Abstract
Losing balance or tripping during obstacle-crossing is one of the most frequent causes of falls in the elderly. As a low speed, low impact exercise, Tai Chi Chuan (TCC) can be promising in helping the elderly develop strategies for improved balance, inter-joint coordination, and end-point control during obstacle-crossing. This study investigates the effects of TCC training on the patterns and variability of the lower-limb inter-joint coordination during obstacle-crossing in the elderly. Fifteen older TCC practitioners and 15 healthy controls crossed obstacles of three different heights, while sagittal angles and angular velocities of the hips, knees and ankles were measured and their phase angles obtained. The continuous relative phases (CRP) of the hip-knee and knee-ankle coordination were also calculated. The standard deviations of the CRP curve points were averaged to obtain deviation phase (DP) values for the stance and swing phases. The TCC group was found to cross obstacles with increased leading and trailing toe-clearances with unaltered CRP values when the swing toe was above the obstacle. Long-term TCC training altered the patterns and magnitudes of the CRPs primarily over double-limb support and significantly reduced the variabilities of leading knee-ankle and trailing hip-knee and knee-ankle CRP curves over the crossing cycle, regardless of obstacle height. The current results suggest that long-term TCC practice was helpful for a crossing strategy with significantly increased foot-obstacle clearances and reduced variability of the way the motions of the lower limb joints are coordinated during obstacle-crossing. These benefits may be explained by the long-lasting effects of continuous practice of the slow movement patterns emphasizing between-limb transfer of body weight in TCC.
Highlights
More than 30% of people aged 65 and over fall at least once during a year, with a higher incidence of falls in frail individuals or those with disabilities (Blake et al, 1988; Tinetti et al, 1988; Campbell et al, 1990; Graafmans et al, 1996)
From the ensemble-averaged phase plots of the leading and trailing joints for both groups, the phase trajectories of the hip and knee were found to be in forms of nearly-closed periodical circles, but those for the ankle had a different form of trajectories with varying amplitudes (Figure 2)
The ensemble-averaged hip-knee continuous relative phases (CRP) curves of the leading and trailing limbs were retained within the range of 0° and 180° for all obstacle heights and for both groups, while those for kneeankle coordination were within around 0° and 360° (Figures 3, 4)
Summary
More than 30% of people aged 65 and over fall at least once during a year, with a higher incidence of falls in frail individuals or those with disabilities (Blake et al, 1988; Tinetti et al, 1988; Campbell et al, 1990; Graafmans et al, 1996). Among the causes of falls in the elderly, losing balance or tripping during obstacle-crossing is one of the most frequent (Overstall et al, 1977; Blake et al, 1988; Tinetti and Speechley, 1989; Campbell et al, 1990; Winter, 1992; McFadyen and Prince, 2002; Di Fabio et al, 2004). Obstacle-crossing during walking is a complex motor task, requiring precise end-point (swing foot) control while maintaining body balance via highly coordinated joint movements (Chen et al, 2004; Chen and Lu, 2006; Lu et al, 2006). There is a need for interventions to help the elderly develop strategies for improved balance, inter-joint coordination, and end-point control during obstacle-crossing. Few studies have explored the benefits of TCC practice on lower limb inter-joint coordination and endpoint control during obstacle-crossing in the elderly
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