Biomedical subjects

P O Riley

Publications and source records attributed to P O Riley.

At least 37 records · Page 2Linked to original sources

PubMed1997

Hip stress during lifting with bent and straight knees.

"Correct" body mechanics during lifting are believed to protect the back by employing knee and hip flexion while keeping the back straight. Lower limb joint stress, however, has been largely ignored. We compared hip cartilage contact stress during "leg lifting" with "back lifting" (lifting with bent or straight knees, respectively) in a subject fitted with a pressure instrumented hip endoprosthesis. Synchronized pressure data and whole-body kinematics and kinetics were collected simultaneously while the subject lifted an 11.8 kg mass from the floor to waist level. The highest pressure, 13.7 MPa, occurred during leg lifting at the antero-lateral femoral head transducers opposed at maximum hip flexion by the postero-superior quadrant of acetabular cartilage. In back lifting, the highest pressure, 11.5 MPa occurred in the supero-lateral aspect of the head, which during hip extension was opposed by the posterior quadrant of the acetabulum. Maximum pressures and hip torques occurred simultaneously with peak hip flexion, during the initial lifting of the burden from the floor. Acetabular contact pressures during leg lifting were on average twice as great as during back lifting, and both techniques generate much greater hip stress than gait (typically 4-6 MPa). Degenerative changes in the articular surface of the acetabulum occur primarily on the postero-superior aspect, corresponding to the locations of peak contact pressures in the present in vivo data. Thus leg lifting puts more stress on the postero-superior region, and probably contributes to more hip cartilage degeneration, than does back lifting. We conclude that although leg lifting may mechanically protect the back, it substantially increases hip cartilage stress.

Aged↗

PubMed1996

Sit to stand from progressively lower seat heights -- alterations in angular velocity.

This study investigates the influence of chair height on the dynamics of sit-to-stand for two age groups. Eleven young (25-36 years) and 10 older (61-79 years) adults participated. Subjects rose from chairs set at four heights relative to knee height. Motion was quantified using a bilateral active-marker-based motion analysis system. Subjects appeared to increase trunk flexion angular velocity to overcome mechanical difficulties of decreasing chair heights. This variable showed a main effect for chair height (P = 0.0001). Time at which knee, hip, and trunk extension angular velocity were attained each demonstrated a chair by age interaction effect (P<0.05). Synchrony of body segment maximum extension angular velocities was altered for the older subjects at the lowest chair heights, suggesting that older individuals begin to change their performance as the task becomes more demanding. RELEVANCE:--Sitting to standing is one of the essential physical tasks used frequently throughout the day. Clinicians are frequently called upon to improve chair rise performance for those with functional limitations. Efforts are likely to be most successful if clinicians understand how healthy individuals accommodate to changing conditions (such as changing chair height) and use that information to interpret the performance of those with impairments and functional limitations.

Journal Article↗

PubMed1995

Phase plane analysis of stability in quiet standing.

We analyzed the standing balance control of 11 healthy subjects and 15 subjects with bilateral vestibular hypofunction (BVH) using phase plane (velocity versus displacement) plots. We hypothesized that maintaining postural stability requires control of both the position and momentum of the center of gravity (CG) and infer that it is advantageous to use both velocity and displacement data to characterize balance control. Phase plane plots provide insight into this dynamic aspect of balance control. We evaluated phase plane plots based on whole body CG and center of pressure (CoP). We varied stability by altering the base of support and visual information. Three different foot placements were used: feet wide apart, feet together, and semitandem stance. Feet together standing was performed with eyes open and with eyes closed. The phase plane plots show changes in stability as base of support is altered or visual input is removed and reveal stability differences between the control and BVH groups. The root mean square variance of velocity and displacement was used to quantify the phase plane information. This parameter showed significant differences between activities and between groups. We conclude that phase plane plots that combine displacement and velocity information are more useful in characterizing balance control than displacement or velocity alone.

Gravitation↗

PubMed1994

Physical therapy management of peripheral vestibular dysfunction: two clinical case reports.

We describe the treatment of two patients with peripheral vestibular dysfunction using a novel, staged exercise program. Response to treatment was documented. The first patient, a 62-year-old woman with unilateral vestibular dysfunction (UVD) and a 6-month history of disequilibrium following herpes zoster oticus resulting in damage to the right inner ear, was treated with an 8-week course of vestibular physical therapy. During the 8 weeks, the patient attended weekly physical therapy sessions and was trained to perform vestibular adaptation exercises on a daily basis at home. The second patient, a 53-year-old woman with progressive disequilibrium secondary to profound bilateral vestibular hypofunction (BVH), was treated with a 16-week course of vestibular physical therapy. During the first 8 weeks, the patient attended weekly physical therapy sessions and was trained to perform vestibular adaptation and substitution exercises on a daily basis at home. During the second 8 weeks, the patient continued performing vestibular physical therapy exercises at home independently. Vestibular function (sinusoidal vertical axis rotation testing), postural control (clinical tests and posturography), stability during the performance of selected activities of daily living (ADLs), and self-perception of symptoms and handicap were measured prior to and at the conclusion of treatment for both patients and at the midpoint of treatment for the patient with BVH. After 8 weeks of treatment, both patients reported improvements in self-perception of symptoms and handicap and demonstrated objective improvements in clinical balance tests, posturography, and several kinematic indicators of stability during the performance of selected ADLs. Further improvements were noted in the patient with BVH after 16 weeks of treatment. Improvements in postural control were noted after 8 weeks of treatment for the patient with UVD and after 16 weeks for the patient with BVH. Vestibular function improved during the course of treatment for the patient with UVD only. These case reports describe two different individualized treatment programs and document self-reported and laboratory-measured functional improvements in two patients with vestibular deficients--one with unilateral damage and one with bilateral damage.

Activities of Daily Living↗

PubMed1993

Knee kinematics and kinetics during locomotor activities of daily living in subjects with knee arthroplasty and in healthy control subjects.

BACKGROUND AND PURPOSE: Knee kinematics and kinetics have not been quantitatively studied during gait, stair negotiation, and rising from a chair in the same subjects, either among healthy control subjects or among subjects with knee joint impairments. Despite this paucity of data, rehabilitation goals often include achieving a specific peak knee torque at a specific, fixed angular velocity. SUBJECTS: We compared the kinematic and kinetic performance of the knees in 15 subjects (19 knees) who had undergone knee arthroplasty (KA group) and 11 healthy subjects (22 knees) who served as a control group. The KA group subjects ranged in age from 61 to 78 years, and the control group subjects ranged in age from 26 to 88 years. The KA group subjects had had knee osteoarthritis, were > or = 1 year postsurgery, and were considered fully rehabilitated. METHODS: All subjects were analyzed during barefoot paced walking, stair ascent and descent, and arising from a chair. RESULTS: Compared with the control subjects, the KA group subjects had significantly different knee sagittal range of motion, angular velocities, and maximum knee moments during loaded knee extension. Vertical ground reactions did not differ significantly between groups. Both groups' maximum extension angular velocity exceeded 350 degrees/s during the swing phase of gait, but the maximum loaded extension velocity averaged only 140 degrees/s (during rising from a chair). Maximum knee flexion moments were approximately 10 to 15 N.m/%BW (knee moments normalized to percentage of body weight in newtons). CONCLUSION AND DISCUSSION: We concluded that locomotor ADLs demand relatively slow loaded angular velocities and low knee torques, a factor that should be considered in knee postarthroplasty exercise prescription.

Activities of Daily Living↗

PubMed1993

Double-blind, placebo-controlled trial of rehabilitation for bilateral vestibular hypofunction: preliminary report.

Vestibular rehabilitation (VR) is increasingly popular, but few data exist to support enthusiasts' claims of efficacy in improving functional abilities of patients with bilateral vestibular hypofunction (BVH). A double-blind, controlled study of eight subjects (mean, 64 +/- 12 years; seven females, one male) with bilateral vestibular hypofunction was conducted. Subjects in group A received 8 weeks of VR followed by 8 weeks of home VR exercises, whereas those in group B received 8 weeks of control treatment (isometric strengthening exercises) followed by 8 weeks of VR. At the end of 8 weeks, group A walked 8% faster and, during paced gait and stair-climbing, with greater stability, evidenced by a 10% larger maximum moment arm and a 17% decreased double-support duration during gait and stair stance. Group B improved less than 1% during the control treatment. Self-reported Dizziness Handicap Inventory scores did not differ significantly between control and active VR. All subjects improved compared with baseline tests at the 16-week post-test on both functional testing and on the Self-reported Dizziness Handicap Inventory scale. We conclude that in this small sample, VR effectively improved functional, dynamic stability during locomotion, but even strengthening exercises result in self-reported symptomatic improvement.

Aged↗

PubMed1993

Biomechanical analysis of body mass transfer during stair ascent and descent of healthy subjects.

The purposes of this study were to: 1) assess whole body center of mass (CM) motion in the frontal, sagittal, and transverse planes; 2) compare CM displacement with center of pressure (CP); and, 3) further define the stance and swing subphases of stair ascent (SA) and stair descent (SD) based on critical CM, CP, and ground reaction force (GRF) events. SA and SD were analyzed on a convenience sample of 11 subjects. Unpaced data were collected from 28 SA trials and 24 SD trials utilizing a bilateral SELSPOT II/TRACK data acquisition system and two Kistler force plates at a sampling frequency of 153 Hz. Twenty-six discrete data points were chosen from each trial for analysis. Each identified point detailed the intersection, separation, maximum or minimum value of CM, CP, or GRF in all three planes. Specific phases of SA and SD are presented and described. The actions of CM, CP, and GRF are presented during each phase. Results further refine the phases originally described by McFayden and Winter. Subtle differences in phases and duration of single and double support are demonstrated between SA and SD. Based on these results, it is apparent that SD is a more dynamic process with greater inherent instability. Knowledge of SA and SD phases and CM/CP dynamics in healthy, normal subjects will permit comparison with patients exhibiting various pathologies. Such comparison should facilitate the development of appropriate intervention strategies.

Adult↗

PubMed1992

In vivo acetabular contact pressures during rehabilitation, Part I: Acute phase.

The authors conducted a two-part study to compare in vivo acetabular contact pressures during the acute and postacute phases of rehabilitation. This report compares in vivo acetabular contact pressures generated during selected "inpatient" rehabilitation activities and their relationship to pain, range of motion, and other clinical indicators. A pressure-instrumented Moore-type endoprosthesis was implanted in a 73-year-old woman who had sustained a femoral neck fracture. Acetabular contact pressures during the first 2 weeks after surgery were rank-ordered. Clinical data, including range of motion, manual muscle test grade, use of pain medication, and independence in gait, were collected simultaneously. Acetabular pressures did not follow the predicted rank order corresponding to the commonly prescribed temporal order of inpatient rehabilitation activities. Isometric hip extension and active hip flexion generated the highest pressures of all the studied activities, including those measured during gait activities. Isometric exercises, therefore, may not be entirely benign preparation for ambulatory activity. Clinical data did not correspond with peak pressure data, suggesting that observed responses to rehabilitation may not be dependable criteria for progressing the acute hip rehabilitation protocol. We discuss applications for rehabilitation programs based on hip contact pressure data as an initial attempt to formulate more defensible rehabilitation approaches for patients with acutely painful hips.

Acetabulum↗

PubMed1992

In vivo acetabular contact pressures during rehabilitation, Part II: Postacute phase.

The authors conducted a two-part study to compare in vivo acetabular contact pressures during the acute and postacute phases of rehabilitation in a single subject with a pressure-instrumented femoral prosthesis. This report compares six common hip rehabilitation activities for resultant in vivo hip pressure magnitudes during the first 5 years after discharge from an acute care hospital. These activities were full, partial, touch-down, and non-weight-bearing ambulation and isometric hip abduction and straight-leg-raising exercises. A pressure-instrumented femoral endoprosthesis implanted in a 73-year-old woman who had sustained a femoral neck fracture provided data for the activities. The activities were rank ordered and compared over time according to peak pressure magnitude. Prescribed weight bearing and exercise type were not good predictors of hip peak pressures in this patient. Maximum pressures occurred by 1 year postdischarge for most activities, with a tendency to stabilize or decline thereafter. Resisted isometric hip abduction exercise demonstrated the most variation over time. The results suggest that hip pressures may be limited by controlling muscle force and movement velocity during postoperative hip rehabilitation activities.

Acetabulum↗

PubMed1992

Trunk kinematics during locomotor activities.

We investigated upper-body (ie, trunk) angular kinematics (motions) during gait, stair climbing and descending, and rising from a chair in two reference frames--relative to the pelvis and to room coordinates. Bilateral kinematic data were collected from 11 healthy subjects (6 female, 5 male), who were 27 to 88 years of age (mean = 58.9, SD = 17.9). During stair climbing, maximum trunk flexion relative to the room was at least double that during stair descending and gait. Arising from a chair required the most trunk flexion/extension range of motion (ROM) but the least abduction/adduction and medial/lateral (internal/external) rotation. Trunk ROM during gait was small (mean less than or equal to 12 degrees) and consistent with previous literature. Trunk range of motion relative to the room during stair climbing and descending was greater than trunk ROM during gait in all planes. The pelvis and trunk rotate in the transverse plane in greater synchrony during stair descending (mean = 8.1 degrees, SD = 5.6 degrees) than during gait (mean = 12.0 degrees, SD = 4.2 degrees). For all activities, trunk frontal and sagittal ROM relative to the pelvis was greater than that relative to the room coordinates. This finding suggests that trunk/pelvis coordination may be used to reduce potentially destabilizing anti-gravity trunk motions during daily activities. We conclude that upper-body kinematics relative to both pelvis and gravity during daily activities are important to locomotor control and should be considered in future studies of patients with locomotor disabilities.

Activities of Daily Living↗

PubMed1991

Mechanics of a constrained chair-rise.

A sit-to-stand task is analyzed by a method which estimates the segmental and whole body center of mass (CoM) kinematics and kinetics using bilateral whole body kinematic data from nine healthy young female subjects. The sit-to-stand, or chair-rise, task is constrained with regard to chair height, pace, initial lower limb position and arm use. The chair-rise maneuver is divided into four phases; (1) the flexion momentum phase; (2) the momentum transfer phase; (3) the vertical extension phase; and (4) the stabilization phase; the first three are examined in detail here. The momentum transfer phase, which immediately follows lift-off from the seat of the chair, is the most dynamic portion of the event, demanding a high degree of coordination. This maneuver is analyzed in order to determine if trunk movement is used only to position the body center of gravity or if the trunk motion generates momentum which is important during the brief but critical period of dynamic equilibrium immediately following lift-off from the chair. Our evidence points to the latter case and indicates that inter-segmental momentum transfer is possible during this period.

Adult↗

PubMed1991

Exercise and gait effects on in vivo hip contact pressures.

Virtually all hip rehabilitation programs include exercise for muscle force development. The specific effects of various exercise modes on the hip joint itself are unknown. We will report on the effects of common exercise modalities on in vivo hip pressures. Four years prior to data collection, a pressure-instrumented Austin-Moore-type endoprosthesis was implanted in an otherwise healthy 73-year-old woman with a traumatic right hip fracture. Hip pressures during various experimental maneuvers were recorded periodically over a 5-year period. We compared measurements of peak pressure and rate of pressure rise obtained during gait with those obtained during isokinetic, isometric, and isotonic lower-limb exercises. Maximal exercise generated greater peak pressures than did gait, and tripling the angular velocity during exercise roughly tripled the rate of pressure rise. Torque production and resultant in vivo hip pressures varied directly during all experiments. Peak pressures and rate of pressure rise apparently can be controlled by varying the subject's exertion. The results reported are from a single subject; therefore, little generalizability is possible for these data. We suggest, however, that articular pressures may be important to rehabilitation planning; these data provide a direct insight into this potentially important exercise prescription consideration.

Aged↗

PubMed1991

Influence of age on dynamics of rising from a chair.

This article describes the sit-to-stand movement in nine healthy elderly adults, ages 61 to 74 years, and compares peak joint angles, torques, and velocities of 11 body segments with data collected from nine young women, ages 25 to 36 years. The subjects in this study rose from a chair under a controlled protocol. An optoelectronic system, two force plates, and two computers were used for data collection and processing. The data are described in relationship to three phases of the task previously described for the young subjects' data. Percentages of difference were calculated for the torques and the velocities. Independent t tests were conducted on maximum angles achieved and total joint excursions. Consistency between groups was demonstrated in the duration of each phase, as well as the body kinematics and kinetics occurring within each phase. There was little difference in maximum torques or velocities. Maximum angles of head-to-trunk extension, head-to-ground flexion, head-to-trunk excursion, and trunk-to-pelvis flexion were significantly different between groups. The differences in head position demonstrated between these two groups may have clinical implications for loss of balance during this task in older patients.

Adult↗

PubMed1990

Modelling of the biomechanics of posture and balance.

A technique for studying the relationship of posture to balance has been developed. To investigate this relationship quantitatively, the human body was treated as consisting of 11 rigid body segments, each with six degrees of freedom. A bilateral Selspot II/TRACK data acquisition system provides position and orientation kinematic data for estimation of the trajectories of the individual body segment centers of gravity. From these, the whole body center of gravity is estimated and compared to concurrent force plate center of force data. Center of gravity and center of force excursions agree where dynamics are not significant. The technique may be employed to study quiet stance, response to postural disturbances, or the initiation and coordination of complex movements such as gait.

Adolescent↗

PubMed1990

Whole-body movements during rising to standing from sitting.

Rising to a standing position from a sitting position is one of the most important activities of daily life. We present a total-body analysis of rising from a chair as performed by nine healthy individuals under controlled conditions. We describe four phases of this activity. Phase I is a flexion-momentum phase used to generate the initial momentum for rising. Phase II begins as the individual leaves the chair seat and ends at maximal ankle dorsiflexion. Forward momentum of the upper body is transferred to forward and upward momentum of the total body. Phase III is an extension phase during which the body rises to its full upright position. Phase IV is a stabilization phase. Kinetics and kinematics of the phases are analyzed. The phases are differentiated in terms of momentum and stability characteristics. Clinical implications of the mechanics of rising are discussed.

Adult↗

PubMed1990

Reliability of a clinical kinematic assessment of the sit-to-stand movement.

We examined the reproducibility of a kinematic assessment of the sit-to-stand movement in 15 healthy subjects using a standardized protocol. We examined the within-rater and between-rater reliability of the assessment using a clinically feasible method, the video-goniometric measurement method, to analyze the task. Two variables were measured to characterize the sit-to-stand movement: 1) joint angles for four body segments (head, trunk, knee, and ankle) and 2) three events (maximal trunk flexion, lift-off, and maximal trunk extension). High reproducibility was found for all joint angles, except for the head angle. Both within-rater and between-rater goniometric measurements were highly reliable (ICC greater than .80). Identification of the events was reproducible within raters and between different raters. We conclude that this method can lead to reliable assessments of a healthy population. The reliability data established in this study can be used to help clinicians determine the impairments of patients.

Adult↗

PubMed1989

Contact pressures from an instrumented hip endoprosthesis.

A pressure-measuring Moore-type endoprosthesis was implanted in a seventy-three-year-old patient who had sustained a displaced fracture of the femoral neck. The measurement and telemetry of contact pressures in the hip began in the operating room, and data were acquired periodically for more than thirty-six months. Unexpectedly high localized contact pressures between the acetabular cartilage and the prosthesis were recorded. Early in the period of recovery, activities such as using a bedpan or performing isometric exercise produced pressures that were close to those recorded during normal walking. The highest pressure, eighteen megapascals, was recorded one year postoperatively, while the patient was rising from a chair. High pressures occurred in the superior and posterior aspects of the acetabulum.

Acetabulum↗

PubMed1987

Evaluating manual control devices for those with tremor disability.

Tremor disabled subjects were tested in two dimensional tracking tasks. The subjects had action tremor due to various etiologies. Both continuous and discrete targets were used. Displacement sensing and force sensing joysticks were compared. The effect of filtering of the control signal was evaluated. Position and velocity control were compared. While individuals were found to benefit from various combinations of control setups, no single control modification or combination of modifications was beneficial to all. It remains necessary to adapt manual control interfaces to the needs of the individual disabled person. Most customizing can be implemented with software.

Humans↗