Circles on pommel horse with a suspended aid: Mass-centre rotation and hip joint moment

Abstract

This is the second study of the series, and its aim was to investigate the influence of using the suspended aid on circle kinetics. In addition to the kinematic data recorded for part one (Fujihara & Gervais, 2012), the pommel reaction forces and the force applied from the suspended aid (aid reaction force) were analysed in relation to the motion of a whole-body mass centre. The hip joint moment was also computed by combining all segments in the lower extremities into a single rigid segment. Generally, the use of the aid changed the magnitude of the mass-centre trajectory or horizontal pommel reaction forces but not their patterns. The results also showed that the net hip joint moment was altered during circles with the aid. In summary, a suspended aid can be used as a progression for a variety of goals because it allows gymnasts to practise circles which would not be possible without the aid. When a suspended aid is used, however, practitioners should be aware of the possible kinetic alteration caused by the external force from the aid.     

Circles on pommel horse with a suspended aid: spatio-temporal characteristics

A suspended aid is popular for learning circles and for refining circle technique on pommel horse. The aim of this study was to investigate the effect of using a suspended aid on the biomechanical characteristics of circles. This first study focused specifically on the spatio-temporal characteristics of circles. Eighteen gymnasts performed three sets of 10 circles with and without a suspended aid on a pommel horse under which two force plates were set. Three-dimensional coordinates were acquired using 13 Qualisys motion tracking cameras operating at 100 Hz. The results showed that circles with the aid were characterised by a smaller body flexion angle, a greater shoulder angle, a greater ankle circle diameter, earlier hand releases, and a longer total duration. In contrast, the body lateral flexion angle, the arm-leaning angle, and the shoulder circle diameter remained relatively similar to circles without the aid. It was confirmed that circles with the aid actually appeared to be more desirable in terms of the movement amplitude. In this sense, a suspended aid could function as spotting, which is often used for a progression to learn gymnastics skills and to let gymnasts experience a desired movement pattern.     

Circles on pommel horse with a suspended aid: Spatio-temporal characteristics

Abstract

We investigated the associations of anthropometry, training, and pre-race experience with race time in 93 recreational male ultra-marathoners (mean age 44.6 years, s = 10.0; body mass 74.0 kg, s = 9.0; height 1.77 m, s = 0.06; body mass index 23.4 kg · m^?2, s = 2.0) in a 100-km ultra-marathon using bivariate and multivariate analysis. In the bivariate analysis, body mass index (r = 0.24), the sum of eight skinfolds (r = 0.55), percent body fat (r = 0.57), weekly running hours (r = ?0.29), weekly running kilometres (r = ?0.49), running speed during training (r = ?0.50), and personal best time in a marathon (r = 0.72) were associated with race time. Results of the multiple regression analysis revealed an independent and negative association of weekly running kilometres and average speed in training with race time, as well as a significant positive association between the sum of eight skinfold thicknesses and race time. There was a significant positive association between 100-km race time and personal best time in a marathon. We conclude that both training and anthropometry were independently associated with race performance. These characteristics remained relevant even when controlling for personal best time in a marathon.     

Circles on pommel horse with a suspended aid: influence of expertise

In the third study of this series, we examined how circles with a suspended aid would vary depending of the gymnast's level of expertise. We analysed circles with the aid performed by three groups of eight gymnasts: expert, intermediate, and developing groups. The gymnasts for the expert and intermediate groups were selected from the previous studies based on judges' evaluation of their non-aid circles. The developing group of eight gymnasts, who were unable to perform circles on pommel horse without an aid, were added to this study and performed three sets of 10 circles on the pommel horse with the aid. Discriminative biomechanical variables identified in the previous two studies were used to compare circles with the aid among the three groups. As a result, the expert group demonstrated a larger pommel reaction force and a smaller aid reaction force than the other two groups, implying that they were less dependent on the aid. The smaller aid reaction force resulted in a smaller net hip joint moment. Furthermore, the expert group showed a shorter total duration and a greater shoulder excursion. In summary, the suspended aid can be used in a progressive manner depending on the gymnast's level of expertise.     

Circles with a suspended aid: reducing pommel reaction forces

The aim of this study was to investigate the influence of a suspended aid on the reaction forces during a basic skill on pommel horse. Twenty gymnasts performed three sets of 10 circles with and without a suspended aid on a pommel horse under which two force plates were set. The results confirmed that the suspended aid could reduce the magnitude of the pommel reaction forces during circles while maintaining the general loading pattern. On the left hand, the average and peak forces were attenuated to 0.59 body weight (BW) and 0.85 BW from 0.76 BW and 1.13 BW, respectively. The right hand experienced slightly larger forces with no-aid trials, but the asymmetry between the hands decreased with the aid. Despite a relatively large variability, all gymnasts experienced smaller impact peak forces with the aid. A suspended aid is most commonly used for a beginner gymnast as an introduction to pommel horse exercises. However, this study confirmed that it can also be useful for all levels of gymnasts who would like to practice pommel horse exercises with reduced pommel reaction forces for a purpose such as a progression for learning a new skill, control of training volume, or rehabilitation.     

Circles with a suspended aid: reducing pommel reaction forces

The aim of this study was to investigate the influence of a suspended aid on the reaction forces during a basic skill on pommel horse. Twenty gymnasts performed three sets of 10 circles with and without a suspended aid on a pommel horse under which two force plates were set. The results confirmed that the suspended aid could reduce the magnitude of the pommel reaction forces during circles while maintaining the general loading pattern. On the left hand, the average and peak forces were attenuated to 0.59 body weight (BW) and 0.85 BW from 0.76 BW and 1.13 BW, respectively. The right hand experienced slightly larger forces with no-aid trials, but the asymmetry between the hands decreased with the aid. Despite a relatively large variability, all gymnasts experienced smaller impact peak forces with the aid. A suspended aid is most commonly used for a beginner gymnast as an introduction to pommel horse exercises. However, this study confirmed that it can also be useful for all levels of gymnasts who would like to practice pommel horse exercises with reduced pommel reaction forces for a purpose such as a progression for learning a new skill, control of training volume, or rehabilitation.     

Kinematics of side and cross circles on pommel horse

Abstract

One of the most fundamental skills on the pommel horse is double leg circles (circles). Circles can be performed on all parts of the pommel horse. It was hypothesized that the different sets of physical constraints of the apparatus require a gymnast to adapt circles technique. The purpose of this study was to quantify how gymnasts modify their technique during circles to accommodate different physical obstacles due to different support surfaces and body orientations. To investigate these adaptations, a comparison of the two most common circles on pommel horse – namely, circles in cross support (cross-circles) and circles in side support (side-circles) – was carried out. Seven elite male gymnasts performed three sets of 10 cross-circles and side-circles on a pommel horse. Three-dimensional coordinates were acquired using 12 Qualisys ProReflex motion tracking cameras operating at 120 Hz. Temporal characteristics, the motion of the centre of mass, and the body angles – flexion and lateral flexion – were analysed. We found that cross-circles took less time to complete a single circle (0.92±0.02 vs. 0.95±0.02 s), had a smaller ratio for the rear support phase (0.15±0.02 vs. 0.18±0.03), a narrower supporting-hand distance (0.33±0.03 vs. 0.52±0.00 m), greater flexion of the body over the rear support phase (44±12° vs. 27±8°), and less lateral flexion of the body over the single-hand support phase (entry: 20±5° vs. 35±3°; exit: 26±4° vs. 33±4°) than side-circles. Our results suggest that gymnasts adapt their technique to the physical constraints imposed by the shape of the pommel horse and the location and orientation of the circles. Cross-circles were characterized by a high rear support position with a narrower hand-spacing, which would require excellent shoulder flexibility and strength. Consequently, lack of these traits may explain the need for greater body flexion in cross-circles than in side-circles during rear support. Understanding the technical differences will facilitate an effective transfer of the technical similarities among different types of circles.     

The effect of combined self- and expert-modelling on the performance of the double leg circle on the pommel horse

Abstract

In this study, we investigated whether video modelling can enhance gymnasts' performance of the circle on a pommel horse. The procedure associated expert-modelling with self-modelling and quantitative performance analysis. Sixteen gymnasts were randomly assigned to one of two groups: (1) a modelling group, which received expert- and self-modelling, and performance feedback, or (2) a control group, which received no feedback. After five sessions of training, an analysis of variance with repeated measures indicated that the gains in the back, entry, front, and exit phases of the circle were greater for the modelling group than for the control group. During the training sessions, the gymnasts in the modelling group improved their body segmental alignment during the back phase more quickly than during the other phases. As predicted, although both groups performed the same number of circles (300 in 5 days, with 10 sequences of 6 circles), the modelling group improved their body segmental alignment more than the control group. It thus appears that immediate video modelling can help to correct complex sports movements such as the circle performed on the pommel horse. However, its effectiveness seemed to be dependent on the complexity of the phase.     

The effect of combined self- and expert-modelling on the performance of the double leg circle on the pommel horse

In this study, we investigated whether video modelling can enhance gymnasts' performance of the circle on a pommel horse. The procedure associated expert-modelling with self-modelling and quantitative performance analysis. Sixteen gymnasts were randomly assigned to one of two groups: (1) a modelling group, which received expert- and self-modelling, and performance feedback, or (2) a control group, which received no feedback. After five sessions of training, an analysis of variance with repeated measures indicated that the gains in the back, entry, front, and exit phases of the circle were greater for the modelling group than for the control group. During the training sessions, the gymnasts in the modelling group improved their body segmental alignment during the back phase more quickly than during the other phases. As predicted, although both groups performed the same number of circles (300 in 5 days, with 10 sequences of 6 circles), the modelling group improved their body segmental alignment more than the control group. It thus appears that immediate video modelling can help to correct complex sports movements such as the circle performed on the pommel horse. However, its effectiveness seemed to be dependent on the complexity of the phase.     

Effects of muscle-tendon length on joint moment and power during sprint starts

The aim of this study was to examine the effects of muscle-tendon length on joint moment and power during maximal sprint starts. Nine male sprinters performed maximal sprint starts from the blocks that were adjusted either to 40 degrees or 65 degrees to the horizontal. Ground reaction forces were recorded at 833 Hz using a force platform and kinematic data were recorded at 200 Hz with a film camera. Joint moments and powers were analysed using kinematic and kinetic data. Muscle - tendon lengths of the medial gastrocnemius, soleus, vastus medialis, rectus femoris and biceps femoris were calculated from the set position to the end of the first single leg contact. The results indicated that block velocity (the horizontal velocity of centre of mass at the end of the block phase) was greater (P < 0.01) in the 40 degrees than in the 65 degrees block angle condition (3.39 +/- 0.23 vs. 3.30 +/- 0.21 m . s(-1)). Similarly, the initial lengths of the gastrocnemius and soleus of the front leg in the block at the beginning of force production until half way through the block phase were longer (P < 0.001) in the 40 degrees than in the 65 degrees block angle condition. The initial length and the length in the middle of the block phase were also longer in the 40 degrees than in the 65 degrees block angle condition both for both the gastrocnemius (P < 0.01) and soleus (P < 0.01-0.05) of the rear leg. In contrast, the initial lengths of the rectus femoris and vastus medialis of the front leg were longer (P < 0.05) in the 65 degrees than in the 40 degrees block angle condition. All differences gradually disappeared during the later block phase. The peak ankle joint moment (P < 0.01) and power (P < 0.05) during the block phase were greater in the 40 degrees than in the 65 degrees block angle condition for the rear leg. The peak ankle joint moment during the block phase was greater (P < 0.05) in the 40 degrees block angle for the front leg, whereas the peak knee joint moment of the rear leg was greater (P < 0.01) in the 65 degrees block angle condition. The results suggest that the longer initial muscle-tendon lengths of the gastrocnemius and soleus in the block phase at the beginning of force production contribute to the greater peak ankle joint moment and power and consequently the greater block velocity during the sprint start.     

增强髋关节力量的重要性——优秀女子短跑运动员秦旺萍的训练启示

以当代短跑训练理论为指导,运用文献资料、个案研究、实验等方法对江苏省女子优秀短跑运动员秦旺萍进行增强髋关节力量训练的跟踪研究。研究认为增强髋关节力量(尤其是伸髋力量)对优秀短跑运动员具有十分重要的意义,它是当代优秀短跑选手以髋为轴高速摆动技术的重要保证,在短跑力量训练中应引起足够的重视。     

Net joint moments and muscle activation in barbell squats without and with restricted anterior leg rotation

Muscle utilisation in squat exercise depends on technique. The purpose of this study was to compare net joint moments (NJMs) and muscle activation during squats without and with restricted leg dorsiflexion. Experienced men (n = 5) and women (n = 4) performed full squats at 80% one repetition maximum. 3D motion analysis, force platform and (EMG) data were collected. Restricting anterior leg rotation reduced anterior leg (P = 0.001) and posterior thigh (P < 0.001) rotations, resulting in a smaller knee flexion range of motion (P < 0.001). At maximum squat depth, ankle plantar flexor (P < 0.001) and knee extensor (P < 0.001) NJM were higher in unrestricted squats. Hip extensor NJM (P = 0.14) was not different between squat types at maximum squat depth. Vastus lateralis (P > 0.05), vastus medialis (P > 0.05) and rectus femoris (P > 0.05) EMG were not different between squat types. Unrestricted squats have higher ankle plantar flexor and knee extensor NJM than previously reported from jumping and landing. However, ankle plantar flexor and knee extensor NJM are lower in restricted squats than previous studies of jumping and landing. The high NJM in unrestricted squat exercise performed through a full range of motion suggests this squat type would be more effective to stimulate adaptations in the lower extremity musculature than restricted squats.     

对“用欧拉角描述人体髋关节运动”论点的商榷

目前有些专家、学者用欧拉角来描述髖关节的运动,然而,欧拉角的运用会出现数学计算上的困难,且所涉及的转轴与人体基本运动轴不一致。本文介绍了与人体运动轴较为相符,且又可避免欧拉角应用时数学计算困难的一种方法,即用布里恩角来描述人体髖关节的定点运动。     

史东鹏与110米栏一级运动员肩、髋、膝3关节等速肌力测试的对比研究

运用澳大利亚KEYHNKK公司生产的“Kinitech”等速肌力测试系统,对史东鹏及我国6名男子110米跨栏一级运动员肩、髋、膝3关节力量测试。结果表明：与一级运动员相比,史东鹏肩、髋、膝3关节肌力特征并不具备明显优势,但其各关节屈伸肌力发展协调、平衡,当角速度逐渐增加时仍能保持较强的肌力输出和较好的爆发力,这可能是史东鹏取得优异成绩的关键所在。     

The effects of cold application and modified PNF stretching techniques on hip joint flexibility in college males.

The purpose of the study was to determine the effects of modified Proprioceptive Neuromuscular Facilitation (PNF) flexibility techniques on hip flexion in college males and to determine if local cold application enhances the effectiveness of these techniques. Male subjects (N = 120), with an average age of 21.5 +/- 2.7 years, were randomly assigned to one of four different kinds of stretching treatments with cold or no cold application (15 per group). Range of motion (ROM) in degrees was determined following four stretching techniques: three modified PNF (PCP, 3-PIECP, 3-PIFCP) and a passive stretch (P). Data were analyzed using a 2 (conditions) x 4 (treatments) ANOVA. There were no significant differences in ROM between cold and no cold conditions. Significant differences existed among ROM techniques (p less than .05). Post hoc analyses revealed that the three modified PNF techniques resulted in greater ROM than the passive stretch technique. However, we conclude that cold application does not influence the effectiveness of selected stretching techniques.     

Functional shoulder ratios with high velocities of shoulder internal rotation are most sensitive to determine shoulder rotation torque imbalance: a cross-sectional study with elite handball players and controls

The aim of the present study was to determine which approach to calculating shoulder ratios is the most sensitive for determining shoulder torque imbalance in handball players. Twenty-six participants (handball athletes, n = 13; healthy controls, n = 13) performed isokinetic concentric and eccentric shoulder internal rotation (IR) and external rotation (ER) assessment at 60, 180 and 300°/s. We used eight approaches to calculating shoulder ratios: four concentric (i.e. concentric ER torque divided by concentric IR torque), and four functional (i.e. eccentric ER torque divided by concentric IR torque) at the velocities of 60, 180 and 300°/s for both IR and ER, and combining 60°/s of ER and 300°/s of IR. A three factorial ANOVA (factors: shoulder ratios, upper limb sides, and groups) along with Tukey’s post-hoc analysis, and effect sizes were calculated. The findings suggested the functional shoulder ratio combining 60°/s of ER and 300°/s of IR is the most sensitive to detect differences between upper limbs for handball players, and between players and controls for the dominant side. The functional shoulder ratio combining 60°/s of ER with 300°/s of IR seems to present advantages over the other approaches for identifying upper limb asymmetries and differences in shoulder torque balance related to throwing.     

Foot and ankle joint movements of dancers and non-dancers: a comparative study

Ballerinas use their ankle joints more extremely and sustain injuries on the ankle joint more frequently than non-dancers. Therefore, the ankle movement of dancers is important and should be studied to prevent injuries. Measuring ankle joint range of motion (ROM) using radiographs could demonstrate the contribution to motion of each joint. The aim of this study was to analyse and compare ankle joint movements and the ratio of each joint’s contribution during movement between dancers and non-dancers, using radiographic images. Dancers have lower dorsiflexion (26.7 ± 6.2°), higher plantarflexion (74.3 ± 7.1°) and higher total (101.1 ± 10.8°) ROMs than non-dancers (33.9 ± 7.0°, 57.2 ± 6.8° and 91.1 ± 9.3°, respectively) (p < 0.05). Although the ROMs were different between the two groups, the ratios of each joint movement were similar between these two groups, in all movements. Regarding total movement, the movement ratio of the talocrural joint was almost 70% and other joints accounted for almost 30% of the movement role in both dancers and non-dancers. Therefore, the differences in ROM between dancers and non-dancers were not a result of a specific joint movement but of all the relevant joints’ collaborative movement.     

Effects of a combined inversion and plantarflexion surface on knee and hip kinematics during landing

Although landing in a plantarflexion and inversion position is a well-known characteristic of lateral ankle sprains, the associated kinematics of the knee and hip is largely unknown. Therefore, the purpose of this study was to examine the changes in knee and hip kinematics during landings on an altered landing surface of combined plantarflexion and inversion. Participants performed five drop landings from 30 cm onto a trapdoor platform in three different conditions: flat landing surface, 25° inversion, or a combined 25° plantarflexion and 25° inversion. Kinematic data were collected using a seven camera motion capture system. A 2 × 3 (leg × surface) repeated measures ANOVA was used for statistical analysis. The combined surface showed decreased knee and hip flexion range of motion (ROM) and increased knee abduction ROM (p < 0.05). The altered landing surface creates a stiff landing pattern where reductions in sagittal plane motion are transferred to the frontal plane, resulting in increased knee abduction. A stiff landing pattern is frequently related to increased risk of anterior cruciate ligament injury. It may be beneficial for athletes at risk to train for alternate methods of increasing their sagittal plane motion of the knee and hip with active knee or trunk flexion.     

Multidimensional joint coupling: a case study visualisation approach to movement coordination and variability

Abstract

A case study visualisation approach to examining the coordination and variability of multiple interacting segments is presented using a whole-body gymnastic skill as the task example. One elite male gymnast performed 10 trials of 10 longswings whilst three-dimensional locations of joint centres were tracked using a motion analysis system. Segment angles were used to define coupling between the arms and trunk, trunk and thighs and thighs and shanks. Rectified continuous relative phase profiles for each interacting couple for 80 longswings were produced. Graphical representations of coordination couplings are presented that include the traditional single coupling, followed by the relational dynamics of two couplings and finally three couplings simultaneously plotted. This method highlights the power of visualisation of movement dynamics and identifies properties of the global interacting segmental couplings that a more formal analysis may not reveal. Visualisation precedes and informs the appropriate qualitative and quantitative analysis of the dynamics.     

The effects of mid-flight whole-body and trunk rotation on landing mechanics: implications for anterior cruciate ligament injuries

ABSTRACT

The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen’s dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen’s dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen’s dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries.