Biomedical subjects

M W Cornwall

Publications and source records attributed to M W Cornwall.

At least 37 records · Page 2Linked to original sources

PubMed1994

The influence of tibialis anterior muscle activity on rearfoot motion during walking.

The purpose of this study was to determine whether tibialis anterior muscle activity influences the rate of rearfoot motion during walking. Two-dimensional rearfoot motion was recorded from 23 feet. The feet were assigned to one of two experimental groups. Muscle activity was recorded from the tibialis anterior muscle using surface electrodes. The early pronators (N = 12) reached maximal pronation within the first 20% of the stance phase. The late pronators (N = 11) reached maximal pronation only after 40% of the stance phase. The results of a t-test showed that there was a significant difference (P < .05) in the time to minimal tibialis anterior muscle activity between the two groups. These results indicate that tibialis anterior muscle activity can influence rearfoot motion during the stance phase of walking. A clinician should consider the muscular system when evaluating and designing a treatment program for patients with foot-related problems. The results of this study also indicate that static nonweightbearing evaluations alone may not provide an accurate picture of the foot during walking.

Adult↗

PubMed1994

Relationship between neutral subtalar joint position and pattern of rearfoot motion during walking.

The purpose of this study was to determine the relationship between the angle formed by the rearfoot when the subtalar joint is positioned in neutral and the pattern of rearfoot motion during walking. Each lower extremity for 50 healthy young adult subjects (mean age 25.5 years) was videotaped and the pattern of rearfoot motion was assessed using two-dimensional analysis. The results indicate that the rearfoot is slightly inverted before heel strike and that the average time to maximum pronation occurs at approximately 37.9% of the stance phase duration. Contrary to a previously published theory, the "neutral" position of the rearfoot for the typical pattern of rearfoot motion during the walking cycle was found to be resting standing foot posture rather than subtalar joint neutral position.

Adult↗

PubMed1994

Plantar pressures during level walking compared with other ambulatory activities.

This study was designed to determine the magnitude of plantar pressures during level walking in comparison to other activities. These activities included climbing up stairs, going down stairs, a simple pivot while walking, and a crossover pivot while walking in normal individuals. Twelve volunteers, six men and six women, mean age 28 years, served as subjects. Data were collected on the dominant foot with an EMED-SF pressure sensor platform as each subject walked barefoot and did each of the five activities. Maximum plantar pressure (MPP) and pressure-time integral (PTI) was found in the metatarsal and heel regions. The results of repeated-measures analysis of variance tests showed that the five experimental conditions were statistically different for both MPP and PTI in the metatarsal and heel regions. Post hoc analysis indicated that MPP and PTI were decreased during the going down stairs condition in the heel and increased during the crossover pivot while walking and pivot while walking conditions for the metatarsal region.

Adult↗

PubMed1994

Effect of temperature on muscle force and rate of muscle force production in men and women.

The use of heat and/or cold is common in many physical therapy treatment programs. Knowledge concerning their effect upon muscular performance would help in the design of exercise programs used with heat or cold. The purpose of this study was to investigate the effect of heating and cooling on maximum voluntary force and rate of force development in the wrist extensor muscles of men and women. The maximum rate of force development was assessed in 30 subjects under three separate conditions: 1) following immersion in a 40 degrees C water bath, 2) following immersion in a 10 degrees C water bath, and 3) a control condition. The results showed that peak force and rate of force development decreased, while time to peak force development increased in males following exposure to cold. In females, only the time to peak force development was found to be altered (increased) by cold exposure. No significant change in the speed of force development was found following heat application in either sex. Investigation of the force-time curve showed that the slope of the curve decreased following cold exposure. This study shows that cold, but not heat, application at temperatures commonly used in rehabilitation is sufficient to cause alterations in the wrist extensor muscle's ability to quickly develop isometric tension.

Adult↗

PubMed1994

Comparison of three methods for obtaining plantar pressures in nonpathologic subjects.

The purpose of this study was to determine if pressure data, collected after taking one step or two steps, were similar to values obtained by using the traditional midgait method. Ten healthy subjects, with a mean age of 27 years, walked across a sensor platform sampling at 70 Hz. Each subject was randomly assigned to take one step, two steps, or multiple steps (midgait method) across the sensor platform. The results of the study indicate that the two-step method, in comparison with the one-step method, provides pressure data more representative of the midgait method, and different values for pressure and force will be obtained, depending on the method of pressure data collection selected by the clinician.

Adult↗

PubMed1994

Muscular fatigue and recovery following alternating isometric contractions at different levels of force.

The purpose of this study was to document the amount and rate of muscular fatigue during alternating levels of isometric contraction similar to that found during the Simulated Aerial Combat Maneuver (SACM). In addition, the time needed to recover from such an exercise was examined. Twenty males between the ages of 22 and 35 years performed an isometric contraction of their right quadriceps muscle at alternating levels of tension (20 and 50% maximum voluntary contraction) until exhaustion. The time at each contraction level was 10 s. After each exhaustive exercise bout, subjects were assigned to one of six recovery intervals (10, 20, 40, 60, 120, and 240 min) followed by a repeat of the exhaustive exercise. All subjects were tested under each of the six recovery intervals. Results showed that the amplitude (RMS) of the myoelectric signal increased while the frequency content of the signal (MPF) decreased over the course of the fatiguing activity. Endurance time (ET) was found to be significantly (p < 0.05) recovered (90.96%) within 60 min after stopping the exercise. Although MPF returned to its prefatigue value within 10 min of rest, the RMS value had still not recovered after 4 h.

Adult↗

PubMed1993

Reducing two-dimensional rearfoot motion variability during walking.

Although three-dimensional movement analysis is the preferred method of assessing rearfoot motion during gait, the high cost of equipment and the time required to use it often make it unreasonable or impractical in a clinical setting. The authors discuss a method of minimizing the variability of rearfoot motion measurements during walking, using two-dimensional analysis when three-dimensional is not available to the clinician.

Biomechanical Phenomena↗

PubMed1993

Vertical forces and plantar pressures in selected aerobic movements versus walking.

Ten subjects between the ages of 19 and 29 years walked and performed four aerobic movements over a force and pressure platform. Peak plantar pressure and peak vertical force data were collected three times on the dominant leg as each subject performed all of the five activities. Peak vertical forces acting on the lower extremities for the low impact aerobic movements were significantly less when compared with the high impact movements. As was expected, no differences were found in peak vertical forces between walking and the low impact aerobic movements. Peak plantar pressures for walking were not significantly different when compared with any of the four aerobic movements studied.

Adult↗

PubMed1992

Measurement of reactive vasodilation during cold gel pack application to nontraumatized ankles.

Conflicting results regarding local vascular response during cryotherapy have been reported in the literature. The purpose of this study was to determine whether application of a cold pack reduced blood volume in a nontraumatized ankle. Thirteen subjects ranging in age from 18 to 30 years (X = 22; SD = 3.9) participated in the study. An impedance plethysmograph, in combination with venous occlusion, was used to measure the changes in local blood volume at the ankle over a 20-minute period for the following three conditions: rest, room-temperature gel pack application, and cold gel pack application. A significant reduction in local blood volume was found for the cold gel pack condition in comparison with the resting condition. This reduction was attributed to a combination of pressure from the weight of the cold gel pack and the pack's temperature. Maximum decrease in blood volume occurred at 13.5 minutes after cold gel pack application. Reactive vasodilation was not observed. The results lend support to the clinical use of a cold gel pack when a reduction in local circulation is desired, such as in the management of acute-phase soft tissue trauma.

Adolescent↗

PubMed1992

Effect of rearfoot posts in reducing forefoot forces. A single-subject design.

The purpose of this study was to assess the effectiveness of a semirigid foot orthosis with a varus wedge on forefoot vertical forces in a 24-year-old female with a compensated rearfoot varus deformity. The results of this study indicate that the use of total contact semirigid foot orthoses reduces the forefoot force-time integral during walking, whether a rearfoot varus wedge was or was not used. The authors recommend that total contact construction of the foot orthoses be considered when a reduction of the forces acting on the forefoot is the goal of treatment.

Adolescent↗

PubMed1992

Effect of insole material on force and plantar pressures during walking.

Twelve subjects between the ages of 24 and 35 years walked barefoot over a pressure platform with the following insole materials placed directly on top of the platform: 1) PPT, 2) Spenco, and 3) Viscolas. Maximum vertical force, vertical force-time integral as well as maximum plantar pressure data were collected for the rearfoot, midfoot, and forefoot regions. The results were not significant for maximum vertical force and vertical force-time integral among the three insole materials when compared to barefoot-only walking. There was, however, a significant reduction in forefoot maximum plantar pressure among the three materials compared to barefoot-only walking. In the rearfoot region, a reduction in maximum plantar pressure was seen only with PPT and Spenco.

Adult↗

PubMed1992

Electromyographic activity while performing the anti-G straining maneuver during high sustained acceleration.

The purpose of this study was to measure the muscle activity during performance of the anti-G straining maneuver (AGSM) at high sustained acceleration stress (+Gz = head-to-foot inertial loading). Ten males were exposed on three separation occasions to a rapid onset rate of 6 + Gz. Subjects wore standard United States Air Force (USAF) anti-G trousers and performed the AGSM until perceived fatigue or until achieving light loss criteria. During each exposure, surface electromyography (EMG) was recorded from the erector spinae, external oblique, bicep femoris, vastus lateralis, and lateral gastrocnemius muscles. The normalized root-mean squares (RMS) and mean power frequency (MPF) for each muscle were calculated and tested for significant differences with an analysis of variance (ANOVA) procedure. The results of this study showed that mean amplitude decreased during the AGSM (35.40%) while MPF showed no significant change. The EMG amplitude of lower extremity muscles decreased (61.45%) while the amplitude of trunk muscles decreased slightly (3.45%). These results indicate that during the performance of the AGSM, motor unit recruitment in lower extremity muscles decrease without evidence of fatigue.

Abdominal Muscles↗

PubMed1991

Effect of acupuncture-point stimulation on diastolic blood pressure in hypertensive subjects: a preliminary study.

Electrical stimulation of four specific acupuncture points (Liver 3, Stomach 36, Large Intestine 11, and the Groove for Lowering Blood Pressure) was examined in order to determine the effect of this stimulation on diastolic blood pressure in 10 subjects with diastolic hypertension. Subjects were randomly divided into two groups: (1) an Acu-ES group, which received electrical stimulation applied to the four antihypertensive acupuncture points, and (2) a Sham-ES group, which received electrical stimulation applied to non-acupuncture-point areas. A repeated-measures analysis of variance revealed a significant, immediate poststimulation reduction of diastolic blood pressure for the Acu-Es group versus the Sham-ES group. Further studies are needed to determine whether there are other acupuncture points, stimulation characteristics, or modalities that can enhance this treatment effect and whether the treatment effect can last for a clinically significant period of time.

Acupuncture Points↗

PubMed1991

Rigid versus soft foot orthoses. A single subject design.

The purpose of this study was to compare the effects of rigid and soft foot orthoses on forefoot and rearfoot forces in a 20-year-old female runner with a history of tibial and metatarsal stress fractures. The results of this study indicate that a soft orthosis significantly reduced vertical forces through the foot during both walking and running. The authors recommend that proper fabrication materials be considered for those patients with a history of foot or lower extremity problems caused by reduced shock attenuation.

Adolescent↗

PubMed1991

Postural sway following inversion sprain of the ankle.

The single-limb sway of 20 individuals with a history of unilateral inversion ankle sprain was compared to that of a control group of 30 individuals without a history of ankle sprain. Using a force platform to obtain center-of-pressure data, the linear distance traveled (mm) and the mean power frequency, (Hz) of postural sway were calculated for each subject. The results of this study showed that postural sway amplitude was significantly greater in the injured group than in the control group. Contrary to previous investigations, this study indicates that individuals with a history of inversion ankle sprain are less stable in single-limb stance compared to a noninjured control group. This decreased stability is evident as much as 2 years following the injury.

Adolescent↗

PubMed1991

Leg-length discrepancy: effect on the amplitude of postural sway.

The purpose of this study was to investigate whether leg-length discrepancy (LLD) influences a person's standing balance as measured by the amplitude of his/her postural sway. Twenty volunteers between the ages of 20 and 32 participated. Eleven individuals with no measurable LLD constituted the control group. The experimental group consisted of nine individuals with at least a 9.5mm LLD. Each subject stood barefoot on a force platform with their feet together. Center-of-pressure data were collected at a rate of 10Hz for 12.8 seconds while the subjects stood with their eyes opened and again with their eyes closed. The amplitude of each person's postural sway in the medial-lateral and anterior-posterior directions was calculated from the center-of-pressure data. The results of the study showed that no significant difference existed between the experimental and control groups. There was, however, a significant difference (p less than .05) between the conditions of eyes opened and closed. These results indicate that individuals with an LLD do not have more postural sway than those without an LLD.

Adult↗

PubMed1990

Energy expenditure of ambulation using the Sure-Gait crutch and the standard axillary crutch.

Energy expenditure is increased for ambulation with various assistive devices such as canes, walkers, and crutches compared with unassisted ambulation. The purpose of the present investigation was to determine whether a significant difference in oxygen consumption and heart rate existed during ambulation with two different types of crutches. Ten healthy male subjects between the ages of 40 and 60 years participated in this study. Each subject ambulated at 1.5 mph on a treadmill using two different types of crutches--the standard axillary crutch and the Sure-Gait crutch. After walking on the treadmill without an assistive device, subjects ambulated using a three-point, swing-to gait pattern with one of the two types of crutches. This procedure was repeated using the other type of crutch. Oxygen consumption and heart rate were analyzed using an analysis of variance for repeated measures design. The results of the study showed a significant difference (p less than .01) between ambulation with crutches and unassisted ambulation for oxygen consumption and heart rate. No difference, however, was found between the two crutch types.

Adult↗

PubMed1984

Median nerve F-wave conduction in healthy subjects.

This study of the normal median nerve was designed to compare techniques of using the shortest and average F-wave latencies, F-wave values between extremities, and F-wave values with the conventional motor response values and to determine the relationships between F-wave latency and arm length. We examined 40 median nerves in 20 subjects with no known pathology. The motor response latency was measured from wrist and elbow stimulation sites by conventional techniques. We then applied multiple stimuli at the same sites to record a series of 10 F-wave latencies and determined shortest and average F-wave latencies. Values of F-wave and M-response conduction are reported. No significant difference was found in F-wave latency or velocity between extremities within subjects, using either the shortest or average latency technique. We propose a formula for calculating the estimated F-wave distal latency based on the conventional motor response distal latency. The F-wave conduction velocities of the forearm were faster and more variable than the motor nerve conduction velocities. A high correlation was found between F-wave distal latency and arm length. Using the method described, the F wave can be a useful measure in evaluating the conduction of proximal segments of peripheral motor nerves.

Adolescent↗