ECSS Paris 2023: OP-BM25
INTRODUCTION: The translation of the base of support represents a promising paradigm to assess dynamic balance control. Dynamometric platforms allow us to quantify postural adjustment objectively throughout the calculation of the Center of Pressure (CoP) displacements. Muscles are engaged to react to these postural perturbations to regain balance and avoid falling. This study aimed to investigate postural responses to unexpected perturbations of the support base through CoP displacements and lower limb muscle co-contractions. METHODS: Twenty-two healthy young adults (Females = 11) participated in the study. They were assessed on a force platform screwed over a servo-controlled, electrically driven supporting platform combining the following independent variables: direction (forward (FW) and backward (BW)), displacement (25mm, 50mm, and 100mm), and ramp rate (100 mm/s and 200 mm/s). The subjects underwent two sets of 12 trials, randomly combining the platform settings. The CoP anterior-posterior trajectory within the 2.5s time window after the perturbation occurred was considered to calculate the following parameters: mean velocity (UP), displacement (Area95), first peak (FP), maximal oscillations (ΔCoPMax), and standard deviation (PPV). The surface electromyography of the tibialis anterior, gastrocnemius lateralis, rectus femoris, biceps femoris, rectus abdominis, and erector spinae was recorded within the same time window to calculate the co-contraction index (CCI) of the shank, thigh, and trunk. Two-way ANOVAs were performed for CoP-related parameters and CCI. Bonferroni post hoc analysis was performed where appropriate. RESULTS: UP and Area95 were influenced by direction (p<0.05), displacement (p<0.01), and ramp rate (p<0.01) with higher values in FW than BW and values that increased with the increment of ramp rate and displacement. Similarly, FP and ΔCoPMax were affected by the direction (p<0.05) and negatively influenced by the increments of ramp rate (p<0.01) and displacement (p<0.001). PPV was not affected by platform direction. Interestingly, lower values of FP and ΔCoPMax occurred in the FW translations. Shank, thigh, and trunk CCI within the 2.5s time window showed no significant trends. CONCLUSION: UP and Area95 results indicated less efficient postural responses in the FW condition. The greater values of FP and ΔCoPMax in BW could depend on the foot-ankle anatomical complex that allows a greater CoP displacement toward the tiptoes. CCI findings did not account for the CoP behavior and warrant further analysis over a shorter time window after the unexpected translation of the platform occurred. REFERENCES: Rizzato et al., Sensors, 2023. doi: 10.3390/s23136203. Brown et al., Gait Posture, 2001. doi: 10.1016/s0966-6362(01)00131-x.
Read CV Giuseppe MarcolinECSS Paris 2023: OP-BM25
INTRODUCTION: Perturbation-based balance training during locomotion has gained interest as an effective way to improve recovery responses and prevent falls in various populations groups1. Next to mechanically induced gait perturbations, exercise in virtual reality (VR) is promising for motor skill learning2. Given that generalisation of adaptations is crucial for effective stability control and fall prevention, this study aimed to assess the transfer of adaptive refinements in balance recovery responses obtained via exercising mechanically or visually induced gait perturbations to unpredictable tripping. METHODS: Within the framework of a work force project, 110 healthy young and middle-aged (18 to 63yrs) postal and industrial workers (i.e. high-risk group for falls) were randomly assigned either to a control group (n=30; no perturbation exercise) or into two perturbation exercise groups (MEC and VR); and walked on a treadmill. The MEC group (n=40) underwent mechanically induced posterior and medio-lateral gait perturbations via ankle and waist pulls using a pneumatically operated brake-and-release system. The VR group (n=40) was given visually induced gait perturbations through rotations of the virtual environment displayed in VR glasses. Prior and following the treadmill tasks, potential transfer effects were examined during walkway negotiation with sudden electronically triggered tripping elements. Training effects on locomotor adaptations and balance recovery improvements during tripping (transfer task) were assessed by analyzing sagittal plane joint kinematics and the components of the margin of stability (MoS) using statistical parametric mapping over the first two recovery steps. Furthermore, the incidence of near-falls and falls in daily life was monitored two weeks prior to and after the treadmill session using a questionnaire. RESULTS: Both intervention groups showed a comparable increase in MoS during the transfer task in relation to pre-exercise (p<0.05). Furthermore, these groups revealed a lower extrapolated center of mass and lower trunk flexion angle during the compensatory steps during tripping post exercise (p<0.05) and reported approximately 25% decrease in near-fall incidents in daily life. The control group did not show any significant changes in balance recovery responses during the transfer task or change in near-fall incidents over the monitored period. CONCLUSION: The current study suggests that repeated visual and mechanical perturbations during walking can lead to adaptive refinements in balance recovery responses and transfer of adaptations to other conditions, enhancing trip-resisting skills. The improvements in dynamic stability during tripping were related to more effective postural adjustments in trunk dynamics leading to less anterior center of mass displacement in response to unpredictable perturbations, which may help to mitigate sudden perturbations to gait in daily life. 1McCrum et al., 2022, FrontSportsActLiving 2Delgado & Der Ananian, 2021, GamesHealthJ
Read CV Anika WeberECSS Paris 2023: OP-BM25
INTRODUCTION: The lower limb maintains stability after a gait perturbation by establishing a new base of support and generating joint moments, thus contributing to balance recovery. However, different perturbations may require distinct strategies, especially for patients. This study was to investigate the characteristics of normal gait and the first recovery step following forward trip perturbations (trip_Rec1) and compensatory strategies produced by the lower extremities in patients with knee osteoarthritis (OA). METHODS: Nine patients with knee OA and 15 age-matched able-bodied healthy older individuals volunteered to participate in this investigation. The measurement sessions were performed on the Gait Real-time Analysis Interactive Lab including normal walking and forward tripping perturbed walking. Lower limb joint angles and joint moments were recorded. An independent samples t-test and one-dimensional statistical mapping were employed for statistical analyses of knee flexion excursions and ankle, knee, hip moments throughout the gait cycle between patients with knee OA and older adults, respectively. RESULTS: Patients with knee OA demonstrated significantly smaller knee flexion excursion than older adults during normal gait (10.70±5.51 vs 17.92±3.48, P=0.0007), whereas no significant difference was observed in the trip_Rec1. At the hip joint, significant differences in sagittal moment were observed between the two groups, at 41.04-58.24% (P < 0.001) in the stance phase and at 71.17-84.74% (P < 0.001) in the swing phase in normal gait, as well as at 56.44-62.63% (P = 0.003) in the stance phase in trip_Rec1. Significant differences in frontal moment were solely observed between the two groups in normal gait at 32.45-41.3% (P < 0.001). CONCLUSION: Patients with knee OA have an increased potential risk of falls during walking due to inherent pathological characteristics. Moreover, the compensation for the hip abduction moment in the frontal plane may keep the gait pattern of patients with knee OA largely consistent with a normal gait as well as with older adults in terms of the stance phase (%). These findings have clinical implications for the rehabilitation of fall-prone older adults and patients requiring gait stabilization, leading to the relevance of physical therapies such as balance-based gait perturbation training.
Read CV Xiping RenECSS Paris 2023: OP-BM25