When hitting forcefully with the hands or feet, optimal performance involves adapting to changes in conditions. For instance, when modifying the distance between the individual and target (or opponent), maintaining performance (e.g., high impact force) requires variability in the movements supporting a given technique [1, 2]. Additionally, the capability to appropriately change which technique is used under different constraints also appears to be important [3]. Implications are that, so long as performance objectives are achieved, increased movement variability can indicate skill in combat sports.

Figure. Experimental design in scaling distance to the boxing bag with examples of movement variability.

Research question

Do experts exhibit more movement variability in response to changes in the individual-target position? Is this in terms of regulating the technique and/or in terms of a greater variety of techniques?

Method and design

The apparatus is a free hanging bag. An expert group of experienced kickboxers (n = 22), and a novice group of inexperienced individuals (n = 22) will strike the bag across seven distances, scaled in proportion to individual leg lengths. They will be asked to strike the bag with force and speed, and using (if possible) a different technique each time. The kinematics of 10 strikes per position will be recorded. The expert group should use more techniques at each position and their ability to do so will be based on changes in how techniques are regulated from one distance to another.


  1. Kim JW, Kwon MS, Yenuga SS, Kwon YH. The effects of target distance on pivot hip, trunk, pelvis, and kicking leg kinematics in Taekwondo roundhouse kicks. Sports Biomechanics. 2010;9(2):98-114.
  2. Falco C, Alvarez O, Castillo I, Estevan I, Martos J, Mugarra F, et al. Influence of the distance in a roundhouse kick’s execution time and impact force in Taekwondo. Journal of Biomechanics. 2009;42(3):242-8.
  3. Hristovski R, Davids K, Ara├║jo D, Button C. How boxers decide to punch a target: Emergent behaviour in nonlinear dynamical movement systems. Journal of Sports Science and Medicine. 2006;CSSI:60-73.


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