Ronita

Cromwell

BS

MS
PhD

University of Illinois at Chicago

University of Illinois at Chicago

University of Illinois at Urbana-Champaign

"The study of head stabilization is a critical area as head stability optimizes sensitivity of sensory systems.  While strategies for successful head stabilization have been described for laboratory tasks, functional activities like walking pose different requirements for the challenge to head stability.  The broad aim of my work is to examine the integration between sensory and motor systems that contribute to head stabilization during functional activities.  My investigations focus on motor control mechanisms underlying dynamic balance during walking tasks.  Maintaining dynamic balance facilitates head stabilization and contributes to optimal function of the vestibulo-ocular reflex.  This type of work has implications for examining falls in older adults and individuals with vestibular dysfunction."

Cromwell, RL, Newton, RA, Carlton, LG: Horizontal plane head stabilization during locomotor tasks. Journal of Motor Behavior 2001; 33: 49-58.

Cromwell, RL, Aadland-Monahan, TK, Nelson, AT, Stern-Sylvestre, SM, Seder, B:  Sagittal plane analysis of head, neck, and trunk kinematics and EMG activity during locomotion.  Journal of  Orthopedic and Sports Physical Therapy in press.

Cromwell, RL, Wellmon, R: Sagittal plane head stabilization during  level walking and ambulation on stairs.  Physiotherapy Research International in press.

Cromwell, RL, Newton, RA, Forrest, G: Head stabilization in older adults while walking under altered visual conditions.  International Society for Posture and Gait Research in press.

Funding

Cromwell, RL: Dynamic control of head stability in older adults.  NIH/NIA $50,000 5/1/99-6/30/00.  The major goal of this project was to examine motor control strategies used by older adults to maintain head stability during walking and how these patterns are affected by changes in visual conditions.

Cromwell, RL: Influence of vision on dynamic balance during walking. NIH/NIDCD $100,000 pending.  The major goal of this project is to examine coordination among the eyes, head and trunk to maintain dynamic balance during walking.

Presentations

Cromwell, RL & Newton, RA:  Relationship between select balance measures and the gait stability ratio.   Presented at the Gerontological Society of America, 53rd Annual Meeting, Washington, DC, 2000.

Cromwell, RL, Newton, RA, Forrest G:  Influence of vision on head stability during walking in older adults. Presented at the Society for Neuroscience 30th Annual Meeting, New Orleans, LA 2000.

Cromwell, RL & Newton, RA: Relationship between select balance measures and the gait stability ratio.   Presented at the APTA Combined Sections Meeting, San Antonio, TX 2001.

Abstracts of Publications

Cromwell, RL, Newton, RA, Carlton, LG: Horizontal plane head stabilization during locomotor tasks. Journal of Motor Behavior 2001; 33: 49-58.

Frequency characteristics of head stabilization were examined during locomotor tasks in healthy young adults.  Tasks included normal walking where arm swing was out of phase with leg movement and three perturbed walking patterns.  The perturbed walking patterns included moving the arms in phase with leg movement, with abnormally large amplitude, and at twice the frequency of leg movement.  Head in space angular velocity was examined at the predominant frequencies of trunk motion.  These data revealed head movements in space occurred at low frequencies (< 4.0 Hz) in all conditions as well as at higher frequencies (> 4.0 Hz) when arms moved at twice the frequency of leg movement.  Head stabilization strategies were determined from head on trunk with respect to (wrt) trunk frequency profiles that were derived from angular velocity data.  During natural walking at low frequencies (< 3.0 Hz), the head on trunk movement was less than trunk movement.  At frequencies > 3.0 Hz, compensatory, equal and opposite, movements insured head stability.  Alterations of arm swing produced compensatory head on trunk wrt trunk movement to guarantee head stability at all frequencies.  Results demonstrated successful head stabilization for frequencies up to 10.0 Hz during locomotor tasks.  Successful head stabilization at high frequencies during voluntary tasks suggests the use of feedforward mechanisms to coordinate head on trunk wrt trunk movements.  Maintenance of head stability during dynamic tasks allows optimal conditions for vestibulo-ocular reflex function.

Cromwell, RL, Aadland-Monahan, TK, Nelson, AT, Stern-Sylvestre, SM, Seder, B:  Sagittal plane analysis of head, neck, and trunk kinematics and EMG activity during locomotion.  Journal of  Orthopedic and Sports Physical Therapy in press.

Study Design.  Descriptive study examining kinematic and electromyographic (EMG) patterns of the upper body during walking.

Objectives.  To examine trunk, neck, and head movements to determine a mechanism for upper body stabilization during walking.

Background.  Dynamic balance of the upper body during walking provides a stable base for function of sensory systems.  Prior investigations of upper body motion during walking were limited to examination of isolated segments, or examination of the upper body as a single unit.  In this study, the upper body is examined as three segments: the trunk, neck and head.

Methods and Measures.  Sagittal plane walking patterns were examined in eight healthy young adults.  Markers placed on the trunk, neck and head segments were recorded on videotape.  Angles were calculated with respect to an external horizontal reference to determine segment position relative to space.  EMG measures were obtained from erector spinae, rectus abdominus, semispinalis capitis and sternocleidomastoid muscles.

Results.  Results showed dynamic stability was accomplished through maintenance of a posture where the trunk was flexed, the neck was extended and the head was flexed.  The trunk segment demonstrated greatest stability with the neck being the least stable of the 3 segments.  Movements of upper body segments showed a tendency for the head and neck to move opposite to the trunk.  EMG data demonstrated erector spinae muscle activity occurring near heel contact of each limb followed by trunk extension.  The remaining muscles exhibited variable patterns of activity.

Conclusions.  These data indicate that movements of the upper body help to maintain a posture that promotes stability of these segments during walking.  The trunk was the most stable of the three segments thereby, providing a stable platform for head and neck movement.  Erector spinae muscle activity contributed to upper body movements by extending the trunk to maintain balance at heel contact.  These results provide a basis for studying changes in dynamic stability that occur with age.

Cromwell, RL, Wellmon, R: Sagittal plane head stabilization during  level walking and ambulation on stairs.  Physiotherapy Research International in press.

Background.  Head stabilization in space provides a stable reference frame for visual and vestibular systems during locomotor tasks.  The purpose of this study was to examine upper body movement patterns used to maintain head stability in response to the increased challenge of stair ambulation.

Methods.  Eight healthy, non-disabled, young adults walked 10 m on a level surface, ascended and descended 4 steps.  Head, neck and trunk angular positions in space were obtained for 3 trials of each condition.  Significant differences in mean head, neck and trunk angular orientation in space and segment excursions were determined.  Cross-correlation analyses between head and neck, neck and trunk, and head and trunk determined movement patterns used for maintaining head stability.  The chi-square test examined the homogeneity of movement pattern distributions for each segment pair across conditions.

Results.  Head in space flexion orientation and angular excursions were greater during stair ascent and greater still during stair descent as compared to level walking.  This indicates a progressively significant increase in the challenge to head stability.  Neck flexion orientation in space and angular excursion were greater during stair descent as compared to level walking.  Movement patterns between segment pairs demonstrated phase leads and lags between segments when threats to head stability were minimal.  With increased challenge to head stability, segments moved synchronously in opposite directions to maintain balance.  With further challenges to head stability, segments moved synchronously in the same direction to maintain body segment alignment.

Conclusions.  Head stabilization was significantly challenged when ascending stairs and is further challenged while descending stairs.  Movement patterns reflected changes associated with challenges to head stability.  Increased head excursion during stair ambulation may reflect the need to orient vision for foot placement.  Results suggest that individuals with visual or vestibular deficits may be at risk for falls during stair ambulation.

Cromwell, RL, Newton, RA, Forrest, G: Head stabilization in older adults while walking under altered visual conditions.  International Society for Posture and Gait Research in press.

     This study examined adaptive motor strategies for head stabilization in older adults while walking with eyes open (EO), eyes closed (EC) and fixed gaze (FG).  Sagittal plane head and trunk angular velocities in space were obtained for 17 older adults and 20 young adults.  Frequency analyses determined head on trunk with respect to trunk gains and phases for the purpose of examining motor patterns.  Average walking velocity and cadence were  also determined.  Older adults decreased walking velocity for all conditions displaying decreased cadence with EC.  Gain values decreased for older adults during EO.  Older adult gains increased during FG, resembling young adult values.  EC produced diminished coordination displaying increased gains and phases.  Adaptations made by older adults during EO walking serve to increase stability and protect against falls.  FG improved movement patterns in older adults.  Without vision, head stability decreased suggesting impaired plasticity of vestibular and proprioceptive systems with age.