# Relation between Step-To-Step Transition Strategies and Walking Pattern in Older Adults
## 4 Discussion  
The aim of this study was to understand the relation between the modifications in walking pattern with aging and with step-to-step transition mode. Based on the transition mode, [PERSON] et al. [9,10] identified two groups of older adults: one group with an anticipated transition (\(\mathrm{Older_{A}}\)) and another with a non-anticipated transition (\(\mathrm{Older_{NA}}\)). They suggested that the emergence of a non-anticipated transition with age could be an early sign of walking impairments and related it to static balance. In the present study, using the same subjects and the same classification of transition mode, we showed that the transition has direct consequence on the gait pattern. Indeed, as hypothesized, our results show that the differences in kinematics and mechanics among Young and \(\mathrm{Older_{NA}}\) are greater than those among Young and \(\mathrm{Older_{A}}\), suggesting that the step-to-step transition mode is reflected in gait pattern. Based on joint kinetics, a handful of studies have documented a distal-to-proximal redistribution of joint effort (e.g., [7,9,14]). Here, we found a reduction in the maximal ankle plantar-flexion during stance (Figure 2B), together with a more inclined trunk, possibly adopted to increase the force generation by the hip extensors [5,8]. As hypothesized, these changes with age were more evident in \(\mathrm{Older_{NA}}\) than in \(\mathrm{Older_{A}}\). In addition, the modifications in intersegmental coordination also reflect the different walking strategy adopted by  
Figure 5: Correlations between step-to-step transition and other gait parameters. Each point represents the stride-averaged value for one subject walking at 1.11 m s\({}^{-1}\). Linear regression lines are also plotted. (**A**) Relationships between the delay between the minimal vertical velocity of the COM (\(\mathrm{Vv_{min}}\)) and foot contact (FC) and joint kinematics: maximal ankle plantar-flexion, mean trunk orientation and maximal hip extension. (**B**) Relationships between the delay between \(\mathrm{Vv_{min}}\) and FC and intersegmental coordination: orientation of the plane (\(u_{3t}\)), ratio between the range of motion of thigh and shank segments and the phase shift between shank and foot segments. (**C**) Relationships between the delay between \(\mathrm{Vv_{min}}\) and FC and the ratio between \(E_{\mathrm{int}}\) measured during T1 and T3. Other indications as in Figure 2.  
Older\({}_{\text{NA}}\), potentially to reduce ankle plantar-flexion at the end of stance [5]. Indeed, compared to Young, the modified orientation of the plane (\(u_{34}\)) observed in Older\({}_{\text{NA}}\) (Figure 3A) is mainly related to a change in the phase shift between the shank and foot elevation angles (Figure 3B) [12,14,25], as Older\({}_{\text{NA}}\) \"lock their ankle\" during mid-stance [26]. These changes in the pattern of intersegmental coordination may result in different trajectories of the COM [27] and thus in a modification of the pendulum-like COM energy exchange. Regarding this COM energy exchange, to our knowledge, no study has identified an effect of age. Indeed, it has been documented that older and young adults perform similar mechanical work to lift and accelerate the COM during walking (and similar % recovery) [18,28]. While we observed similar results among Young and Older\({}_{\text{A}}\), our results underline a greater W\({}_{\text{COM}}\), partly due to a smaller % recovery in Older\({}_{\text{NA}}\) as compared to Young (Figure 4B). In addition, the pendular energy savings \(E_{\text{int}}\) is modified with the transition mode (Figure 4B) and diminished in non-anticipated walking pattern. Indeed, in Older\({}_{\text{NA}}\), a greater amount of the energy transformation is performed during T3 as compared to T1, when the COM falls and accelerates forward. This modification could be due to the inability of Older\({}_{\text{NA}}\) to accelerate the COM upward before double stance because of a lack of trailing leg push-off at the end of stance ([11]; Figure 1A).