Elsevier

Gait & Posture

Volume 42, Issue 2, July 2015, Pages 152-157
Gait & Posture

Age-related differences in inter-joint coordination during stair walking transitions

https://doi.org/10.1016/j.gaitpost.2015.05.003Get rights and content

Highlights

  • The independent control of adjacent joints in older adults is diminished.

  • Reduced variability of inter-joint coordination in older adults is observed.

  • Coordination between proximal joints is responsive to age-related changes.

Abstract

Stair negotiation is one of the most difficult and hazardous locomotor tasks for older adults with fall-related accidences reported frequently. Since knowledge about inter-joint coordination during stair walking provides insights to age-related changes in neuromuscular control of gait that can inform prevention or intervention strategies, the current study investigated the effect of age on the pattern and variability of inter-joint coordination during stair-floor transitions during gait. Gait and motion analyses of the lower extremities of 20 young and 20 older adults during floor to stair (F-S) and stair to floor (S-F) walking transitions provided continuous measures of relative phase (CRP) that assessed inter-joint coordination of the hip, knee, and angle joints. The mean absolute relative phase (MARP) and deviation phase (DP) provided descriptive metrics for CRP pattern and variability respectively. For hip-knee CRP pattern, older adults demonstrated significantly smaller MARP than young adults in stance and most swing phases during F-S and S-F. For knee-ankle, older adults showed a significant smaller MARP of the trailing limb during S-F than young adults. In most stance and swing phases, the hip-knee DP values of older adults were significantly lower than that of young adults. Significant lower knee-ankle DP values of older adults were only detected in swing phase during S-F. The findings suggest that normal aging adults have less independent control of adjacent joints compared to younger adults suggesting they have less flexibility to modulate inter-joints coordination appropriately during stair walking transitions.

Introduction

Stair negotiation is one of the most difficult and hazardous locomotor tasks for older adults [1], [2]. In a sample of 310 healthy older adults, more than 45% reported difficulties in stair negotiation [1]. While difficulties in stair ascending were associated with poor balance and gait abnormality, difficulties in stair descending were related to higher fall incidences [1]. Stair-related falls caused nonfatal injuries in more than 55,000 older adults in the United States and accounted for more than 10% of fatal fall accidents [2]. Additionally, falls induced by missteps during stair descending are especially dangerous and may result in serious injuries, such as head trauma or limb fractures [3].

In comparison to level ground walking, the capability to negotiate the stairs can be challenging for older adults due to the greater demands on motor functions. Many studies about the effect of age on stair negotiation have been focused on single joint kinematics, kinetics, muscle activities, or center of mass and center of pressure control. When negotiating the stairs, older adults show high variability in foot clearance [4], poor balance control during the stair to floor transition [5], reduced single joint motions [6], and difficulties in redistributing the joint moments [7]. They also tend to walk with a high proportion of maximal capacity, early activations of quadriceps, and increased muscle co-contraction which is described as a compensatory mechanism of increased joint stiffness for stability [8], [9].

Stair walking transitions were reported to be particular dangerous [10]. The mechanics of transition strides between stair and level ground have been recognized as unique features in anticipatory adjustments for the upcoming surfaces, requiring a greater effort in the ankle plantarflexor and increased lower limb range of motion compared to other strides on the staircase [10], [11]. Since declines in musculoskeletal functions may alter motor patterns in high demanding tasks and deficits in contrast sensitivity may hinder the detection of stair transition regions in older adults [4], [8], [12], further investigations on the transitions strides between stair and level ground may provide insightful information of stair-related falls in older adults.

High levels of neuromuscular control integrated with sensory inputs to produce coordinated limb movements are essential to regulate the initiation, termination, intensity, and adaptability of locomotion [13]. The neuromuscular controller has shown to take advantage of motor redundancy to provide a flexible control over motor tasks that requires good coordination among multiple joints [14]. As such, poor coordination among joints during gait could result in imbalance or tripping [15]. Aging is frequently accompanied with deteriorated central nervous system function and impaired proprioception which is critical in planning and updating inter-joint coordination when performing functional activities [16], [17]. Due to the degeneration of neuromuscular system, age-related differences in inter-joint coordination could be more pronounced than the differences in individual joints and were considered as one of the important functional features to reveal the declines in gait functions as well as the occasions of fall risks in older adults [18], [19]. However, to our knowledge, no study has yet reported the transition strides between stair and level ground from the perspective of neuromuscular control.

Certain aspects of inter-joint coordination of human movement have been successfully assessed by adopting phase portraits constructed by the motions of two joints or segments [20]. With the use of joint angle-velocity phase portraits, continuous relative phase (CRP) evaluates the differences in four quadrants arctangent phase angles between two joints or segments to provide a continuous measurement of the interaction between joints or segments throughout the gait cycle [21]. Investigating inter-joint coordination using CRP could provide insights into the essential timing and sequencing of movement control between joints, and the coordination variability could reflect the flexibility of this control [20], [21], [22]. The information could be used to enhance the safety of stair walking transitions in older adults and improve the development of rehabilitation interventions. The purpose of this study was to investigate the effects of age on the pattern and variability of lower limb inter-joint coordination in healthy adults during stair walking transitions. We hypothesized that during stair walking transitions (1) the patterns of inter-joint coordination of older adults would be different from that of young adults; (2) the variability of inter-joint coordination would be smaller among older adults than young adults.

Section snippets

Method

Forty adults were recruited: twenty healthy young adults (10 men, 10 women, age = 25.0 ± 4.5 yrs, height = 171.4 ± 8.6 cm, weight = 70.5 ± 10.9 kg, exercise time per week = 2.9 ± 2.1 h) and 20 healthy older adults (10 men, 10 women, age = 74.3 ± 5.9 yrs, height = 162.7 ± 8.5 cm, weight = 71.6 ± 17.4 kg, exercise time per week = 2.7 ± 1.8 h). Prior to participation, each study participant provided signed consent to the experimental procedure approved by the Institutional Review Board. All participants had no current or histories of

Results

During F-S and S-F walking transitions, older adults walked significantly slower (p < .001) with shorter stride length (p = .008 for F-S and p < .001 for S-F) when compared to young adults; however, significant group difference in step width was not detected (Table 1). For both young and older adults, the stride length and step width of F-S condition were significantly smaller than that of S-F condition (p  .016; Table 1).

Fig. 1 illustrates the mean hip-knee and knee-ankle CRP curves of young and

Discussion

Older adults walked with more in phase hip-knee coordination pattern during stair walking transitions. Such differences between age groups were less notable in the knee-ankle coordination pattern, as its difference was only observed in swing phase of the trailing limb during stair to floor walking transition. These findings partially support our first hypothesis that the patterns of inter-joint coordination of older adults would be different from that of young adults.

The locked in phase pattern

Conclusion

The study demonstrated that the inter-joint coordination during stair walking transition was different in young and older adults. The pattern and variability of inter-joint coordination was consistent and reduced in older adults relative to young adults. Our findings suggest that examining and facilitating lower limb inter-joint coordination of older adults during stair walking transition could be an important factor in the development of stair-related fall prevention program.

Conflict of interest

There are no conflicts of interest associated with this research.

Acknowledgements

We thank Niall O’Brien, Jacob Banks, Amanda Rivard for helping with the data collection and the assistance of Rick Holihan and Peter Teare in stair construction. Funding for this project included the Liberty Mutual Harvard School of Public Health Occupational Safety and Health Post-doctoral Program.

References (30)

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