Distance reached in the Anteromedial Reach Test as a function of learning and leg length

The anteromedial reach test (ART) is a new outcome measure for assessing dynamic knee stability in anterior cruciate ligament-injured patients. The effect of learning and leg length on distance reached in the ART was examined. Thirty-two healthy volunteers performed 15 trials of the ART on each leg. There was a moderate correlation (r = .44-.50) between reach distance and leg length, therefore reach distances were normalized for leg length. Normalized reach distance increased significantly over the 15 trials (p < .01), reaching a plateau after 8 trials, identified by a moving average graph. It is recommended that participants be afforded eight practice trials and that reach distances be normalized by expressing them as a percentage of leg length.     

Conference communications

Abstract

The objective of this study was to provide anthropometric, physiological, and performance characteristics of an elite international handball team. Twenty-one elite handball players were tested and categorized according to their playing positions (goalkeepers, backs, pivots, and wings). Testing consisted of anthropometric and physiological measures of height, body mass, percentage body fat and endurance ([Vdot]O_2max), performance measures of speed (5, 10, and 30 m), strength (bench press and squat), unilateral and bilateral horizontal jumping ability, and a 5-jump horizontal test. Significant differences were found between player positions for some anthropometric characteristics (height and percentage body fat) but not for the physiological or performance characteristics. Strong correlations were noted between single leg horizontal jumping distances with 5-, 10-, and 30-m sprint times (r = 0.51–0.80; P < 0.01). The best predictors of sprint times were single leg horizontal jumping with the dominant leg and the distance measured for the 5-jump test, which when combined accounted for 72% of the common variance associated with sprint ability. In conclusion, performance abilities between positions in elite team-handball players appear to be very similar. Single leg horizontal jumping distance could be a specific standardized test for predicting sprinting ability in elite handball players.     

Could Slackline Training Complement the FIFA 11+ Programme Regarding Training of Neuromuscular Control?

The current study compared changes in neuromuscular control between slackline training and the stabilization training elements of the FIFA 11+ programme. Twenty-five students in 2 groups performed a 12-unit training programme. The slackline training group (n?=?13) exclusively trained with a slackline. The stabilization training group (n?=?12) practised exercises as described in the second part of the FIFA 11+ programme. Improvements in balance were assessed using three tests for dynamic, quasi-static, and perturbed postural control: the star excursion balance test (SEBT), the closed-eye single-leg stance, and the MFT S3-Check. Both groups significantly improved the stability and sensorimotor index of the MFT S3-Check (p?<?.001), their range on the SEBT (p?<?.001), and the duration of closed-eye single-leg stance (p?<?.001). The group?×?training interaction was significant for the MFT S3-Check (stability index: p?=?.042; sensorimotor index: p?=?.004) and the SEBT (dominant leg: p?=?.003; averaged both legs: p?=?.016), with the slackline training group showing a larger training effect than the stabilization training group. The results of the present study suggest that slackline training offers similar – or better – improvements in neuromuscular control as the FIFA 11+ warm-up programme. If compliance with the FIFA 11+ programme is declining, then slacklining might offer an alternative approach to reach the training goals of improved sensorimotor control.     

Gender differences in foot shape: a study of Chinese young adults

One important extrinsic factor that causes foot deformity and pain in women is footwear. Women's sports shoes are designed as smaller versions of men's shoes. Based on this, the current study aims to identify foot shape in 1,236 Chinese young adult men and 1,085 Chinese young adult women. Three-dimensional foot shape data were collected through video filming. Nineteen foot shape variables were measured, including girth (4 variables), length (4 variables), width (3 variables), height (7 variables), and angle (1 variable). A comparison of foot measures within the range of the common foot length (FL) categories indicates that women showed significantly smaller values of foot measures in width, height, and girth than men. Three foot types were classified, and distributions of different foot shapes within the same FL were found between women and men. Foot width, medial ball length, ball angle, and instep height showed significant differences among foot types in the same FL for both genders. There were differences in the foot shape between Chinese young women and men, which should be considered in the design of Chinese young adults’ sports shoes.     

Biomechanical considerations of distance kicking in Australian Rules football

Kicking for distance in Australian Rules football is an important skill. Here, I examine technical aspects that contribute to achieving maximal kick distance. Twenty-eight elite players kicked for distance while being videoed at 500 Hz. Two-dimensional digitized data of nine body landmarks and the football were used to calculate kinematic parameters from kicking foot toe-off to the instant before ball contact. Longer kick distances were associated with greater foot speeds and shank angular velocities at ball contact, larger last step lengths, and greater distances from the ground when ball contact occurred. Foot speed, shank angular velocity, and ball position relative to the support foot at ball contact were included in the best regression predicting distance. A continuum of technique was evident among the kickers. At one end, kickers displayed relatively larger knee angular velocities and smaller thigh angular velocities at ball contact. At the other end, kickers produced relatively larger thigh angular velocities and smaller knee angular velocities at ball contact. To increase kicking distance, increasing foot speed and shank angular velocity at ball contact, increasing the last step length, and optimizing ball position relative to the ground and support foot are recommended.     

Reliability of a Unilateral Horizontal Leg Power Test to Assess Stretch Load Tolerance

Drop jumping has previously been used to measure fast stretch shorten cycle (SSC) ability and stretch load tolerance. To the knowledge of these authors a test does not exist to achieve this in the horizontal direction. The purpose of this study therefore was to estimate the reliability of a new unilateral horizontal leg power test to assess these qualities. Participants (N = 10) performed three jumps on each leg from distances of 80%, 120%, and 160% of leg length onto a force plate, followed immediately by a jump for maximal distance onto a synthetic track. No significant between- leg differences (p > .05) were found for the dependent variables of ground contact time (GCT), peak propulsive vertical ground reaction force, peak propulsive horizontal ground reaction force, and distances jumped (DJ).Within-trial variability (coefficients of variation) ranged from 3.6% to 10.9%, and test-retest reliability intraclass correlation coefficients from 0.80 to 0.95. GCT and DJ were the variables with highest reliability between trials and days. These two variables should be used to indicate fast SSC (GCT) ability and stretch load tolerance (DJ-GCT) in the horizontal direction. The relationship of these measures to functional performance needs to be established.     

External load training does not alter balance performance in well-trained women

This study investigated the influence of external load training (ELT) on static and dynamic balance. Nineteen females stratified into two groups (ELT = 9, control = 10) completed three testing sessions over 6 weeks. The ELT group wore weighted vests (WV) of ~8% body mass for 32 h/week during daily living and three training sessions/week for 3 weeks. Following completion of ELT, a 3 week detraining (DET) phase was completed. Bilateral and unilateral static balance were assessed with eyes open and closed. Dynamic balance was assessed using the star excursion balance test (SEBT). Static and dynamic balance variables were analysed using a 2 (group) x 3 (time) between participants repeated measures ANOVA (p < 0.05). Results revealed significant reductions in average centre of pressure (COP) velocity in the control group on the non-dominant limb with eyes closed, and significantly greater reach distances in the ELT group on the SEBT for the posteromedial and medial directions on the dominant limb (p < 0.05). These findings suggest the ELT group did not significantly improve their balance in comparison to the control group. However, future research should further examine this unique, supplemental training method and the impact on balance performance.     

Biomechanical considerations of distance kicking in Australian Rules football

Kicking for distance in Australian Rules football is an important skill. Here, I examine technical aspects that contribute to achieving maximal kick distance. Twenty-eight elite players kicked for distance while being videoed at 500 Hz. Two-dimensional digitized data of nine body landmarks and the football were used to calculate kinematic parameters from kicking foot toe-off to the instant before ball contact. Longer kick distances were associated with greater foot speeds and shank angular velocities at ball contact, larger last step lengths, and greater distances from the ground when ball contact occurred. Foot speed, shank angular velocity, and ball position relative to the support foot at ball contact were included in the best regression predicting distance. A continuum of technique was evident among the kickers. At one end, kickers displayed relatively larger knee angular velocities and smaller thigh angular velocities at ball contact. At the other end, kickers produced relatively larger thigh angular velocities and smaller knee angular velocities at ball contact. To increase kicking distance, increasing foot speed and shank angular velocity at ball contact, increasing the last step length, and optimizing ball position relative to the ground and support foot are recommended.     

Gender differences in foot shape: a study of Chinese young adults

One important extrinsic factor that causes foot deformity and pain in women is footwear. Women's sports shoes are designed as smaller versions of men's shoes. Based on this, the current study aims to identify foot shape in 1,236 Chinese young adult men and 1,085 Chinese young adult women. Three-dimensional foot shape data were collected through video filming. Nineteen foot shape variables were measured, including girth (4 variables), length (4 variables), width (3 variables), height (7 variables), and angle (1 variable). A comparison of foot measures within the range of the common foot length (FL) categories indicates that women showed significantly smaller values of foot measures in width, height, and girth than men. Three foot types were classified, and distributions of different foot shapes within the same FL were found between women and men. Foot width, medial ball length, ball angle, and instep height showed significant differences among foot types in the same FL for both genders. There were differences in the foot shape between Chinese young women and men, which should be considered in the design of Chinese young adults' sports shoes.     

System approach to games and competitive playing: Reply to Lebed (2006)

Abstract

The maximal step length test has been proposed to evaluate the risk of falls among the elderly, although the test is confusing and prone to errors due to two types of test methods. The maximal double-step length test may be used to evaluate both leg function and the functional difference between the left and right legs, but its measurement and evaluation methods have not been studied extensively. The aims of the present study were to compare the maximal single- and double-step length tests, and to highlight differences between the sexes and between the dominant and non-dominant legs. Fifty healthy adults free from lower-limb disorders conducted the above step tests twice, once with the dominant and once with the non-dominant leg. The former test requires individuals to return the stepping leg to the original position or to draw the other leg to the step leg after stepping out maximally with either leg from a standing posture while maintaining body stability with the supporting leg. The latter test requires individuals to step forward with either leg maximally, after similarly stepping with the other leg and to draw the first stepping leg to the second stepping leg. The above tests are defined as the single- and double-step length test, respectively. Step lengths were measured in both tests, and these values were used for analysis. Correlations among step length tests conducted with the dominant and non-dominant legs were very high (r=0.82–0.97). Significant sex differences were found in all step length tests, and males were superior to females. No significant difference between legs was found in any test. In summary, the relationship between the maximal single- and double-step length tests was very high and step lengths showed a significant sex difference.     

Measuring kinematic changes of the foot using a gyro sensor during intense running

Abstract

Gyro sensor has been used to measure foot pronation during running with reliable results in previous studies, and the signals were not affected by the vibration of heel strikes. The purpose of this study was to observe the kinematic changes of the foot during intense running using a 3-axis gyro sensor. Fifteen male participants (average age: 24.5 ± 1.7 years; mean height: 174.1 ± 3.3 cm; mean body weight: 71.0 ± 5.5 kg) were recruited in this study. Foot kinematic changes were observed in 30-min intense running protocols. The comparisons of the signals from gyro and motion analysis system were also performed to determine the accuracy of the gyro and showed positive results. In the main experiment, the ankle range of motion (ROM) in the frontal plane, measured using a motion system, showed a significant increase over time. Accordingly, peak angular velocity in the frontal plane also showed a significant increase. The correlation between ankle ROM and peak angular velocity in the frontal plane is significantly high (r = 0.975). Moreover, peak angular velocity in the frontal plane is also significantly correlated with both rate of perceived exertion (RPE) (r = 0.911) and heart rate (r = 0.960). This study concluded that an alarm system for foot kinematic changes related to running injuries can be built based on the peak angular velocity of the foot in the frontal plane.     

Flexibility training in preadolescent female athletes: Acute and long-term effects of intermittent and continuous static stretching

This study compared the acute and long-term effects of intermittent and continuous static stretching training on straight leg raise range of motion (ROM). Seventy-seven preadolescent female gymnasts were divided into a stretching (n = 57), and a control group (n = 20). The stretching group performed static stretching of the hip extensors of both legs, three times per week for 15 weeks. One leg performed intermittent (3 × 30 s with 30 s rest) while the other leg performed continuous stretching (90 s). ROM pre- and post-stretching was measured at baseline, on weeks 3, 6, 9, 12, 15 and after 2 weeks of detraining. ROM was increased during both intermittent and continuous stretching training, but remained unchanged in the control group. Intermittent stretching conferred a larger improvement in ROM compared to both continuous stretching and control from week 3, until the end of training, and following detraining (p = 0.045 to 0.001 and d = 0.80 to 1.41). During detraining, ROM after the intermittent protocol decreased (p = 0.001), while it was maintained after the continuous protocol (p = 0.36). Acute increases in ROM following the intermittent stretching were also larger than in the continuous (p = 0.038). Intermittent stretching was more effective than continuous, for both long-term and acute ROM enhancement in preadolescent female athletes.     

Kinematic effects of a short-term fatigue protocol on punt-kicking performance

The punt kick is a fundamental skill used in several team sports; however, there has been a lack of research on how fatigue affects its technique. The purpose of this study was to determine the effects of short-term fatigue on punt-kicking performance. Eight elite and sub-elite Australian Football players performed maximal drop punt kicks on their preferred leg prior to, during and after a match-specific fatigue protocol. Optotrak Certus collected kinematic data from kick foot toe-off until ball contact. Repeated-measures analysis of variance showed a significant increase in 20 m sprint times after each short-term protocol, indicating fatigue. Foot speed did not significantly change with fatigue; however, increases in the range of motion at the pelvis and kicking thigh, along with increases in kicking thigh angular velocity, occurred. For the support leg, maximum knee flexion angular velocity increased while there was greater flexion found at the knee and hip, and greater range of motion at the knee. Players are able to make kinematic adaptations in order to maintain foot speed while punting for maximal distance after short-term efforts.     

Centre of pressure correlates with pyramid performance in acrobatic gymnastics

Acrobatic gymnasts need excellent balance control to execute pyramids where one gymnast is supported by another. The objectives of this study were: (1) to describe balance performance by assessing the centre of pressure displacement in a group of acrobatic gymnasts executing pyramids; (2) to determine the relationship between the parameters describing the centre of pressure oscillations and pyramid score; and (3) to examine the role of each foot in providing a solid base of support to maintain the balance of the pyramid. Sixteen acrobatic gymnasts grouped in pairs performed a Half pyramid and a Straddle pyramid held for 7 s on two force platforms. Path length, variance, range trajectory, and surface area of the centre of pressure of each foot were examined to analyse the balance of the pyramid. The path length was correlated with the pyramid score (Straddle: p = 0.692 [large]; Half: p = 0.407 [moderate]). There were differences in the functions of each leg to maintain balance, with the non-preferred leg supporting a higher weight of the pyramid while the preferred leg performed control movements to maintain balance. The results suggested that quantitative analysis of balance can provide important information on pyramid performance.     

The effects of increased shooting distance in the basketball jump shot

Three‐dimensional video techniques (50 Hz) were used to obtain images of basketball jump shots from one of three distances ‐ short range (group 1, n = 5); medium range (group 2, n = 5); long range (group 3, n = 5) ‐ from the basket, as performed by members of the men's quarter‐finalist teams at the games of the XVI Universiade in Sheffield in 1991. Fifteen sequences were digitized, beginning 20 frames prior to take‐off to 10 frames after release. To facilitate analysis, the sequences were rotated about the ball position in the final frame so that the shot direction was parallel to one of the pre‐defined orthogonal axes.

Mean (+1 s.d.) ball release speed was found to increase with distance from the basket (group 1 = 3.04±0.65 m s‐¹, group 2 = 4.71+0.74 m s‐¹, group 3 = 6.24 + 0.80 m s‘¹), while mean release angles were similar for all groups (group 1=48.8 + 10.1°, group 2 = 47.8 + 5.8°, group 3 = 51.9 + 5.5°). The increased impulse necessary for the ball to reach the basket at increased shooting distances was derived from both an increase in angular velocity of the elbow joint of the shooting arm and an increased velocity of the centre of mass in the direction of the basket at release. Centre of mass speed at take‐off was found to be influenced to a greater extent by the angular velocity of the ankle joint than that of the knee or hip joints. Rotation of the hip and shoulder axes, facilitated by the forward placement of the foot on the side of the shooting arm (antero‐posterior separation values: group 1 = 0.17 + 0.11 m, group 2 = 0.10 + 0.14 m, group 3 = 0.09 + 0.09 m) was utilized by all except one subject. All subjects also used an amount of medio‐lateral foot separation which, along with antero‐posterior separation, promoted stability.

All the subjects released the ball while airborne. Both the maximum jump height and the height of the jump at release tended to decrease as shooting distance increased. For short‐range shots, release occurred after the peak of the jump, but increasingly prior to the peak as shooting distance increased.     

A descriptive study of step alignment and foot positioning relative to the tee by professional rugby union goal-kickers

This study describes foot positioning during the final two steps of the approach to the ball amongst professional rugby goal-kickers. A 3D optical motion capture system was used to test 15 goal-kickers performing 10 goal-kicks. The distance and direction of each step, as well as individual foot contact positions relative to the tee, were measured. The intra- and inter-subject variability was calculated as well as the correlation (Pearson) between the measurements and participant anthropometrics. Inter-subject variability for the final foot position was lowest (placed 0.03 ± 0.07 m behind and 0.33 ± 0.03 m lateral to the tee) and highest for the penultimate step distance (0.666 ± 0.149 m), performed at an angle of 36.1 ± 8.5° external to the final step. The final step length was 1.523 ± 0.124 m, executed at an external angle of 35.5 ± 7.4° to the target line. The intra-subject variability was very low; distances and angles for the 10 kicks varied per participant by 1.6–3.1 cm and 0.7–1.6°, respectively. The results show that even though the participants had variability in their run-up to the tee, final foot position next to the tee was very similar and consistent. Furthermore, the inter- and intra-subject variability could not be attributed to differences in anthropometry. These findings may be useful as normative reference data for coaching, although further work is required to understand the role of other factors such as approach speed and body alignment.     

Increased foot-stretcher height improves rowing performance: evidence from biomechanical perspectives on water

Abstract

The aim of this study was to investigate whether changes on foot-stretcher height were associated with characteristics of better rowing performance. Ten male rowers performed a 200 m rowing trial at their racing rate at each of three foot-stretcher heights. A single scull was equipped with an accelerometer to collect boat acceleration, an impeller with embedded magnets to collect boat speed, specially designed gate sensors to collect gate force and angle, and a compact string potentiometer to collect leg drive length. All sensor signals were sampled at 50 Hz. A one-way repeated measures ANOVA showed that raising foot-stretcher position had a significant reduction on total gate angle and leg drive length. However, a raised foot-stretcher position had a deeper negative peak of boat acceleration at the catch, a lower boat fluctuation, a faster leg drive speed, a larger gate force for the port and starboard side separately. This could be attributed to the optimisation of the magnitude and direction of the foot force with a raised foot-stretcher position. Although there was a significant negative influence of a raised foot-stretcher position on two kinematic variables, biomechanical evidence suggested that a raised foot-stretcher position could contribute to the improvement of rowing performance.     

Impact of hockey skate design on ankle motion and force production

Dynamic forces and range of motion (ROM) were measured during on-ice skating using a standard hockey skate and a modified skate (MS) with an altered tendon guard and eyelet configuration. The objective of this study was to determine if these modifications resulted in biomechanical and performance changes during on-ice skating skills. The right skate of each type was instrumented with a calibrated strain gauge force transducer system to measure medial?Clateral and vertical forces during ice skating. In addition, a goniometer was placed about the ankle and rear foot to measure ROM during skating. Ten subjects executed three skills: forward skating, crossovers inside foot and crossovers outside foot. The MS demonstrated significant gains of 5°?C9° in dorsi-plantarflexion ROM (p?<?0.05). Total peak force occurred later during plantarflexion, suggesting a more prolonged and effective force generation with the MS during a given skating stride. A 14?C20?% increase (p?>?0.05) in mean work and power output was noted with the MS, although no improved times were observed during the skating skills. Potentially, some players may need a period of familiarization to take advantage of the design alterations of the MS.     

The influence of water depth on kinematic and spatiotemporal gait parameters during aquatic treadmill walking

The purpose of this study was to investigate kinematic and spatiotemporal variables of aquatic treadmill walking at three different water depths. A total of 15 healthy individuals completed three two-minute walking trials at three different water depths. The aquatic treadmill walking was conducted at waist-depth, chest-depth and neck-depth, while a customised 3-D underwater motion analysis system captured their walking. Each participant’s self-selected walking speed at the waist level was used as a reference speed, which was applied to the remaining two test conditions. A repeated measures ANOVA showed statistically significant differences among the three walking conditions in stride length, cadence, peak hip extension, hip range of motion (ROM), peak ankle plantar flexion and ankle ROM (All p values < 0.05). The participants walked with increased stride length and decreased cadence during neck level as compared to waist and chest level. They also showed increased ankle ROM and decreased hip ROM as the water depth rose from waist and chest to the neck level. However, our study found no significant difference between waist and chest level water in all variables. Hydrodynamics, such as buoyancy and drag force, in response to changes in water depths, can affect gait patterns during aquatic treadmill walking.     

河南省少儿男子篮球运动员身体形态的特征分析

研究河南省篮球传统项目学校少儿男子(小学组)9支学校篮球队运动员的身体形态指标共计11项,进行测量所获取的数据加以分析。研究表明:1)经因子分析提取少儿篮球运动员的身体形态的优先发展特征分别是:体重、小腿长、大腿长、小臂长、足长、腕长。2)对决定少儿篮球运动员的身体形态5个因子为因变量,以训练年限为自变量再进行回归分析表明:随着训练年数的增加,小腿长度、大腿长度、足长、腕长具有显著性差异P0.05,下肢的发展优于上肢;而体重和小臂长度具有不显著性差异P0.05。