# Relation between Step-To-Step Transition Strategies and Walking Pattern in Older Adults
###### Abstract  
In older adults, two different modes of step-to-step transition have been observed: an anticipated mode when the reflection of the centre of mass of the body (COM) begins before double stance and another when the transition begins during double stance. However, the impact of transition mode on gait kinetics and kinematics has not been investigated. Age and step-to-step-transition-related differences in intersepmental coordination and in the COM trajectory during walking were identified. Fifteen young (24.1 \(\pm\) 0.7 y.o.) and thirty-six older adults (74.5 \(\pm\) 5.0 y.o.) walked on a treadmill at 1.11 m s\({}^{-1}\) and 1.67 m s\({}^{-1}\). Lower-limb motion and ground reaction force were recorded. The COM dynamics were evaluated by measuring the pendulum-like exchange of the COM energies. While all young adults and 21 of the older adults used an anticipated transition, 15 older adults presented a non-anticipated transition. Previously documented changes of intersegmental coordination with age were accentuated in older adults with non-anticipated transition (_p_ < 0.001). Moreover, older adults with non-anticipated transition had a smaller pendulum-like energy exchange than older adults with anticipated transition (_p_ = 0.03). The timing of COM redirection is linked to kinematic and mechanic modification of gait and could potentially be used as a quantitative assessment of age-related decline in gait. 25 March 2  
since the down-to-up redirection of the centre of mass of the body (COM) begins during the double stance and lacked the activation of distal extensor muscles at the end of the stance [11]. In contrast, the anticipated transition mode occurs when the redirection begins before the contact of the leading leg, initiated by the push of the trailing leg. In addition to the inherently different ratio between the vertical push of the leading and trailing legs, static balance performance was linked with the transition mode [10]. Indeed, older adults with a non-anticipated transition mode exhibited a greater centre of pressure excursion during standing compared to younger and older adults with anticipated transition. However, how the different transition strategies affect the resultant walking pattern has never been investigated to our knowledge. The aim of this study was to identify age and step-to-step-transition-related differences in the kinematics and kinetics of walking at different speeds. To do that, the kinematics and kinetics data collected at the same time and on the same subjects as in [PERSON] et al. [10] were analysed. In particular, we intended to analyse the intersegmental coordination of the lower limb segment, using a principal component analysis [7; 12; 13; 14], and the dynamics of the COM, focusing on the pendulum-like exchange of mechanical energies during walking [15; 16]. A modified coordination pattern, mainly linked to a more in-phase shank  
Figure 1: Definition of the step-to-step transition modes. (**A**) Mean curves of the vertical component of the ground reaction force (GRF, expressed in body weight) acting upon each leg separately (continuous line: leading leg; dotted line: trailing leg) for young and older groups with an anticipated (Older\({}_{\rm A}\)) and non-anticipated step-to-step transition (Older\({}_{\rm NA}\)). (**B**) Left: time of occurrence distribution of V\({}_{\rm min}\) relative to foot contact (FC). Negative values indicate anticipated transition. Right: ratio between the mean value of impact force on the leading leg (F\({}_{\rm leading}\)) and on the trailing leg (F\({}_{\rm trailing}\)) during the step-to-step transition. Bars correspond to mean value and the line to 1 standard deviation. White: young adults; grey: older adults with anticipated step-to-step transition; black: older adults with non-anticipated step-to-step transition (all plots are redrawn with permission from [PERSON] et al. [10]). and foot motion, has previously been documented in older adults, especially at slow walking speeds [7; 14; 17].