduces RMSE by selecting subsets of combinations of maximal voluntary isometric contraction (MVIC) trials that minimize RMSE. Twelve participants performed 3 elbow MVIC in flexion and in extension. An upper-limb electromyographic-driven musculoskeletal model was created to optimize maximum muscle stress and estimate the maximal isometric force of the biceps brachii, brachialis, brachioradialis, and triceps brachii. Maximal isometric forces were computed from all possible combinations of flexion-extension trials. The combinations producing the smallest RMSE significantly reduced the normalized RMSE to 7.4% compared with the combination containing all trials (9.0%). Maximal isometric forces ranged between 114–806 N, 64–409 N, 236–1511 N, and 556–3434 N for the brachii, brachialis, brachioradialis, and triceps brachii, respectively. These large variations suggest that customization is required to reduce the difference between models and actual participants’ maximal isometric force. While the smallest previously reported RMSE was 10.3%, the proposed method reduced the RMSE to 7.4%, which may increase the confidence of muscle force estimation.

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Mostafa Yaghoubi, Mohamad Mahdi Esfehani, Hossein Asghar Hosseini, Yaser Alikhajeh and Sarah P. Shultz

The aim of this study was to compare muscle activity patterns between inexperienced and experienced water polo players while taking an overhead shot. The study was carried out with a group of 12 water polo players and an inexperienced group of 10 healthy participants. Signals were recorded by surface electromyography from six different muscles. The average and standard deviation of the normalized electrical activity, time to peak, time broadness, and muscle sequencing during the overhead shot were determined for each muscle in both groups and compared with each other. In water polo players, the normalized electrical activities of triceps brachii, pectoralis major, and wrist flexors were greater than other muscles, while in the inexperienced group the triceps brachii specifically played an important role. There was minimal activation of the middle deltoid and biceps brachii in water polo players. Increased times to peak and time broadness of muscles were found in the inexperienced group compared to experienced water polo players; this difference may be explained by different neuromuscular proprioception. Only experienced water polo players activated the observed muscles in a specific sequence, from proximal to distal. Therefore, coaches should emphasize smooth and quick transitions from proximal to distal segments, with less importance placed on individual muscle strengthening.

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Guillaume Gaudet, Maxime Raison, Fabien Dal Maso, Sofiane Achiche and Mickael Begon

The aim of this study is to determine the intra- and intersession reliability of nonnormalized surface electromyography (sEMG) on the muscles actuating the forearm during maximum voluntary isometric contractions (MVIC). A subobjective of this study is to determine the intra- and intersession reliability of forearm MVIC force or torque, which is a prerequisite to assess sEMG reliability. Eighteen healthy adults participated at 4 different times: baseline, 1-h post, 6-h post, and 24-h post. They performed 3 MVIC trials of forearm flexion, extension, pronation, and supination. sEMG of the biceps brachii short head, brachialis, brachioradialis, triceps brachii long head, pronator teres, and pronator quadratus were measured. The intraclass correlation coefficient (ICC) on MVIC ranged from 0.36 to 0.99. Reliability was excellent for flexion, extension, and supination MVIC for both intra- and intersession. The ICC on sEMG ranged from 0.58 to 0.99. sEMG reliability was excellent for brachialis, brachioradialis, and pronator quadratus, and good to excellent for triceps brachii, biceps brachii, and pronator teres. This study shows that performing 3 MVICs is sufficient to obtain highly reliable maximal sEMG over 24 h for the main muscles actuating the forearm. These results confirm the potential of sEMG for muscle motor functional monitoring.

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Se-yeon Park, Won-gyu Yoo, Hun Kwon, Dong-hyun Kim, Si-eun Lee and Mi-jin Park

Activation of the upper trapezius, lower trapezius, serratus anterior, and triceps brachii muscles was measured, while center of pressure excursion beneath the hands was simultaneously monitored, during the performance of a push-up exercise on both a stable and an unstable base of support. The activation levels of all muscles were significantly greater for the unstable support surface when compared to those for a stable support surface (p < 0.05). A negative correlation was found between activation of the serriatus anterior muscle and center of pressure excursion (r = -0.64, p < 0.05). Performance of the push-up exercise on an unstable support surface appears to elicit greater muscle activation than a standard push-up exercise performed on a stable support surface.

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Robert U. Newton, William J. Kraemer, Keijo Häkkinen, Brendan J. Humphries and Aron J. Murphy

The aim of this study was to investigate the kinematics, kinetics, and neural activation of the traditional bench press movement performed explosively and the explosive bench throw in which the barbell was projected from the hands. Seventeen male subjects completed three trials with a bar weight of 45% of the subject's previously determined 1RM. Performance was significantly higher during the throw movement compared to the press for average velocity, peak velocity, average force, average power, and peak power. Average muscle activity during the concentric phase for pectoralis major, anterior deltoid, triceps brachii, and biceps brachii was higher for the throw condition. It was concluded that performing traditional press movements rapidly with light loads does not create ideal loading conditions for the neuromuscular system with regard to explosive strength production, especially in the final stages of the movement, because ballistic weight loading conditions where the resistance was accelerated throughout the movement resulted in a greater velocity of movement, force output, and EMG activity.

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Vinícius Yan Santos Nascimento, Rafaela Joyce Barbosa Torres, Natália Barros Beltrão, Priscila Soares dos Santos, André Luiz Torres Pirauá, Valéria Mayaly Alves de Oliveira, Ana Carolina Rodarti Pitangui and Rodrigo Cappato de Araújo

This study evaluated the effects of instability on the EMG activity of scapular stabilizing and upper limb muscles during exercises with axial and rotational load. Twenty male volunteers (20.9 ± 1.8 years, 174.1 ± 0.04 cm, 73.17 ± 8.77 kg) experienced in strength training participated in a crossover design. Muscle activation of anterior deltoid (AD), posterior deltoid (PD), pectoralis major (PM), biceps brachii (BB), triceps brachii (TB), upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) were determined on both conditions. Participants performed a single series of 10 repetitions of bench press and fly exercises on stable (bench) and unstable (proprioceptive disc) conditions at 60% of 1-RM. The Friedman test and post hoc Dunn’s indicated that the unstable condition showed greater EMG activity for AD (P = .001) and BB (P = .002) on the fly exercise, SA (P = .001) and LT (P = .048) on the bench press, and PM (P ≤ .002) on both exercises. These results show that using an unstable surface in exercises with rotational load provides superior EMG activity of the agonist muscles, while in exercise with axial load, the instability favors EMG activity of the scapular stabilizing muscles.