“Integrity” is widely recognized as a quality of intentional and structured movement. Have a look at Roger Federer perform a backhand, his movement is fluid and lithe, and this tells us he is performing in an optimal way. And just as surely, we know that tennis novices are doing somehow very wrong as they hack away at the ball with jagged strokes. The quality of expert movement noticeable to the eye, and seems to have something to do with a certain smoothness. But is there a way to objectively measure this integrity of motion quality?

As someone trained in the Feldenkrais Method, I understand there are ways to learn to move with more ease and fluidity, and this can help with physical ease and fluid range of motion. But the Feldenkrais Method doesn’t offer any way to define or measure movement integrity with any tests. Instead, it is acknowledged that motion integrity is probably too individual, situationally dependent and complex to measure with simple assessments.  

By contrast, many physical therapists, such as Shirley Sahrmann and Gray Cook, have defined movement quality with objective tests that seek to set apart “dysfunctions” in coordination with movement. However, the research has generally not been kind to these efforts, leading many people to dismiss the hope of scientifically measuring general coordinative skills. 

Personally, I have never doubted that motion integrity is a very real thing. To prove that it exists, you need only look at the flowing movement of an Cirque du Soleil performer. But can this quality be described in a way that is objective, outside of a a certain display of strength? 

A recent paper argues that “smoothness” may be an essential quality all good movements, and that this quality can be measured. Here’s a link to the paper by John Keily, Craig Pickering and David Collins called Smoothness: An Unexplored Window into Coordinated Running Proficiency. Following is a brief summary. 

Defining motion integrity: the minimum jerk model 

motion integrity is best understood as the opposite of movement that is “jerky.” While smooth movement creates an impression of fluid continuity “non-smooth movements, in contrast, changing hastily of erratic discordance and of disjointed, unpredictable control.”

This distinction is useful because jerky movement can be seen in terms of the rate of accelerations of movement. Thus, smoothness involves a minimum of abrupt, intermittent, changes in accelerations, relative joint positions and motion trajectories.” These can be measured, and the measurements are now more understood with the availability of wearable motion-sensing technology. But there has been surprisingly little research examining this data, even though preliminary findings are very interesting. 

Research on smooth movement 

Previous research has shown that smoothness of movement improves along with development of movement skill in a variety of contexts, including infant motor development, walking, writing, rock climbing, golfing, and throwing. For example, the club head trajectories of skilled golfers are smoother than those of novices. Further, declines in function are correlated with increased jerkiness, as seen in aging, injury, neurological damage, or distraction during driving. Tests of smoothness in activities like sit to stand or postural sway can predict injury risk in sports or activities of daily life. 

Why is smooth movement and motion integrity so important? 

Smooth movement is created by muscles that are working properly, There is a certain gliding of each muscle from origin to insertion along side other muscles, not bound to fascia but smoothly gliding in unison with surrounding muscles. This creates a positive feedback loop: increased predictability makes control easier, which makes movement smoother, which enhances the integrity of motion. This is the difference between just kind of throwing your legs in front of you to walk when your muscles are not primed and conditioned to preform all needed action, and having them firing well and intentionally placing them in front of you so your weight distributes evenly through the IT band and down through the muscles of the leg where your weight is evenly distributed through the tarsals.