July 2013

Kicking biomechanics: Importance of balance

7soccer-iStock472091aKicking is a whole-body movement that is responsive to a wide range of constraints related to the task, the environment, and the athlete. Preliminary research also suggests that balance control in the support leg plays a key role in athletes’ kicking performance.

By David I. Anderson, PhD, and Ben Sidaway, PT, PhD

Kicking, a fundamental motor skill usually acquired during childhood, can be adapted to accomplish a range of different task goals. Although it is most commonly associated with the sport of soccer (called football in most of the world), kicking is commonplace in martial arts, American football, Australian football, rugby union, rugby league, some contemporary fitness classes, and a variety of other sports. Consequently, a deeper understanding of kicking has implications for sports scientists seeking to improve kicking performance as well as for clinicians interested in rehabilitating lower limb function. Studying kicking tasks can also advance understanding of processes underlying the control and learning of complex multisegmented movements.1,2

Despite the prevalence of kicking in sports and the large body of research on kicking that has accumulated over the last 25 years, many gaps remain in our understanding of the motion. Although controlling whole-body balance and posture are critical to the expression of all skilled physical activity, most examinations of kicking have focused on the kicking leg, with few examining the role of the support leg in facilitating effective and efficient kicking motion of the opposite leg.3-6

The kicking leg

Kicking is a complex pattern of whole-body joint and segment motions that occur in multiple planes. Understandably, most of what we know about kicking has come from the work of sports scientists examining kicking in soccer. It is not clear to what extent research on the soccer kick can be generalized to kicking movements adapted for other purposes, however, it is well established that variations in the task goal of the soccer kick (e.g., for accuracy vs distance or passing vs scoring a goal) can have pronounced effects on movement kinematics and kinetics.7-9 These effects highlight how sensitive all movements are to variations in constraints related to the task, the performer, and the environment.10,11

7soccer-iStock1159728aKicking leg kinematics

Many of the biomechanical descriptions of the soccer kick have been restricted to the two-dimensional motions of the kicking leg in the sagittal plane.9,12 This highlights the difficulty in accurately and reliably quantifying joint and segment motions occurring in the transverse plane around the long axes of limb segments and represents a major limitation in our understanding of segmental contributions to skilled kicking movements. Nevertheless, one of the most prominent features of the soccer kick is the proximal-to-distal sequencing of the segments of the kicking leg, and the unfolding of this sequence is most obvious in the sagittal plane.

A number of studies have highlighted the importance of the proximal-to-distal sequence of segmental angular velocities in generating a high linear velocity in the kicking foot.13-17 The linear velocity of the kicking foot is highly correlated with the resultant ball velocity.16,18-20 To generate linear velocity at the foot a skilled kicker will first rotate the hip backward into extension and flex the knee during the backswing phase of the kick. As the hip begins to flex, the knee continues to flex slightly, and then is held in this position for a brief period as the hip continues to flex. The knee begins to extend before the hip reaches maximal angular velocity,1 and, as the angular velocity of the hip declines, the knee velocity increases until the foot’s impact with the ball. Knee angular velocities can be as high as 1900°/s34 and resultant ball velocities of 35 m/s have been recorded in naturalistic settings.21

Kicking leg kinetics

The kinetic features of the soccer kick are less well understood than the kinematic features. Putnam’s24 seminal work demonstrated that the kicking movement is characterized by a complex blend of forces generated by muscle moments, motion-dependent moments that result from interactions among joints and segments, and gravitational forces. Hip flexion moments are nearly twice as large as knee extension moments14,17,22-26 and the smallest moments are associated with ankle plantar flexion.22 The most influential moments appear to be the extensor moment generated by the muscles that cross the knee joint and the moment associated with the angular velocity of the thigh.13,20,27

The specific time course of the moments at each joint during the kick has not yet been reliably established; various studies have reported different patterns.8,9 The values of the moments at each joint have also varied considerably, likely reflecting the range of methodologies that have been used to examine those moments, variations in data smoothing techniques, limitations in the assumptions of the inverse dynamic models used to estimate the moments, and differences in task constraints.

Coordination changes in the kicking leg

Considerable interest has been shown in how athletes acquire skilled coordination in the kicking leg. Drawing on the work of Bernstein,28 Anderson and Sidaway1 first described the learning curve for kicking as the process of freezing and then freeing degrees of freedom in the kicking leg. Novice kickers initially froze degrees of freedom by constraining the ranges of motion at the hip and knee joints. After 20 practice sessions, the kickers had significantly increased the range of motion at the hip and knee and had developed a qualitatively different pattern of coordination between the hip and knee joints, reflected primarily by an earlier onset of knee extension relative to the maximal angular velocity of the hip. Because the maximum linear velocity of the foot increased from prepractice to postpractice, without a concomitant increase in the maximum angular velocity of the hip, the release of degrees of freedom had presumably allowed a pattern of coordination to emerge that enabled the shank to exploit the momentum of the thigh. This conclusion is consistent with data showing the motion-dependent moment acting at the knee appears to compensate for the counterintuitive reversal of the muscle moment from extensor to flexor just prior to ball impact in skilled kickers.20

More recent research has shown that coordination changes in the kicking leg are task-specific and learner-specific.2,29-31  In some cases, degrees of freedom are constrained, then released, and then constrained again, consistent with the proposition that alternating reducing and increasing degrees of freedom is an ideal way to induce changes in coordination.32

Balance in kicking performance

Although balance control is presumed to be a fundamental constraint on the organization of skilled movement, it is surprising how few empirical studies have attempted to examine this presumption. Much of the work in this area has focused on acquisition of skills during the first year of life, when it is easier to see how limitations in infants’ ability to control their relationship to the environment constrain the expression of skilled activity. Many researchers have noted that control over balance and posture paces the emergence of all other skills, as skillful activity can occur only if infants can consistently regulate that relationship to the environment.3,5,6,33-35

Because kicking places considerable demands on postural control, it would seem to be an ideal task for studying the contribution that balance makes to skilled performance. Yet much of the research linking postural control to skilled performance has been done in sports like pistol shooting and rifle shooting, in which static balance is critical.36-38  Nevertheless, researchers are beginning to pay greater attention to the importance of dynamic balance in a range of different sports39 and some evidence suggests that highly skilled soccer players have better general balance control than less-skilled players.40

In one of the only studies to address an aspect of balance control during kicking, Shan and Westerhoff 41 examined the role of horizontal elevation of the arm on the nonkicking side on the maximal instep kick in skilled soccer players. While many researchers have assumed the arm plays a pivotal role in maintenance of balance during the kick,9 Shan and Westerhoff 41 argued that its primary function is to create a diagonal “tension arc” that helps generate velocity in the kicking leg by taking advantage of the stretch–shorten cycle in the hip flexors.

The support leg

Very little attention in the literature has been devoted to examining the role of the support leg in kicking performance. Lees and colleagues42 reported that skilled soccer players executing a maximal instep kick generated flexion/extension joint moments of 4, 3.2, and 2.2 Nm/kg for the hip, knee, and ankle joints, respectively. The support leg knee and ankle moments are much larger than those reported for the kicking leg.9

An early study found no correlations between ground reaction forces on the support leg and maximum kicking velocity.43 In contrast, Barfield19 reported significant correlations between mediolateral ground reaction forces and maximum kicking velocity on the dominant kicking leg but not the nondominant kicking leg in skilled soccer players. Similarly, Clagg and colleagues44 reported that female soccer players used greater pulling torques and smaller braking torques in the dominant than in the nondominant plant leg while kicking.

Surprisingly, though Orloff and colleagues45 found higher mediolateral ground reaction forces in female soccer players than male soccer players, no differences between men and women were seen in maximum kicking velocities. Despite these inconsistences, it is important to note that skilled soccer players have been shown to demonstrate superior unipedal balance and different unipedal balance control strategies than less-skilled players.46

To further examine the importance of the support leg in kicking, we47 provided unskilled kickers with external postural support by allowing the hand contralateral to the kicking leg to grasp a rigid support. The provision of this augmented support significantly increased ball velocity, suggesting that postural control over the support leg makes an important contribution to kicking performance.

More recently we attempted to quantify the role of the support leg in kicking performance through a correlation approach.48 We reasoned that single-leg balance on the support leg should predict kicking performance on the opposite leg if balance control was important for performance. Participants kicked a soccer ball with the right and left legs for maximum accuracy and velocity and performed single-leg balance on a force plate for 30 seconds with the right and left legs. Single-leg balance was significantly correlated with kicking accuracy, but not velocity. Dominant (right) leg kicking accuracy correlated more strongly with nondominant (left) leg balance than dominant (right) leg balance. (The right leg was the dominant leg in all study participants.) The same was not true, however, for nondominant (left) leg kicking accuracy, which was significantly correlated with nondominant (left) leg balance but not correlated with dominant (right) leg balance.

The asymmetrical nature of the results was interpreted as support for the dynamic dominance model of motor lateralization suggested by Sainburg and colleagues.49-51 This model proposes that each cerebral hemisphere/limb system becomes specialized for controlling different aspects of task performance. Although evidence in support of the model is confined to the upper extremity, if the dynamic dominance model holds for the lower extremities it would predict that the right leg/left hemisphere system would be specialized for trajectory control and the left leg/right hemisphere system for stability control in right-leg dominant kickers, consistent with what was found in our kicking study.

The specificity of balance

The lack of association between single-leg balance and kicking velocity ran counter to our prediction, suggesting the stability requirements associated with balancing on one leg are different from those required to support the body when swinging the kicking leg at maximal velocity. The finding may not be surprising given that substantial differences in the way posture is organized to facilitate movement have been documented for highly similar tasks. For example, the organization of anticipatory postural adjustments in a French kickboxing task was quite different when the boxers were required to kick a bag with minimal versus maximal force52 and when the bag was kicked with the same force but the kick was initiated with the kicking foot on or off the ground.53 Because there seems to be a high degree of task specificity in the way posture is organized to facilitate movement, it is likely that a more dynamic test of single-leg balance, such as hopping or swinging the free leg while standing on a force plate, would predict the capacity to generate maximum kicking velocity.


Much remains to be learned about how kicking is organized and how kicking performance might be improved. Researchers are increasingly realizing that kicking is a whole-body movement that is responsive to a wide range of constraints related to the task, the environment, and the performer. Recent research has confirmed that control of balance plays an important role in kicking performance, though clearly more work is needed in this area. Further studies on the relationship between balance and kicking can make broader contributions to our understanding of how complex skills are organized and acquired. Such understanding can in turn contribute to the development of strategies to facilitate the acquisition and reacquisition of movement skills.

David Anderson, PhD, is a professor of kinesiology at San Francisco State University. Ben Sidaway, PT, PhD, is a professor of physical therapy at Husson University in Bangor, ME.

  1. Anderson DI, Sidaway B. Coordination changes associated with practice of a soccer kick. Res Q Exerc Sport 1994;65(2):93-99.
  2. Chow JY, Davids K, Button C, Koh M. Coordination changes in a discrete multi-articular action as a function of practice. Acta Psychol 2008;127(1):163-176.
  3. Gibson EJ, Pick AD. An ecological approach to perceptual learning and development. London: Oxford University Press; 2000.
  4. Massion J, Deat A. Two modes of coordination between movement and posture. In: Requin J, Stelmach GE, eds. Tutorials in motor neuroscience. Dordrecht, Netherlands: Kluwer Academic Publishers; 1991:199-208.
  5. Reed ES. Changing theories of postural development. In: Woollacott MH, Shumway-Cook A, eds. Development of posture and gait across the lifespan. Columbia, SC: University of South Carolina Press; 1989:3-24.
  6. Rochat P, Bullinger A. Posture and functional action in infancy. In: Vyt A, Bloch H, Bronstein M, eds. Early child development in the French tradition. Hillsdale, NJ: Erlbaum; 1994:15-34.
  7. Alcock AM, Gilleard W, Hunter AB, et al. Curve and instep kick kinematics in elite female footballers. J Sports Sci 2012;30(4):387-394.
  8. Kellis E, Katis A. Biomechanical characteristics and determinants of instep soccer kick. J Sports Sci Med 2007;6(2):154-165.
  9. Lees A, Barton G, Robinson M. The influence of the Cardan rotation sequence in the reconstruction of angular orientation data for the lower limb in the soccer kick. J Sports Sci 2010;28(4):445-450.
  10. Davids K, Button C, Bennett S. Dynamics of skill acquisition: A constraints-led approach. Champaign, IL: Human Kinetics; 2008.
  11. Newell KM. Coordination, control and skill. In: Goodman D, Franks I, Wilberg RB, eds. Differing perspectives in motor learning, memory, and control. Amsterdam: North-Holland; 1985:295-317.
  12. Lees A, Nolan L. The biomechanics of soccer: A review. J Sports Sci 1998;16(3):211-234.
  13. Dörge HC, Andersen TB, Sørensen H, Simonsen EB. Biomechanical differences in soccer kicking with the preferred and the non-preferred leg. J Sports Sci 2002;20(4):293-299.
  14. Dörge H, Andersen TB, Sørensen H, et al. EMG activity of the iliopsoas muscle and leg kinetics during the soccer place kick. Scand J Med Sci Sports 1999;9(4):195-200.
  15. Huang T, Roberts E, Youm Y. Biomechanics of kicking. In: Ghista D, ed. Human body dynamics: impact, occupational, and athletic aspects. Oxford: Clarendon Press; 1982:407-443.
  16. Levanon J, Dapena J. Comparison of the kinematics of the full-instep and pass kicks in soccer. Med Sci Sports Exerc 1998;30(6):917-927.
  17. Nunome H, Asai T, Ikegami Y, Sakurai S. Three dimensional kinetic analysis of side-foot and instep kicks. Med Sci Sports Exerc 2002;34(12):2028-2036.
  18. Asami T, Nolte V. Analysis of powerful ball kicking. In: Matsui H, Kobayashi K, eds. Biomechanics VIII-B. Champaign, IL: Human Kinetics; 1983:695-700.
  19. Barfield WR. Effects of selected kinematic and kinetic variables on instep kicking with dominant and nondominant limbs. J Hum Mov Stud 1995;29:251-272.
  20. Nunome H, Ikegami Y, Kozakai R, et al. Segmental dynamics of soccer instep kick with the preferred and non-preferred leg. J Sports Sci 2006;24(5):529-541.
  21. Ekblom B. Football (soccer). London: Blackwell Scientific Publications; 1994.
  22. Luhtanen P. Kinematics and kinetics of maximal instep kicking in junior soccer players. In: Reilly T, Lees A, Davids K, Murphy WJ, eds. Science and football. London: E & FN Spon; 1988:441-448.
  23. Robertson DGE, Mosher RE. Work and power of the leg muscles in soccer kicking. In: Winter D, ed. Biomechanics IX-B. Champaign, IL: Human Kinetics; 1985:533-538.
  24. Putnam CA. A segment interaction analysis of proximal-to-distal sequential segment motion patterns. Med Sci Sports Exerc 1991;23(1):130-144.
  25. Roberts E, Zernicke R, Youm Y, Huang T. Kinetic parameters of kicking. In: Nelson R, Morehouse C, eds. Biomechanics IV. Baltimore: University Park Press; 1974:157-162.
  26. Zernicke RF, Roberts EM. Lower extremity forces and torques during systematic variation of non-weight bearing motion. Med Sci Sports 1978;10(1):21-26.
  27. Kellis E, Katis A, Vrabas IS. Effects of an intermittent exercise fatigue protocol on biomechanics of soccer kick performance. Scand J Med Sci Sports 2006;16(5):334-344.
  28. Bernstein NA. The co-ordination and regulation of movements. London: Pergamon Press; 1967.
  29. Chow JY, Davids K, Button C, Koh M. Organization of motor degrees of freedom during the soccer chip: An analysis of skilled performance. Int J Sport Psychol 2006;37(2/3):207-229.
  30. Chow JY, Davids K, Button C, Koh M. Variation in coordination of a discrete multi-articular action as a function of skill level. J Mot Behav 2007;39(6):463-479.
  31. Hodges NJ, Hayes S, Horn RR, Williams AM. Changes in co-ordination, control and outcome as a result of extended practice on a novel motor skill. Ergonomics 2005;48(11):1672-1685.
  32. Berthouze L, Lungarella M. Motor skill acquisition under environmental perturbations: on the necessity of alternate freezing and freeing degrees of freedom. Adapt Behav 2004;12(1): 47-64.
  33. Bril B, Brenière Y. Postural requirements and progression velocity in young walkers. J Motor Behav 1992;24(1):105-116.
  34. Jouen F, Lepecq J, Gapenne O. Frames of reference underlying early movement coordination. In: Savelsbergh GJP, ed. The development of coordination in infancy. Amsterdam: Elsevier; 1993:237-263.
  35. Thelen E, Smith LB. A dynamic systems approach to the development of cognition and action. Cambridge, MA: MIT Press; 1994.
  36. Aalto H, Pyykkö I, Ilmarinen R, et al. Postural stability in shooters. ORL J Otorhinolaryngol Relat Spec 1990;52(4):232-238.
  37. Era P, Konttinen N, Mehto P, et al. Postural stability and skilled performance – a study on top-level and naïve rifle shooters. J Biomech 1996;29(3):301-306.
  38. Herpin G, Gauchard GC, Lion A, et al. Sensorimotor specificities in balance control of expert fencers and pistol shooters. J Electromyogr Kinesiol 2010;20(1):162-169.
  39. Hrysomallis C. Balance ability and athletic performance. Sports Med 2011;41(3): 221-232.
  40. Paillard, T, Noé F. Effect of expertise and visual contribution on postural control in soccer. Scand J Med Sci Sports 2006;16(5):345-348.
  41. Shan G, Westerhoff W. Full-body kinematic characteristics of the maximal instep kick by male soccer players and parameters related to kick quality. Sports Biomech 2005;4(1):59-72.
  42. Lees A, Steward I, Rahnama N, Barton G. Understanding lower limb function in the performance of the maximal instep kick in soccer. In: Reilly T, Atkinson G, eds. Proceedings of the 6th International Conference on Sport, Leisure and Ergonomics. London: Routledge; 2009:149-160.
  43. Rodano R, Tavana R. Three-dimensional analysis of instep kick in professional soccer players. In: Reilly T, Clarys J, Stibbe A, eds. Science and Football II. New York: E & FN Spon; 1993:357-361.
  44. Clagg SE, Warnock A, Thomas, JS. Kinetic analyses of maximal effort soccer kicks in female collegiate athletes. Sports Biomech 2009;8(2):141-153.
  45. Orloff H, Sumida B, Chow J, et al. Ground reaction forces and kinematics of plant leg position during instep kicking in male and female collegiate soccer players. Sports Biomech 2008;7(2):238-247.
  46. Paillard T, Noé F, Rivière T, et al. Postural performance and strategy in the unipedal stance of soccer players at different levels of competition. J Athl Train 2006;41(2):172-176.
  47. Sidaway B, Anderson DI, Matthew B, et al. The role of postural support in the control of kicking. Presented at the North American Society for the Psychology of Sport and Physical Activity Annual Meeting, San Diego, CA, June 2007.
  48. Chew-Bullock T, Anderson DI, Hamel K, et al. Kicking performance in relation to balance ability over the support leg. Hum Mov Sci 2012;31(6):615-623.
  49. Schaefer SY, Haaland KY, Sainburg RL. Dissociation of initial trajectory and final position errors during visuomotor adaptation following unilateral stroke. Brain Res 2009;1298:78-91.
  50. Schaefer SY, Haaland KY, Sainburg RL. Hemispheric specialization and functional impact of ipsilesional deficits in movement coordination and accuracy. Neuropsychologia 2009;47(13):2953-2966.
  51. Wang J, Sainburg RL. The dominant and nondominant arms are specialized for stabilizing different features of task performance. Exp Brain Res 2007;178(4):565-570.
  52. Béraud P, Gahéry Y. Relationships between the force of voluntary leg movements and the associated postural adjustments. Neurosci Lett 1995;194(3):177-180.
  53. Béraud P, Gahéry Y. Posturo-kinetic effects on kicking movements of a lack of initial ground support under the moving leg. Neurosci Lett 1997;226(1):5-8.

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