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Increased oxygenated hemoglobin concentration of the prefrontal cortex (PFC) has been observed during linear walking, particularly when there is a high attention demand on the task, like in dual-task (DT) paradigms. Despite the knowledge that cognitive and motor demands depend on the complexity of the motor task, most studies have only focused on usual walking, while little is known for more challenging tasks, such as curved paths. To explore the relationship between cortical activation and gait biomechanics, 20 healthy young adults were asked to perform linear and curvilinear walking trajectories in single-task and DT conditions. PFC activation was assessed using functional near-infrared spectroscopy, while gait quality with four inertial measurement units. The Figure-of-8-Walk-Test was adopted as the curvilinear trajectory, with the "Serial 7s" test as concurrent cognitive task. Results show that walking along curvilinear trajectories in DT led to increased PFC activation and decreased motor performance. Under DT walking, the neural correlates of executive function and gait control tend to be modified in response to the cognitive resources imposed by the motor task. Being more representative of real-life situations, this approach to curved walking has the potential to reveal crucial information and to improve people' s balance, safety, and life's quality.

Background: The initiation in human locomotion is defined as the transition between upright stance and steady-state gait. While past literature abundantly investigated the initiation in bipedal gait, the initiation of handstand walking remains unexplored., Research Question: The current study aims to characterise the centre of pressure (CoP) and centre of mass (CoM) trajectory of handstand walking initiation as well as the spatiotemporal and kinematic parameters and balance strategy of this task. Also, the study examined the CoP trajectory similarity within- and between-participants using a coefficient of multiple correlation analysis., Methods: Nineteen gymnasts took part in this study. Handstand walking initiation trials were recorded using force plates and a stereophotogrammetric system. CoM and CoP trajectories were analysed during the Baseline, Preparation and Execution phases of the motor task., Results: We found that to successfully perform the handstand walking initiation, a shift of the CoM forward and towards the stance hand is required as a result of a lateral and posterior CoP shift. All participants performed a similar CoP pattern in the mediolateral direction, whereas two anteroposterior CoP displacement strategies were identified across participants based on different timing execution of posterior CoP shift. While CoP and CoM kinematic differences were identified during the Preparation Phase due to the adopted strategy, no significant difference was found in the Execution Phase for the spatiotemporal and kinematic characteristics., Significance: A better understanding of the required CoP/CoM patterns and balance control provides the basis for further neuromechanics research on the topic and could contribute to individualise training protocols to improve the learning of the task., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: Chronic low back pain (CLBP) is associated with an increased trunk stiffness and muscle coactivation during walking. However, it is still unclear whether CLBP individuals are unable to control neuromechanically their upper body motion during a sudden termination of gait (GT), which involves a challenging balance transition from walking to standing., Research Question: Does CLBP elicit neuromuscular and kinematic changes which are specific to walking and GT?., Methods: Eleven individuals with non-specific CLBP and 11 healthy controls performed walking and sudden GT in response to an external visual cue. 3D kinematic characteristics of thorax, lumbar and pelvis were obtained, with measures of range of motion (ROM) and intra-subject variability of segmental movement being calculated. Electromyographic activity of lumbar and abdominal muscles was recorded to calculate bilateral as well as dorsoventral muscle coactivation., Results: CLBP group reported greater transverse ROM of the lumbar segment during walking and GT compared to healthy controls. Thorax sagittal ROM was higher in CLBP than healthy participants during GT. Greater overall movement variability in the transverse plane was observed in the CLBP group while walking, whereas GT produced greater variability of lumbar frontal motion. CLBP participants showed higher bilateral lumbar coactivation compared to healthy participants after the stopping stimulus delivery during GT., Significance: These results suggest that CLBP can elicit a wider and more variable movement of the upper body during walking and GT, especially in the transverse plane and at lumbar level. Alterations in upper body motor control appeared to depend on task, plane of motion and segmental level. Therefore, these findings should be considered by practitioners when screening before planning specific training interventions for recovery of motor control patterns in CLBP population., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Dynamic motor imagery (dMI) is a motor imagery task associated with movements partially mimicking those mentally represented. As well as conventional motor imagery, dMI has been typically assessed by mental chronometry tasks. In this paper, an instrumented approach was proposed for quantifying the correspondence between upper and lower limb oscillatory movements performed on the spot during the dMI of walking vs. during actual walking. Magneto-inertial measurement units were used to measure limb swinging in three different groups: young adults, older adults and stroke patients. Participants were tested in four experimental conditions: (i) simple limb swinging; (ii) limb swinging while imagining to walk (dMI-task); (iii) mental chronometry task, without any movement (pure MI); (iv) actual level walking at comfortable speed. Limb swinging was characterized in terms of the angular velocity, frequency of oscillations and sinusoidal waveform. The dMI was effective at reproducing upper limb oscillations more similar to those occurring during walking for all the three groups, but some exceptions occurred for lower limbs. This finding could be related to the sensory feedback, stretch reflexes and ground reaction forces occurring for lower limbs and not for upper limbs during walking. In conclusion, the instrumented approach through wearable motion devices adds significant information to the current dMI approach, further supporting their applications in neurorehabilitation for monitoring imagery training protocols in patients with stroke.

Human locomotion is the product of complex dynamic systems, which rely on physical capacities as well as cognitive functions. In our daily life, we mostly experience forward walking, but also backward stepping can occur, as in protective stepping. In this work, we investigated the electroencephalographic (EEG) correlates of cognitive processing underpinning step initiation by means of movement-related cortical potentials (MRCPs) analysis and force-plates recordings. Healthy young volunteers (N = 11) performed self-paced forward- and backward-oriented steps on two force platforms, which were synchronized to simultaneous EEG recordings. MRCPs and their source localization analyses were computed. Results demonstrate the involvement of cognitive processing during step preparation and execution, as showed by the prefrontal activity, which was enhanced in backward stepping. Further, the parietal activity was larger in forward than backward stepping, while motor-related regions were involved in both step directions. Thus, the neural timing and sources of forward and backward stepping suggest a functional distinction of these two actions, which undergo different cortical organizations. Backward stepping requires enhanced cognitive control and can be regarded as an avoidance behavior, while forward stepping would be assimilated to an oriented-to-action behavior mainly localized over parietal areas. In conclusion, preparing body locomotion involves high cognitive processing, with step direction showing different cortical organization and functional specialization., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background:: The observation of upper body movement is gaining interest in the gait analysis community. Recent studies involved the use of body-worn motion sensors, allowing translation of laboratory measurements to real-life settings in the context of patient monitoring and fall prevention., Objectives:: It was shown that amputee persons demonstrate altered acceleration patterns due to the presence of prosthetic components, while no information is available on how accelerations propagate upwards to the head during level walking. This descriptive study aims to fill this gap., Study Design:: Original research report., Methods:: Twenty definitive prosthesis users with transtibial amputation and 20 age-matched able-bodied individuals participated in the study. Three magneto-inertial measurement units were placed at head, sternum and pelvis level to assess acceleration root mean square. Three repetitions of the 10-m walking test were performed at a self-selected speed., Results:: Acceleration root mean square was significantly larger at pelvis and head level in individuals with amputation than in able-bodied participants, mainly in the transverse plane ( p < 0.05). Differences were also observed in how accelerations propagate upwards, highlighting that a different motor strategy is adopted in amputee persons gait to compensate for increased instability., Conclusion:: The obtained parameters allow an objective mobility assessment of amputee persons that can integrate with the traditional clinical approach., Clinical Relevance: Transtibial amputees exhibit asymmetries due to the sound limb's support prevalence during gait: this is evidenced by amplified accelerations on the transverse plane and by related differences in upper body movement control. Assessing these accelerations and their attenuations upwards may be helpful to understand amputee's motor strategies and to improve prosthetic training.

Dynamic balance control-characterised as movement of the trunk and lower limbs-was assessed during fixation of a fixed target, smooth pursuits and saccadic eye movements in ten young (22.9 ± 1.5 years) and ten older (72.1 ± 8.2 years) healthy females walking overground. Participants were presented with visual stimuli to initiate eye movements, and posture and gaze were assessed with motion analysis and eye tracking equipment. The results showed an increase in medial/lateral (ML) trunk movement (C7: p = 0.012; sacrum: p = 0.009) and step-width variability (p = 0.052) during smooth pursuits compared to a fixed target, with no changes for saccades compared to a fixed target. The elders demonstrated greater ML trunk movement (sacrum: p = 0.037) and step-width variability (p = 0.037) than the younger adults throughout, although this did not interact with the eye movements. The findings showed that smooth pursuits decreased balance control in young and older adults similarly, which was likely a consequence of more complicated retinal flow. Since healthy elders are typically already at a postural disadvantage, further decreases in balance caused by smooth pursuits are undesirable.

Purpose: An understanding of the neuromechanical responses to bench stepping with external loading is important for exercise prescription, especially in older women who are more at risk than men for disability. This study was designed to describe and compare such responses to repeated bench stepping with external loading between young and older women., Methods: Eight young (25 ± 2.7 years) and nine older (70 ± 3.3 years) medically stable women performed repeated stepping on a bench of either 20 or 25 cm either unloaded or with 2.5, 5, 7.5 or 10 % of body mass (BM) incorporated into a weighted vest. Ground reaction forces, peak power output and agonist-antagonist neuromuscular activation around the knee joint were evaluated., Results: Peak power output was 44 % lower in the older than in the younger women. At a step height of 25 cm, peak power (PP) in the young women was 7 % greater with an external load of 7.5 % body mass compared with no loading, while in the older women there was a tendency for PP to be higher with an external load of 2.5 % body mass. Neuromuscular activation of the vastus lateralis muscle was 60 % higher in the older than in the young women., Conclusions: Older women performed repeated weighted-vest stepping with lower power output but greater knee muscle activation compared to younger counterparts. Peak power output during stepping may be achieved at 7.5 % BM loading in young women and either 2.5 or 10 % BM in older women, depending on desired step height.

The aim of the present study was to investigate the effect of task complexity on the capability to reproduce rhythmic patterns. Sedentary musically illiterate individuals (age: 34.8±4.2 yrs; M±SD) were administered a rhythmic test including three rhythmic patterns to be reproduced by means of finger-tapping, foot-tapping and walking. For the quantification of subjects' ability in the reproduction of rhythmic patterns, qualitative and quantitative parameters were submitted to analysis. A stereophotogrammetric system was used to reconstruct and evaluate individual performances. The findings indicated a good internal stability of the rhythmic reproduction, suggesting that the present experimental design is suitable to discriminate the participants' rhythmic ability. Qualitative aspects of rhythmic reproduction (i.e., speed of execution and temporal ratios between events) varied as a function of the perceptual-motor requirements of the rhythmic reproduction task, with larger reproduction deviations in the walking task., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Moving in real environments requires to consider not only ecological motor tasks (e.g., curvilinear walking), but also the cognitive load associated with the motor performance [1,2]. Wearable technology provides non-invasive monitoring solutions for both aspects, through inertial sensors and functional Near-Infrared Spectroscopy (fNIRS) technique. Specifically, fNIRS assesses cortical activity through the hemodynamic response of the brain [3] and can be performed while the participant freely moves in the environment [3,4]. In this context, the prefrontal cortex (PFC) is of particular interest: it regulates executive functions and has the potential to reveal crucial information related to cognitive processes and dynamic gait indices [1,3,4]. While it is well known that different motor tasks are characterized by different PFC activations, it is not clearly understood how PFC activation changes with increased complexity of balance locomotion tasks yet. Therefore, the study aims at filling this gap investigating motor-cognitive interference in balance and gait tasks of increasing difficulty. Twenty healthy young adults (11 females, 24.4±2.7 years) randomly performed four different motor tasks of 60 s each related to dynamic (linear walking, LW, and tandem walking, TW) and static (doubleleg stance, DLS, and single-leg stance, SLS) balance while wearing: i) a fNIRS brain cap (Brite 24, Artinis, The Netherlands) to measure the PFC changes in oxygenated hemoglobin (ΔO2Hb), and ii) 4 synchronized measurement units (IMUs, Opal, APDM, USA) at sternum, pelvis and both lateral malleoli to quantify gait and balance motor patterns. Repeated measures ANOVA (ΔO2Hb) and t-tests (IMUs) were computed to investigate differences among tasks. fNIRS (top panel) and IMUs (bottom panels) results are displayed in Fig. 1. As expected, more challenging motor tasks (TW and SLS) require greater PFC activation, suggesting the use of additional attentional resources during tasks of increased difficulty. In addition, motor performance suffers of tasks complexity, as clearly emerge from dynamic gait indices and postural parameters. This study lays foundation for better understanding the motor-cognitive interference in ecological gait and balance tasks. [ABSTRACT FROM AUTHOR]