SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Biceps brachii muscle

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The effects of protein supplementation on muscle thickness and strength seem largely dependent on its composition. The current study aimed at comparing the impact of an oral supplementation with vegetable Pea protein (NUTRALYS®) vs. Whey protein and Placebo on biceps brachii muscle thickness and strength after a 12-week resistance training program.

Concepts: Clinical trial, Biceps curl, Scapula, Placebo, Muscle, Triceps brachii muscle, Biceps brachii muscle

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McAllister, MJ, Schilling, BK, Hammond, KG, Weiss, LW, and Farney, TM. Effect of grip width on electromyographic activity during the upright row. J Strength Cond Res 27(1): 181-187, 2013-The upright row (URR) is commonly used to develop the deltoid and upper back musculature. However, little information exists concerning muscle recruitment during variations of this exercise. Sixteen weight-trained men completed 2 repetitions each in the URR with 3 grip conditions: 50, 100, and 200% of the biacromial breadth (BAB). The load was the same for all grip conditions and was equal to 85% of the 1RM determined at 100% BAB. Repeated measures analyses of variance were used to compare the maximal activity of the anterior deltoid (AD), lateral deltoid (LD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), and biceps brachii (BB) during the 3 grip widths for eccentric and concentric actions. Significant differences (p < 0.05) were noted in concentric muscle activity for LD (p < 0.001) and PD (p < 0.001), and in eccentric muscle activity for AD (p = 0.023), LD (p < 0.001), UT (p < 0.001), MT (p < 0.001), and BB (p = 0.003). Bonferroni post hoc analysis revealed significant pairwise differences in the concentric actions from the LD (50% vs. 200% BAB and 100% vs. 200% BAB) and PD (50% vs. 200% BAB and 100% vs. 200% BAB), and eccentric actions of the LD (all comparisons), UT (all comparisons), MT (50% vs. 200% BAB and 100% vs. 200% BAB), and BB (50% vs. 200% BAB), with large-to-very-large effect sizes (ESs). Moderate-to-large ESs were noted for several nonsignificant comparisons. The main findings of this investigation are increased deltoid and trapezius activity with increasing grip width, and correspondingly less BB activity. Therefore, those who seek to maximize involvement of the deltoid and trapezius muscles during the URR should use a wide grip.

Concepts: Muscle contraction, Biceps brachii muscle, Muscles of the upper limb, Glenohumeral joint, Deltoid muscle, Electromyography, Clavicle, Muscle

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Anterior cruciate ligament (ACL) injuries are a burdensome condition due to potential surgical requirements and increased risk of long term debilitation. Previous studies indicate that muscle forces play an important role in the development of ligamentous loading, yet these studies have typically used cadaveric models considering only the knee-spanning quadriceps, hamstrings and gastrocnemius muscle groups. Using a musculoskeletal modelling approach, we investigated how lower-limb muscles produce and oppose key tibiofemoral reaction forces and moments during the weight acceptance phase of unanticipated sidestep cutting. Muscles capable of opposing (or controlling the magnitude of) the anterior shear force and the external valgus moment at the knee are thought to be have the greatest potential for protecting the anterior cruciate ligament from injury. We found the best muscles for generating posterior shear to be the soleus, biceps femoris long head and medial hamstrings, providing up to 173N, 111N and 77N of force directly opposing the anterior shear force. The valgus moment was primarily opposed by the gluteus medius, gluteus maximus and piriformis, with these muscles providing contributions of up to 32 Nm, 19 Nm and 21 Nm towards a knee varus moment, respectively. Our findings highlight key muscle targets for ACL preventative and rehabilitative interventions.

Concepts: Biceps brachii muscle, Extension, Energy, Cruciate ligament, Muscle, Force, Anterior cruciate ligament, Knee

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BACKGROUND: Since the 18th century, the existence of ulnar nerve innervation of the medial head of the triceps brachii muscle has been controversial. The evidence for or against such innervation has been based on macroscopic dissection, an unsuitable method for studying intraneural topography or intramuscular branching. The study of smaller specimens (embryos or fetuses) by means of serial histologic sections may resolve the controversy. QUESTIONS/PURPOSES: Using fetal specimens and histology we determined the contributions of the ulnar and radial nerves to innervation of the triceps brachii muscle. METHODS: We histologically examined 15 embryonic and fetal arms. Radial nerve branches obtained from six adult arms were analyzed immunohistochemically to determine motor fiber content. RESULTS: The medial head of the triceps brachii muscle was always innervated by the radial nerve (ulnar collateral branch). The branches seeming to leave the ulnar nerve at elbow level were the continuation of the radial nerve that had joined the ulnar nerve sheath via a connection in the axillary region. Immunohistochemistry revealed motor and nonmotor fibers in this radial nerve branch. CONCLUSIONS: A connection between the radial and ulnar nerves sometimes may exist, resulting in an apparent ulnar nerve origin of muscular branches to the medial head of the triceps, even though in all our specimens the fibers could be traced back to the radial nerve. CLINICAL RELEVANCE: Before performing or suggesting new muscle and nerve transpositions using this apparent ulnar innervation, the real origin should be confirmed to avoid failure.

Concepts: Radial sulcus, Ulnar nerve, Brachial plexus, Nerve, Muscle, Biceps brachii muscle, Triceps brachii muscle, Radial nerve

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/st> The influence of the muscular response elicited by neurostimulation on the success rate of interscalene block using a catheter (ISC) is unknown. In this investigation, we compared the success rate of ISC placement as indicated by biceps or deltoid, triceps, or both twitches.

Concepts: Muscles of the upper limb, Muscle, Triceps brachii muscle, Biceps brachii muscle

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Although mechanomyography (MMG) reflects local vibrations from contracting muscle fibers, it also includes bulk movement: deformation in global soft tissue around measuring points. To distinguish between them, we compared the multi-channel MMG of resting muscle, which dominantly reflected the bulk movement caused by arterial pulsations, to that of the contracting muscle. The MMG signals were measured at five points around the upper arms of 10 male subjects during resting and during isometric ramp contraction from 5% to 85% of maximal voluntary contraction (MVC) of the biceps brachii muscle. The characteristics of bulk movement were defined as the amplitude distribution and phase relation among the five MMG signals. The bulk movement characteristics during the rest state were not necessarily the same among the subjects. However, below 30Hz, each subject’s characteristics remained the same from the rest state (0% MVC) to the contracting state (80% MVC), at which the bulk movement mainly originates from muscle contraction activity. Results show that the MMG of the low frequency domain (<30Hz) includes bulk movement depending on the mechanical deformation characteristics of each subject's body, for a wide range of muscle contraction intensities.

Concepts: Biceps curl, Scapula, Phase, Triceps brachii muscle, Muscle contraction, Biceps brachii muscle, Muscle

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The aim of this study was to compare different endurance parameters of elbow extensors between senior and junior athletes. A group of 23 junior (16.2±0.8years, BMI 21.8±2.9 kg/m2) and 16 senior athletes (23.1±6.2y, BMI 23.6±4.2 kg/m2) volunteered for the study. Strength measurements were performed on the isoacceleration dynamometer (5 sets of 10 maximal elbow extensions, 1 min resting period between each set). The following strength parameters were measured: maximal strength (MS), endurance strength (ES), fatigue rate (FR) and decrease in strength (DS). Both arms triceps brachii muscle mass (MM) was calculated using a series of cross-sectional images of upper arms obtained by the MRI. Triceps brachii muscle mass for both arms in senior athletes showed significantly higher values (1286.9±323.7 g) compared to young athletes (948.9±171.1 g, p<0.01). ES was 50% higher in seniors, while FR was 10% higher in juniors. MS was 35% higher in seniors, but no difference was discovered when this parameter was expressed in relation to muscle mass. DS was significantly different between juniors and seniors, except in absolute values. No significant correlation was found between triceps brachii muscle mass and FR or DS. Different values of strength decrease throughout multiple contractions could be attributed to different characteristics of various sports.

Concepts: Ulna, Elbow, Triceps brachii muscle, Biceps brachii muscle

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This case study examined body composition changes of a cerebral palsy (CP) athlete, in the 12 weeks prior to the London 2012 Paralympic Games. The aim was to monitor body composition of an athlete in preparation for the London Paralympic Games as part of the optimisation of performance. Within a 12 week period, body composition assessments were completed alongside an incremental 7×200 m swimming performance test, each separated by 6 weeks. One ISAK trained anthropometrist recorded body mass, sum of 8 skinfold thicknesses (biceps, triceps, subscapular, iliac crest, supraspinale, abdominal, front thigh and medial calf), girths (arm, waist, hips and calf), alongside calculations of mid upper arm muscle circumference (MUAMC). With the athlete’s non-affected side being the left side, additional measurements of arm and calf circumference, bicep and triceps skinfold and MUAMC were also assessed. Sum of 8 skinfolds fluctuated over weeks 1, 6 and 12 with 65.8 mm, 60.7 mm and 63.0 mm respectively. Arm circumference in the dominant left arm increased in the 12 week period 29.7 cm, 29.4 cm and 30.5 cm respectively, with the non-dominant right arm maintaining arm circumference over the same period. Performance in the final 200 m of the incremental performance test improved at each time point. 1.2% improvement in performance was noted between weeks 1 and 6 and a 2.1% improvement between weeks 6 and 12. A total performance improvement of 3.2% was noted from the start to end of the 12 week period. This case study highlights in a CP athlete, performance and body composition changes in the lead into major competition. There was little change in body composition but improvements in performance. This suggests that minimal body fat is not critical in CP swimming performance. However, the athlete maintained muscle mass which may suggest that functional mass is more an indicator of performance and provides a direction for future work.

Concepts: International Paralympic Committee, Biceps brachii muscle, Adipose tissue, Olympic Games, Human anatomy, Muscle, 2012 Summer Paralympics, Paralympic Games

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This study investigated the changes in muscular activity and tissue oxygenation while lifting and lowering a load of 20, 40, 60 or 80 % of one repetition maximum (1RM) with elbow flexor muscles until failure. The surface electromyogram (EMG) was recorded in biceps brachii (BB), brachioradialis (BRD) and triceps brachii (TB). For BB, a tissue oxygenation index (TOI) and a normalized total hemoglobin index (nTHI) were recorded by near-infrared spectroscopy. The number of repetitions decreased with the increase in load (P < 0.001), and the four loading conditions induced a decrease in MVC force immediately after failure (P < 0.001). The average of rectified EMG amplitude (aEMG) of elbow flexors increased for all loads during muscle shortening (SHO) and lengthening (LEN) phases of the movement (P < 0.05), except for the 80 % load during LEN phase. At failure, the aEMG was greater during the SHO than the LEN phase (P < 0.05), except for the 20 % load. TOI decreased for all loads and phases (P < 0.05) but less (P < 0.01) for the 20 % than 60 and 80 % loads (P < 0.01), and for LEN compared with SHO phase. At failure, TOI was negatively associated with aEMG during the SHO (r 2 = 0.99) and LEN (r 2 = 0.82) phases, while TOI and aEMG were positively associated with load magnitude (r 2 > 0.90) in both movement phases. This study emphasizes the influence of load magnitude and movement phase (SHO and LEN) on neuromuscular and oxydative adjustments during movements that involve lifting and lowering a load until failure.

Concepts: Extension, Brachioradialis, Elbow, Flexion, Flexor muscle, Muscle, Triceps brachii muscle, Biceps brachii muscle

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Dunnick, DD, Brown, LE, Coburn, JW, Lynn, SK, and Barillas, SR. Bench press upper-body muscle activation between stable and unstable loads. J Strength Cond Res 29(12): 3279-3283, 2015-The bench press is one of the most commonly used upper-body exercises in training and is performed with many different variations, including unstable loads (ULs). Although there is much research on use of an unstable surface, there is little to none on the use of an UL. The purpose of this study was to investigate muscle activation during the bench press while using a stable load (SL) vs. UL. Twenty resistance-trained men (age = 24.1 ± 2 years; ht = 177.5 ± 5.8 cm; mass = 88.7 ± 13.7 kg) completed 2 experimental conditions (SL and UL) at 2 different intensities (60 and 80% one repetition maximum). Unstable load was achieved by hanging 16 kg kettlebells by elastic bands from the end of the bar. All trial lifts were set to a 2-second cadence with a slight pause at the bottom. Subjects had electrodes attached to 5 muscles (pectoralis major, anterior deltoid, medial deltoid, triceps brachii, and latissimus dorsi) and performed 3 isometric bench press trials to normalize electromyographic data. All 5 muscles demonstrated significantly greater activation at 80% compared with 60% load and during concentric compared with eccentric actions. These results suggest that upper body muscle activation is not different in the bench press between UL and SL. Therefore, coaches should use their preference when designing training programs.

Concepts: Biceps brachii muscle, Barbell, Muscles of the upper limb, Trigraph, Pectoralis major muscle, Muscle contraction, Bench press, Triceps brachii muscle