Three-dimensional analysis of a lofted instep kick by male and female footballers

TL;DR: Increased variation in direction of segment motion, increased backswing and formation of a tension arc by females compared to males, may be related to anthropometric, strength and muscle activation differences.

Abstract: There is a paucity of data describing the lofted instep kick and little information on the kinematic differences between male and female footballers. This study provides a preliminary investigation into the differences in motion patterns between the sexes. A four-camera motion analysis system videoed 13 amateur footballers (7 female and 6 male) attempting a standardised task that represented a lofted instep kick of approximately 35 m. Footballers performed 20 kicks, with the three trials categorised closest to the standardised distance retained for statistical analysis. Three-dimensional motion patterns for kicks of 35 m illustrated that female footballers produced greater fluctuation in movement patterns for pelvic, hip joint and thoracolumbar spine motion in the frontal plane; thorax and hip joint transverse rotation; and ankle dorsiflexion/plantarflexion motion. Peak hip extension (P = 0.018), impact hip abduction (P = 0.032), impact ankle plantar flexion (P = 0.030) and resultant ball velocity (P = 0.004) differed significantly between sexes. Principle component analysis highlighted associations between kinematic variables related to ball velocity and sex including a reduced hip abduction and increased internal rotation approaching impact, and greater peak knee flexion, respectively. In summary, increased variation in direction of segment motion, increased backswing and formation of a tension arc by females compared to males, may be related to anthropometric, strength and muscle activation differences. Specifically, this exploratory study indicates future research would benefit from exploring trunk, pelvis and hip kinematics and kinetics, and whether training the trunk, pelvis and hip musculature assists female footballers.

Summary

Introduction

• 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.

Methods

• 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

• 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).

Protocol

• 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).

Results

• 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.

Discussion

• 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.

Conclusion

• 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.

Full text

1
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
Corresponding Author:
Dr Tina Smith
Now at:
Institute of Sport, University of Wolverhampton,
Gorway Road, Walsall, WS1 3BD, UK
Tel: +44 (0)1902 322824
E-mail: Tina.Smith@wlv.ac.uk
Second Author:
Assoc Prof Wendy Gilleard
School of Health and Human Sciences,
Southern Cross University, PO Box 157, Lismore, NSW, 2480, Australia
Tel: +61 (0)2 6620 3501
E-mail: wendy.gilleard@scu.edu.au
As accepted for publication in European Journal of Sport Science, ©Taylor & Francis
24
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November 2014
DOI: http://dx.doi.org/10.1080/17461391.2014.992477
Acknowledgements
The authors would like to thank Dr Peter Shaw for his assistance with the statistical analysis.
No financial support was received to carry out this study

2
Abstract
There is a paucity of data describing the lofted instep kick, and little information on the
kinematic differences between male and female footballers. This study provides a
preliminary investigation into the differences in motion patterns between the sexes. A
four camera motion analysis system videoed thirteen amateur footballers (seven female,
six male) attempting a standardised task that represented a lofted instep kick of
approximately 35 m. Footballers performed twenty kicks, with the three trials categorised
closest to the standardised distance retained for statistical analysis. Three-dimensional
motion patterns for kicks of 35 m illustrated that female footballers produced greater
fluctuation in movement patterns for pelvic, hip joint and thoracolumbar spine motion in
the frontal plane; thorax and hip joint transverse rotation; and ankle dorsiflexion /
plantarflexion motion. Peak hip extension (P = 0.018), impact hip abduction (P = 0.032),
impact ankle plantar flexion (P = 0.030) and resultant ball velocity (P = 0.004) differed
significantly between sexes. Principle Component Analysis highlighted associations
between kinematic variables related to ball velocity and sex including a reduced hip
abduction and increased internal rotation approaching impact, and greater peak knee
flexion, respectively. In summary, increased variation in direction of segment motion,
increased backswing and formation of a tension arc by females compared to males, may
be related to anthropometric, strength and muscle activation differences. Specifically this
exploratory study indicates future research would benefit from exploring trunk, pelvis and
hip kinematics and kinetics, and whether training the trunk, pelvis and hip musculature
assists female footballers.
Key words: hip, kinematics, football, soccer, thoracolumbar spine

3
Introduction
Differences between men and women’s football have been noted in terms of strategies and styles
of play which may be attributed to the female footballers being less capable of performing a
long, lofted kick (Scott, 1999). Although this potential difference in lofted instep kicking exists,
there is a paucity of research on three dimensional kinematics of the kick for either sex, therefore
initial descriptive and cross sectional studies are required to serve as a guide for future research
in the area (Bishop, 2008).
Kinematic differences between the sexes during maximal instep kicking have included less
effective use of the tension arc (Shan, 2009) by skilled female players. 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). Whether the tension
arc is a characteristic of lofted instep kicking or used to a lesser or greater extent by either sex
has not been previously reported. 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.
Historically coaching practice advocates a backward leaning trunk at impact for a lofted instep
kick (Hargreaves, 1990; Hughes, 1994) and this continues to be used (CoachesColleague, 2009).
Research on trunk inclination for instep kicking has reported differing degrees of backward lean
between two professional players (Lees & Nolan, 2002) and for male and female players (Orloff
et al., 2008), indicating that clarification of trunk inclination for lofted instep kicking is required.
The lack of consensus in existing literature and the scarcity of research on the three-dimensional
motion of the lofted instep kick highlight the need for more studies in this area, especially the
need to explore trunk and hip motion.

4
The aim of the study was to investigate differences in joint angular displacement, ball and foot
velocity between males and females performing a standardised lofted instep kick. It was
hypothesised that differences in hip and trunk joint angular displacement would be evident
between sexes performing a standardised lofted instep kicking task, and males would display a
greater ball velocity at impact. In addition the three-dimensional motion of male and female
footballers performing a 35m plus lofted instep kick was quantified and described.
Methods
Seven female (age: 25.3  7.6 y, height: 164.8 ± 4.8 cm, body mass: 68.5 ± 9.7 kg) and six male
(age: 22.3  3.4 y, height: 182.0 ± 4.0 cm, body mass: 81.9 ± 10.8 kg) experienced amateur
football players volunteered for the study. 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
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.
Measurements recorded were thigh (trochanterion: the most superior point on the greater
trochanter to tibiale laterale: most superior point on lateral border of head of tibia), tibiale

5
laterale height (tibiale laterale to floor), tibia (tibiale mediale: most superior point on the medial
border of the head of the tibia to sphyrion tibiale: most distal tip of the medial malleolus of the
tibia), foot (most 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). 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).
Protocol
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. The
duration and intensity of activities increased each phase. Markers were attached to the 4
th
and
10
th
thoracic vertebrae spinous process, the angle of the 8
th
rib on the left and right, the posterior
superior illiac spines, sacrum (S
4
spinous process), greater trochanter of the femur, lateral
femoral epicondyle, mid-thigh 10 cm vertically above the patella base, the right lateral malleolus
of the fibula and on the subjects’ footwear directly over the 5
th
metatarsal head to define the
thorax, pelvis, thigh, knee and foot segments (Gilleard, Crosbie, & Smith, 2002). Following a
demonstration, participants carried out five practice kicks. Participants were videoed in standing
neutral posture before a standardised definition of the aims of the task was conveyed. 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. However, 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. The number of practice trials selected was typically twelve. Participants were then

Frequently asked questions

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.