Shoulder Horizontal Flexion Research Articles

An analysis of whole-body kinematics, muscle strength and activity during cross-step topspin among table tennis players

ABSTRACT This study examined the differences of muscle strength, electromyography (EMG) and whole-body kinematics during maximum cross-step table tennis topspin between advanced and intermediate players. Ten advanced and ten intermediate players performed both voluntary isokinetic contraction test and forehand topspin strokes with maximum-effort towards cross-court target zone. The results indicated that advanced players generated significantly greater maximum racket speeds during forward swing phase (P < 0.05). At the instant of the topspin stroke, significantly smaller shoulder horizontal flexion and elbow flexion angles, but larger joint angular velocities in advanced players (P < 0.05). Moreover, advanced players exhibited longer muscle firing duration of anterior deltoid and biceps brachii as well as higher root mean squares and EMG integrals of the abdominal external oblique, anterior deltoid and biceps brachii muscles than the intermediate players (P < 0.05). Furthermore, the isokinetic results showed higher shoulder abduction/adduction, hip flexion/extension and knee flexion torques at fast speed (240°/s) and higher elbow flexion torque at medium speed (120°/s) in advanced players (P < 0.05). The findings suggest that higher activation of the deltoid, biceps and abdominal external oblique muscles as well as larger muscle strength under higher speed conditions would be the plausible key factors to maximise racket and joint angular velocities in forehand topspin.

Identifying coordination between joint movements during a throwing task with multiple degrees of freedom.

It is known that coordination between joint movements is crucial for the achievement of motor tasks and has been studied extensively. Especially, in sports biomechanics, researchers are interested in determining which joint movements are coordinated to achieve a motor task. However, this issue cannot be easily addressed with the methods employed in previous studies. Therefore, we aimed to propose a method for identifying joint coordination. Subsequently, we examined which joint movements were coordinated using accurate overhead throwing, which required reduction in vertical hand velocity variability. Fourteen baseball players participated by attempting throwing using a motion capture system. The index of coordination for each joint movement and the effect of deviation of one joint movement on vertical hand velocity were quantified. Our results showed that the shoulder internal/external rotation angle (θ1-IE) and the other joint movements or the shoulder horizontal flexion/extension angular velocity (ω1-FE) and the other joint movements were coordinated. These results could be explained by the fact that the effects of the deviation of the shoulder internal rotation angle (θ1-I) and shoulder horizontal flexion angular velocity (ω1-F) on vertical hand velocity were larger than those of the other joint movements. This meant that it was necessary to cancel the deviations of θ1-IE and ω1-FE by the other joint movements. These findings indicate that the method proposed in this study enables the identification of which joint movements are coordinated in multiple degrees of freedom.

Dry swing training with a light bat increases bat speed

Baseball training usually includes dry swing training to improve batting ability. However, no consensus has been reached on the relationship between bat weight and the increase in post-dry swing training bat speed. We hypothesized that dry swing training with a light bat would increase post dry swing training bat speed. Therefore, the purpose of this study was to examine the effect of dry swing training with a light bat on post dry swing training bat speed by comparing a light bat group with a heavy bat group. A total of 34 healthy male students from a university baseball team were randomly divided into a light bat group (n = 17) and a heavy bat group (n = 17). Subjects performed 100 dry swings per day, twice a week for eight weeks. The light bat group performed dry swing training with a 10.6 oz bat and the heavy bat group with a 38.8 oz bat. Bat speed and muscle power were measured before and after the intervention. There was no interaction between the intervention and post dry swing training bat speed, knee extension strength, shoulder horizontal flexion, or hand grip strength. There was a main effect of the intervention on post dry swing training bat speed and shoulder horizontal flexion. Bat speed increased in both groups, but without significant group differences in intervention effects. Since light bat loads in this study were very low, dry swing training with a light bat may be more effective and less strenuous.

Arm Armor System Performance Study: Net Effect (Perceptual Response) Analysis

This study compares the net effect of wearing different shoulder/arm armor systems on garment impediment perception and wearer acceptability. Two independent variables in this study were armor systems and shoulder/ arm movements. There were four armor systems of control garment and arm armor systems A, B, and C as well as five types of arm/shoulder movements, (shoulder flexion, should extension, shoulder abduction, shoulder horizontal flexion, and shoulder horizontal extension). Ten male volunteers wearing size medium battle dress uniform (BDU) with recent relevant military experience participated in this study. The volunteers performed shoulder/arm movements (while wearing each armor treatments) and completed the garment impediment perception as well as wearer acceptability scales. The body areas of neck side, shoulder top, and armscye front showed the highest frequency of reported impediments. Resistance to movement and localized pressure were the most frequently mentioned types of impediment. The armor system B had the most areas of impediment, and was rated as more restrictive than the control garment and armor system A for each movement. For wearer acceptability, no significant differences were found between the control garment and armor system A for all eight items; this indicated that subjects did not perceive a difference between wearing the control garment and armor system A. There was a trend for wearer acceptability to decrease from wearing the control garment to armor systems A to C to B.

Efeitos crônicos do flexionamento estático sobre parâmetros neuromusculares em adultos jovens

INTRODUÇÃO: O treinamento engloba, dentre outras qualidades físicas, a flexibilidade e a força. Assim, conhecer as inter-relações mútuas entre essas qualidades físicas potencializaria a eficácia do treino. OBJETIVO: Verificar as alterações nos parâmetros neuromusculares em um programa de flexionamento estático, após 12 semanas de intervenção. MÉTODOS: Participaram 70 cadetes, com idade média de 17,03 ± 1,14 anos, divididos em dois grupos: grupo experimental (GF, n = 35) e grupo controle (GC, n = 35). A força foi avaliada através de 1RM de contração estática nos movimentos de flexão e extensão horizontal de ombro (FFHO/FEHO) e extensão da coluna lombar (FECL). A flexibilidade foi avaliada pelo protocolo LABIFIE de goniometria nos movimentos de flexão e extensão horizontal de ombro (FHO/EHO) e flexão da coluna lombar (FCL). A concentração de hidroxiprolina na urina coletada pelo método Nordin foi realizada pelo protocolo HPROLI 2h. RESULTADOS: A ANOVA de medidas repetidas demonstrou aumento significativo para FHO (∆% = 3,9%; p = 0,001), EHO (∆% = 21,1%; p = 0,001), FCL (∆% = 73,8%; p = 0,001), FFHO (∆% = 20,4%; p = 0,001) e FECL (∆% = 4,0%; p = 0,008) do pré para o pós-teste. Os níveis de hidroxiprolina não apresentaram alterações significativas. Nas comparações intergrupos, foram encontradas diferenças significativas para FHO (p = 0,016), EHO (p = 0,005), FCL (p = 0,004), FFHO (p = 0,001) e FECL (p = 0,007). O poder do experimento observado foi de 86% para um beta calculado de 0,14. CONCLUSÃO: O flexionamento estático foi capaz de melhorar tanto a flexibilidade como a força.

The Effects of Resistance Training Performed in Water on Muscle Strength in the Elderly

The purpose of the present study was to compare the effects of a program of resistance training in water-based exercises (RWE) with those of a program without resistance control in water-based exercises (WEs). Twenty-seven women (aged 60-74 years) were randomly assigned to the RWE group (n = 10), WE group (n = 10), or nontraining control (CON) group (n = 7). The RWE and WE groups trained classes with aerobic exercises and localized muscular resistance exercises for 50 minutes, twice a week for 12 weeks. For the RWE group, the program included 4 mesocycles of 3 weeks-respectively, 4 sets of 15 repetitions, 4 sets of 12 repetitions, 5 sets of 10 repetitions, and 5 sets of 8 repetitions-of shoulder horizontal flexion exercise at maximum speed, with the use of resistive equipment. For the WE group, the training was not periodized, and the resistance in the localized muscular exercises was not controlled. One repetition maximum (1RM) was measured on a pectoral fly machine at baseline and after the training period. The level of significance adopted was p ≤ 0.05. The results showed that the only significant increase in 1RM (10.89%, p < 0.001) occurred in the RWE group after training. In conclusion, these findings suggest that WEs with emphasis on resistance training in a periodized program can efficiently increase maximum strength in elderly women. Thus, it is suggested that the strategies used in WE programs be modified to offer suitable stimuli for the development of strength.

Kinesthetic perceptions of intrinsic anterior-posterior axes.

The purpose of this research was to investigate whether kinesthetic and proprioceptive perceptions of "straight ahead" were defined by a head- or trunk-fixed axis. Subjects were instructed to align the forearm with the head or trunk anterior-posterior (a/p) axis by elbow flexion or extension in the horizontal plane in five different conditions. In each condition the experimenter varied initial elbow and shoulder horizontal flexion or extension angles and head and/or trunk orientation (by rotation about a vertical axis) on each trial before the subject moved the forearm to align it with the head or trunk axis. The upper limb motion was voluntarily constrained to the horizontal plane through the shoulder. Variable errors were significantly lower when subjects aligned the forearm to the trunk-fixed a/p axis. Furthermore, the perceptual errors showed a greater dependence on body segment orientations when the forearm was aligned to the head axis than to the trunk axis. We conclude that the trunk a/p axis is preferred to the head a/p axis for specifying upper limb segment orientations in the horizontal plane at the kinesthetic perceptual level.

The Effect of Size and Fabric Weight of Protective Coveralls on Range of Gross Body Motions

This study evaluated the effects of garment size and fabric weight on range-of-motion (ROM). Ten male subjects performed a series of twelve gross body movements while wearing each of nine similarly styled coveralls. The coveralls were undersized, appropriately sized, and oversized, and were constructed from three different weights of poly/cotton fabric. A balanced 3 x 3 repeated measures experimental design was used, along with a seminude control condition. ROM was measured with a two-arm manual goniometer. Garment size significantly affected (p < .05) ROM for all movements except shoulder extension and trunk lateral flexion. Compared to seminude ROM, undersized garments reduced the mean ROM by as much as 24% in the case of hip flexion. Fabric weights on ROM were significant for shoulder extension and elbow, hip, knee, and shoulder horizontal flexion. Fabric weight affected ROM less than garment size. Interaction effects between fabric weight and size generally were not significant. These results demonstrate that undersized garments can measurably reduce the wearer's movement capability. Providers of protective clothing should ensure that garments are not undersized and should consider the benefits of oversizing against possible safety and wearer acceptance problems.