Coordinative variability and overuse injury

Abstract

Overuse injuries are generally defined as a repetitive micro-trauma to tissue. Many researchers have associated particular biomechanical parameters as an indicator of such injuries. However, while these parameters have been reported in single studies, in many instances, it has been difficult to verify these parameters as causative to the injury. We have investigated overuse injuries, such as patella-femoral pain syndrome, using a dynamical systems approach. Using such methods, the importance of the structure of coordinative variability (i.e. the variability of the interaction between segments or joints) becomes apparent. We view coordinative variability as functionally important to the movement and different from end-point or goal variability. Using concepts derived from the work of Bernstein, we conducted studies using a continuous relative phase and/or modified vector coding approaches to investigate the coordinative variability of overuse injuries. Consistently, we have found that the higher variability state of a coordinative structure is the healthy state while the lower variability state is the unhealthy or pathological state. It is clear that very high coordinative variability could also result in injury and that there must be a window of ‘higher variability’ in which non-injured athletes function. While this finding that coordinative variability is functional has been shown in several studies, it is still not clear if reduced variability contributes to or results from the injury. Studies are currently underway to determine the potential reasons for the reduced variability in injured athletes. Nevertheless, our laboratory believes that this understanding of how joints interact can be important in understanding overuse injuries.

Quantifying lumbar–pelvis coordination during gait using a modified vector coding technique

“…The authors further concluded that this increase in the in-phase relationship resulted from an increase in pelvis frontal plane ROM. Although the technique utilised to assess coordination and variability should be based on the question asked in the study (Hamill et al, 2012) the use of CRP limits the analysis of coordination to the phase relationship between two segments. On the other hand, vector coding and the proposed four coordination phases (Chang et al, 2008) provides an additional insight to the dominancy of one segment over another and this can offer more valuable information in a clinical setting (Seay et al, 2011).…”

Effect of natural trunk inclination on variability in soleus inhibition and tibialis anterior activation during gait initiation in young adults

“…In most research in motor control, variability is traditionally equated with noise, detrimental to system performance and is typically eliminated from data as a source of error [4,5]. Techniques for reducing and eliminating both within-and between-participants variability have been used.…”

Movement variability and pain: Searching for a solution

“…VARelements above the upper limit implies that the motor system is too unstable and noisy, whereas VARelements below the lower limit indicates the system is too stereotypical, less likely to exhibit exploratory behaviour, and thus less capable of adapting to perturbations ) and more likely to overload specific tissues (Hamill, 2012). However, it is unclear what magnitude of VARelements should be deemed optimal, and at what point VARelements crosses an upper or lower limit to become too much or too little, respectively.…”

“…lateral epicondylalgia) with chronic musculoskeletal pain (Bartlett et al 2007;Hamill et al 2012). This interpretation is consistent with the variability-overuse hypothesis (Wheat, 2005;Bartlett et al 2007) and loss of complexity hypothesis (Lipsitz et al 2002;Hamill et al 2012), which suggest that injury will emerge once the reduction of VARelements reaches a critical threshold/limit.…”