The role of peripheral visual cues in planning and controlling movement :|ban investigation of which cues provided by different parts of the visual field influence the execution of movement and how they work to control upper and lower limb motion.

Visual cues have previously been classified as visual exproprioceptive, when defining the relative position of the body within the environment and are continuously updated while moving (online), and visual exteroceptive when describing static features of the environment which are typically elaborated offline (feedforward). However peripheral visual cues involved in the control of movement have not previously been clearly defined using this classification. Hence the role played by peripheral visual cues in the planning and/or online control of movement remains unclear. The aim of this thesis was to provide a systematic understanding of the importance of peripheral visual cues in several types of movement, namely overground locomotion, adaptive gait, postural stability and reaching and grasping. 3D motion capture techniques were used to collect limb and whole body kinematics during such movements. Visual peripheral cues were manipulated by visual field occlusion conditions or by the employment of point-lights in a dark room. Results showed that the visual cues provided by different parts of the peripheral visual field are mainly used for online fine tuning of limb trajectory towards a target (either a floor-based obstacle or an object to grasp). The absence of peripheral visual cues while moving disrupted the spatio-temporal dynamic relationship between subject and target and resulted in increased margins of safety between body and target and increased time and variability of several dependent measures. These findings argue in favour of the classification of peripheral visual cues as visual exproprioceptive

The use of the greater trochanter marker in the thigh segment model: Implications for hip and knee frontal and transverse plane motion

AbstractBackgroundThe greater trochanter marker is commonly used in 3-dimensional (3D) models; however, its influence on hip and knee kinematics during gait is unclear. Understanding the influence of the greater trochanter marker is important when quantifying frontal and transverse plane hip and knee kinematics, parameters which are particularly relevant to investigate in individuals with conditions such as patellofemoral pain, knee osteoarthritis, anterior cruciate ligament (ACL) injury, and hip pain. The aim of this study was to evaluate the effect of including the greater trochanter in the construction of the thigh segment on hip and knee kinematics during gait.Methods3D kinematics were collected in 19 healthy subjects during walking using a surface marker system. Hip and knee angles were compared across two thigh segment definitions (with and without greater trochanter) at two time points during stance: peak knee flexion (PKF) and minimum knee flexion (MinKF).ResultsHip and knee angles differed in magnitude and direction in the transverse plane at both time points. In the thigh model with the greater trochanter the hip was more externally rotated than in the thigh model without the greater trochanter (PKF: −9.34° ± 5.21° vs. 1.40° ± 5.22°, MinKF: −5.68° ± 4.24° vs. 5.01° ± 4.86°; p < 0.001). In the thigh model with the greater trochanter, the knee angle was more internally rotated compared to the knee angle calculated using the thigh definition without the greater trochanter (PKF: 14.67° ± 6.78° vs. 4.33° ± 4.18°, MinKF: 10.54° ± 6.71° vs. −0.01° ± 2.69°; p < 0.001). Small but significant differences were detected in the sagittal and frontal plane angles at both time points (p < 0.001).ConclusionHip and knee kinematics differed across different segment definitions including or excluding the greater trochanter marker, especially in the transverse plane. Therefore when considering whether to include the greater trochanter in the thigh segment model when using a surface markers to calculate 3D kinematics for movement assessment, it is important to have a clear understanding of the effect of different marker sets and segment models in use

Classification of lower extremity movement patterns based on visual assessment: reliability and correlation with 2-dimensional video analysis

CONTEXT: Abnormal movement patterns have been implicated in lower extremity injury. Reliable, valid, and easily implemented assessment methods are needed to examine existing musculoskeletal disorders and investigate predictive factors for lower extremity injury. OBJECTIVE: To determine the reliability of experienced and novice testers in making visual assessments of lower extremity movement patterns and to characterize the construct validity of the visual assessments. DESIGN: Cross-sectional study. SETTING: University athletic department and research laboratory. PATIENTS OR OTHER PARTICIPANTS: Convenience sample of 30 undergraduate and graduate students who regularly participate in athletics (age = 19.3 ± 4.5 years). Testers were 2 experienced physical therapists and 1 novice postdoctoral fellow (nonclinician). MAIN OUTCOME MEASURE(S): We took videos of 30 athletes performing the single-legged squat. Three testers observed the videos on 2 occasions and classified the lower extremity movement as dynamic valgus, no change, or dynamic varus. The classification was based on the estimated change in frontal-plane projection angle (FPPA) of the knee from single-legged stance to maximum single-legged squat depth. The actual FPPA change was measured quantitatively. We used percentage agreement and weighted κ to examine tester reliability and to determine construct validity of the visual assessment. RESULTS: The κ values for intratester and intertester reliability ranged from 0.75 to 0.90, indicating substantial to excellent reliability. Percentage agreement between the visual assessment and the quantitative FPPA change category was 90%, with a κ value of 0.85. CONCLUSIONS: Visual assessments were made reliably by experienced and novice testers. Additionally, movement-pattern categories based on visual assessments were in excellent agreement with objective methods to measure FPPA change. Therefore, visual assessments can be used in the clinic to assess movement patterns associated with musculoskeletal disorders and in large epidemiologic studies to assess the association between lower extremity movement patterns and musculoskeletal injury

Peripheral visual cues affect minimum-foot-clearance during overground locomotion

NoThe importance of peripheral visual cues in the control of minimum-foot-clearance during overground locomotion on a clear path was investigated. Eleven subjects walked at their natural speed whilst wearing goggles providing four different visual conditions: upper occlusion, lower occlusion, circumferential–peripheral occlusion and full vision. Results showed that under circumferential– peripheral occlusion, subjects were more cautious and increased minimum-foot-clearance and decreased walking speed and step length. The minimum-foot-clearance increase can be interpreted as a motor control strategy aiming to safely clear the ground when online visual exproprioceptive cues from the body are not available. The lack of minimum-foot-clearance increase in lower occlusion suggests that the view of a clear pathway from beyond two steps combined with visual exproprioception and optic flow in the upper field were adequate to guide gait. A suggested accompanying safety strategy of reducing the amount of variability of minimum-foot-clearance under circumferential–peripheral occlusion conditions was not found, likely due to the lack of online visual exproprioceptive cues provided by the peripheral visual field for fine-tuning foot trajectory

Is lower peripheral information weighted differently as a function of step number during step climbing?

The importance of peripheral visual information during stair climbing and how peripheral visual information is weighted as a function of step number during step climbing is unclear. Previous authors postulated that the knowledge of predictable characteristics of the steps may decrease reliance on foveal vision and transfer the online visual guidance of stair climbing to peripheral vision. Hence the aim of this study was to investigate if and how the occlusion of the lower peripheral visual field influenced stair climbing and if peripheral visual information was weighted differently between steps. Ten young adult male participants ascended a 5-step staircase under 2 visual conditions: full vision (FV) and lower visual occlusion (LO). Kinematic data (100 Hz) were collected. The effect of Vision and Step condition on vertical forefoot clearance was examined with a Repeated Measures 2-way ANOVA. Tukey's HSD test was used for post-hoc comparisons. A significant interaction Vision x Step and main effect of Step were found (p <= 0.04): vertical forefoot clearance was greater in LO compared to FV condition only on the 1st and the 2nd steps (p < 0.013) and on the last step compared to the other steps (p < 0.01). These findings suggest that online peripheral visual information is more relevant when negotiating the first two steps, rather than the end of a staircase and that the steps subsequent the first few ones may require different information likely based on proprioception or working memory of the step height

Utility of Peripheral Visual Cues in Planning and Controlling Adaptive Gait

NoThe purpose of this article is to determine the relative importance to adaptive locomotion of peripheral visual cues provided by different parts of the visual field. Twelve subjects completed obstacle crossing trials while wearing goggles that provided four visual conditions: upper visual field occlusion, lower visual field occlusion (LO), circumferential peripheral visual field occlusion (CPO), and full vision. The obstacle was either positioned as a lone structure or within a doorframe. Given that subjects completed the task safely without cues from the lower or peripheral visual field, this suggests that subjects used exteroceptive information provided in a feed-forward manner under these conditions. LO and CPO led to increased foot placement distance from the obstacle and to increased toe clearance over the obstacle with a reduced crossing-walking velocity. The increased variability of dependent measures under LO and CPO suggests that exproprioceptive information from the peripheral visual field is generally used to provide online control of lower limbs. The presence of the doorframe facilitated lead-foot placement under LO by providing exproprioceptive cues in the upper visual field. However, under CPO conditions, the doorframe led to a further reduction in crossing velocity and increase in trail-foot horizontal distance and lead-toe clearance, which may have been because of concerns about hitting the doorframe with the head and/or upper body. Our findings suggest that exteroceptive cues are provided by the central visual field and are used in a feed-forward manner to plan the gait adaptations required to safely negotiate an obstacle, whereas exproprioceptive information is provided by the peripheral visual field and used online to “fine tune” adaptive gait. The loss of the upper and lower peripheral visual fields together had a greater effect on adaptive gait compared with the loss of the lower visual field alone, likely because of the absence of lamellar flow visual cues used to control egomotion