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1.
Abstract

The aim of the present study was to determine whether changing stance width would result in a corresponding change in postural and/or pistol stability. Twelve national-standard male air pistol shooters performed 10 shots each at five stance widths (30 cm, 45 cm, 60 cm, 75 cm, and 90 cm). Postural stability was determined by measuring centre-of-pressure changes with a dual force-platform system. Shooting mechanics measures were determined by a NOPTEL ST-2000 optoelectronic training system. Medial-lateral centre-of-pressure excursion (F 4,44 = 7.17, P < 0.001, effect size = 0.99) and speed (F 4,44 = 77.03, P < 0.001, effect size = 3.88) were reduced as stance width decreased. Centre of gravity fine (the percentage of time held within an area the size of the ten-ring) improved during narrower stance widths (F 4,32 = 12.49, P < 0.001, effect size = 0.71). Our findings suggest that stance width affects postural and pistol stability in national-standard air pistol athletes. Moreover, the current method of suggesting a wider stance to improve shooting performance should be reconsidered and perhaps air-pistol shooters should use a 30-cm stance width to improve postural stability and shooting performance.  相似文献   

2.
The aim of the present study was to determine whether changing stance width would result in a corresponding change in postural and/or pistol stability. Twelve national-standard male air pistol shooters performed 10 shots each at five stance widths (30 cm, 45 cm, 60 cm, 75 cm, and 90 cm). Postural stability was determined by measuring centre-of-pressure changes with a dual force-platform system. Shooting mechanics measures were determined by a NOPTEL ST-2000 optoelectronic training system. Medial-lateral centre-of-pressure excursion (F?,?? = 7.17, P < 0.001, effect size = 0.99) and speed (F?,?? = 77.03, P < 0.001, effect size = 3.88) were reduced as stance width decreased. Centre of gravity fine (the percentage of time held within an area the size of the ten-ring) improved during narrower stance widths (F?,?? = 12.49, P < 0.001, effect size = 0.71). Our findings suggest that stance width affects postural and pistol stability in national-standard air pistol athletes. Moreover, the current method of suggesting a wider stance to improve shooting performance should be reconsidered and perhaps air-pistol shooters should use a 30-cm stance width to improve postural stability and shooting performance.  相似文献   

3.
The combined event is a crucial aspect of the modern pentathlon competition, but little is known about how shooting performance changes through the event. This study aimed to identify (i) how performance-related variables changed within each shooting series and (ii) how performance-related variables changed between each shooting series. Seventeen modern pentathletes completed combined event trials. An optoelectronic shooting system recorded score and pistol movement, and force platforms recorded centre of pressure movement 1 s prior to every shot. Heart rate and blood lactate values were recorded throughout the event. Whilst heart rate and blood lactate significantly increased between series (P < 0.05), there were no accompanying changes in the time period that participants spent aiming at the target, shot score, pistol movement or centre of pressure movement (P > 0.05). Thus, combined event shooting performance following each running phase appears similar to shooting performance following only 20 m of running. This finding has potential implications for the way in which modern pentathletes train for combined event shooting, and highlights the need for modern pentathletes to establish new methods with which to enhance shooting accuracy.  相似文献   

4.
The treadmill is an attractive device for the investigation of human locomotion, yet the extent to which lower limb kinematics differ from overground running remains a controversial topic. This study aimed to provide an extensive three-dimensional kinematic comparison of the lower extremities during overground and treadmill running. Twelve participants ran at 4.0 m/s ( ± 5%) in both treadmill and overground conditions. Angular kinematic parameters of the lower extremities during the stance phase were collected at 250 Hz using an eight-camera motion analysis system. Hip, knee, and ankle joint kinematics were quantified in the sagittal, coronal, and transverse planes, and contrasted using paired t-tests. Of the analysed parameters hip flexion at footstrike and ankle excursion to peak angle were found to be significantly reduced during treadmill running by 12° (p = 0.001) and 6.6° (p = 0.010), respectively. Treadmill running was found to be associated with significantly greater peak ankle eversion (by 6.3°, p = 0.006). It was concluded that the mechanics of treadmill running cannot be generalized to overground running.  相似文献   

5.
This study compared knee angle-specific neuromuscular adaptations after two low-volume isometric leg press complex training programmes performed at different muscle lengths. Fifteen young males were divided into two groups and trained three times per week for 6 weeks. One group (n?=?8) performed 5–7 sets of 3 s maximum isometric leg press exercise, with 4?min recovery, with knee angle at 85°?±?2° (longer muscle-tendon unit length; L-MTU). The other group (n?=?7) performed the same isometric training at a knee angle of 145°?±?2° (180°?=?full extension; shorter muscle-tendon unit length; S-MTU). During the recovery after each set of isometric exercise, participants performed two CMJ every minute, as a form of complex training. Maximum isometric force (MIF) and rate of force development (RFD) were measured over a wide range of knee angles. Countermovement jump (CMJ) performance and maximum half-squat strength (1RM) were also assessed. Training at S-MTU induced a large increase of MIF (22–58%, p?p?p?=?0.001). In contrast, training at L-MTU, resulted in a moderate and similar (≈12.3%, p?=?0.028) improvement of force at all knee angles. CMJ performance and 1RM were equally increased in both groups after training by 10.4%?±?8.3% and 7.8%?±?4.7% (p?相似文献   

6.
This study performed an analysis of the push-off forces of elite-short-track speed skaters using a new designed instrumented short-track speed skate with the aim to improve short-track skating performance. Four different skating strokes were distinguished for short-track speed skaters at speed. The strokes differed in stroke time, force level in both normal and lateral directions, and the centre of pressure (COP) on the blade. Within the homogeneous group of male elite speed skaters (N = 6), diversity of execution of the force patterns in the four phases of skating was evident, while skating at the same velocities. The male participants (N = 6) with a better personal record (PR) kept the COP more to the rear of their blades while hanging into the curve (r = 0.82, p < 0.05), leaving the curve (r = 0.86, p < 0.05), and entering the straight (r = 0.76, p < 0.10). Furthermore, the male skaters with a better PR showed a trend of a lower lateral peak force while entering the curve (r = 0.74, p < 0.10). Females showed a trend towards applying higher body weight normalised lateral forces than the males, while skating at imposed lower velocities.  相似文献   

7.
Abstract

Thirty young adult males performed the vertical jump (jump and reach) at knee angles of 65, 90, and 115 degrees while using lateral and anterior-posterior foot spacings of 0, 5, 10, and 15 inches. The preliminary position was held momentarily before jumping, and every subject jumped three times at each of the 48 combinations of knee angles and foot spacings. The average of the three jumps was considered the subject's score for each preliminary stance. The results revealed that: (a) knee angle, lateral foot spacing, and anterior posterior foot spacing exert independent effects on vertical jumping performance; and (b) the most effective preliminary stance seems to be one in which the knee angle is approximately 115° with the feet spread from 5 to 10 inches laterally and slightly in excess of 5 inches anteriorly-posteriorly.  相似文献   

8.
The objective of this study was to identify biomechanical predictors for accuracy and speed of the wrist shot in floorball, comparing two different starting feet positions.

Ten floorball players performed 2 series of 10 stationary wrist shots, in 2 different positions (feet at a right angle to the end of the stick, oriented towards a target and feet parallel to the end of the stick and to the target). A 12-camera motion capture system, tracking reflective markers on key landmarks, was used to record participant and stick kinematics. Accuracy of the shot was quantified by distance of impact from target centre. Player gaze was approximated from head position.

Shot accuracy was significantly better (P = 0.007) when feet were at right angle (0.22 [0.14] m) than when they were parallel (0.27 [0.20] m). Ball speed was no significantly different (P = 0.485) between the right angle position (23.50 [17.52] m · s?1) and the parallel position (23.50 [17.95] m · s?1). Between self-selected position and imposed position, there was no significant difference. Players looking at the target during shooting had greater accuracy. Regression models suggested that ball speed was mainly influenced, in both positions, by the flexion of the supporting leg (ankle, knee and hip), by the rotation of the hip and of the trunk, especially for the spine angles, and by the rotation and abduction–adduction movements of the wrist of the hand on the top of the stick. The comparison between players showed important differences in these technical skills.  相似文献   

9.

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.  相似文献   

10.
Ankle sprain is a common injury in volleyball. Poor stabilometric performance (SP) is associated with high risks of sustaining ankle sprain. Balance training can improve SP and reduce ankle sprain, but no research has studied the effects of detraining on SP in highly trained athletes. The purpose of this study was to determine the effects of one-month postseason break on SP in female volleyball players. Eleven NCAA female volleyball players participated in two eye-closed single-leg stance tests before and after a one-month postseason break. Stance time, center of pressure (COP) area, COP standard deviation, and COP mean velocity were assessed during the tests. During the postseason break, subjects conducted self-selected exercise and the average training duration was 87% lower compared to the competition season. Subjects demonstrated significant increases in anterioposterior (A/P) COP standard deviation (1.6 ± 0.4 vs. 1.8 ± 0.4 cm, p = 0.05), mediolateral (M/L) COP velocity (6.5 ± 1.5 vs. 7.1 ± 1.3 cm/s, p = 0.05), and overall COP velocity (10.1 ± 2.0 vs. 11.6 ± 1.9 cm/s, p = 0.02) after postseason break. SP decreased in highly trained female volleyball players after one-month postseason break. The decrease in SP indicated a possible increased risk for ankle sprain injury.  相似文献   

11.
Abstract

Despite the importance of the Combined Event to the modern pentathlon competition, little is known about performance in the event. This study aimed to (i) identify the key variables affecting Combined Event shooting performance, and the extent to which these corresponded with those identified for precision shooting and (ii) investigate the impact of changing shooting format, and whether more successful precision shooters were also more successful in the Combined Event. Seven modern pentathletes and three pistol shooters completed precision and Combined Event trials. An opto-electronic shooting system recorded score and pistol movements, whilst force platforms recorded centre of pressure movements 1 s prior to every shot. Intra-individual analysis revealed that the extent of associations between variables was participant-specific, highlighting the need for individual analysis of performance. No participants displayed matching associations between variables for precision and Combined Event shooting, emphasising the difference between performances in the two events. Both groups experienced significantly reduced scores, and increased pistol and body movements for Combined Event shooting (P < 0.05). Despite the pistol shooters’ greater precision shooting ability, no significant differences were evident between the groups’ Combined Event performances (P > 0.05). This implies that experience in one event does not guarantee success in the other, indicating the importance of event specific training.  相似文献   

12.
The aim of this investigation is to assess the effectiveness of a 6-week balance training (BT) protocol, integrated in regular training sessions, on postural sway of young female volleyball players (n = 26, age 13.0 ± 0.2 years) divided into two groups (intervention and control; 13 per group). Trials were performed for bipedal and unipedal stance conditions before and after the BT protocol, using a pressure platform to collect center-of-pressure (COP) time series that were processed to calculate sway area, COP path length, and maximum displacement range in anteroposterior and mediolateral directions. The intervention group exhibited smaller sway areas in eyes closed conditions (intervention = 42.76 mm2, control = 67.60 mm2; p < 0.05) and Romberg quotients (intervention = 1.11 mm, control = 1.82 mm) in bipedal stance, while all the other parameters were unaffected. BT also reduced sway area (intervention = 122.70 mm2, control = 187.18 mm2) and anteroposterior COP displacements (intervention = 20.18 mm, control = 22.38 mm) of the non-dominant limb for single-leg stance. No significant change was found for the dominant limb. Although it is possible to hypothesize a beneficial effect of BT on young athletes, further investigations are required to clarify its actual effect on balance performance with respect to normal volleyball training.  相似文献   

13.
ABSTRACT

Knee joint coordination during jump landing in different directions is an important consideration for injury prevention. The aim of the current study was to investigate knee and hip kinematics on the non-dominant and dominant limbs during landing. A total of 19 female volleyball athletes performed single-leg jump-landing tests in four directions; forward (0°), diagonal (30° and 60°) and lateral (90°) directions. Kinematic and ground reaction force data were collected using a 10-camera Vicon system and an AMTI force plate. Knee and hip joint angles, and knee angular velocities were calculated using a lower extremity model in Visual3D. A two factor repeated measures ANOVA was performed to explore limb dominance and jump direction. Significant differences were seen between the jump directions for; angular velocity at initial contact (p < 0.001), angular velocity at peak vertical ground reaction force (p < 0.001), and knee flexion excursion (p = 0.016). Knee coordination was observed to be poorer in the early phase of velocity-angle plot during landing in lateral direction compared to forward and diagonal directions. The non-dominant limb seemed to have better coordination than the dominant limb during multi-direction jump landing. Therefore, dominant limbs appear to be at a higher injury risk than non-dominant limbs.  相似文献   

14.
This study investigated the effects of both anterior–posterior position and inclination of a back plate positioned on a starting platform on swimming start performance. Ten male college swimmers performed eight starts with varying combinations of take-off angle (normal and lower), inclination angle (10°, 25°, 45°, and 65°) and position (0.29, 0.44, and 0.59 m from the front edge of the starting block). Two-way repeated measures analysis of variance (ANOVA; take-off angle × back plate) for four conditions with take-off angles (normal and lower) and inclinations (10° and 45°), and one-way ANOVA for comparisons between four inclinations and three positions were carried out. Multiple comparisons were made using Bonferroni's method. The main effects of the take-off angle were on the vertical and resultant take-off velocities [F(1,18) = 36.72, p < 0.001 and F(1,18) = 9.58, p = 0.013, respectively]. Comparisons between the plate positions showed that the 5 m time of the 0.29 m condition was significantly longer, the take-off angle and vertical take-off velocity of the 0.59 m condition were significantly lower, and horizontal and resultant take-off velocities of the 0.29 m condition were significantly less. Rear foot take-off times were significantly longer in the ascending order: 0.29, 0.44, and 0.59 m.  相似文献   

15.
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.  相似文献   

16.
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 FastrakTM 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 ± 0.2°) was significantly different than the mean angle recorded on the standard ergometer ( ? 5.4 ± 3.4°) (p = 0.007) whilst the angles recorded on the modified ergometer (1.4 ± 0.8°) were statistically equivalent to the inclinometer recordings (p = 0.660). 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.  相似文献   

17.
Abstract

In taekwondo, the stance position can potentially affect kick performance. The aim of this study was to analyse mechanical variables in the roundhouse kick in taekwondo according to three stance positions (0°, 45°, 90°). Nine experienced taekwondo athletes performed consecutive kicking trials in a random order according to these three relative positions of the feet on the ground. Measurements for the mechanical analysis were performed using two 3D force plates and an eight-camera motion capture system. The taekwondo athletes’ reaction and execution times were shorter when starting from the 0° and 45° stance positions than from the 90° position (P < 0.05). Moreover, the ground reaction force was negatively correlated with execution time and positively with velocity of thigh and shank. Our results suggest that the stance position affects the execution technique of taekwondo athletes’ kicks. It is suggested that athletes should not adopt the 90° stance position because it will not enable them to achieve the best performance in the roundhouse kick.  相似文献   

18.
Abstract

This study investigated compound spatial and temporal measures of interpersonal interactions purported to constrain the emergence of affordances for passing direction in the team sport of futsal. For this purpose, attacker–defender interactions in 37 sequences of play from a futsal competition in which 24 male professional players participated (M=30.04 years, SD=4.10) were filmed and analysed using TACTO software. Relative angle data were used as measures to study coordination tendencies that emerged between players during performance. Results showed that the direction for a pass emerged from relative angles between: (1) the vector from a ball carrier to ball receiver and the vector from the ball carrier to the nearest defender (70°) (p<0.01) and (2) the vector from a ball carrier to ball receiver and the vector from the ball carrier to a ball receiver's nearest defender (31°) (p < 0.01). Furthermore, passing direction was also constrained by temporal information from the emergence of both angles, since the pass was performed to attacker–defender dyads with the highest velocities of these angles (p < 0.05). Results suggested that decisions on selecting the direction of a pass in the team sport of futsal emerged at critical values of these key compound motion measures.  相似文献   

19.
ABSTRACT

This study aimed to investigate why futsal players decide to dribble. For this purpose, we analysed 396 trials comprising the dribbles (n = 132), passes (n = 131) or shots (n = 133), performed by 70 male futsal players. Passing and shooting angles, and interpersonal distance, including their rates of change (velocity and variability), were regarded as measures of interpersonal coordination tendency and a comparison was made among dribbling, passing and shooting situations. In addition, the variables identified as constraints on deciding to dribble were analysed in relation to age categories, dribbling outcomes and futsal court zone. Results revealed that passing and shooting angles, and interpersonal distance showed higher variability in dribbling than in passing and shooting situations. The findings allowed us to conclude that decision-making on dribbling was influenced by the variabilities of passing angles as well as shooting and interpersonal distance, and that success in dribbling was affected by the variability of interpersonal distance. Such variabilities were interpreted concerning their meaning of risk and/or uncertainty in the execution of motor skills.  相似文献   

20.
Golf requires proper dynamic balance to accurately control the club head through a harmonious coordination of each human segment and joint. In this study, we evaluated the ability for dynamic balance during a golf swing by using the centre of mass (COM)–centre of pressure (COP) inclination variables. Twelve professional, 13 amateur and 10 novice golfers participated in this study. Six infrared cameras, two force platforms and SB-Clinic software were used to measure the net COM and COP trajectories. In order to evaluate dynamic balance ability, the COM–COP inclination angle, COM–COP inclination angular velocity and normalised COM–COP inclination angular jerk were used. Professional golfer group revealed a smaller COM–COP inclination angle and angular velocity than novice golfer group in the lead/trail direction (P < 0.01). In the normalised COM–COP inclination angular jerk, the professional golfer group showed a lower value than the other two groups in all directions. Professional golfers tend to exhibit improved dynamic balance, and this can be attributed to the neuromusculoskeletal system that maintains balance with proper postural control. This study has the potential to allow for an evaluation of the dynamic balance mechanism and will provide useful basic information for swing training and prevention of golf injuries.  相似文献   

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