Abstract
Mechanical stability criteria are able to explain balance and robustness during simple motions, however, humans have learned many complex balancing tasks for which science lacks a thorough understanding. In this work, we analyzed slackline balancing to define general balance performance indicators. The goal is to not only measure slackline expertise, but to be able to quantify stability during any balance task. For this, we compared beginners that had never balanced on a slackline before to professional slackline athletes. Further, all participants performed a static balance test, based on which we divided beginners into a balance-experienced and a balance-inexperienced group. On average, the balance experienced group was able to balance twice as long on the slackline and therefore, we showed that this static balance experience is a predictor of slackline balance performance. Based on over 300 balancing trials on the slackline of 20 participants, we then defined and evaluated over 30 balance metrics. The parameters can be grouped into quantification of stability and recovery movements, balance specific skills and balance strategies. We found that normalized angular momentum and center of mass acceleration are measures for overall stability, with lower values representing better stability and fewer recovery movements. We showed that improved hand coordination and adjusted stance leg compliance are valuable skills for balance tasks. especially when controlling external forces. Looking at posture and movement strategies, we found that professional slackliners have adapted a different mean pose with larger inertia and an upright head position, when compared to beginners.
Highlights
In challenging balance exercises signs of stable or impaired balance are much more obvious than in every day situations
The protocol consisted of subject preparation, a static balance test and two rounds of slackline balancing with a 5 min break in between, all of which will be described in the following paragraphs
We analyzed slackline balancing for beginners that had never balanced on a slackline before and compared them to professional slackline athletes
Summary
In challenging balance exercises signs of stable or impaired balance are much more obvious than in every day situations. Only a few studies are available on slackline balancing: Training effects of slackline balancing on posture, neuromuscular performance and other balance tasks have been well-studied (Donath et al, 2013, 2015). They found task specific improvements but limited transfer to other balance tasks. Serrien et al (2016) and Serrien et al (2017) employed self-organizing maps to analyze kinematic motion capture before and after a 6 weeks training intervention They found that the balance coordination pattern changed significantly by means of increased range of motion and decreased velocity in joints. In previous work we proposed normalized angular momentum, CoM acceleration, kinetic energy and stance foot acceleration as performance indicators for slackline balancing (Stein and Mombaur, 2019)
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