Three-dimensional analysis of a lofted instep kick by male and female footballers
Summary (3 min read)
- The formation of a tension arc involves over extension of the kick side hip, trunk rotation towards the non-kick side and over-extension and abduction of the arm on the non-kick side at the beginning of the kick, which is released approaching foot-ball impact (Shan & Westerhoff, 2005).
- Exploration of the movement characteristics of the trunk, hip and pelvis in female footballers is required to understand this motion and the implications for a lofted instep kick.
- All participants were currently playing in the top divisions of the regional football league where the study took place, and skilled in the ability to perform a lofted instep kick.
- Ethical clearance was granted by the institutions human research ethics committee and all participants gave their written informed consent.
- Participants attended familiarisation sessions prior to testing, within the sports hall testing location.
- Anthropometry protocols, followed guidelines supported by the International Society for the Advancement of Kinanthropometry (ISAK) (Norton & Olds, 1996).
- Anatomical landmarks were located and marked using a fibre tip pen with all measurements taken to the nearest 0.1 cm using large sliding calipers from a Harpenden Anthropometer Measuring Set (Holtain Ltd, Crosswell, UK).
- Each variable was measured in turn with results being recorded by an assistant and repeated back to the tester for clarification, these measurements were then repeated twice more.
- The median value for each variable was reported.
- Test-retest reliability of five participants indicated excellent agreement across tests, the greatest standard error of the measurement observed for the thigh (1.4cm, ICC 0.94), whilst the remaining variables ranged from 0.1 – 0.9cm (ICC 0.96 to 1.00).
- All participants carried out a standardised 15 minute warm-up that comprised of phases of jogging and running based activities interspersed with static and dynamic stretching.
- Previous research indicates variability for a maximal instep kick is suitably low over five trials (Lees & Rahnama, 2013) indicating the five practice kicks may have been sufficient to stabilise kinematic performance.
- Participants were allowed a further self-selected number of practice trials due the break imposed by the recording of a neutral posture and reading of task definition.
- Two flat retro reflective markers were affixed to the ball.
- The motion analysis system-configuration showed excellent test-retest and trial-to-trial reliability, ICC > 0.99, similar to other reports under static conditions (Vander Linden, Carlson, & Hubbard, 1992; Wilson et al., 1999).
Data Processing and Analysis
- Only one male participant did not self-report as right-foot dominant, and prior to the decision to include their data in the study, their kinematic profiles were inspected to ensure their data fell within 95% confidence intervals of the remaining male participant’s data.
- Segmental coordinate systems were constructed based on the method by Grood and Suntay (1983).
- Angular displacement data was time normalised between final toe-off of right foot preceding foot-ball impact and foot-ball impact (total kick time) and ensemble-averaged for each participant.
- Threedimensional angular displacement data were reported for the thoracolumbar spine (relative motion between thorax and pelvis) and right hip joints and thoracic, pelvic and right thigh segments.
- Independent t-tests were used to investigate anthropometric and kinematic differences between sexes (P < 0.05).
- Male footballers were significantly taller, heavier and had longer limb lengths than their female counterparts (P range < 0.001 to 0.038); however there was no significant difference in biiliocristale breadth (P = 0.576).
- The high percent close agreement indicated a small spread of the data, as ICC’s are affected by reduced range in the data (Rey, Plapp, Stewart, Richards, & Bashir, 1987) this would account for the low ICC’s rather than a high degree of variation in the movement between trials.
- Significant differences between sexes were reported for peak hip extension, hip abduction at impact, ankle planter flexion at impact and resultant ball velocity, all displaying a large effect size (Table 1).
- Angular displacement variables and corresponding loadings for the two components extracted from the PCA are provided in Table 2.
- Variables with loadings > |0.50| were interpreted within each component.
- The female footballers had significantly increased peak hip extension just prior to heel-strike (Table 1), suggesting they were aiming to maximise backswing before making ball contact.
- Anterior tilt to increase the segmental contribution of the pelvis to the end point velocity of the kicking limb at impact is therefore indicated as an alternative strategy to increasing ball velocity.
- Females displayed a greater initial rotation of the thorax towards the left, but maintained a similar amount of thoracolumbar spine external rotation in the first half of the kick due to a greater amount of pelvis rotation to the right.
- It is acknowledged that there were limitations to the current study.
- As the kicking task was standardised, a 35m kick was near maximal for females but not for males and therefore further study will identify whether similar strategies are adopted by male footballers performing a maximal distance lofted instep kick.
- Differences in movement patterns between sexes were observed and there was increased variation in the direction of motion for pelvis obliquity, hip joint and thoracolumbar spine abduction / adduction, thorax and hip joint transverse rotation and ankle dorsi / plantar flexion, when performing a lofted instep kick.
- Increased hip extension by females during the final step suggested they adopted a momentum strategy, to impart force to the ball during lofted instep kicking.
- The current study suggests that anthropometric, strength or muscle activation differences may be responsible for variations between the sexes.
- This study also reported the thorax as moving anteriorily and towards the ball in the frontal plane approaching impact.
- Therefore suggesting coaching points to lean backwards and away from the ball during lofted instep kicking should be reconsidered.
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Cites background from "Three-dimensional analysis of a lof..."
...Anatomical differences in pelvic anatomy as well as sex-specific dynamic move ment patterns are postulated to contribute to this finding and support concepts in current literature where differences in kicking kinematics are observed between sexes (1,2,5,21,26,29,40,41)....
"Three-dimensional analysis of a lof..." refers background in this paper
...The majority of the kinematic data showed excellent trial-to-trial reliability with ICC > 0.75 (Shrout & Fleiss, 1979) and percent close agreement (5°) 50–100%....
"Three-dimensional analysis of a lof..." refers methods in this paper
...Segmental coordinate systems were constructed based on the method by Grood and Suntay (1983)....
"Three-dimensional analysis of a lof..." refers background or methods in this paper
...Anthropometry protocols followed guidelines supported by the International Society for the Advancement of Kinanthropometry (Norton & Olds, 1996)....
...…posterior point of calcaneus to anterior portion of first distal phalanx), pelvis (biiliocristale breadth: distance between left and right iliocristale –most lateral aspect of iliac crest on a line drawn vertically from the middle of the armpit) and bitrochanteric breadth (Norton & Olds, 1996)....
"Three-dimensional analysis of a lof..." refers result in this paper
...As in previous studies on low-instep kicking (Barfield, Kirkendall, & Yu, 2002; Lees & Nolan, 2002), the mean foot velocity was lower than the mean ball velocity (Lees & Nolan, 1998), indicating other factors associated with impact are important in generating ball velocity....
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Frequently Asked Questions (2)
Q1. What have the authors contributed in "Title: three-dimensional analysis of a lofted instep kick by male and female footballers running title: sex differences in lofted instep kicking word count: 4174" ?
In this paper, the authors investigate differences in joint angular displacement, ball and foot velocity between males and females performing a standardised lofted instep kick.
Q2. What are the future works mentioned in the paper "Title: three-dimensional analysis of a lofted instep kick by male and female footballers running title: sex differences in lofted instep kicking word count: 4174" ?
Future research should further explore the mechanisms behind the differences reported, with a focus on the trunk, pelvis and hip joint musculature. Therefore suggesting coaching points to lean backwards and away from the ball during lofted instep kicking should be reconsidered.