Biomechanical characteristics of stepping in older Tai Chi practitioners
Highlights
► Compared stepping characteristics of 10 older Tai Chi (TC) and 10 age-matched non-TC individuals. ► Stepping was in the forward and backward directions, with and without mental distractions (MD). ► Both groups had similar step initiation time, step length and forward step width. ► MD delayed step initiation and foot contact time, and shortened step length in both groups. ► TC group had shorter preparation and foot contact time, and wider backward step than non-TC group.
Introduction
The growing body of scientific studies on Tai Chi (TC), a traditional Chinese martial art, has shown that long-term practice of TC by older adults can lead to significant reduction in accidental falls [1]. As the older adult population increases rapidly and fall incidents increase with advancing age, TC has gained popularity among older adults as a therapeutic exercise to improve postural balance and prevent falls.
The mechanism by which TC prevents falls is still unclear. Most falls occur during ambulation [2] and involve taking one or multiple steps in the falling direction prior to the fall occurrence [3], [4]. These pre-fall steps, called protective voluntary stepping, are critical for determining whether a person is going to recover from an impending fall. A faster stepping response to a trigger such as a trip or slip allows people to catch the falling body sooner than a slower stepping response and is shown to be associated with forward trip fall frequencies in older adults [5]. A longer and/or wider step in the falling direction provides a wider base of support and has also shown to be a significant predictor of frequent falls [6]. Moreover, studies comparing the protective stepping characteristics of older adults and young adults have found significantly more frequent steps and significantly shorter and earlier steps in the older population [3], [7], [8].
Since TC practice can effectively reduce fall incidents in older adults and protective voluntary stepping is associated with falls, it is logical to postulate that TC practitioners may step faster and better than their counterparts. To date, there are limited studies investigating the stepping characteristics of TC practitioners. Nnodim et al. compared the effect of a 10-week TC intervention to that of a dynamic balance and stepping exercise in older adults [9]. The authors only reported the relative changes in stepping between the two interventions. Hass et al. investigated the center of pressure (COP) trajectory changes of gait initiation in older adults after 48 weeks of TC practice [10]. The authors reported an increased posterior displacement of the COP in preparation for foot off post training, which may lead to a larger forward momentum and a potentially faster step. In addition, a few other studies have reported a positive TC training effect in recovery kinematics from a slip during walking [11], and in rhythmic forward–backward weight-shift [12]. All these studies support that TC practice may lead to changes in stepping characteristics that are critical for fall prevention.
Moreover, studies show that people are at a higher risk of falls when they are multitasking or being mentally distracted [13]. Yet, few studies have investigated the biomechanical characteristics of stepping under mental distractions. One study by Melzer and Oddsson compared the temporal characteristics of step initiation with and without distractions and found that older adults had a substantial increase in the initiation phase with distraction compared to the young [14]. However, there is growing body of studies reporting positive outcomes of mind/body exercises on motor function and performance [15], and on standing balance in older adults [16]. Since TC practice involves the mind and the body, it is likely that TC practitioners are less affected by mental distractions when taking a step.
The purpose of this study was to investigate and compare the biomechanical characteristics of forward and backward stepping in older TC practitioners and age-matched controls in response to an auditory cue with and without mental distractions. It was hypothesized that long-term TC practitioners would step better in terms of timing and stability, either without or with mental distractions.
Section snippets
Subjects
The study included community-dwelling older adults aged 55 years and older. They were all physically fit, functionally independent, and had no neural, muscular, or cerebrovascular diseases likely to affect balance. They were excluded if they were taking centrally active medications or alcohol regularly. The TC practitioners were required to have practiced TC on a regular basis for more than two years, and the controls had not practiced TC at all.
All subjects were voluntarily recruited in
Subject information
A total of 20 subjects (six males) participated in the study, with a mean age of 67 ± 10 years. There was no significant group difference in all subject's characteristics (see Table 1) except for TC practice experience. TC practitioners had practiced TC for an average of 18 years, with a range from 2 to 38 years. The frequency of TC practice ranged from three to seven days/week, a minimum of 1 h each time. The most common form of TC was the long-form Yang style. Also, subjects in both groups
Discussion
This study is aimed at comparing the biomechanical characteristics of forward and backward stepping in older TC practitioners and age-matched controls with and without mental distractions. Overall, the results show that mental distraction slows down the step initiation and foot contact time, and decreases step length in both TC and NTC practitioners. However, compared to NTC practitioners, long-term TC practitioners have less preparation time to lift up the stepping foot, are faster to land the
Conclusions
This study compared the differences between older TC and NTC practitioners in step initiation characteristics with and without mental distraction. It was found that mental distraction significantly delayed step times and shortened step length in both groups. However, TC practitioners had a shorter preparation time to lift the stepping foot, a shorter step foot contact time, and a wider backward step width than NTC practitioners regardless of mental distraction. These group differences are in
Conflict of Interest
The author testifies that there was no conflict of interest.
Acknowledgements
The author would like to thank Bao Tak Fai Tai Chi Institute and senior centers and retirement housing facilities in the Burlington, VT area for assistance with subject recruitment. The author was responsible for all aspects of this work.
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