Genevieve Williams a, Gareth Irwin a, David G. Kerwin a & Karl M. Newell b a Cardiff School of Sport, University of Wales Institute, Cardiff, UK

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1 This article was downloaded by: [ ] On: 19 July 2012, At: 03:53 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Sports Biomechanics Publication details, including instructions for authors and subscription information: Kinematic changes during learning the longswing on high bar Genevieve Williams a, Gareth Irwin a, David G. Kerwin a & Karl M. Newell b a Cardiff School of Sport, University of Wales Institute, Cardiff, UK b Department of Kinesiology, Pennsylvania State University, University Park, PA, USA Version of record first published: 05 Dec 2011 To cite this article: Genevieve Williams, Gareth Irwin, David G. Kerwin & Karl M. Newell (2012): Kinematic changes during learning the longswing on high bar, Sports Biomechanics, 11:1, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Sports Biomechanics March 2012; 11(1): Kinematic changes during learning the longswing on high bar GENEVIEVE WILLIAMS 1, GARETH IRWIN 1, DAVID G. KERWIN 1,& KARL M. NEWELL 2 1 Cardiff School of Sport, University of Wales Institute, Cardiff, UK, and 2 Department of Kinesiology, Pennsylvania State University, University Park, PA, USA (Received 3 December 2010; accepted 19 July 2011) Abstract The purpose of this study is to provide evidence of technique changes during learning a sports-specific skill, the looped bar longswing (LLS). Thirteen male participants with no previous high bar experience took part in a training study. Kinematic data were collected using a CODA motion analysis system (200 Hz) during eight weekly testing sessions. Analyses focused on the amplitude of swing and the functional phase (FP) actions, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical. Three groups were identified based on the number of sessions it took each participant to perform the LLS (G1: most successful, G2: intermediate, and G3: least successful). All participants were able to significantly increase swing amplitude over the training period ( p, 0.05). For each participant the hip FP started significantly: later for G1, earlier for G2, and did not change for G3. Extension actions at the shoulders were dissimilar to those reported for elite gymnasts performing the longswing. The FP of the hips provides a mechanism to distinguish between the learners of different skill levels. The study has provided support for a single-subject design when investigating technique changes during learning. Keywords: Gymnastics, technique, functional phase Introduction The empirical study of motor learning describes changes in the capability to produce a skilled action that is acquired as a result of practice or experience. Based on empirical evidence, theories of motor learning are concerned with understanding how movements are coordinated and controlled to become more skilful; more effectively and efficiently meeting task demands (Newell, 1985). Sport is a domain where motor learning theory is particularly applicable to practice (Čoh et al., 2004). However, limited empirical motor learning studies have been undertaken in the natural physical setting of sport, rendering much of the application of motor learning theory to a sports training environment speculative. The sport of gymnastics provides a particularly useful vehicle to study the skill learning process as success is directly related to a performer s technique. Specifically, technical form and body position during gymnastics skills are defined and judged according to the Fédération Internationale de Gymnastique (FIG, 2009) Code of Points. In the current Correspondence: Genevieve Williams, Cardiff School of Sport, University of Wales Institute, Cyncoed Campus, Cyncoed Road, Cardiff, UK, gewilliams@uwic.ac.uk ISSN print/issn online q 2012 Taylor & Francis

3 Kinematic changes during learning the longswing on high bar 21 study, the men s gymnastics skill of the longswing on high bar was chosen as a vehicle to examine technique changes during learning. The longswing is a fundamental skill on the high bar apparatus, consisting of a rotation about the horizontal bar axis in the vertical plane, where the gymnast swings from handstand to handstand (Brüggermann et al., 1994). Correct technical form for the longswing, stated within the FIG Code of Points (2009), requires the gymnast s arms and legs to be fully extended throughout. Therefore, basic technique consists of flexion and extension actions occurring at the hips and shoulders as the gymnast rotates about the bar. The basic version of the longswing is not always seen in competition due to the mechanical advantages of further manipulating the body shape. However, the basic longswing underpins successful performance on the men s high bar apparatus due to its association with the development of more complex longswings and skills (Readhead, 1997). During the initial stages of learning the longswing, modifications are made to the interaction between the performer s hands and the bar for safety reasons. Specifically, during competition, swinging on high bar is performed with a chalked bar, in order to increasefrictionbetweenprotectivehandguardswornbythegymnastsandthehighbar. However, during learning, hand guards are not worn, instead the longswing is performed with loops which attach the performer to a polished high bar. Therefore, for safety reasons the looped bar longswing (LLS) was adopted for the current study (Figure 1). Further support for the use of the LLS comes from the previous biomechanical research which has shown that there are minimal technique differences between the actions at the hips and shoulders between the LLS and the chalked bar longswing (Irwin & Kerwin, 2007b). The biomechanics of performing successful longswings is well understood. Within contemporary literature, longswings have been examined for two purposes. For example, Figure 1. Illustration of the LLS on high bar.

4 22 G. Williams et al. groups from Cologne and Loughborough have examined the adapted longswing preceding release and re-grasp and dismount skills (Arampatzis & Brüggemann, 1998, 1999, 2001; Yeadon & Hiley, 2000; Hiley & Yeadon, 2003a, 2003b). Alternatively, researchers from Cardiff have looked at the traditional longswing due to its association with skill development (Irwin & Kerwin, 2005, 2007a, 2007b). Researchers concur that there are a number of key kinematic characteristics of technique that are related to successful longswing performance (Arampatzis & Brüggemann, 1999; Yeadon & Hiley, 2000). For example, key actions of the hips and shoulders were termed functional phase (FP) actions by Irwin and Kerwin (2005). Specifically, FP actions constituted the hyperextension to flexion action of the hips and a flexion to extension action of the shoulders occurring beneath the lower vertical of the bar. These joint angles were defined with the joint centre as their origin and measured relative to their adjoining segments. However, the key information reported by these authors was the angular position of the gymnast s centre of mass (CM) with respect to the bar during the swing (circle angle) at the points at which the key discrete hip and shoulder joint angles occurred. Based on the empirical data from four elite gymnasts, the authors reported that during the traditional chalked bar longswing, the circle angles at the start and the end of the FP were 249 ^ 58 and 338 ^ 108 for the hip, and 252 ^ 208 and 362 ^ 68 for the shoulder. These values are based on the performer being at a circle angle of 908 and 4508 when in handstand above the bar. In addition, it was reported that 70% of gymnasts musculoskeletal work occurred during the FP of the skill (Irwin & Kerwin, 2007b). However, to date, no studies have provided evidence of how these key technique variables change during learning the longswing. Knowledge of the biomechanics of successful longswings provides a theoretical underpinning to address more applied issues associated with longswing technique. In addition, a key theme of this paper was to create a motor learning study in an ecologically valid sports training environment. A first step in describing changes in technique is the one focussed on single joint kinematics. This study aimed to examine how the kinematics of technique, specifically related to the FP, changed during learning the LLS. The relevance of this research lies within understanding how people learn complex motor skills, while providing ecologically valid examples from a sports training environment. Methods Participants Ethical approval was gained from the host university s Ethics Committee prior to the onset of the study. Thirteen male participants gave voluntary informed consent to take part (M ^ SD; age, 20 ^ 3 years; mass, 73.0 ^ 7.1 kg; and stature, 1.77 ^ 0.06 m). All participants were recreational athletes with no prior high bar experience. Eligibility to take part in the study was granted after participants successfully completed a health questionnaire and had been screened for the capability to perform skills reflective of the physical demands of the LLS and its associated progressions (Readhead, 1997). Procedure Initially, participants were shown videos and received an explanation of the aims of the LLS. Eight testing sessions then took place, on the same day of every week for 8 weeks. Between testing sessions, participants completed a structured training session.

5 Kinematic changes during learning the longswing on high bar 23 During testing sessions, each participant completed five trials of three LLS attempts after a warm-up. The bar was highly polished to reduce the coefficient of fiction, preventing the occurrence of grip-lock while swinging (Samuelson et al., 1996). Loops were fitted by a national-level gymnastics coach (Readhead, 1997). Any tears or blisters to afflict the hands meant that the participant would be removed from the study. During each trial, participants were given the ongoing aim of increasing their swing amplitude by beginning higher on the downswing and ending higher on the upswing, until ideally, they were able to perform the complete LLS. Participants were instructed to keep knees and elbows fully extended during swinging. A national-level gymnastics coach provided support to assist each participant in gaining initial angular momentum, removing the need to learn the trolley swing (a movement used to generate the initial swing). The coaches maintained consistency in the amount of assistance each performer received, and once the swing had started additional support was removed and data collection occurred. During the swing technical instruction was provided by the coach and kept to the relevant recommended techniques (Readhead, 1997, p. 189). Specifically, the coach emphasised three key technical points for the skill: an extended body shape during the downswing, the hips lead the swing under the bar, and rapid acceleration of the legs into the upswing, closing the hip and shoulder angles. Training sessions were run by the gymnastics coach and took place in a gymnasium. Training sessions comprised the structured implementation of longswing-specific skill progressions and conditioning exercises designed to replicate activities performed by novice gymnasts in a typical gymnastics coaching environment. For example, training exercises were categorised by three themes: conditioning exercises, for example holding a handstand; early skill progressions, such as the looped pendulum swing; and advanced skill progressions, such as an assisted looped layaway and swing down. Detailed examples of these exercises can be found in the Readhead (1997) men s gymnastics coaching manual and Irwin and Kerwin (2005). Participants trained together and each individual performed all the selected exercises. Data collection In order to obtain individual-specific body segment inertia parameters, anthropometric data were obtained using the digital image technique reported by Gittoes et al. (2009; Canon EOS400D SLR, Tokyo, Japan) for use within Yeadon s (1990) geometric inertia model. Kinematic data (200 Hz) were collected using an automated 3D motion capture system (CODAmotion, Charnwood Dynamics Ltd, Leicester, UK). Two CX1 scanners provided a field of view exceeding 2.5 m around the centre of the bar. Active markers were placed on the lateral aspect of each participant s right side at the estimated centre of rotation of the shoulder and the elbow, mid forearm, greater trochanter, femoral condyle, lateral malleolus, fifth metatarsophalangeal, and the centre of the underside of the bar. Data were collected for each trial performed by each participant. Data analysis Bilateral symmetry of movement was assumed and consequently planar analysis was conducted (Irwin & Kerwin, 2001). Coordinate data were processed using the kernel smooth function ksmooth (MathCad14e, Parametric Technology Corporation, Needham, MA, USA) with the smoothing parameter set to This routine has similar characteristics to a Butterworth low-pass digital filter with cut-off frequency set to 4.5 Hz (Kerwin & Irwin, 2010).

6 24 G. Williams et al. Estimation of the total body CM was performed in CODA Motion Analysis Software V6.68, 2001 (Charnwood Dynamics Ltd). The circle angle was based on a classic mechanical definition, where a circle angle of 908 and 4508 saw the CM of the gymnast above the bar (in handstand). Hip angle was defined by the lines joining the shoulder centre, greater trochanter, and femoral condyle markers. Shoulder angle was defined by the lines joining elbow, shoulder, and greater trochanter markers. Knee angle was defined by the line joining the greater trochanter, femoral condyle, and lateral malleolus. Angle data were differentiated with respect to time using a variation of Ridder s divided difference method (Press et al., 1992) to create angular velocity profiles. Swing 2 (the middle swing) in each trial was analysed due to the possibility that swings 1 and 3 could be contaminated by the coach s manual intervention. In order to provide inter-performer comparison between swings, data were interpolated in 18 increments of rotation about the bar. Variables For each swing the following variables were analysed: swing amplitude, circle position at the start and end of the FP, and hip and shoulder angles at the start and end of the FP. Continuous joint angle profiles of the hips, shoulders, and knees throughout the skill were also analysed. Grouping of participants Initial observations of swing amplitude for each performer identified three groups of participants (G1, G2, and G3). The groups were defined based on the session by which participants were able to perform the LLS: G1: most successful (n ¼ 4): participants were able to perform the LLS by Session 3. G2: intermediate (n ¼ 5): participants were able to perform the LLS by Session 8. G3: least successful (n ¼ 4): participants were unable to perform the LLS by Session 8. Statistical analysis Differences between discrete variables across testing sessions were quantified using repeated measures analysis of variance (RM ANOVA), based on a single subject design. The level of statistical significance was set a priori to p, 0.05, where the Bonferroni correction was applied for multiple comparisons. Mauchly s test was used to determine the sphericity assumption within the data; where sphericity was violated, probability was corrected according to the Greenhouse Geisser procedure. Pearson s correlation coefficients were calculated in order to investigate pairwise correlations between swing amplitude and key FP variables (start and end of the hip and shoulder FP, joint angles at the start and end of the hip and shoulder FP) for each group of participants over eight sessions. Results Differences across testing sessions (RM ANOVA) There was a significant improvement in swing amplitude for each participant over eight sessions ( p, 0.05; Figure 2, Table I). Post hoc tests revealed significant improvements in swing amplitude for participants in G1 between adjacent Sessions 1 2 3; G2 between

7 Kinematic changes during learning the longswing on high bar 25 Figure 2. Swing amplitude for a group of 13 novice performers learning the LLS on high bar during eight testing sessions. Circles represent performers in G1, diamonds represent performers in G2 and crosses represent performers in G3. Table I. Swing amplitude of five swings during each testing sessions for participants learning the LLS on high bar. Swing amplitude (8), M ^ SD Session Group Participant PT ^ ^ ^ ^ ^ ^ ^ ^ 0 PT ^ ^ ^ ^ ^ ^ ^ ^ 0 PT ^ ^ ^ ^ ^ ^ ^ ^ 0 PT ^ ^ ^ ^ ^ ^ ^ ^ 0 2 PT ^ ^ ^ ^ ^ ^ ^ ^ 26 PT ^ ^ ^ ^ ^ ^ ^ ^ 11 PT ^ ^ ^ ^ ^ ^ ^ ^ 39 PT ^ ^ ^ ^ ^ ^ ^ ^ 48 PT ^ ^ ^ ^ ^ ^ ^ ^ 62 3 PT ^ ^ ^ ^ ^ ^ ^ ^ 15 PT ^ ^ ^ ^ ^ ^ ^ ^ 26 PT ^ ^ ^ ^ ^ ^ ^ ^ 9 PT ^ ^ ^ ^ ^ ^ ^ ^ 11 Sessions and 5 6 7; G3 between Sessions and ( p, 0.05). Participants in G1 had the highest swing amplitude during Session 1, where participants in G3 had the smallest (Table I). For individual participants, placement of the start of the hip FP was related to group. For each participant in G1, start of the hip FP became significantly later in the circle during the learning period (Sessions 1 8; p, 0.05; Figure 3). In contrast, four out of five participants in G2 performed the start of the hip FP significantly earlier in the circle between Sessions 1 and 8 ( p, 0.05; Figure 3). For participants in G3, no significant differences were observed in the start of hip FP between Sessions 1 and 8 (Figure 3). The end of the hip FP became significantly later in the circle between Sessions 1 and 8 for participants in G1 and G2 ( p, 0.05).

8 26 G. Williams et al. Figure 3. Average FP of the hips (black line) and shoulders (light grey line) and swing amplitude (dark grey) performed during eight sessions by a group of novices learning the LLS on high bar. Placement of the start of the shoulder FP was highly variable within sessions and did not show a pattern of change for the 13 participants. Placement of the end of the shoulder FP showed no significant change across session for 10 participants. However, for a single participant from each group the placement of the shoulder FP was significantly different (earlier for G1 between Sessions 3 and 8, for G3 between Sessions 1 and 5, and later for G2 between Sessions 1 and 8; Figure 3). For all participants, maximum hip hyperextension angle significantly reduced between Sessions 1 and 8 ( p, 0.05; Figure 4). Maximum hip flexion did not show a consistent pattern of change for any of the participants.

9 Kinematic changes during learning the longswing on high bar 27 Figure 4. Hip (black line) and shoulder (grey line) joint angle profiles for a representative swing for a performer in G3 (PT05) during Session 8. Dashed lines identify the start (FP1) and end (FP2) of the FPof the hips (H) and shoulders (S). Table II. Group mean correlations between swing amplitude, start (1) and end (2) of the hip (Hip) and shoulder (Sho) FP, and corresponding joint angles (H1, 2; S1, 2). Hip FP1 Hip FP2 Sho FP1 Sho FP2 Hip1 Hip2 Sho1 Sho2 G1 0.8* 0.95* -0.84* 0.68* 0.80* * G2-0.92* 0.87* * 0.96* -0.72* G * * 0.87* * *p, For all participants there was no significant difference in maximum shoulder flexion angle between Sessions 1 and 8. Maximum shoulder extension significantly reduced between Sessions 1 and 8 (Figure 4). Hip joint angle profiles comprised a single hyperextension to flexion action occurring under the lower vertical (for example, Figure 4). Unlike the hip angle profiles, the shoulder angle profiles did not comprise a continual flexion to extension action during the shoulder FP. Rather, for 12 participants, the shoulder joint angle profile contained a number of plateaus between maximum flexion and maximum extension (for example, Figure 4). The plateaus during the closing of the shoulder angle occurred between a circle position of 2508 and 3208 as the performers passed under the lower vertical. A single participant did not show this pattern of shoulder extension within the FP but rather a single extension action. This participant was the first to be able to perform the LLS. Knee joint angle profiles revealed that all participants performed some knee flexion during swings. More specifically, performers in G1 performed a slight knee flexion (20 308) during the upswing. Performers in G2 showed the highest knee flexion during the upswing in Week 7, with two participants performing up to a maximum of 608 of knee flexion during the upswing. On the other hand, performers in G3 flexed their knees during the downswing and the upswing, particularly during early sessions. Group correlations Pairwise correlations between swing amplitude and key FP variables for each group of participants are shown in Table II. Correlation between swing amplitude and start of the hip FP was significant and positive for G1, significant and negative for G2, and nonsignificant for G3 (Table II).

10 28 G. Williams et al. Significant positive correlations between swing amplitude and the end of the hip FP, end of the shoulder FP, and hip angle at the start of the hip FP were common for G1, G2, and G3 (Table II). Discussion This study aimed to examine how kinematics of technique, specifically related to the FP, changed during learning the LLS. The relevance of this research lies within understanding how people learn complex motor skills, while providing ecologically valid examples from a sports training environment (Elliot et al., 2006; Kerwin & Irwin, 2008). The reach of ecological validity within this study was defined by three key aspects of the training intervention. Specifically, a national-level gymnastic coach ran all training sessions and was responsible for overseeing LLS attempts during testing sessions. The national-level coach followed recommended progressions and key feedback for learning the LLS as documented by Readhead (1997), and training sessions took place in a typical gymnastic training environment. The importance of defining the environmental and task constraints during an intervention is directly linked to the value of the findings in practice. Although further study would be required to determine the robustness of the results found in this study, the study has provided an example of how technique changes during learning a sports-specific skill within an ecologically valid training environment. In the course of the study, swing amplitude was found to significantly increase for each participant. Three groups were identified based on the session in which participants were able to perform the LLS: G1, G2, and G3. The participants in G1 were able to perform the LLS by Session 3; participants in G2 were able to perform the LLS by Session 8; and participants in G3 were unable to perform the LLS during the study period. During Session 1, participants in G1 obtained the greatest swing amplitudes, while participants in G2 had mid-range swing amplitudes and participants in G3 began with the smallest swing amplitudes. Therefore, the results of this study highlight that those participants who performed most successfully in the initial attempt developed the skill the quickest (G1). Evidence from motor learning literature indicates that learning rate is individual and task specific even when a persistent change is apparent across subjects (Newell et al., 2001). Motor learning theory suggests that the initial capability of a novice to perform a skill depends on motor experience of similar tasks; the information provided about the movement task to be performed; as well as physiological and psychological factors such as strength and motivation (Latash, 1998). During this study, participants were provided with the same information regarding the aims of the LLS and the desired characteristics of technique to achieve it. It is likely that prior motor experience and physiological factors could be the main sources of differences in initial ability. Recognising how initial skill level is related to learning rate could be linked to tailoring individual-specific training interventions for this skill, particularly as specific characteristics of technique were related to performance level during the training period. Individual-specific training interventions have been suggested to be the most effective aid to learning, that is, they enable a performer to move from a novice technique to a more successful technique in the least amount of time through the practice methods provided (Čoh et al., 2004). When analysing the differences in key LLS variables over sessions, an initial single subject design was chosen to avoid creating a mythical average performer during the difference analysis (Dufek et al., 1995). Thereafter, pairwise correlations were performed by way of group analysis in order to identify if unique relationships existed between swing amplitude and key variables for each group of participants. It should be noted that for the performance measure of the LLS, swing amplitude, there was a maximum value of 3608 which creates a

11 Kinematic changes during learning the longswing on high bar 29 ceiling effect. As participants reached swing amplitudes of 3608, statistical analysis would have been impacted. Consequently, during the difference test (ANOVA), significant improvements in swing amplitude were measured from Session 1 until the session of successful completion. Correlations were performed with values from all eight sessions, maintaining a conservative measure for the correlation between swing amplitude and key FP variables when 3608 swing amplitude was reached. For this reason, Figure 3 provides invaluable descriptive information, arguably lost within the statistical analysis. In addition, large standard deviations were noted in swing amplitudes during sessions leading up to 3608 swing amplitude, demonstrating inter-trial variability. This is an example of important learning information overlooked in the statistical difference analysis over sessions but clearly highlighted in Table I. Based on difference analysis, it was identified that the change in hip FP variables was common for individual performers who were in the same group (G1, G2, and G3). Furthermore, pairwise correlations performed by way of group analysis supported the difference analysis for the hip FP, where unique relationships were found between swing amplitude and hip FP variables for G1, G2, and G3. Specifically, participants in G1 started and ended the hip FP significantly later in the circle during the learning period (difference) and as swing amplitude increased (correlation). Starting the hip FP nearer the lower vertical is a technique paralleled in coaching and biomechanical literature (Readhead, 1997; Yeadon & Hiley, 2000; Irwin & Kerwin, 2005). For performers in G1, the increase in swing amplitude could be explained based on the mechanics of the longswing detailed by Yeadon and Hiley (2000). By performing the hip FP action later in the downswing, the body of the performers remained extended for a longer duration during the downswing. Maintaining an extended body position increases the moment of the performers weight about the bar and therefore during the downswing increases the gain in the performers angular momentum. As long as the performer was able to decrease the distance between his CM and the bar during the upswing by performing flexion of the hips and extension of the shoulders, he is able to create a positive energy balance between angular momentum gained during the down swing and lost during the upswing, either by increasing swing amplitude or returning to the handstand position (Yeadon & Hiley, 2000). On the contrary, participants in G2 started the hip FP earlier during the learning period and as swing amplitude increased. Therefore, although participants in G2 were improving swing amplitude, they were using a different technique to those in G1, and one not advocated in biomechanics or coaching literature. Based on the mechanics of the longswing, detailed by Yeadon and Hiley (2000), initiating the FP early suggests that the CM of the performer moved closer to the bar, decreasing the moment of the performers weight about the bar. Therefore, the early arching action of performers in G2 would result in decreasing the moment of the performers weight about the bar, resulting in a deficit between the actual gain and the possible gain in the performers angular momentum during the downswing. This is particularly important because loss in the performer s angular momentum during the upswing needs to be less than the gain in angular momentum during the downswing in order for the performer to either increase swing amplitude or return to handstand (Yeadon & Hiley, 2000). A possible explanation for early hip extension is linked to performers in G2 not creating or maintaining a straight position from the top of the swing to the intended start of the FP. Coaching literature has identified a dish (closing of the shoulder and hip angles) preceding the FP action, which may be used as a mechanism to prevent early hip extension (Readhead, 1997). The reasons that a hyper-extended position was formed early in the downswing may include a lack of awareness of body position during the downswing (Busquets et al., 2009), or the physical inability to maintain a straight position while forces

12 30 G. Williams et al. on the body are tending to create an arch shape. Therefore, key coaching points for the LLS go beyond the biomechanically important FP, as suggested by Busquets et al. (2009). Based on the analysis in this study, it is suggested that increased swing amplitude by performers in G2 is facilitated by the reduction in hip angle that defined the start of the FP. Therefore, although the joint is hyper-extending during the downswing, causing the CM to move closer to the bar and reducing the moment of the performer, by lessening the amount of hyperextension the performer remains more extended, increasing the gain in angular momentum during the downswing (Yeadon & Hiley, 2000). In addition, it is hypothesised that a large amount of musculoskeletal work was done at the hips during the FP. Newell (1985) provided an operational definition of skill, highlighting that motor control literature often characterises a more skilled performance as a more efficient performance. Therefore, a kinetic analysis could provide valuable information to help explain the differences between the techniques, specifically the different strategies for initiation of the FP actions of performers in G2 compared to those of G1. Participants who were unable to successfully perform the skill did not significantly change the start or end of the hip FP within the circle or have a significant correlation between swing amplitude and hip FP variables (G3). Newell et al. (1989) suggested that variability in movement patterns permits the exploration of a motor-perceptual workspace, and is therefore an inherent characteristic of functional dynamical systems when learning a given motor task. During this training study, the more successful participants (G1 and G2) appeared able to alter placement of the hip FP in order to create a movement pattern to increase swing amplitude. However, less successful participants (G3) did not significantly change the placement of the hip FP. G3 performed hip hyper-extension from the peak circle reached during the downswing (Figure 3). Therefore, these performers did not exploit the forces of gravity in order to increase angular momentum during the downswing (Yeadon & Hiley, 2000). The reason these performers did not execute an extended position during the downswing although they were being instructed to do so is thought to be linked to either strength of the performers or their awareness of body shape. Significant increase in swing amplitude between Sessions 1 and 8 is thought to be due to the reduction in the magnitude of hip hyper-extension during this phase. In order to facilitate the progression of technique for G3, literature suggests decreasing the complexity of the task, for example, slowing it down or separating out the components of the skill (Čoh et al., 2004). Specifically, in gymnastics, coaches use a variety of modes of practice to teach skills (Readhead, 1997). The key tools used by coaches for developing gymnastics skills are preparatory activities known as skill progressions. Irwin and Kerwin (2005) suggested that for skill progressions to adhere to the principle of specificity of training, the progression needed to replicate the spatial, temporal, and variability characteristics of the final skill. Their methods began to address the concepts surrounding the importance of variability in movement patterns performed by elite gymnasts; however, the functional role of increased movement variability during learning is highlighted in this study. Higher order analyses, such as measures of inter-limb coordination, have been used as a more sensitive measure of technique variability (Newell et al., 1989; Hamill et al., 1999; Irwin & Kerwin, 2005; Bartlett et al., 2007). Moreover, the organisational properties of the motor system are central to the operational distinctions of coordination, control, and skill provided by Newell (1895). Therefore, quantifying coordination and coordination variability between the movements of the hips and shoulders could provide further insight into technique changes during learning the longswing. Common technique changes for all groups were identified. For example, the ends of the hip and shoulder FP were performed later as swing amplitude increased for G1, G2, and G3.

13 Kinematic changes during learning the longswing on high bar 31 This common characteristic of change is thought to be linked to higher swing amplitude permitting the end of the FP later in the circle. In addition, hip angle at the start of the FP was significantly less extended. This is suggested to demonstrate a common technique change for novices learning the longswing, and suggested to be linked to maintaining a more extended position at the beginning of the swing. FP of the shoulder was highly variable within session for G1, G2, and G3. Therefore, difference or correlation analysis did not highlight significant changes or relationships. A possible explanation for the lack of statistical change in shoulder FP variables could be linked to the continuous angle profiles of the shoulder. Continuous profiles of the shoulder joint angle highlighted a technique uncharacteristic of previously reported longswings performed by elite gymnasts. Specifically, during this study, change in angular displacement of the shoulder joint contained a number of plateaus between maximum flexion and maximum extension (Figure 4). The onset of the shoulder FP occurred earlier than the suggested values for elite longswings (Irwin & Kerwin, 2005). Only one participant was able to perform the shoulder FP close to the lower vertical without a double extension action. This participant had the highest swing amplitude in Session 1, and was first to successfully perform the LLS. Consequently, this study highlighted that 12 out of 13 novices from a sporting population were unable to maintain an extended body position followed by a single shoulder extension during the downswing of the LLS. A possible reason for the lack of a pronounced shoulder flexion at the start of the shoulder FP could be a limiting amount of flexibility at the shoulder of the participants. Furthermore, plateaus in the closing of the shoulder joint could indicate that a maximal amount of work was being done within the shoulder FP, explaining plateaus in closing occurring when large forces acted to open the shoulder joint (between 2508 and 3208). Using a four-segment computer simulation model, Yeadon and Hiley (2000) theoretically determined that when joint torques at the hips and shoulders were limited to realistic values for an elite gymnast, the position of hip flexion and shoulder extension became later in the circle and further from the theoretically optimal lower vertical position; highlighting that joint torque limits are an influential factor in performing hip and shoulder extension under the lower vertical. Additionally, the importance of the shoulder FP has been highlighted in the work of Irwin and Kerwin (2007b), who identified that 70% of the work by elite performers was during the FP, 67% of which was contributed by the shoulders. The FP of the shoulder is suggested to be related to utilising the elastic properties in the bar and the transfer of angular momentum from the legs and torso. Therefore, the actions of the shoulder during elite longswings may be the result of more complex body and bar interactions than evident in a kinematic analysis alone. Consequently, further analysis of these novice data is required to investigate the musculoskeletal contribution of the shoulders during the FP of the LLS. Although a key coaching point for the skill was to maintain straight legs throughout the swing, all participants performed some knee flexion. More specifically, knee flexion for G1 and G2 was performed during the upswing. From a mechanical perspective, flexing the knees during the upswing would move the CM of the performer closer to the bar, contributing to the reduction of the performer s moment of inertia, and therefore reducing the loss of his angular momentum. A relative increase in the amount of knee flexion during the upswing compared to knee flexion during the downswing is therefore a contributing factor to the increase in swing amplitude for performers in G1 and G2. For performers in G3, knee flexion was performed during both the downswing and the upswing. From a mechanical perspective, knee flexion would also have an impact upon the hip moment, where for the same hip action less moment would be required if the performer had bent knees. Irwin and Kerwin (2007b) omitted the contribution of the knees from kinematic and kinetic

14 32 G. Williams et al. analysis of the longswing performed by elite gymnasts based on the relatively small magnitude of the knee contribution to the overall musculoskeletal work performed during the skill (Irwin & Kerwin, 2007b). However, the mechanical contribution of the knees for novices performing the LLS is unknown. Therefore, these results have highlighted that a kinetic analysis is required in order to increase the understanding of the effect of knee flexion upon the mechanics of the LLS for performers as they learn this skill. Conclusion Using swing amplitude as a performance measure, the FP of the hips has provided a mechanism to distinguish between learners. This study has highlighted that as a performer learns the LLS it is important for a coach to identify the placement of the FP of the hips as well as progression of swing amplitude. In addition, the results of the study have provided support for the use of a single subject design approach when examining technique changes during learning, while providing ecologically valid evidence of how biomechanical characteristics of technique change significantly during learning the LLS. Future work is required to evaluate the robustness of the selection criteria used to identify three groups, for example, by establishing if groups of novices would consistently emerge if this study were repeated. Furthermore, research is required to explain the technique changes found in this study by looking at the interaction between the hip shoulder and knee joints via a coordination and coordination variability analysis and to examine how the musculoskeletal contribution of these joints changes during learning. References Arampatzis, A., & Brüggemann, G.-P. (1998). A mathematical high bar human body model for analysing and interpreting mechanical energetic processes on the high bar. Journal of Biomechanics, 31, Arampatzis, A., & Brüggeman, G.-P. (1999). Mechanical energetic processes during the giant swing exercise before dismounts and flight elements on the high bar and the uneven parallel bars. Journal of Biomechanics, 32, Arampatzis, A., & Brüggeman, G.-P. (2001). Mechanical energetic processes during the giant swing exercise before Tkatchev exercise. Journal of Biomechanics, 34, Bartlett, R., Wheat, J., & Robins, M. (2007). Is movement variability important for sports biomechanists? Sports Biomechanics, 6, Brüggermann, G.-P., Cheetham, P. J., Alp, Y., & Arampatzis, D. (1994). Approach to a biomechanical profile of dismounts and release-regrasp skills of the high bar. Journal of Applied Biomechanics, 10, Busquets, A., Marina, M., Irurtia, A., & Angulo-Burroso, R. M. (2009, August). Practice and talent effects in swing high bar inter-joint coordination of novice adults. Poster session presented at the annual meeting of the International Society of Biomechanics in Sport, Limerick, Ireland Čoh, M., Jovanović-Golubović, D., & Bratić, M. (2004). Motor learning in sport. Physical Education in Sport, 2, Dufek, J. S., Bates, B. T., Stergiou, N., & James, C. R. (1995). Interactive effects between group and single-subject response patterns. Human Movement Science, 14, Elliot, B., Alderson, J., & Denver, E. (2006, July). Field verses laboratory testing in sports biomechanics: System and modelling errors. Paper presented at the annual meeting of the International Society of Biomechanics in Sport, Salzburg, Austria. Fédération Internationale de Gymnastique (FIG). (2009). Code de pointage: Gymnastique artistique masculine [Code of points: Artistic gymnastics for men]. Moutier, Switzerland: FIG. Gittoes, M. J. R., Bezodis, I. N., & Wilson, C. (2009). An image based approach to obtaining anthropometric measurements for athlete-specific inertia modelling. Journal of Applied Biomechanics, 25, Hamill, J., van Emmerik, R. E. A., Heiderscheit, B. C., & Li, L. (1999). A dynamical systems approach to lower extremity running injuries. Clinical Biomechanics, 14,

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