Key Factors and Timing Patterns in the Tennis Forehand of Different Skill Levels

The main purpose of the present study was to quantify and compare selected kinematic variables and their timing during the tennis forehand of different skill levels. An eight-camera 400 Hz, Vicon motion analysis system recorded kinematic data of six ATP- professionals (elite) and seven high performance (HP) players when shots were played cross court and down the line. Timing of the maximum angles, linear and angular velocities was measured prior to and after impact. A total of twelve strokes per subject were analyzed from the beginning to the end of horizontal racquet movement. Significant differences (p < 0.01) and large effect sizes were observed between elite and HP players in the timing of maximum pelvis (-0.075 ± 0.008 vs. -0.093 ± 0.012 s) and trunk angular velocities (-0.057 ± 0.004 vs. -0.075 ± 0.011 s) before impact. The elite group showed a tendency (p < 0.05) towards higher peak horizontal shoulder (3.0 ± 0.4 vs. 2.5 ± 0.4 m·s^-1) and racquet velocities (33.1 ± 2.4 vs. 31.1 ± 1.9 m·s^-1) compared to the HP players. Depending on the situation (cross court vs. down the line), different peak hip, racquet and separation angles were found for both groups. Similar peak values were detected between groups for maximum angular velocities and displacement of key variables that had been selected for analysis. The findings of this study can be vital for successful player development, improved performance or injury prevention. The later occurrence of maximum angular pelvis and trunk rotations were the main reasons for the tendency towards higher horizontal shoulder and racquet velocities in the elite group.

Key points

• Different timing of maximum angular pelvis and trunk rotations separated the elite from the high performance players.
• The elite group tended to reach higher horizontal shoulder and racquet velocities than the high performance group.
• In addition to maximum angular velocities, maximum racquet, shoulder, and hip alignment angles were similar between groups.
• To improve the forehand performance level of their athletes, coaches should focus on proper pelvis and trunk rotation.

Key words: Biomechanics, racquet speed, kinematics, proximal-to-distal sequencing     

Movement Characteristics of Elite Tennis Players on Hard Courts with Respect to the Direction of Ground Strokes

Previous studies of movement characteristics in tennis have considered the effect of playing surface but have assumed that playing strategies are simply determined by the surface as opposed to being under an individual’s control. This study considered the selection of cross court or down the line ground strokes as being indicative of playing strategy and measured the outcome of playing these shots in terms of the opponent’s movements. Matches (N = 8) at the 2011 ATP tournament 500 Valencia were recorded and analysed using SAGIT, a computer vision tracking system that allowed both players’ movements to be tracked automatically, albeit with operator supervision. The data was split into (N = 188) games for analysis purposes and these lasted a median 174.24 seconds with active time (ball in play) a median proportion of 34.89% (IQR = 10.64%) of total time. During the active time losers of games tended to cover less distance (median = 80.17 m), move quicker (median = 1.38 m·s^-1), spend more time in the defensive zones (median = 14.24 s) and less in the offensive zones (median = 44.74 s). These results suggested that game winners tended to dominate game losers, forcing them to exhibit behaviors typically associated with a defensive strategy. Defensive and offensive strategy are not well defined currently and future investigations should consider movements in relation to individual shots, in particular their velocities, at the rally level and by different individuals to better understand successful performance.

Key Points

• During the active time losers of games covered less distance, moved quicker, spend more time in the defensive zones and less in the offensive zones.
• These results suggested that game winners tended to dominate game losers, forcing them to exhibit behaviors typically associated with a defensive strategy.
• There are no differences between the proportion of cross court shots and down the line shots played by game winners and game losers.
• Future research should consider individual shots at the rally level to better understand successful performance and ultimately strategy.

Key words: Motion analysis, tactics, winners, losers, differences     

Adjusted Landing Technique Reduces the Load on the Achilles Tendon in Badminton Players

Achilles tendon (AT) rupture is common among recreational male badminton players. We hypothesize that a landing technique following forehand jump strokes with the landing foot in a neutral position often performed by recreational players and occasionally by elite players may expose the AT to higher loads than a scissor kick jump (SKJ) technique with the leg/foot externally rotated. The study aimed to investigate if recreational players could reduce the load in the AT when adopting the SKJ technique compared to their habitual landing technique with the foot in a neutral position and secondarily to compare the AT force between recreational players and elite players. Ten recreational male players performed simulated jump strokes in a biomechanical laboratory using both their original technique and the SKJ technique traditionally used by elite players. For comparison reasons ten elite players performed SKJs. Landing kinematics and AT forces were captured and calculated using 3D movement analysis. The landing leg was more externally rotated in the recreational players'' adjusted technique (78 ± 10 degrees, p < 0.001) compared to 22 ± 21 degrees in recreational players'' original technique. The peak AT force of the recreational players was significantly higher for the original technique compared to the adjusted technique (68 ± 19 N/kg vs. 50 ± 14 N/kg, p = 0.005). Additionally, the peak AT forces observed during the recreational players’ original technique was higher, though not significantly, than those observed for elite players (55 ± 11 N/kg, p = 0.017). / = 0.016 due to a Bonferroni correction. These findings indicate that recreational badminton players that normally land with the foot in a neutral position, may reduce their AT load by 25% when adopting the SKJ technique of elite players and land with the leg/foot in an externally rotated position. Key points

• The Achilles tendon load is influenced by the rotation of the lower leg when badminton players perform scissor kick jump on the rear court in badminton.
• The subgroup of recreational players in the present study reduced their AT landing forces significantly when adapting the scissor-kick jump technique, traditionally employed by elite players, without compromising performance parameters such as jump height.
• The AT landing forces of recreational badminton players who perform forehand jump strokes with minimum upper-body rotation, may exceed those elite players experience during scissor-kick jump landings.
• These findings suggest that badminton coaches should focus on upper-body rotation during forehand jump strokes to facilitate the external leg/foot position in the subsequent landing, to lower AT forces and potentially the risk of sustaining an AT injury.

Key words: Biomechanics, foot work, scissor kick jump     

Changes in the Game Characteristics of a Badminton Match: A Longitudinal Study through the Olympic Game Finals Analysis in Men’s Singles

The goal of this study was to analyze, through a longitudinal study, the Olympic Badminton Men’s singles finals from the Barcelona Games (1992) to the London Games (2012) to assess some changes of the Badminton game characteristics. Six Olympic finals have been analyzed based on the official video of the Olympic Games (OG) through the temporal structure and with a notational approach. In total, 537 rallies and 5537 strokes have been analyzed. The results show a change in the game’s temporal structure: a significant difference in the rally time, rest time and number of shots per rally (all p<0.0001; 0.09 < η² < 0.16). Moreover, the shot frequency shows a 34.0% increase (p<0.000001; η² = 0.17), whereas the work density revealed a 58.2% decrease (from 78% to 30.8%) as well as the effective playing time (-34.5% from 34.7±1.4% to 22.7±1.4%). This argues for an increase in the intensity of the game and a necessity for the player to use a longer resting time to recover. Lastly, the strokes distribution and the percentage of unforced and forced mistakes did not show any differences throughout the OG analysis, except for the use of the clear. This results impact on the way the training of Badminton players should be designed, especially in the temporal structure and intensity.

Key points

• Badminton game has become faster, with an important increase in the shot frequency (+34%)
• The effective playing time has decreased between first to last Olympic Games (-34.5%)
• The strokes distribution and the percentage of unforced and forced errors show no differences through the OG analysis, except for the use of the clear

Key words: Notational analysis, elite, racket sport, video analysis, shuttlecock     

Hydration Status and Fluid Balance of Elite European Youth Soccer Players during Consecutive Training Sessions

The objective of the study was to investigate the hydration status and fluid balance of elite European youth soccer players during three consecutive training sessions. Fourteen males (age 16.9 ± 0.8 years, height 1.79 ± 0.06 m, body mass (BM) 70.6 ± 5.0 kg) had their hydration status assessed from first morning urine samples (baseline) and pre- and post-training using urine specific gravity (USG) measures, and their fluid balance calculated from pre- to post-training BM change, corrected for fluid intake and urine output. Most participants were hypohydrated upon waking (USG >1.020; 77% on days 1 and 3, and 62% on day 2). There was no significant difference between first morning and pre-training USG (p = 0.11) and no influence of training session (p = 0.34) or time (pre- vs. post-training; p = 0.16) on USG. Significant BM loss occurred in sessions 1-3 (0.69 ± 0.22, 0.42 ± 0.25, and 0.38 ± 0.30 kg respectively, p < 0.05). Mean fluid intake in sessions 1-3 was 425 ± 185, 355 ± 161, and 247 ± 157 ml, respectively (p < 0.05). Participants replaced on average 71.3 ± 64.1% (range 0-363.6%) of fluid losses across the three sessions. Body mass loss, fluid intake, and USG measures showed large inter-individual variation. Elite young European soccer players likely wake and present for training hypohydrated, when a USG threshold of 1.020 is applied. When training in a cool environment with ad libitum access to fluid, replacing ~71% of sweat losses results in minimal hypohydration (<1% BM). Consumption of fluid ad libitum throughout training appears to prevent excessive (≥2% BM) dehydration, as advised by current fluid intake guidelines. Current fluid intake guidelines appear applicable for elite European youth soccer players training in a cool environment.

Key Points

• The paper demonstrates a notable inter-participant variation in first morning, pre- and post-training hydration status and fluid balance of elite young European soccer players.
• On average, elite young European soccer players are hypohydrated upon waking and remain hypohydrated before and after training.
• Elite young European soccer players display varied fluid intake volumes during training, but on average do not consume sufficient fluid to offset fluid losses.
• Consecutive training sessions do not significantly impair hydration status, suggesting that elite young European soccer players consume sufficient fluid between training to maintain a stable hydration status and prevent excessive (≥2% body mass) dehydration
• Current fluid intake guidelines appear applicable to this population when training in a cool environment

Key words: Specific gravity, exercise, urine, adolescent     

DHA- Rich Fish Oil Improves Complex Reaction Time in Female Elite Soccer Players

Omega-3 fatty acids (n-3) has shown to improve neuromotor function. This study examined the effects of docosahexaenoic acid (DHA) on complex reaction time, precision and efficiency, in female elite soccer players. 24 players from two Spanish female soccer Super League teams were randomly selected and assigned to two experimental groups, then administered, in a double-blind manner, 3.5 g·day^-1 of either DHA-rich fish oil (FO =12) or olive oil (OO = 12) over 4 weeks of training. Two measurements (pre- and post-treatment) of complex reaction time and precision were taken. Participants had to press different buttons and pedals with left and right hands and feet, or stop responding, according to visual and auditory stimuli. Multivariate analysis of variance displayed an interaction between supplement administration (pre/post) and experimental group (FO/OO) on complex reaction time (FO pre = 0.713 ± 0.142 ms, FO post = 0.623 ± 0.109 ms, OO pre = 0.682 ± 1.132 ms, OO post = 0.715 ± 0.159 ms; p = 0.004) and efficiency (FO pre = 40.88 ± 17.41, FO post = 57.12 ± 11.05, OO pre = 49.52 ± 14.63, OO post = 49. 50 ± 11.01; p = 0.003). It was concluded that after 4 weeks of supplementation with FO, there was a significant improvement in the neuromotor function of female elite soccer players.

Key points

• The results obtained from the study suggest that supplementation with DHA produced perceptual-motor benefits in female elite athletes.
• DHA could be a beneficial supplement in sports where decision making and reaction time efficiency are of importance.

Key words: Fatty acids, omega 3, efficiency, decision-making     

Nutritional Practices of National Female Soccer Players: Analysis and Recommendations

The aim of the study was to establish the nutritional practices and activity patterns of elite female soccer players. The nutritional intake of 16 female England Soccer players was self-reported over a seven-day period. Participants were provided with written and verbal guidelines for the completion of the diaries. Training details were also recorded, and used in combination with BMR predictions to calculate daily energy expenditure. Energy, macronutrient and micronutrient intakes were determined using DietMaster 4.0 software. Results suggest that energy intake was low (1904 ± 366.3 kcal) in relation to previous recommendations for soccer players. Energy expenditure (2153.5 ± 596.2 kcal) was not significantly different (p > 0.05) from intake, suggesting energy balance was achieved. Carbohydrate (53.8 ± 6.8%), protein (16.8 ± 2.1%) and fat (28.8 ± 6.6%) intakes were in line with recommendations. Fluid intake (2466 ± 1350.5ml·day^-1) was sufficient to meet baseline recommendations, but would need to be higher to meet the additional requirement of training and competition. With the exception of vitamin A and iron, all micronutrient intakes were higher than the DRI. In conclusion, recommendations for female soccer players are to encourage consumption of carbohydrate-electrolyte beverages to enhance carbohydrate intake and increase fluid intake, and ensure sufficient iron rich foods are included in the diet to meet the DRI.

Key points

• Female soccer players demonstrate a low energy intake in relation to predicted requirements, but were in energy balance in this study.
• Increased carbohydrate intake may be beneficial to both training and competition performance of elite female soccer players
• Fluid requirements should be addressed on an individual basis and matched to player requirements.
• The iron status of female soccer players may be compromised due to insufficient dietary intake to meet the DRV.

Key words: Energy, intake, expenditure, carbohydrate, fluid, micronutrient     

Game-Related Statistics that Discriminated Winning,Drawing and Losing Teams from the Spanish Soccer League

The aim of the present study was to analyze men’s football competitions, trying to identify which game-related statistics allow to discriminate winning, drawing and losing teams. The sample used corresponded to 380 games from the 2008-2009 season of the Spanish Men’s Professional League. The game-related statistics gathered were: total shots, shots on goal, effectiveness, assists, crosses, offsides commited and received, corners, ball possession, crosses against, fouls committed and received, corners against, yellow and red cards, and venue. An univariate (t-test) and multivariate (discriminant) analysis of data was done. The results showed that winning teams had averages that were significantly higher for the following game statistics: total shots (p < 0.001), shots on goal (p < 0.01), effectiveness (p < 0.01), assists (p < 0.01), offsides committed (p < 0.01) and crosses against (p < 0.01). Losing teams had significantly higher averages in the variable crosses (p < 0.01), offsides received (p < 0. 01) and red cards (p < 0.01). Discriminant analysis allowed to conclude the following: the variables that discriminate between winning, drawing and losing teams were the total shots, shots on goal, crosses, crosses against, ball possession and venue. Coaches and players should be aware for these different profiles in order to increase knowledge about game cognitive and motor solicitation and, therefore, to evaluate specificity at the time of practice and game planning.

Key points

• This paper increases the knowledge about soccer match analysis.
• Give normative values to establish practice and match objectives.
• Give applications ideas to connect research with coaches’ practice.

Key words: Association football, game-related statistics, discriminant analysis, match analysis     

Daytime Napping Benefits Passing Performance and Scanning Activity in Elite Soccer Players

The present study explored the effect of a daytime napping opportunity on scanning activity, which is an essential component of successful soccer performance. Fourteen male elite collegiate soccer players performed the Trail Making Test (TMT), which was used to assess complex visual attention. In addition, a soccer passing test, modified with reference to the Loughborough Soccer Passing Test, was used to evaluate passing performance as well as scanning activity. A cross-over design was applied to examine nap and no-nap interventions. Participants (N = 14, mean age: 21.6 SD = 0.5 years, height: 1.73 ± 0.06 m, body mass: 67.1 ± 4.5 kg) were randomly allocated to a midday nap (40 minutes) or no-nap group. Subjective sleepiness was measured using the Karolinska Sleepiness Scale, and perceptive fatigue was evaluated by the visual analog scale. There were no significant differences in subjective measurements or TMT between the nap and no-nap groups. However, the performance time for the passing test and scanning activity was significantly shorter (p < 0.001) and scanning activity was significantly more frequent in the nap condition than in the no-nap condition (p < 0.00005). These results suggest that daytime napping is beneficial for soccer-related cognitive function, represented by visuospatial processing and decision-making, and particularly as a potential countermeasure to mental fatigue. Considering that inadequate sleep and residual fatigue are commonly observed in elite soccer, this finding may have practical implications for the preparation of players. Key points

• The effect of daytime napping on passing performance, complex visual attention and scanning activity of elite collegiate soccer players were examined.
• The speed of passing and scanning activity was significantly shorter in the nap condition than in the no-nap condition.
• Scanning activity was significantly more frequent in the nap condition than in the no-nap condition.
• Daytime napping is likely to benefit soccer-related cognitive function, represented by visuospatial processing and decision-making.

Key words: Nap, fatigue, sports, soccer, performance, scanning activity     

3D Reconstruction of Phalangeal and Metacarpal Bones of Male Judo Players and Sedentary Men by MDCT Images

This study has been performed to reveal hand bone peculiarities of elite male judoists by comparing their phalangeal and metacarpal bones with those of sedentary men on the basis of biometric ratio of the bones by means of three-dimensional (3D) reconstruction of multidetector computed tomography (MDCT) images. For this purpose, the axial images of the right and left hands of 8 elite male judo players (mean age: 22.0 ± 2.9 years, mean weight: 64.0 ± 4.9 kg) and 8 sedentary men (mean age: 26.0 ± 2.8 years, mean weight: 69.0 ± 3.6 kg) were obtained from MDCT. After semi-automatic segmentation and manual editing, the tracings of bone surfaces were stacked and overlaid to be reconstructed as the 3D images by the 3D program. All biometrical measurements of the reconstructed images of the bones were automatically calculated by this program to analyze statistically. This study showed that the differences between biometric ratios of judoist and sedentary men’s hand bones were significant contrary to null hypothesis which was established as there is no difference between biometric hand bone ratios of these men of both groups. Therefore null hypothesis was rejected. Author suggests that intense clutching actions practised in judo sports can most probably lead to some hand bone proliferations. 3D reconstructed results belonging to the judo players and sedentary men help orthopaedists to diagnose pathological formations related to hand bones of judoists and may be used for anatomical education in medicine faculties, respectively. We hope that the results from the biometric and reconstructive techniques carried out in this work will contribute to the present knowledge on judoist and shed light on the future studies on sports medicine related to skeletal structure of other sportsmen.

Key points

• Image processing of hands of sedentary man and male judo players.
• 3D models of hands of those men by using MDCT images.
• The results from those models compared in terms of volume, surface areas, and length changes for all individual hand bones.

Key words: CT imaging, three-dimensional reconstruction, judo players, sedentary men, morphometry     

Improved Motor-Timing: Effects of Synchronized Metro-Nome Training on Golf Shot Accuracy

This study investigates the effect of synchronized metronome training (SMT) on motor timing and how this training might affect golf shot accuracy. Twenty-six experienced male golfers participated (mean age 27 years; mean golf handicap 12.6) in this study. Pre- and post-test investigations of golf shots made by three different clubs were conducted by use of a golf simulator. The golfers were randomized into two groups: a SMT group and a Control group. After the pre-test, the golfers in the SMT group completed a 4-week SMT program designed to improve their motor timing, the golfers in the Control group were merely training their golf-swings during the same time period. No differences between the two groups were found from the pre-test outcomes, either for motor timing scores or for golf shot accuracy. However, the post-test results after the 4-weeks SMT showed evident motor timing improvements. Additionally, significant improvements for golf shot accuracy were found for the SMT group and with less variability in their performance. No such improvements were found for the golfers in the Control group. As with previous studies that used a SMT program, this study’s results provide further evidence that motor timing can be improved by SMT and that such timing improvement also improves golf accuracy.

Key points

• This study investigates the effect of synchronized metronome training (SMT) on motor timing and how this training might affect golf shot accuracy.
• A randomized control group design was used.
• The 4 week SMT intervention showed significant improvements in motor timing, golf shot accuracy, and lead to less variability.
• We conclude that this study’s results provide further evidence that motor timing can be improved by SMT training and that such timing improvement also improves golf accuracy.

Key words: Golf accuracy, motor timing, golf shot variability, metronome training     

Effect of Court Dimensions on Players’ External and Internal Load during Small-Sided Handball Games

The aim of this study was to investigate the effect of three different court dimensions on the internal and external load during small-sided handball games. Six male amateur handball players took part in this study and participated in three different 8-min 3vs3 (plus goalkeepers) small-sided handball games (each repeated twice). The three court dimensions were 12×24m, 30×15m and 32×16m. Through Global Positioning System devices (SPI pro elite 15Hz, GPSports) and video analysis, the following parameters were recorded: cyclic and acyclic movements (distance covered and number of technical actions executed), heart rate, and rating of perceived exertion (RPE). Total distance travelled increased with court dimensions (885.2m ± 66.6m in 24×12m; 980.0m ± 73.4m in 30×15m; 1095.0m ± 112.9m in 32×16m, p < 0.05). The analysis of distance covered in the four speed zones (0–1.4 m·s^-1; 1.4–3.4 m·s^-1; 3.4–5.2 m·s^-1; >5.2 m·s^-1) highlighted substantial differences: playing with the 30×15m court in comparison to the 24×12m, the players covered less distance in the first speed zone (p = 0.012; ES = 0.70) and more distance in the second (p = 0.049; ES = 0.73) and third (p = 0.012; ES = 0.51) speed zones. Statistical differences were also found between the 24×12m and 32×16m courts: the players covered more distance in the second and third speed zones (p = 0.013, ES = 0.76; p = 0.023 ES = 0.69) with the 32×16m court in comparison to the 24×12m. There was no significant effect of court dimensions on the technical parameters (number of team actions, passes, piston movements toward goal and defensive activities), the number of specific handball jumps and changes of direction, and the time spent in the different heart rate zones. Considering the average data of all the experimental conditions together (24×12m, 30×15m, 32×16m), a pronounced statistical difference was highlighted between the values in first two HR zones and the last two (p < 0.05; large ES). The rating of perceived exertion was significantly higher during the drill with the 32×16m court compared with the 24×12m one (p < 0.05; ES = 2.34). Our findings indicate that changing court dimensions during small-sided handball games can be used to manipulate both external and internal loads on the players.

Key points

• To cover the specific game demands, more specific training methodologies have been developed in many sport games.
• Specific game exercises may provide a useful conditioning stimulus, together with technical and tactical training components.
• Changing court dimensions during small-sided handball games can be used to manipulate both external and internal loads on the players.
• The high ratio of cyclic activity per minute and the high HR values recorded during SSHGs make this type of drills extremely useful for aerobic power training.

Key Words: Handball, sport-specific training, video analysis, Global Positioning System (GPS)     

Why do They Engage in Such Hard Programs? The Search for Excellence in Youth Basketball

Excellent performance in sport has a strong positive relationship with the accumulated hours of practice. The specialization years are seen as a decisive moment to lift the skill level, athletic readiness and commitment but the selection and orientation of talent has been strongly dependent of biological and motor variables. The purpose of this study is to describe the achievement and motivation variables that can explain the belonging to an elite competitive level of young basketball players. Eighty-two basketball players under 16 years fulfilled the WOFO Questionnaire (Spence and Helmreich, 1983), and an adapted version of the DPMQ (De Bruin, Rikers and Schmidt, 2007). Forty players (mean age 15. 8 ± 0.96) were engaged in high performance centres and forty-two (mean age 15.6 ± 1.01) played in national level clubs. A decision tree and a random forest analysis between elite and national level players were performed. The most discriminant variable was Will to Excel, with 85,2% true positives in elite or national level. Mastery and competitiveness did not enter the final model. The will to reach excellence in performance can be considered as a condition to engage in more specialized and demanding practice. The assessment of the path to expertise only through motor variables or through the accumulated hours of deliberate practice is limited and can lead to mistaken identification or orientation of young sport talents. The use of a more comprehensive model is needed.

Key points

• Excellent performance in sport has a strong positive relationship with the accumulated hours of practice.
• It seems reasonable that if the young athletes are better selected, have better training conditions and practice and compete more time with better teammates and opponents, the chance of becoming competent adult athletes is greater.
• A self orientation to excellence may play a crucial role in persistence in practice, in order to achieve higher standards in competition.
• The specific motivation that underpins participation at different levels and help the coaches to be sensitive to non-biological or non-functional variables, leading to a better knowledge and caring of the adolescents they teach.
• The assessment of the path to expertise only through motor variables or through the accumulated hours of deliberate practice is limited and can lead to mistaken identification or orientation of young sport talents.

Key words: Youth, talent specialization, motivation, expertise.     

Sagittal Spinal Morphology in Highly Trained Adolescent Tennis Players

Sports with a predominance of forward-bending and extension postures have been associated with alterations in the sagittal spinal curvatures and greater risk of spinal injury. Because, the tennis players adopt these postures, the aims of this study were: 1) to describe spinal curvatures and pelvic tilt in male and female highly trained adolescent tennis players during relaxed standing posture and with thoracic spine corrected (in prone lying on the floor); and 2) to determine the frequency of thoracic hyperkyphosis and lumbar hypo/hyper lordosis in these postures. Forty adolescent tennis players (24 male and 16 female) aged 13-18 years, participated voluntarily in this study. The Spinal Mouse system was used to measure sagittal spinal curvatures and pelvic tilt. The mean values in the relaxed standing posture were 43.83° ± 7.87° (thoracic kyphosis), - 27.58° ± 7.01° (lumbar lordosis), and 13.38° ± 5.57° (pelvic tilt) for male tennis players, respectively; and 36.13° ± 6.69° (thoracic kyphosis), - 32.69° ± 5.06° (lumbar lordosis), 20.94° ± 5.36° (pelvic tilt) for female tennis players (p < 0.05 between genders in all spinal parameters). The male and female tennis players showed a frequency of 62.5% and 93.8% (p = 0.032) for neutral thoracic kyphosis, and 83.3% and 93.8% (p = 0.062) in neutral lumbar lordosis, respectively. In conclusion, due to the high percentage of neutral spinal curvatures in both male and female tennis players, to practice tennis in these levels does not alter sagittal spinal morphology in the relaxed standing posture in adolescent highly trained tennis players.

Key Points

• This study evaluated thoracic and lumbar spinal curvatures and pelvic tilt during several postures in young highly trained tennis players.
• Female tennis players showed statistically significant greater anterior pelvic tilt, lumbar lordosis and lower thoracic kyphosis than male tennis players.
• The high percentage of neutral thoracic kyphosis and lumbar lordosis posture in both groups of young tennis players in relaxed standing might affirm that tennis does not negatively affect sagittal spinal posture at these ages.
• A specific postural program could be recommended to improve the slumped sitting and maximal trunk flexion in knees extended postures.

Key words: Spinal mouse, posture, thoracic, lumbar, pelvic     

The Relationship of Intra-Individual Release Variability with Distance and Shooting Performance in Basketball

The aim of this study was to investigate the role of release parameter changes within individuals (intra-individual) on basketball shooting performance across both free throws and three-point shots, and identify whether any velocity dependence exists. Twelve male basketball players were recorded shooting seventy-five three-point shots (6.75 m) and fifty free throws (4.19 m). Ball release parameters were estimated by combining an analytic trajectory model including drag, a least squares estimator, and gradient-based release distance compensation. Intra-individual release velocity standard deviations (SD) were found to be significantly smaller across all distances ([0.05-0.13 m/s] when compared to statistics reported by other studies [0.2-0.8 m/s]). Despite an increase in lower body motion and a 24% increase in release velocity (p < 0.001) as shooting distance increased, no increases in intra-individual release velocity or angle SD were observed indicating velocity-dependent changes in release parameters were absent. Shooting performance was found to be strongly correlated to the release velocity SD (r = -0.96, p < 0.001, for three-point shots, and r = -0.88, p < 0.001, for free throws). Release angle SD (1.2 ± 0.24 deg, for three-point shots, and 1.3 ± 0.26 deg, for free throws) showed no increase with distance and unrelated to performance. These findings suggest that velocity-dependent factors have minimal contribution to shooting strategies and an individual’s ability to control release velocity at any distance is a primary factor in determining their shooting performance.Key points

• Individual shooting release velocity and angle standard deviations do not increase as distance and lower limb activity increase and remain similar for three-point shots and free throws.
• Release velocity standard deviation alone accurately predicts shooting performance.
• Velocity-dependent factors have minimal contribution to basketball shooting strategies.

Key words: Throwing, trajectory variability, shooting kinematics, sports biomechanics, release parameter     

Golfing Skill Level Postural Control Differences: A Brief Report

Golfers have better balance than their age-matched counterparts; however, it is uncertain if this persists during the swing as a function of skill level. The purpose of the study was to investigate dynamic postural control (center of mass (COM) motion) measured during different phases of the swing in golfers of varying proficiency. Eighteen healthy golfers were grouped by handicap: novice (no handicap, n = 7), intermediate (handicap 15-19, n = 7), and advanced (handicap 9-14, n = 4). Indoor testing was performed hitting 3 tee shots using a common driver. A five-camera (60 Hz) motion analysis system (9 markers) was used to extract kinematics data. There were no significant group differences in gender, age, or BMI. Advanced players had lower COM displacement with respect to address at the time of maximum arm speed (p = 0. 001) compared to intermediate (57%, p = 0.014) and novice (73%, p = 0.023). These changes persisted after COM distance and time normalization. Advanced golfers had improved COM linearity during the downswing (p < 0.001) compared to intermediate (30%, p = 0.029) and novice (51%, p < 0.001). Advanced players had decreased COM displacement at the time of maximum arm speed and a more linear COM path during the early downswing. Further study should focus on these changes during ball launch conditions.

Key points

• Studies suggest that static and dynamic balance is important in golf. However, none have investigated dynamic postural control during the golf swing in golfers of varying proficiency.
• Our findings suggest advanced players demonstrated improved postural control at the point of maximum arm speed when compared to less skilled players. Furthermore, center of mass acceleration in advanced players is closer to impact than less-skilled players.
• We observed an increased center of mass linearity of trajectory during the early downswing for advanced players over novice players. We theorized this strategy may help advanced golfers to improve the economy of COM motion during golf swing and improve the performance of the shot.

Key words: Golf Balance, Body worn sensor, postural compensatory strategy.     

Time of Day – Effects on Motor Coordination and Reactive Strength in Elite Athletes and Untrained Adolescents

Objectives: the issue of time-of-day effects on performance is crucial when considering the goal of reaching peak results in sport disciplines. The present study was designed to examine time-of-day effects in adolescents on motor coordination, assessed with Hirtz’s battery and neuromuscular components of strength, evaluated with reactive strength tests. Methods: forty-two elite female gymnasts, aged 13.3 ± 0.5 years (Mean ± SD), were recruited for the study. Fifty healthy female students (aged 12.8 ± 1.7 years) served as the control group. All participants underwent the testing sessions over two days at two different times of day in a randomized order. Results: Oral temperature was measured at the two times of the day and a significant diurnal variation (p < 0.01) in both groups was found. MANOVA revealed significant group differences in the overall tests (p < 0.01). The gymnast group showed no significant differences in the coordination tests with respect to the time of day, but significant differences were observed for reactive strength as assessed with the vertical jump tests (p < 0.01). Gyamnasts attained better results in the evening in the reactive strength tests [flight time (F_1.90 = 17.322 p < 0.01) and ground contact time (F_1.90 = 8.372; p < 0.01) of the hopping test]. Conclusion: the temperature effect was more evident in the reactive strength tests and orientation test, especially in the gymnast group in which this effect added to their usual training time effect. The time-since-awakening influenced coordination performances in complex tasks more than reaction strength tests in simple tasks. The main outcome of the study was that we did not observe time-of-day effects on coordination skills in elite gymnasts and in untrained adolescents. The time of day in which athletes usually trained these skills could influence these results.

Key points

• The results obtained in this study suggested that the best time to perform a particular task depends specifically on the nature of the task, the precise size of the cognitive load and the level of practice of the participants.
• In the field of practice, it is incumbent for coaches to organise sports selection based on reactive strength, using the morning hours for untrained adolescents, when alertness and the benefits of sleeping could improve performance. Evening hours, conversely, should be used for elite gymnasts who specifically train at that time (specific “temporal training effect”).
• These study results cannot give indications about the best time of the day to organize selection tests based on coordination skills.

Key words: Circadian rhythm, closed skill sports, gymnasts, motor tasks, temperature     

Season-to-Season Variations of Physiological Fitness Within a Squad of Professional Male Soccer Players

The purpose of this study was to examine season-to-season variations in physiological fitness parameters among a 1^st team squad of professional adult male soccer players for the confirmatory purposes of identifying normative responses (immediately prior to pre-season training (PPS), mid-season (MID), and end-of-season (EOS)). Test-retest data were collected from a student population on the primary dependent variables of anaerobic threshold (AT) and maximal aerobic power (VO₂ max) to define meaningful measurement change in excess of test-retest technical error between test-to-test performances. Participants from a pool of 42 professional soccer players were tested over a set sequence of tests during the 3-year period: 1) basic anthropometry, 2) countermovement jump (CMJ) tests 3) a combined AT and VO₂ max test. Over the 3-year period there were no test-to-test changes in mean VO₂ max performance exceeding pre-defined limits of test agreement (mean of eight measures: 61.6 ± 0.6 ml·kg^-1·min^-1). In contrast, VO₂ at AT was significantly higher at the MID test occasion in seasons 2 (+4.8%; p = 0.04, p < 0.05) and 3 (+6.8%; p = 0.03, p < 0.05). The CMJ tests showed a test-to-test improvement of 6.3% (best of 3 jumps) (p = 0.03, p < 0.05) and 10.3% (20-s sustained jumping test) (p = 0.007, p < 0.01) between PPS2 and MID2 and thereafter remained stable. Anthropometrics were unaffected. In summary, despite some personnel changes in the elite cohort between test-to-test occasions, VO₂ max values did not vary significantly over the study which supports previous short-term observations suggesting a general ‘elite’ threshold of 60 ml·kg^-1 min. Interestingly, AT significantly varied where VO₂ max was stable and these variations also coincided with on- and off-seasons suggesting that AT is a better indication of acute training state than VO₂ max.

Key points

• Maximal aerobic power remains fairly stable across inter- and intra-season measurements.
• Anaerobic threshold appears more sensitive of training state confirming our earlier observations.
• The professional players tended to attain optimal performances at the mid-season interval over the 3 seasons, presumably prior to the development of accumulative fatigue.

Key words: Aerobic power, anaerobic threshold, countermovement jump, elite athletes     

Increased Distance of Shooting on Basketball Jump Shot

The present study analyzed the effect of increased distance on basketball jump shot outcome and performance. Ten male expert basketball players were filmed and a number of kinematic variables analyzed during jump shot that were performed from three conditions to represent close, intermediate and far distances (2.8, 4.6, and 6.4m, respectively). Shot accuracy decreased from 59% (close) to 37% (far), in function of the task constraints (p < 0.05). Ball release height decreased (p < 0.05) from 2.46 m (close) to 2.38m (intermediate) and to 2.33m (long). Release angle also decreased (p < 0.05) when shot was performed from close (78.92°) in comparison to intermediate distances (65.60°). While, ball release velocity increased (p < 0.05) from 4.39 m/s (close) to 5.75 m·s^-1 (intermediate) to 6.89 m·s^-1 (far). These changes in ball release height, angle and velocity, related to movement performance adaptations were suggested as the main factors that influence jump shot accuracy when distance is augmented.

Key points

• The increased distance leads to greater spatial con-straint over shot movement that demands an adapta-tion of the movement for the regulation of the accu-racy and the impulse generation to release the ball.
• The reduction in balls release height and release angle, in addition to the increase in balls release ve-locity, were suggested as the main factors that de-creased shot accuracy with the distance increased.
• Players should look for release angles of shooting that provide an optimal balls release velocity to im-prove accuracy.

Key words: Jump shot, distance of shooting, basketball, motor control, biomechanics