首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Impact is an important aspect of the kicking skill. This study examined foot and ball motion during impact and compared distance and accuracy punt kicks. Two-dimensional high-speed video (4000 Hz) captured data of the shank, foot and ball through impact of 11 elite performers kicking for maximal distance and towards a target 20 m in distance. Four phases were identified during impact, with an overall reduction in foot velocity of 5.0 m · s?1 (± 1.1 m · s?1) and increase in ball velocity of 22.7 m · s?1 (± 2.3 m · s?1) from the start to end of contact. Higher foot velocity was found in distance compared to accuracy kicks (22.1 ± 1.6 m · s?1 vs. 17.7 ± 0.9 m · s?1, P < 0.05), and was considered to produce the significant differences in all impact characteristics excluding foot-to-ball speed ratio. Ankle motion differed between the kicking tasks; distance kicks were characterised by greater rigidity compared to accuracy kicks evident by larger force (834 ± 107 N vs. 588 ± 64 N) and smaller change in ankle angle (2.2 ± 3.3° vs. 7.2 ± 6.4°). Greater rigidity was obtained by altering the position of the ankle at impact start; distance kicks were characterised by greater plantarflexion (130.1 ± 5.8° vs. 123.0 ± 7.9°, P < 0.05), indicating rigidity maybe actively controlled for specific tasks.  相似文献   

2.
This study assessed kinematic differences between different foot strike patterns and their relationship with peak vertical instantaneous loading rate (VILR) of the ground reaction force (GRF). Fifty-two runners ran at 3.2 m · s?1 while we recorded GRF and lower limb kinematics and determined foot strike pattern: Typical or Atypical rearfoot strike (RFS), midfoot strike (MFS) of forefoot strike (FFS). Typical RFS had longer contact times and a lower leg stiffness than Atypical RFS and MFS. Typical RFS showed a dorsiflexed ankle (7.2 ± 3.5°) and positive foot angle (20.4 ± 4.8°) at initial contact while MFS showed a plantar flexed ankle (?10.4 ± 6.3°) and more horizontal foot (1.6 ± 3.1°). Atypical RFS showed a plantar flexed ankle (?3.1 ± 4.4°) and a small foot angle (7.0 ± 5.1°) at initial contact and had the highest VILR. For the RFS (Typical and Atypical RFS), foot angle at initial contact showed the highest correlation with VILR (r = ?0.68). The observed higher VILR in Atypical RFS could be related to both ankle and foot kinematics and global running style that indicate a limited use of known kinematic impact absorbing “strategies” such as initial ankle dorsiflexion in MFS or initial ankle plantar flexion in Typical RFS.  相似文献   

3.
The purpose of this study was to investigate the kinematic and metabolic effects of running on an irregular surface. We also examined how altering the frontal plane foot angle (inversion/eversion) at contact using real-time visual feedback would affect these other variables. Sixteen participants completed three running bouts lasting 5–7 minutes each on an irregular surface (IS) treadmill, a traditional smooth surface (SS) treadmill, and on SS while receiving visual feedback of the frontal plane foot angle at contact (SSF) with a goal of matching IS foot angle on SS. Frontal plane foot angle increased 40% from IS to SS (IS: 8.4 ± 4.09°, SS: 11.8 ± 4.52°, P < 0.0001, ES 1.40). Knee flexion angle at contact decreased 33% from IS to SS (IS: 9.2 ± 4.88°, SS: 6.2 ± 5.03°, P < 0.0001, ES 1.30). Rate of oxygen consumption decreased by 10% from IS to SS (IS: 37.9 ± 5.68 ml·kg?1·min?1, SS: 34.1 ± 5.07 ml·kg?1·min?1, P < 0.0001, ES 3.05). PSD of leg accelerations decreased by 38% (IS: 0.17 ± 0.07 g2/Hz, SS: 0.106 ± 0.05 g2/Hz, P < 0.000, ES 1.69). Frontal plane foot angle decreased by 14% from SS to SSF (SS: 11.8 ± 4.52°, SSF: 10.1 ± 4.42°, P = 0.027. ES 0.62) but did not result in significant changes in any other variables. There were no significant differences in shock attenuation between any conditions (IS: ?9.8 ± 2.26 dB, SS: ?9.5 ± 3.12 dB, SSF: ?9.9 ± 2.62 dB, P = 0.671). Running with greater eversion on the irregular surface may be an attempt by runners to reduce the perceived potential of an inversion ankle sprain. As a partial compensation for the decreased foot angle, runners increased knee flexion. This maintained shock attenuation but increased the rate of oxygen consumption. Altering the foot angle at contact using feedback on the SS caused the knee angle at contact to increase, but did not change shock attenuation or metabolic cost.  相似文献   

4.
This study investigated how manipulating first step width affects 3D external force production, centre of mass (CoM) motion and performance in athletic sprinting. Eight male and 2 female competitive sprinters (100m PB: 11.03 ± 0.36 s male and 11.6 ± 0.45 s female) performed 10 maximal effort block starts. External force and three-dimensional kinematics were recorded in both the block and first stance phases. Five trials were performed with the athletes performing their preferred technique (Skating) and five trials with the athletes running inside a 0.3 m lane (Narrow). By reducing step width from a mean of 0.31 ± 0.06 m (Skating) to 0.19 ± 0.03 m (Narrow), reductions were found between the two styles in medial block and medial 1st stance impulses, 1st stance anterior toe-off velocity and mediolateral motion of the CoM. No differences were found in block time, step length, stance time, average net resultant force vector, net anteroposterior impulse nor normalised external power. Step width correlated positively with medial impulse but not with braking nor net anteroposterior impulse. Despite less medially directed forces and less mediolateral motion of the CoM in the Narrow trials, no immediate improvement to performance was found by restricting step width.  相似文献   

5.
Joint angles of the throwing limb were examined from the acceleration phase up until release for the sidearm throwing motion when using a flying disc. 17 individuals (ten skilled, seven unskilled) threw a disc as far as possible ten times. Throwing motions were recorded using three-dimensional high-speed videography. The initial condition of disc release and joint angle kinematics of the upper limb during the throwing motion were obtained. Mean ( ± standard deviation) throwing distance and disc spin rate were significantly greater for skilled throwers (51.4 ± 6.6 m, 12.9 ± 1.3 rps) than for unskilled throwers (29.5 ± 7.6 m, 9.4 ± 1.3 rps), although there was no significant difference in initial velocity of the disc between the two groups (skilled: 21.7 ± 1.7 m/s; unskilled: 20.7 ± 2.5 m/s). A marked difference in motion of supination/pronation of the forearm before disc release was identified, with the forearm supinated in the final acceleration phase leading up to disc release for the unskilled participants, while the forearm was pronated in the same phase for the skilled participants. These differences in joint kinematics could be related to differences in disc spin rate, and thus led to the substantial differences in throwing distance.  相似文献   

6.
The purpose of this paper was to establish postural cues in kicking that may be of use to goalkeepers. Eight male soccer players (age 20.5 ± 1.1 yrs; height 1.78 ± 0.053 m; mass 75.18 ± 9.66 kg) performed three types of kick: a low side-foot kick to the left hand corner of the goal, a low side-foot kick straight ahead, and a low instep kick straight ahead. Kicks were recorded by an optoelectronic motion analysis system at 240 Hz. At kicking foot take-off (about 200 ms before ball contact) the variables which were significantly different and could act as cues were support foot progression angle, pelvis rotation, and kicking hip and ankle flexion. The support foot progression angle was considered to be the most valuable of these variables as its angle coincided with the direction of ball projection. The other variables were less clear in their interpretation and so less valuable for a goalkeeper to use for decision making. Cues appearing after support foot contact were thought unlikely to be of value to a goalkeeper in their decision making. These include kicking leg knee flexion angle, and support leg shank and thigh angles.  相似文献   

7.
The purpose of this study was to investigate differences in the support leg joint moment and moment power between side-step (SS) and cross-step (CS) cutting techniques with a prescribed 90° cutting angle. Ground reaction forces (1,000 Hz) and three-dimensional kinematics (250 Hz) of SS and CS cutting techniques were collected from 20 male college athletes. Normalised peak knee extension moment was larger in the SS technique than in the CS technique (0.40 ± 0.10 in SS; 0.26 ± 0.08 in CS). In the SS technique, the knee extensors ( ? 0.10 ± 0.06 in SS; ? 0.02 ± 0.04 in CS) and ankle plantarflexors ( ? 0.12 ± 0.05 in SS; ? 0.07 ± 0.03 in CS) did significantly more negative work (normalised). The direction change angle (40.5 ± 8.7° in SS; 33.0 ± 6.8° in CS) and the decrease in horizontal velocity of the centre of mass ( ? 0.63 ± 0.23 m/s in SS; ? 0.31 ± 0.23 m/s in CS) were significantly larger in the SS technique. These results suggest that the SS technique is an effective means of changing running direction at the expense of velocity of the centre of mass and that the CS technique is better for minimising the reduction in horizontal velocity of the centre of mass.  相似文献   

8.
Abstract

The purpose was to evaluate the traditional method, of visually focusing on the ball, in comparison to focusing on the hole, during the putting stroke. The study design consisted of a pretest, a 4-week practice period, and a posttest. Participants (n = 31, handicap: 18.7 ± 10.4) practised using only one of the two gaze techniques. Testing consisted of having all participants putt using both gaze techniques from both a 1.22 m and a 4 m distance. Five putts were executed for each gaze technique/putt length combination for a total of 20 putts in each testing session per participant. The kinematics of every putting stroke executed during testing (1240 strokes) were captured using a TOMI® system. There was a significant improvement in putting success for both groups following practice (P = 0.001). Practising while visually focusing on the hole, resulted in a statistically significant reduction in putter speed variability in comparison to practising while visually focusing on the ball (P = 0.017). Visually focusing on the hole did not meaningfully (nor statistically) affect the quality of impact as assessed by the variability in face angle, stroke path, and impact spot at the precise moment the putter head contacted the ball.  相似文献   

9.
The purpose of this study was to quantify trunk axial rotation and angular acceleration in pitching and batting of elite baseball players. Healthy professional baseball pitchers (n = 40) and batters (n = 40) were studied. Reflective markers attached to each athlete were tracked at 240 Hz with an eight-camera automated digitizing system. Trunk axial rotation was computed as the angle between the pelvis and the upper trunk in the transverse plane. Trunk angular acceleration was the second derivative of axial rotation. Maximum trunk axial rotation (55 ± 6°) and angular acceleration (11,600 ± 3,100 °/s2) in pitching occurred before ball release, approximately at the instant the front foot landed. Maximum trunk axial rotation (46 ± 9°) and angular acceleration (7,200 ± 2,800 °/s2) in batting occurred in the follow-through after ball contact. Thus, the most demanding instant for the trunk and spine was near front foot contact for pitching and after ball contact for batting.  相似文献   

10.
Abstract

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.  相似文献   

11.
Due to the significant amount of time dancers spend on the forefoot, loads on the metatarsophalangeal joints are likely high, yet vary between dance movements. The purpose of this study was to compare joint motion and net joint moments at the metatarsophalangeal joints during three different dance movements ranging in demands at the foot and ankle joints. Ten healthy, female dancers (27.6 ± 3.2 years; 56.3 ± 6.9 kg; 1.6 ± 0.1 m) with an average 21.7 ± 4.9 years of dance training performed relevés (rising up onto the toes), sautés (vertical bipedal jumps), and saut de chat leaps (split jumps involving both vertical and horizontal components). Metatarsophalangeal joint kinematics and kinetics in the sagittal plane were calculated. Total excursion and peak net joint moments during rising or push-off were compared between the three dance movements. Greater extension of the metatarsophalangeal joints was seen during relevés compared to sautés or saut de chat leaps, and the largest metatarsophalangeal net joint moments were seen during saut de chat leaps. The metatarsophalangeal joints frequently and repetitively manage external loads and substantial metatarsophalangeal extension during these three dance movements, which may contribute to the high rate of foot and ankle injuries in dancers.  相似文献   

12.
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   

13.
The aim of this study was to analyse the characteristics of the asymmetries in the dominant and non-dominant limbs when kicking stationary and rolling balls. Ten experienced Brazilian amateur futsal players participated in this study. Each participant performed kicks under two conditions (stationary ball vs. rolling ball) with the dominant and non-dominant limbs (five kicks per condition per limb). We analysed the kicking accuracy, ball and foot velocities, angular joint displacement and velocity. The asymmetry between the dominant and non-dominant limbs was analysed by symmetry index and two-way repeated measures ANOVA. The results did not reveal any interaction between the condition and limb for ball velocity, foot velocity and accuracy. However, kicking with the dominant limb in both kicks showed higher ball velocity (stationary ball: dominant – 24.27 ± 2.21 m · s?1 and non-dominant – 21.62 ± 2.26 m · s?1; rolling ball: dominant – 23.88 ± 2.71 m · s?1 and non-dominant – 21.42 ± 2.25 m · s?1), foot velocity (stationary ball: dominant – 17.61 ± 1.87 m · s?1 and non-dominant – 15.58 ± 2.69 m · s?1; rolling ball: dominant – 17.25 ± 2.26 m · s?1 and non-dominant – 14.77 ± 2.35 m · s?1) and accuracy (stationary ball: dominant – 1.17 ± 0.84 m and non-dominant – 1.56 ± 1.30 m; rolling ball: dominant – 1.31 ± 0.91 m and non-dominant – 1.97 ± 1.44 m). In addition, the angular joint adjustments were dependent on the limb in both kicks (the kicks with non-dominant limb showed lower hip external rotation than the kicks with the dominant limb), indicating that the hip joint is important in kick performance. In conclusion, the kicks with the non-dominant limb showed different angular adjustments in comparison to kicks with the dominant limb. In addition, kicking a rolling ball with the non-dominant limb showed higher asymmetry for accuracy, indicating that complex kicks are more asymmetric.  相似文献   

14.
This study investigated the three-dimensional (3-D) pedaling kinematics using a noncircular chainring system and a conventional system. Five cyclists pedaled at their preferred cadence at a workload of 300 W using two crank systems. Flexion/extension of the hip, knee and ankle as well as shank rotation, foot adduction/abduction, and pedal angle were measured. Joint range of motion (ROM) and angular displacements were compared between the systems. Sagittal plane ROM was significantly greater (P < 0.05) at the hip (noncircular system = 39 ± 3°; conventional system = 34 ± 4°) the knee (noncircular system = 69 ± 4°; conventional system = 57 ± 10°), and ankle (noncircular system = 21 ± 2°; conventional system = 19 ± 4°) resulting in greater pedal ROM (noncircular system = 43 ± 3°; conventional system = 37 ± 5°) while using the noncircular system. Shank rotation ROM was significantly lower (P < 0.05) while using the noncircular chainring (noncircular system = 10 ± 1°; conventional system = 14 ± 1°). These results support a significant effect of the noncircular chainring system on pedaling kinematics during submaximal exercise.  相似文献   

15.
The aim of this study was to determine if selected kinematic measures (foot strike index [SI], knee contact angle and overstride angle) were different between aquatic treadmill (ATM) and land treadmill (LTM) running, and to determine if these measures were altered during LTM running as a result of 6 weeks of ATM training. Acute effects were tested using 15 competitive distance runners who completed 1 session of running on each treadmill type at 5 different running speeds. Subsequently, three recreational runners completed 6 weeks of ATM training following a single-subject baseline, intervention and withdrawal experiment. Kinematic measures were quantified from digitisation of video. Regardless of speed, SI values during ATM running (61.3 ± 17%) were significantly greater (P = 0.002) than LTM running (42.7 ± 23%). Training on the ATM did not change (pre/post) the SI (26 ± 3.2/27 ± 3.1), knee contact angle (165 ± 0.3/164 ± 0.8) or overstride angle (89 ± 0.4/89 ± 0.1) during LTM running. Although SI values were different between acute ATM and LTM running, 6 weeks of ATM training did not appear to alter LTM running kinematics as evidenced by no change in kinematic values from baseline to post intervention assessments.  相似文献   

16.
Abstract

The aim of the present study was to examine the effects of movement intensity and path linearity on global positioning system (GPS) distance validity and reliability. One participant wore eight 1-Hz GPS receivers while walking, jogging, running, and sprinting over linear and non-linear 200-m courses. Five trials were performed at each intensity of movement on each 200-m course. One receiver was excluded from analysis due to errors during data collection. The results from seven GPS receivers showed the mean (±s) and percent bias of the GPS distance values on the 200-m linear course were 205.8 ± 2.4 m (2.8%), 201.8 ± 2.8 m (0.8%), 203.1 ± 2.2 m (1.5%), and 205.2 ± 4 m (2.5%) for the walk, jog, run, and sprint trial respectively. Walk and sprint distances were significantly different from jogging and running distances (P < 0.05). The GPS distance values on the 200-m non-linear course were 198.9 ± 3.5 m (?0.5%), 188.3 ± 2 m (?5.8%), 184.6 ± 2.9 m (?7.7%), and 180.4 ± 5.7 m (?9.8%) for the walk, jog, run, and sprint trial respectively; these were significantly lower than those for the corresponding values on the linear course (P < 0.05). Differences between all non-linear movement intensities were significant (P < 0.05). The overall coefficient of variation within and between receivers was 2.6% and 2.8% respectively. Path linearity and movement intensity appear to affect GPS distance accuracy via inherent positioning errors, update rate, and conditions of use; reliability decreases with movement intensity.  相似文献   

17.
The reliability of grinding performance was assessed in 18 current Emirates Team New Zealand America's Cup sailors in two test sessions separated by 5 h using a custom-built ergometer. Sixteen different grinding conditions that varied by load (Light 39 N·m, Moderate 48 N·m, Heavy 68 N·m), deck heel (Flat 0° control, Downhill 25°, Uphill 25°, Right 25°, Left 25°), and grinding direction (forwards, backwards) were assessed using peak power and external work over 5 s during maximal-effort 8-s grinds. Reliability statistics included the difference in mean (Mdiff), standard error of measurement (SEM), and intraclass correlation coefficients (ICC). External work (SEM = 1.6–6.9%; ICC = 0.91–0.99) was a more consistent performance measure than peak power (SEM = 1.3–9.6%; ICC = 0.84–0.99) across all test conditions. Testing under different load conditions resulted in external work SEMs of 1.6–3.9% with performance more reliable in lighter load conditions. Grinding performance during different heel conditions was less reliable (external work SEMs = 4.6–6.9%). Grinding direction (forward or backward) did not appear to affect performance reliability, although external work was 10–15% higher in forward grinding. Reliability is acceptable across various loads, but testing under different heel conditions may need some protocol development to allow the detection of smaller differences in performance.  相似文献   

18.
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   

19.
ABSTRACT

The majority of barefoot running studies have not considered speed as an influential factor on foot strike pattern. The aim of this study was to investigate differences in foot strike pattern and spatiotemporal characteristics between barefoot and shod overground running at varying speeds. We first determined maximal running speed (Vm) over 50 m in 15 recreationally active men who self-reported as habitual rearfoot strikers. Participants then completed shod and barefoot running trials at different speeds equivalent to approximately 90%, 80%, 70% and 60% of Vm. Sagittal plane two-dimensional (2D) foot-ground contact angle, ankle plantar-dorsi flexion angle, contact time, flight time, step length and step rate variables for each trial were recorded. A significant interaction effect of running speed and footwear condition (p < 0.05) on foot-ground contact angle, ankle plantar-dorsi flexion angle and contact time was observed. There was a main effect of running speed (p < 0.01) on flight time, step length and step rate. There was a main effect of footwear condition on step length (p < 0.01). Participants were more inclined to plantarflex the ankle and contact the ground with the forefoot at higher percentages of Vm, especially when running barefoot.  相似文献   

20.
Rearfoot external eversion moments due to ground reaction forces (GRF) during running have been suggested to contribute to overuse running injuries. This study aimed to identify primary factors inducing these rearfoot external eversion moments. Fourteen healthy men ran barefoot across a force plate embedded in the middle of 30-m runway with 3.30 ± 0.17 m · s–1. Total rearfoot external eversion/inversion moments (Mtot) were broken down into the component Mxy due to medio-lateral GRF (Fxy) and the component Mz due to vertical GRF (Fz). Ankle joint centre height and medio-lateral distance from the centre of pressure to the ankle joint centre (a_cop) were calculated as the moment arm of these moments. Mxy dominated Mtot just after heel contact, with the magnitude strongly dependent on Fxy, which was most likely caused by the medio-lateral foot velocity before heel contact. Mz then became the main generator of Mtot throughout the first half of the stance phase, during which a_cop was the critical factor influencing the magnitude. Medio-lateral foot velocity before heel contact and medio-lateral distance from the centre of pressure to the ankle joint centre throughout the first half of the stance phase were identified as primary factors inducing the rearfoot external eversion moment.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号