Showing papers in "Sports Biomechanics in 2009"
TL;DR: It was hypothesized that variability decreases as level of competition increases, and pitchers who advanced to higher levels exhibited less variability in their motions, implying no particular skill level has increased risk of injury due to variation in joint kinetics.
Abstract: The aim of this study was to compare within-individual variability in baseball pitching among various levels of competition. It was hypothesized that variability decreases as level of competition increases. Five fastballs were analysed for 93 healthy male baseball pitchers (20 youth, 19 high school, 20 college, 20 Minor League, and 14 Major League level pitchers). Eleven kinematic, four temporal, and six kinetic parameters were quantified with a 240-Hz automated digitizing system. Three multiple analyses of variance were used to compare individual standard deviations for kinematic, temporal, and kinetic parameters among the five competition levels. There was a significant overall difference in kinematics and in six of the eleven kinematic parameters analysed: foot placement, knee flexion, pelvis angular velocity, elbow flexion, shoulder external rotation, and trunk forward tilt. Individual standard deviations tended to be greatest for youth pitchers, and decreased for higher levels of competition. Thus pitchers who advanced to higher levels exhibited less variability in their motions. Differences in temporal variation were non-significant; thus variability in pitching coordination was not improved at higher levels. Differences in kinetic variation were non-significant, implying no particular skill level has increased risk of injury due to variation in joint kinetics.
200 citations
TL;DR: Authors of sports biomechanics research reports are encouraged to analyse and present their data accounting for the experiment-wise Type I error rate, as well as reporting data documenting the size or practical significance of effects reaching their standard of statistical significance.
Abstract: Errors in statistical analysis of multiple dependent variables and in documenting the size of effects are common in the scientific and biomechanical literature In this paper, I review these errors and several solutions that can improve the validity of sports biomechanics research reports Studies examining multiple dependent variables should either control for the inflation of Type I errors (eg Holm's procedure) during multiple comparisons or use multivariate analysis of variance to focus on the structure and interaction of the dependent variables When statistically significant differences are observed, research reports should provide confidence limits or effect sizes to document the size of the effects Authors of sports biomechanics research reports are encouraged to analyse and present their data accounting for the experiment-wise Type I error rate, as well as reporting data documenting the size or practical significance of effects reaching their standard of statistical significance
128 citations
TL;DR: Previous literature regarding the biomechanical principles of flatwater kayaking and certain design modifications in the context of its application to improving paddling performance are reviewed to aid coaches in the development of more specific training programmes for their athletes.
Abstract: Successful kayak paddling requires a powerful and skilful paddler with an appropriately designed kayak and blade to effectively maximize power to provide forward propulsion and minimize negative drag forces. With a greater understanding of the biomechanical properties and design characteristics of kayaking, coaches and athletes can work towards successful paddling performances. Examination of what is occurring biomechanically under the stress of competition is an important step in improving race times. Since the introduction of kayaking as a sport, an increase in the understanding and research behind the biomechanics of flatwater kayaking has, in part, contributed to improved race times. This information may aid coaches in the development of more specific training programmes for their athletes. It is the purpose of this paper to review previous literature regarding the biomechanical principles of flatwater kayaking and certain design modifications in the context of its application to improving paddling pe...
125 citations
TL;DR: The study explored the use of functional principal component analysis (f-PCA), a multivariate data analysis, for assessing and classifying the kinematics and kinetics of the knee joint in competitive race walkers.
Abstract: This study considered the problem of identifying and evaluating the factors of individual performance during race walking In particular, the study explored the use of functional principal component analysis (f-PCA), a multivariate data analysis, for assessing and classifying the kinematics and kinetics of the knee joint in competitive race walkers Seven race walkers of international and national level participated to the study An optoelectronic system and a force platform were used to capture three-dimensional kinematics and kinetics of lower limbs during the race walking cycle Functional principal component analysis was applied bilaterally to the sagittal knee angle and net moment data, because knee joint motion is fundamental to race walking technique Scatterplots of principal component scores provided evidence of athletes' technical differences and asymmetries even when traditional analysis (mean +/- s curves) was not effective Principal components provided indications for race walkers' classification and identified potentially important technical differences between higher and lower skilled athletes Therefore, f-PCA might represent a future aid for the fine analysis of sports movements, if consistently applied to performance monitoring
105 citations
TL;DR: The adductor longus appears to be at risk of strain injury during its transition from hip extension to hip flexion and this knowledge could be applied to muscle injury prevention and rehabilitation programs to aid with treatment of adducter longus related groin pain.
Abstract: Groin pain is a common cause of athletic disability and often involves the adductor longus. A common complaint of patients with groin problems is pain while preparing to kick the ball. The purpose of this study was to examine muscle length and activation of the adductor longus while kicking a soccer ball. Three-dimensional joint positions and muscle activation were obtained from 15 National Collegiate Athletic Association (NCAA) Division 1 male soccer players during maximal effort kicks. Musculoskeletal modeling techniques incorporating joint position and muscle attachments were used to estimate adductor longus length from the beginning of the kicking leg's swing phase until ball strike. The maximum rate of stretch of the adductor longus (22.3 +/- 5.3 cm/s) and maximum hip extension (23.3 +/- 8.80) occurred near 40% of swing phase. Activation of the adductor longus occurred between 10% and 50% of the swing phase. Adductor longus maximum length occurred at 65% of the swing phase. Maximum hip abduction (25.3 +/- 5.40) occurred at 80% of swing phase. The adductor longus appears to be at risk of strain injury during its transition from hip extension to hip flexion. This knowledge could be applied to muscle injury prevention and rehabilitation programs to aid with treatment of adductor longus related groin pain.
81 citations
TL;DR: A new method is presented that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick and finds that most of the thrust is produced by the feet.
Abstract: We present a new method that combines the use of laser body scans, underwater video footage, software-based animation, and a fully unsteady computational fluid dynamics technique to simulate and examine the hydrodynamics of the dolphin kick. The focus of the current work is to model this particular stroke in all its complexity with minimal ad-hoc assumptions or simplifications. Simulations of one female and one male swimmer (both at about 1.7 m beneath the water surface) at velocities of 0.95 and 1.31 m/s and Strouhal numbers of 1.21 and 1.06 respectively are presented. Vorticity and fluid velocity profiles in the wake are examined in detail for both swimmers. A three-dimensional vortex ring is clearly identified in the wake for one of the cases and a two-dimensional slice through the ring corroborates previous experiments of Miwa et al. (2006). We also find that most of the thrust is produced by the feet and in both cases the down-kick produces much larger thrust than the up-kick.
68 citations
TL;DR: Findings highlight the functional importance of the adductor muscle group and hip abduction–adduction in skating performance as well as indirectly support the notion that groin strain injury potential increases with skating speed.
Abstract: Adductor strain injuries are prevalent in ice hockey. It has long been speculated that adductor muscular strains may be caused by repeated eccentric contractions which decelerate the leg during a stride. The purpose of this study was to investigate the relationship of skating speed with muscle activity and lower limb kinematics, with a particular focus on the role of the hip adductors. Seven collegiate ice hockey players consented to participate. Surface electromyography (EMG) and kinematics of the lower extremities were measured at three skating velocities 3.33 m/s (slow), 5.00 m/s (medium) and 6.66 m/s (fast). The adductor magnus muscle exhibited disproportionately larger increases in peak muscle activation and significantly prolonged activation with increased speed. Stride rate and stride length also increased significantly with skating velocity, in contrast, hip, knee and ankle total ranges of motion did not. To accommodate for the increased stride rate with higher skating speeds, the rate of hip abduction increased significantly in concert with activations of adductor magnus indicating a substantial eccentric contraction. In conclusion, these findings highlight the functional importance of the adductor muscle group and hip abduction-adduction in skating performance as well as indirectly support the notion that groin strain injury potential increases with skating speed.
61 citations
TL;DR: Although not significantly different, moderate to high effect size differences were recorded for pelvis rotation, elbow extension and elbow rotation ranges of motion.
Abstract: This study sought to identify kinematic differences in finger-spin bowling actions required to generate variations in ball speed and spin between different playing groups. A 12-camera Vicon system recorded the off-spin bowling actions of six elite and 13 high-performance spin bowlers, and the "doosra" actions of four elite and two high-performance players. Forearm abduction and fixed elbow flexion in the bowling arm were higher for the elite players compared with the high-performance players. The elite bowlers when compared with the high-performance players delivered the off-break at a statistically significant higher velocity (75.1 and 67.1 km/hr respectively) and with a higher level of spin (26.7 and 22.2 rev/s respectively). Large effect sizes were seen between ball rotation, pelvic and shoulder alignment rotations in the transverse plane. Elbow extension was larger for elite bowlers over the period upper arm horizontal to ball release. Compared to the off-break, larger ranges of shoulder horizontal rotation, elbow and wrist extension were evident for the "doosra". Furthermore, the "doosra" was bowled with a significantly longer stride length and lower ball release height. Although not significantly different, moderate to high effect size differences were recorded for pelvis rotation, elbow extension and elbow rotation ranges of motion.
60 citations
TL;DR: diagonal roller skiing performance was linked to a longer cycle length, greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.
Abstract: Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9 degrees; 11 km/h). Performance was correlated to cycle length (r = 0.77; P < 0.05), relative leg swing (r = 0.71), and gliding time (r = 0.74), hip flexion range of motion (ROM) during swing (r = 0.73) and knee extension ROM during gliding (r = 0.71). Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r= -0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.
49 citations
TL;DR: 1RM strength and force were shown to be greater in the bench press, while velocity and power outputs were greater for the bench pull across the range of loads, which can most likely be attributed to differences in muscle architecture, which may have training implications for these muscles.
Abstract: Understanding how loading affects power production in resistance training is a key step in identifying the most optimal way of training muscular power - an essential trait in most sporting movements. Twelve elite male sailors with extensive strength-training experience participated in a comparison of kinematics and kinetics from the upper body musculature, with upper body push (bench press) and pull (bench pull) movements performed across loads of 10-100% of one repetition maximum (1RM). 1RM strength and force were shown to be greater in the bench press, while velocity and power outputs were greater for the bench pull across the range of loads. While power output was at a similar level for the two movements at a low load (10% 1RM), significantly greater power outputs were observed for the bench pull in comparison to the bench press with increased load. Power output (Pmax) was maximized at higher relative loads for both mean and peak power in the bench pull (78.6 +/- 5.7% and 70.4 +/- 5.4% of 1RM) compared to the bench press (53.3 +/- 1.7% and 49.7 +/- 4.4% of 1RM). Findings can most likely be attributed to differences in muscle architecture, which may have training implications for these muscles.
35 citations
TL;DR: It is shown that specific aspects of fast bowling technique are changeable over a two-year period in elite level fast bowlers and this may be attributed to coaching intervention.
Abstract: Fast bowling in cricket is an activity that is well recognised as having high injury prevalence and there has been debate regarding the most effective fast bowling technique. The aim of this study was to determine whether two-year coaching interventions conducted in a group of elite young fast bowlers resulted in fast bowling technique alteration. Selected kinematics of the bowling action of 14 elite young fast bowlers were measured using an 18 camera Vicon Motion Analysis system before and after two-year coaching interventions that addressed specific elements of fast bowling technique. Mann-Whitney tests were used to determine whether any changes in kinematic variables occurred pre- and post-intervention between those who had the coaching interventions and those who didn't. The coaching interventions, when applied, resulted in a more side-on shoulder alignment at back foot contact (BFC) (p = 0.002) and decreased shoulder counter-rotation (p = 0.001) however, there was no difference in the degree of change in back and front knee flexion angles or lower trunk side-flexion. This study has clearly shown that specific aspects of fast bowling technique are changeable over a two-year period in elite level fast bowlers and this may be attributed to coaching intervention.
TL;DR: Comparisons of biomechanical discrete and continuous variables across four elite male gymnasts performing a series of handspring front somersault vaults on the traditional horse and the new table found differences in hip flexion at board take-off and strike angle on the table.
Abstract: The traditional "horse" was replaced by a new vaulting "table" in artistic gymnastics competitions in 2001. The aim of this study was to determine whether the table led to a change in vaulting technique. This was achieved by comparing three-dimensional video-based analyses (50Hz) of selected biomechanical discrete and continuous variables across four elite male gymnasts performing a series of handspring front somersault vaults on the traditional horse and the new table. Individual joint and inter-segment coupling (continuous relative phase) were used to quantify techniques used on the two apparatuses. Differences were attributed in part to the design and construction of the new table. No differences were observed for the approach and take-off from the board. Significant differences in hip flexion at board take-off and strike angle on the table were observed. One of the effects of the latter was an increase in vertical take-off velocity compared with the horse. Individual strategies were observed in hip and shoulder coordination patterns that were obscured when group data were considered. Close monitoring of the evolution of skill on this new apparatus is paramount for gymnastics coaching, and further studies of current elite competitive vaulting techniques are required.
TL;DR: Even in collegiate athletes who train to be able to kick efficiently with either leg, differences in peak joint torques emerge between the dominant and non-dominant plant legs, particularly when participants kick from an off-axis approach.
Abstract: To determine the effect of plant leg and approach condition on the torques of the hip, knee, and ankle in soccer kicking tasks, nine female collegiate soccer players performed a series of kicking tasks from three different approach conditions. Kinematic data of the hip, knee, and ankle were recorded and joint torques of the plant leg were calculated. Peak flexor torque of the hip and ankle was greater for the dominant than the non-dominant plant leg for center and off-axis approach conditions (P < 0.05), while the opposite was true for peak extension torque for the hip and knee (P < 0.05). Similar effects of plant leg dominance emerged for peak internal and external rotation torques as well for peak abduction and adduction torques. In summary, these results indicate that participants use greater pulling torques and smaller braking torques in the dominant plant leg compared with the non-dominant plant leg. Thus, even in collegiate athletes who train to be able to kick efficiently with either leg, differences in peak joint torques emerge between the dominant and non-dominant plant legs, particularly when participants kick from an off-axis approach.
TL;DR: In conclusion, elite runners may utilize elastic energy more effectively, which, in combination with minimum concentric work, leads to improvements in their running performance.
Abstract: The aim of this study was to determine whether elite 1500-m runners differ in their running kinematics from national-standard 1500-m runners. Six national-standard male runners (seasonal best: 3 min 49.2 s ± 3.2 s) were assessed during the second lap of a 1500-m race. Their running kinematics was then compared with those of five elite runners (seasonal best: 3 min 35.6 s ± 2.6 s) analysed during the second lap of the men's 1500-m final at the 2005 World Championships. Data were collected using two high-speed cameras operating at 200 Hz with a three-dimensional pan and tilt system. Running speed was the same for both groups. Despite the similar contact times, the minimum knee angle during the stance phase was greater and the average extension velocity of the knee angle in the same phase slower in the elite runners than in the national-standard runners. In addition, the running technique of the elite runners appears to be characterized by a more efficient function of the hip joint. In conclusion, elite runn...
TL;DR: It is recommended that further research is required to fully appreciate the complexity of UUS and examine how humans can further optimise performance.
Abstract: Undulatory underwater swimming (UUS) occurs in the starts and turns of three of the four competitive swimming strokes and plays a significant role in overall swimming performance. The majority of research examining UUS is comparative in nature, dominated by studies comparing aquatic animals' undulatory locomotion with the UUS performance of humans. More recently, research directly examining human forms of UUS have been undertaken, providing further insight into the factors which influence swimming velocity and efficiency. This paper reviews studies which have examined the hydromechanical, biomechanical, and coordination aspects of UUS performance in both animals and humans. The present work provides a comprehensive evaluation of the key factors which combine to influence UUS performance examining (1) the role of end-effector frequency and body amplitudes in the production of a propulsive waveform, (2) the effects of morphology on the wavelength of the propulsive waveform and its subsequent impact on the mode of UUS adopted, and (3) the interactions of the undulatory movements to simultaneously optimise propulsive impulse whilst minimising the active drag experienced. In conclusion, the review recommends that further research is required to fully appreciate the complexity of UUS and examine how humans can further optimise performance.
TL;DR: The trunk and hip positions at the initial contact with the floor and the range of motions of the knee and ankle were key kinematic parameters for reducing the vertical peak ground reaction forces and extending the time from theInitial contact to the occurrence of this peak force, which consequently reduced the mean loading rate upon landing.
Abstract: The purpose of this study was to assess the effects of jumping distance on the landing mechanics after a volleyball spike, to help in injury prevention and training for safer landing. Ground reaction forces and three-dimensional kinematic data were collected from six male university right-handed volleyball players under "Normal" and "Long" jumping distance conditions of landing after a spike. The results revealed that the landings under the Long jumping distance condition produced significantly greater centre of gravity velocities and larger mean loading rates. Although data were collected for bilateral landings with the two feet contacting the force platform at the same time, landing motion was asymmetric and the left leg was considered to play a more critical role in the absorption of the landing impact. The trunk and hip positions at the initial contact with the floor and the range of motions of the knee and ankle were key kinematic parameters for reducing the vertical peak ground reaction forces and extending the time from the initial contact to the occurrence of this peak force, which consequently reduced the mean loading rate upon landing.
TL;DR: Joint movements in the transverse plane at or before the initiation event for the dive for the pelvis and thorax are the causation for subsequent asymmetries, indicating that there is an advantage in having prior knowledge of limb preference in an opposing goalkeeper.
Abstract: This study biomechanically quantified the movement patterns for six elite goalkeepers making diving saves to their preferred and non-preferred side at three different dive heights. Synchronised three-dimensional kinematic and kinetic biomechanical data analysis found diving direction to significantly (P < 0.05) influence the movement patterns of the diving save. The non-preferred side displayed greater lateral rotation of the pelvis and thorax at the initiation event. These over-rotational differences were reduced during the time on plate phase with the thorax displaying no significant difference at take-off; although a difference still remained for the pelvis. These over rotations were subsequently linked to greater peak knee joint moments, lower peak ankle joint moments, less hip extension at take-off, and for the centre of mass (COM) to travel slower and less directly to the ball, as measured by the net projection angle at take-off. These results indicate that joint movements in the transverse plane at or before the initiation event for the dive for the pelvis and thorax are the causation for subsequent asymmetries. These observed differences indicate that there is an advantage in having prior knowledge of limb preference in an opposing goalkeeper.
TL;DR: A significant effect of the noncircular chainring system on pedaling kinematics during submaximal exercise is supported.
Abstract: This study investigated the three-dimensional (3-D) pedaling kinematics using a noncircular chainring system and a conventional system. Five cyclists pedaled at their preferred cadence at a workload of 300 W using two crank systems. Flexion/extension of the hip, knee and ankle as well as shank rotation, foot adduction/abduction, and pedal angle were measured. Joint range of motion (ROM) and angular displacements were compared between the systems. Sagittal plane ROM was significantly greater (P < 0.05) at the hip (noncircular system = 39 ± 3°; conventional system = 34 ± 4°) the knee (noncircular system = 69 ± 4°; conventional system = 57 ± 10°), and ankle (noncircular system = 21 ± 2°; conventional system = 19 ± 4°) resulting in greater pedal ROM (noncircular system = 43 ± 3°; conventional system = 37 ± 5°) while using the noncircular system. Shank rotation ROM was significantly lower (P < 0.05) while using the noncircular chainring (noncircular system = 10 ± 1°; conventional system = 14 ± 1°). These resul...
TL;DR: Investigation in elite male rowers found that earlier lumbar power generation and extension did not appear to directly affect performance measures of the short shank group, and so can be attributed to a technical adaptation developed to maximise rowing performance.
Abstract: The effect of anthropometric differences in shank to thigh length ratio upon timing and magnitude of joint power production during the drive phase of the rowing stroke was investigated in 14 elite male rowers. Rowers were tested on the RowPerfect ergometer which was instrumented at the handle and foot stretcher to measure force generation, and a nine segment inverse dynamics model used to calculate the rower's joint and overall power production. Rowers were divided into two groups according to relative shank thigh ratio. Time to half lumbar power generation was significantly earlier in shorter shank rowers (p = 0.028) compared to longer shank rowers, who showed no lumbar power generation during the same period of the drive phase. Rowers with a relatively shorter shank demonstrated earlier lumbar power generation during the drive phase resulting from restricted rotation of the pelvic segment requiring increased lumbar extension in these rowers. Earlier lumbar power generation and extension did not appear t...
TL;DR: Overall, overground speed was highly repeatable within an individual (α = 0.96–0.98) and researchers might consider using self-selected speed when investigating overground running mechanics with different foot–ground interface conditions.
Abstract: In this study, we examined whether self-selected overground running speed was consistent (1) with perceived overground speed on the treadmill and (2) among barefoot and three footwear conditions. Participants ran across a 20-m runway 10 times for each overground condition, with running speed calculated from kinematic data. For the treadmill condition, the participants were instructed to run at a speed that felt similar to their overground speed. This treadmill speed was chosen upon perception, with the display covered from the participant's view. Repeated-measures analysis of variance was used to detect differences in speed between overground and treadmill running, and also among barefoot and footwear conditions. Coefficient alpha (α) was calculated to determine repeatability of observations in each overground condition. The speed was higher during overground (3.65 ± 0.40 m/s) than treadmill (2.25 ± 0.75 m/s) running but did not differ among the barefoot and the three footwear conditions. Overall, overgro...
TL;DR: Results indicate that the presence of ferrous material in a standard ergometer reduced the accuracy and increased the variability of data collected with the electromagnetic device, however, information collected on largely non-ferrous ergometers can provide coaches, biomechanists and clinicians with a quick and effective way to measure trunk kinematics during ergometer rowing.
Abstract: The aim of the study was to determine the accuracy and variability of an electromagnetic device in measuring spinal kinematics on a traditional and replica rowing ergometer Kinematic data collected from the 3-Space Fastrak system using a Standard Concept II ergometer were compared with a replica ergometer that was in part, composed of non-ferrous materials (modified ergometer) The Fastrak's sensors were fixed to a wooden "spine" with known angles (as measured by an inclinometer) The mean inclinometer angle from four sensors (1 +/- 020) was significantly different than the mean angle recorded on the standard ergometer (-54 +/- 340) (p = 0007) whilst the angles recorded on the modified ergometer (14 +/- 080) were statistically equivalent to the inclinometer recordings (p = 0660) These results indicate that the presence of ferrous material in a standard ergometer reduced the accuracy and increased the variability of data collected with the electromagnetic device However, information collected on largely non-ferrous ergometers can provide coaches, biomechanists and clinicians with a quick and effective way to measure trunk kinematics during ergometer rowing
TL;DR: The principal mechanics of circles are analyzed to suggest that the circles were composed of vertical movements and two kinds of rotations: rotation of the centre of mass and rotation ofThe body itself about the centreOf mass are phase dependent.
Abstract: The aim of this study was to analyse the principal mechanics of circles. Seventeen university male gymnasts performed circles on an instrumented pommel horse model that enabled the pommel reaction forces to be recorded at 1000 Hz with two force plates. The circles were also videotaped using two digital video cameras operating at 60 frames per second. During circles, the vertical component of the reaction forces peaked in the double-hand support phases. Changes in the velocity of the centre of mass corresponded to the change in the tangential components of horizontal reaction forces. The velocity of the centre of mass had its peaks in the single-hand support phases and its local minimums in the double-hand support phases. The velocity of the ankles and that of the centre of mass of the head and trunk were minimal in the single-hand support phases and were maximal in the double-hand support phases. These results suggest that the circles were composed of vertical movements and two kinds of rotations: rotatio...
TL;DR: Although the optimum technique found close to the gymnasts' own technique was more demanding in terms of the strength required, it offered the potential for more consistent performance and future developments in skill complexity.
Abstract: The felge, or undersomersault, on parallel bars has become an important skill in men's artistic gymnastics as it forms the basis of many complex variations. To receive no deductions from the judges, the felge must be performed without demonstrating the use of strength to achieve the final handstand position. Two male gymnasts each performed nine trials of the felge from handstand to handstand while data were recorded using an automatic motion capture system. The highest and lowest scoring trials of each gymnast, as determined by four international judges, were chosen for further analysis. The technique used by each gymnast was optimized using a computer simulation model so that the final handstand position could be achieved with straight arms. Two separate optimizations found different techniques identified in the coaching literature that are used by gymnasts. Optimum simulations resulted in improved performances through a combination of increased vertical velocity and height of the mass centre at release. Although the optimum technique found close to the gymnasts' own technique was more demanding in terms of the strength required, it offered the potential for more consistent performance and future developments in skill complexity.
TL;DR: Results suggest that to achieve a faster upstream gate performance, paddlers should concentrate on the distance between their head and the inside pole, however, there would be an optimal distance beyond which any further reduction in the distance would impede technique and performance.
Abstract: The aim of this study was to determine how the path chosen by elite slalom paddlers influences the time taken to negotiate an upstream gate. Six trials for international men's single kayak (MK1) (n = 11) and single canoe (C1) (n = 6) paddlers were digitized for a left-hand upstream gate. Results revealed that the absolute variability of paddlers increased as their total time increased (r = 0.594), but the coefficient of variation remained constant. There was a strong correlation (r = 0.89, each individual trial; r = 0.93, mean total time for each participant) between boat trajectory and the total time. The MK1 and C1 paddlers used similar strategies to negotiate an upstream gate. There were significant differences (P < 0.05) between the boat trajectory of the fastest and slowest paddlers (average distance between paddler's head and the inside pole). These results suggest that to achieve a faster upstream gate performance, paddlers should concentrate on the distance between their head and the inside pole. However, there would be an optimal distance beyond which any further reduction in the distance would impede technique and performance.
TL;DR: The accuracy and reliability of a new method of calculating ball location from simulated television coverage and known pitch markings will be sufficient for most practical uses in an applied sport environment, although the level of accuracy required will depend on the specific application.
Abstract: The ability to determine a specific location on a football (soccer) pitch from television footage would provide a cost-effective method of obtaining competition-specific information on many professional and international teams. This study presents the accuracy and reliability of a new method of calculating ball location from simulated television coverage and known pitch markings. The coordinates of 99 markers of known location on a football pitch were digitized from video. An intersection point was determined from the equations of two lines that form pitch markings and the relationship from this point to other known pitch coordinates was calculated using a curve-fitting based method. Average error between known and reconstructed measures was 0.21 m for pitch width and 0.11 m for pitch length from a view simulating television coverage. Inter- and intra-rater reliability analyses showed researchers could consistently reconstruct pitch locations to within less than half a metre. The accuracy and reliability of this method will be sufficient for most practical uses in an applied sport environment, although the level of accuracy required will depend on the specific application. This method could be applied to other sports to determine specific locations on a pitch or court or to improve current competition analysis systems.
TL;DR: It was determined that a shear-generated flexion moment or a compression-flexion load would generate significant stresses and strains in the discs, together with sufficient posterior-anterior displacement and rotational angulation of the vertebrae, to place the mid and lower cervical spine at risk of clinical instability or disc herniation.
Abstract: A complete and detailed three-dimensional finite element model of the human cervical spine (C1–C7), including soft and hard tissues, was created using a digitized geometric measurement tool. The model was validated against existing experimental studies in flexion, extension, lateral bending, and axial rotation. The aims of this study were to use the model to simulate the mechanisms of injury scenarios, such as diving and football accidents, and to correlate the external and internal responses of the spinal components to disc herniation and clinical instability. It was determined that a shear-generated flexion moment of about 10 Nm or a compression-flexion load of 450 N would generate significant stresses and strains in the discs, together with sufficient posterior-anterior displacement and rotational angulation of the vertebrae, to place the mid and lower cervical spine at risk of clinical instability or disc herniation. The results revealed that the location of the maximum stresses in the discs could not...
TL;DR: Backward grinding performance in America's Cup sailing could be improved using a training intervention to increase power capability in the upper-body pull movement, and the likelihood of a detrimental effect was low and therefore implementation could be recommended.
Abstract: This study determined whether backward grinding performance in America's Cup sailing could be improved using a training intervention to increase power capability in the upper-body pull movement. Fourteen elite male sailors (34.9 ± 5.9 years; 98.1 ± 14.4 kg; 186.6 ± 7.7 cm) were allocated into experimental (speed-focussed) and control groups. Grinding performance was assessed using a grinding ergometer and an instrumented Smith machine measured force, velocity and power during the bench pull exercise. Conventional training produced significant improvements in bench pull 1 RM (5.2 ± 4.0%; p = 0.016) and maximum force production (5.4 ± 4.0%; p = 0.014). Speed-focussed training improved maximum power (7.8 ± 4.9%; p = 0.009), power at 1RM (10.3 ± 8.9%; p = 0.019) and maximum velocity (8.4 ± 2.6%; p = 0.0002). Backward grinding performance showed greater improvements in the experimental group than the control group for moderate (+1.8%) and heavy load (+6.0%) grinding. Changes in maximum power output and power a...
TL;DR: This study demonstrates that TKE production during recovery in a race was not replicated during training, and stresses the importance of training appropriately for the energy expenditure during high-stroke rate recovery.
Abstract: Total kinetic energy (TKE) was calculated for 28 Canadian national team Olympic rowers during training on water, comparing low-stroke rates (18–22 stroke/min) and high-stroke rates (32–40 stroke/min), using video analysis. Stroke duration was normalized to 100%, beginning and ending at the “catches”, with the drive phase occurring first and recovery second. Two discrete points were identified during the stroke, both occurring when the fingers had the same horizontal position as the ankles (i.e. mid-drive and mid-recovery). The ratios of recovery-to-drive TKE at these points for the entire body at low and high-stroke rates were 0.36 ± 0.34 and 1.26 ± 0.54 respectively. Significant differences were found for the lower leg, upper arm and forearm segments, and within the female groups. Low-stroke rate is a typical training pace and high-stroke rate is analogous to a race pace. This study demonstrates that TKE production during recovery in a race was not replicated during training. While training at low-stroke...
TL;DR: Regardless of skill level, the realization of the potential performance benefits associated with longer drivers is, to some degree, likely to be individual-specific and suitable research designs emphasizing the individual are required.
Abstract: In a recent study published in Sports Biomechanics (Volume 7, pages 322–332), Kenny et al.(2008) reported increases in carry distances with no concomitant decrease in accuracy as
shaft length of golf drivers increased between 1.156m (45.5 inches) and 1.270m (50 inches). Although these findings are of interest to golfers, club fitters, and the custodians of
the game, there are several issues that need to be verified before the results of this study can be fully accepted and their universality established.
TL;DR: In this paper, the effect of shaft length on swing weights was investigated and the results of the study were presented in terms of the acquired data rather than relying on previously accepted anecdotal wisdom.
Abstract: The central theme of our paper (Sports Biomechanics, 2008, Volume 7, pages 322–332) was to ascertain the effect of shaft length and since this parameter cannot be changed in isolation, certain decisions were made as to which characteristics of the clubs to keep controlled and which should be allowed to vary naturally with shaft length, such as swingweight. The parameters that were controlled were mentioned in the paper together with those that were allowed to vary inherently with the shaft length. Nevertheless, the results of the study, in this context, were presented in a robust and clear manner. The results of the study were presented in terms of the acquired data rather than relying on previously accepted anecdotal wisdom. The authors wish to thank Paul Glazier for raising a discussion related to some of the aspects of our paper. We welcome here the opportunity to comment on and clarify his three points.