Conventional thought suggests that for most distinct movement patterns (e.g. squat, lift, sit, push, pull, step, lunge, bend, twist etc.) there is an ideal form or technique. In contrary to this emerging research suggests that variation in movement is actually quite ‘normal’, such that no movement is ever repeated in the same way twice (1). In this article we discuss how loss of movement variation is associated with increased incidence of injury and reduced performance. We go on to recommend that traditional training and rehabilitation may be extended to include strategies to increase movement variation.
Movement is highly complex and composed of an array of variable patterns and forms. For each and every movement, muscle synergies emerge in response to our goal, our psychology, environment and the physical constraints of our body (flexibility, mobility, strength, stability). Performance parameters such as strength, speed, accuracy and force are largely determined by the quality of these neuromuscular synergies.
In attempting to understand movement, musculoskeletal therapists and coaches often construct models of ideal form and technique that guide rehabilitation and training strategies. In musculoskeletal rehabilitation we emphasize returning a patient to a ‘normal’ or ideal posture following injury. We ‘re-train’ patterns of movement to reduce biomechanical stress (e.g. teaching ‘neutral spine’ or bending only from the knees when we lift), but is there such a thing as normal or ideal movement?
Research indicates that a single stimulus can lead to a variety of different movement responses in healthy individuals (3). The same individual may select two totally different strategies for achieving a functional goal under two sets of different circumstances or environments (1). Likewise, two individuals under the same environmental constraints may carry out the same functional task using significantly different strategies (1). Variability in movement helps individuals adapt to unique movement challenges. The capacity to make rapid changes to neurophysiological and behavioral responses to environmental challenges may be a key factor in reducing the likelihood of injury.
‘Healthy and adaptive biological systems depend on variability of behavior to ensure optimal functioning and an appropriate level of organizational complexity.’
Rather than seeing increased movement variability, we actually see more rigid patterns of movement following injury. For example, people with low back pain show decreased variability in the timing of anticipatory postural adjustments (Jacobs, JV, Henry). Injury also reduces (1). Lateral ankle sprains alter activation patterns of ankle muscles long after the initial injury, causing motor instability, and increased likelihood of reoccurance of injury. (Hopkins Evertor/invertor muscle activation). The loss of ankle stability in these cases reduces movement variability during single leg jump-landing compared to healthy controls (5). Injury compromises the ability of the body to adapt effectively (1) and reduces our ability to adapt to environmental challenges causing increased tissue loading. It has been proposed that loss of movement variability or ‘behavioral rigidity’ may predispose repetitively uneven loading of the articular surfaces, increasing risk of chondral damage and osteoarthritis (1). Pain, loss of stability, loss of mobility and even psychological factors such as fear of movement or concern regarding re-injury may all be factors predisposing loss of movement variability.
A reasonable question to ask is if variability in structure and function is actually quite normal even in people without pain, why assume that inter-individual variations actually predispose injury? Why would we try to return people to ‘normal’ as part of a rehabilitative program? Why bother to try to alter biomechanics and movement at all? Is movement education as part of a preventative program invalid?
As a therapist and personal trainer I am a big advocate of preventative intervention as part of a functional approach. I will try to use the example of sport coaching to try to answer why this is.