Abstract
Obstacle crossing challenges balance and increases the risk of falls in older people. Knowledge of the control strategies adopted by older people will be helpful for the study of the mechanisms of falls during obstacle crossing and the development of fall-prevention approaches. A mechanical model of the body combined with measured gait data was used to study the control strategies adopted by 17 healthy older and 17 young adults when crossing obstacles of different heights, in terms of the best-compromise weighting sets for the objectives of minimizing energy expenditure and maximizing the toe-obstacle and heel-obstacle clearances. The older group showed increased leading toe-obstacle clearance and trailing toe-obstacle distance, but decreased leading heel-obstacle distance. Compared with the young, the crossing strategy of older people emphasized the foot-obstacle clearance to reduce the risk of tripping, at the expense of energy expenditure. It appears that the multi-objective optimal control strategy relies on the muscular strength of the lower extremities and precise end-point control. Therefore, maintaining or improving the muscle strength and the ability of limb position control is critical for safe and successful obstacle-crossing in the older population.
Highlights
Obstacle crossing challenges balance and is considered one of the daily activities that increases the risk of falls in older people [1,2,3]
An a priori power analysis based on pilot results using G*POWER [30] determined that a projected sample size of 11 subjects for each group would be needed for two-way mixeddesign analysis of variance (ANOVA) with a power of 0.8 and a large effect size (Cohen’s d = 0.8) at a significance level of 0.05
The older group was found to cross obstacles with significantly increased weightings to the heel- and toe-clearances, but decreased energy expenditure weightings when compared with the young group (Figure 3), supporting the hypothesis posed in the current study
Summary
Obstacle crossing challenges balance and is considered one of the daily activities that increases the risk of falls in older people [1,2,3]. Loss of balance and inability to recover balance are the main contributing factors to falling during obstacle crossing in older people [4]. While increasing foot-clearance may help reduce the risk of tripping [9,10,11], the associated alteration of the whole-body posture may place greater challenges on body balance [6,7]. In this case, extra muscular effort and work at the joints in the stance limb will be required to maintain body balance or recover balance in cases where imbalance occurs. Similar knowledge in older adults will be helpful for developing intervention strategies for fall prevention in the older population
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