Biomedical subjects

Michael S Orendurff

Publications and source records attributed to Michael S Orendurff.

8 recordsLinked to original sources

PubMed2006

Video task analysis of turning during activities of daily living.

Nearly every daily activity that requires locomotion requires turning, yet most gait research has focused on straight ahead walking. Research on turning has primarily been limited to laboratory or clinical settings, and little is known about turning in the home or community environments. The purpose of this study was to investigate turning behavior in the field during certain activities of daily living. Eleven able-bodied subjects were filmed from a posterior view from the waist down as they walked through four courses designed to simulate activities of daily living. Subjects walked from one office to another, from an office to a parking lot, through a convenience store, and through a cafeteria. A single investigator classified each step from the video data as either straight or turning. A repeatability analysis was performed on the office to office course. Results showed that turning steps made up a considerable portion of steps taken. The office to parking lot, store, office to office and cafeteria courses had turn percentages of 8%, 35%, 45%, and 50%, respectively. The repeatability analysis revealed R(2) values of .850 or greater for four out of five turn classifications. Turning makes up a large portion of steps taken during activities of daily living, yet clinical practice focuses primarily on straight ahead walking. The results of this study suggest the need to consider turning maneuvers in clinical practice.

Activities of Daily Living↗

PubMed2006

Prosthetic intervention effects on activity of lower-extremity amputees.

OBJECTIVE: To investigate the effect of prosthetic interventions on the functional mobility of lower-extremity amputees. DESIGN: Crossover with repeated measures. SETTING: Household and community environment. PARTICIPANTS: Twelve transtibial and 5 transfemoral amputees. INTERVENTIONS: For transtibial amputees, shock-absorbing versus rigid pylons. For transfemoral amputees, C-Leg versus Mauch SNS knees. MAIN OUTCOME MEASURES: Daily activity level (step count) and duration (minutes of activity). RESULTS: Pylon type had no effect on the daily activity level or duration of transtibial amputees. Knee type had no effect on the daily activity level or duration of transfemoral amputees. Transtibial amputees were more active on weekdays (3079+/-1515 steps/d) than weekends (2386+/-1225 steps/d) (P=.007). In general, lower-extremity amputees perform numerous short-duration bouts of activity (1-2 min) consisting of fewer than 17 steps/min, but activities of more than 15 minutes in duration were relatively rare (<1 per day). CONCLUSIONS: Intervention had no effect on amputee activity level and duration. Higher weekday activity levels of transtibial amputees suggest their vocational activities are more demanding than recreational activities. The fitting, alignment, and design of prosthetic components should be optimized for 1 to 2 minute bouts of activity consisting of only a few dozen steps.

Adult↗

PubMed2006

A comparison of gastrocnemius muscle-tendon unit length during gait using anatomic, cadaveric and MRI models.

Computing the length of a specific muscle is often of interest both in the study of human movement and the optimization of surgical techniques. The objective of this study was to compare three widely used methods of calculating gastrocnemius muscle-tendon unit (MTU) length. Gastrocnemius MTU length was calculated from the sagittal knee and ankle kinematics of 20 normal adults using three different methods: one based on cadaveric dissection and joint manipulation, one based on anatomic computer software modeling with insertion points obtained from cadavers and the third based on MRI measurements. All methods were normalized to percent anatomic neutral length (%ANL) with 100% at full knee extension and neutral ankle plantar-dorsiflexion. At the longest length (terminal stance), mean values (% ANL+/-standard deviation) were found to be 99.3+/-0.8, 101.8+/-0.5 and 102.4+/-0.7 for the MRI, cadaveric and anatomic methods, respectively. During the shortest length (early swing), the MRI, cadaveric and anatomic methods had mean values of 93.0+/-0.6, 92.2+/-2.0 and 91.9+/-2.1% ANL, respectively. All methods showed statistically significant differences (p<0.01) from each other in terminal stance and early swing, while loading and terminal swing lengths were similar among all methods. The gastrocnemius MTU calculated using the MRI-based method was found to be the shortest. Additional research is needed in order to validate a model for calculating gastrocnemius MTU length using in vivo methods of estimating the gastrocnemius moment arm at the knee and ankle.

Biomechanical Phenomena↗

PubMed2006

The kinematics and kinetics of turning: limb asymmetries associated with walking a circular path.

The biomechanics of changing direction while walking has been largely neglected despite its obvious relevancy to functional mobility. The world is filled with turns that must be negotiated. These turns carry an increased risk of injury due to a decrease in stability. A VICON 612 system measured joint kinematics and kinetics on 10 normal subjects for straight line walking (ST); turning, inside foot strike (IN); and turning, outside foot strike (OUT). All trials were completed at a self-selected walking speed and across a range of speeds from 0.6 to 1.3 m/s; the turn radius was 1 m. Significant differences between the conditions were detected using a mixed effects repeated measures ANCOVA with walking speed as a covariate. The most pronounced differences were demonstrated in the mediolateral ground reaction force impulse: in straight walking the impulses tended to shift the body toward the contralateral limb. In turning, the IN and OUT impulses shifted the body toward the ipsilateral and contralateral limbs, respectively. Knee flexion during stance was increased on the IN limb, while ankle plantarflexion increased on the OUT limb consistent with body lean during turning; differences in joint kinetics during turning were negligible. Self-selected turning was significantly slower than walking straight ahead (0.96+/-0.12 m/s versus 1.61+/-0.22 m/s) and turning at very slow speeds showed a non-uniform center of mass trajectory. Understanding the mechanisms of turning will provide insights driving design, therapy and intervention to increase functional navigation in amputees, the elderly and individuals with neuromuscular pathologies.

Adult↗

PubMed2005

Triceps surae force, length and velocity during walking.

Individuals with neuromuscular conditions may develop muscle contractures that limit joint motion. Decreased muscle length is clinically obvious, but deviations in other functional characteristics of muscle, such as underlying weakness or decreased shortening velocity are more obscure. Therefore, a more comprehensive assessment of muscle characteristics may be required to fully restore function in these individuals. To provide normative comparison data on the force, length and velocity of the triceps surae during walking, 20 adults free from neuromuscular and orthopedic problems were assessed using instrumented gait analysis. Kinematic and kinetic data were used to calculate gastrocnemius and soleus length and velocity, and plantarflexor force during walking. Gastrocnemius length was shortest in early swing and longest in terminal swing and again in midstance. Soleus length was longest throughout the period of single limb stance and was shortest at foot-off. Gastrocnemius shortening velocity was greatest in early swing phase whereas soleus shortening velocity was greatest in pre-swing. Plantarflexor force increased steadily throughout stance phase and peaked in terminal stance at 33.8+/-3.6 N/kg bodyweight. These data provide target levels on the functional parameters of plantarflexor force, length and velocity in order that therapeutic and surgical interventions could be focused on the deviations observed, and the outcomes of these interventions more objectively assessed.

Adult↗

PubMed2002

Length and force of the gastrocnemius and soleus during gait following tendo Achilles lengthenings in children with equinus.

Nine subjects (12 sides) with cerebral palsy who walked in equnius were evaluated prior to and 1 year after surgical tendo Achilles lengthening. Gastrocnemius and soleus length [Gait Posture, 6 (1997) 9] and plantarflexor force [Gait Posture, 6 (1997) 9; J Biomech, 23 (1990) 495] were calculated. The length of the gastrocnemius and soleus increased significantly (P<0.01) following the intervention. Force output of the triceps surae during push-off increased significantly (13.95 N/kg body weight (BW) preop to 30.31 N/kg BW postop; P<0.01). Assessment of the force-length capacity of the triceps surae in candidates for tendo Achilles lengthenings may identify individuals at risk of residual weakness and iatrogenic crouch.

Achilles Tendon↗

PubMedDate not supplied

The effect of walking speed on center of mass displacement.

The movement of the center of mass (COM) during human walking has been hypothesized to follow a sinusoidal pattern in the vertical and mediolateral directions. The vertical COM displacement has been shown to increase with velocity, but little is known about the mediolateral movement of the COM. In our evaluation of the mediolateral COM displacement at several walking speeds, 10 normal subjects walked at their self-selected speed and then at 0.7, 1.0, 1.2, and 1.6 m/s in random order. We calculated COM location from a 15-segment, full-body kinematic model using segmental analysis. Mediolateral COM displacement was 6.99 +/- 1.34 cm at the slowest walking speed and decreased to 3.85 +/- 1.41 cm at the fastest speed (p < 0.05). Vertical COM excursion increased from 2.74 +/- 0.52 at the slowest speed to 4.83 +/- 0.92 at the fastest speed (p < 0.05). The data suggest that the relationship between the vertical and mediolateral COM excursions changes substantially with walking speed. Clinicians who use observational gait analysis to assess walking problems should be aware that even normal individuals show significant mediolateral COM displacement at slow speeds. Excessive vertical COM displacement that is obvious at moderate walking speeds may be masked at slow walking speeds.

Adult↗

PubMedDate not supplied

Gait efficiency using the C-Leg.

Microprocessor-controlled prosthetic knees are claimed to improve gait efficiency in transfemoral (TF) amputees. This hypothesis was tested in a prospective randomized crossover trial that compared the Mauch SNS knee and the C-Leg microprocessor-controlled knee in eight TF amputees. The subjects were given a 3-month acclimation period in each knee. Then, their net oxygen cost (mL/kg/m) was measured while they walked overground at four speeds in random order: 0.8 m/s, 1.0 m/s, 1.3 m/s, and self-selected walking speed (SSWS). The C-Leg caused small reductions in net oxygen cost that were not statistically significant compared with the Mauch SNS at any of the walking speeds (p > 0.190). Subjects chose higher SSWSs with the C-Leg compared with the Mauch SNS (mean +/- standard deviation = 1.31 +/- 0.12 m/s vs 1.21 +/- 0.10 m/s, respectively, p = 0.046) but did not incur higher oxygen costs (p = 0.270), which suggests greater efficiency only at their SSWS.

Adult↗