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Dr. Richard C. Nelson: The Penn State Biomechanics Laboratory and Its Impact on My Career

James S. Walton

as my career developed. In regard to the minicomputer and other instrumentation in the biomechanics laboratory, it would be inappropriate not to recognize the significant contributions made by Mr. Ken Petak, our “resident genius,” who wrote low-level programs in machine code that interfaced with

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Dr. Richard C. Nelson: Behind the Scenes

Doris I. Miller

analysis programs. In retrospect, perhaps it all started with Dick’s vision of an automated 16-mm film analysis system. He believed that progress in the field had been stymied by “the lack of adequate instrumentation systems for recording and analyzing biomechanical data.” 6 In the Biomechanics Laboratory

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Agreement Between Different Days of activPAL and Actigraph GT3X Measurement of Sedentary Behavior and Physical Activity During the School Hours in Elementary Children

Luciana L.S. Barboza, Larissa Gandarela, Josefa Graziele S. Santana, Ellen Caroline M. Silva, Elondark S. Machado, Roberto Jerônimo S. Silva, Thayse N. Gomes, and Danilo R. Silva

not disturb the routine at school), it was only possible to evaluate for 4 days, and these days were considered representative of a usual week, serving as a reference for comparison with the other number of days evaluated. Instrumentation and Procedure Information about sex and date of birth was

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Instrumentation to Quantify Exercise Using an Impulse Inertial System

Todd C. Phillips, Sean S. Kohles, John F. Orwin, Lori Thein Brody, Ronald P. McCabe, and Ray Vanderby Jr.

An impulse-momentum exercise system was instrumented for collection of kinematic and kinetic data during shoulder exercise. The objective of this study was to quantify the dynamics of an exercise system that utilizes a weighted shuttle (22.2 N) traveling on a rail system and evaluate its efficacy as an exercise and rehabilitative tool. Two healthy adults (mean age. 30.0 years) were tested utilizing 2 protocols. The first protocol required the subject to maintain tension in the system while externally rotating the upper arm from neutral to 90° relative to the shoulder and then internally rotating back to the initial position. In me second protocol, the range of motion was similar, but each subject was instructed to carry out the exercise as rapidly as possible without regard to the tension in the rope, thus creating an impulsive load. Average peak loads up to 87.9 and 137.0 N were recorded using the first and second protocols. respectively. Average maximum loads using the second protocol were approximately 50 N greater than those using the first protocol (p < .05). Representative calculations demonstrated that less mechanical work was performed during the first protocol (−3.8 to −45.9%). Qualitatively the shuttle acceleration curves appear dramatically different, although similar average peak accelerations are achieved during use (4.12 vs. 3.47 m/s2, protocol I vs. protocol 2, respectively).

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Application of Scientific Instrumentation in a Clinical Setting

Semyon M. Slobounov, Robert Simon, Wayne Sebastianelli, Angela Carlson, and William E. Buckley

A variety of assessment devices have been developed for scientific investigation on human movement that can also be used to assess the progress of a rehabilitation program. The present investigation was undertaken to show how this technology can be combined with the most aggressive type of medical intervention and rehabilitation. Advanced technology was used to assess the physical rehabilitation parameters of active range of motion (AROM) and sport-specific functional progression for an Olympic-caliber diver who had bilateral wrist problems. AROM was measured for both wrists using a Flock of Birds motion-tracking device, and functional progression was assessed with an Advanced Mechanical Technology Inc. force platform for measuring the center of pressure (CP) area. The results of the treatment were clinically favorable, with an increase in AROM and a decrease in the CP area for functional motor control. The technology provided useful information about the progress of a rehabilitation program.

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A Device for Simultaneous Measurement of Pressure and Shear Force Distribution on the Plantar Surface of the Foot

Brian L. Davis, Julie E. Perry, Donald C. Neth, and Kevin C. Waters

A device has been designed to simultaneously measure the vertical pressure and the anterior-posterior and medial-lateral distributed shearing forces under the plantar surface of the foot. The device uses strain gauge technology and consists of 16 individual transducers (each with a surface area measuring 2.5 × 2.5 cm) arranged in a 4 × 4 array. The sampling frequency is 37 Hz and data may be collected for 2 s. The device was calibrated under both static and dynamic conditions and revealed excellent linearity (±5%), minimal hysteresis (±7.5%), and very good agreement between applied and measured loads (±5%). Vector addition of the distributed loads gave resultant forces that were qualitatively very similar to those obtained from a standard force plate. Data are presented for measurements from the forefoot of 4 diabetic subjects during the initiation of gait, demonstrating that distributed shear and pressure on the sole of the foot can be measured simultaneously.

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Low-Budget Instrumentation of a Conventional Leg Press to Measure Reliable Isometric-Strength Capacity

Heiner Baur, Alessia Severina Groppa, Regula Limacher, and Lorenz Radlinger

Maximum strength and rate of force development (RFD) are 2 important strength characteristics for everyday tasks and athletic performance. Measurements of both parameters must be reliable. Expensive isokinetic devices with isometric modes are often used. The possibility of cost-effective measurements in a practical setting would facilitate quality control. The purpose of this study was to assess the reliability of measurements of maximum isometric strength (Fmax) and RFD on a conventional leg press. Sixteen subjects (23 ± 2 y, 1.68 ± 0.05 m, 59 ± 5 kg) were tested twice within 1 session. After warm-up, subjects performed 2 times 5 trials eliciting maximum voluntary isometric contractions on an instrumented leg press (1- and 2-legged randomized). Fmax (N) and RFD (N/s) were extracted from force-time curves. Reliability was determined for Fmax and RFD by calculating the intraclass correlation coefficient (ICC), the rest-retest variability (TRV), and the bias and limits of agreement. Reliability measures revealed good to excellent ICCs of .80-.93. TRV showed mean differences between measurement sessions of 0.4-6.9%. The systematic error was low compared with the absolute mean values (Fmax 5-6%, RFD 1-4%). The implementation of a force transducer into a conventional leg press provides a viable procedure to assess Fmax and RFD. Both performance parameters can be assessed with good to excellent reliability allowing quality control of interventions.

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Validation and Repeatability of a Shoulder Biomechanics Data Collection Methodology and Instrumentation

Jason S. Scibek and Christopher R. Carcia

The purpose of our study was to establish criterion-related validity and repeatability of a shoulder biomechanics testing protocol involving an electromagnetic tracking system (Flock of Birds [FoB]). Eleven subjects completed humeral elevation tasks in the sagittal, scapular, and frontal planes on two occasions. Shoulder kinematics were assessed with a digital inclinometer and the FoB. Intrasession and intersession repeatability for orthopedic angles, and humeral and scapular kinematics ranged from moderate to excellent. Correlation analyses revealed strong relationships between inclinometer and FoB measures of humeral motion, yet considerable mean differences were noted between the measurement devices. Our results validate use of the FoB for measuring humeral kinematics and establish our testing protocol as reliable. We must continue to consider factors that can impact system accuracy and the effects they may have on kinematic descriptions and how data are reported.

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Pilot Study of Novel Test Instrumentation to Evaluate Therapeutic Horseback Riding

V. Marie Fox, Valorie A. Lawlor, and Marvin W. Luttges

A novel test instrument was designed to objectively quantify the progress of persons who participated in therapeutic horseback riding programs. Nineteen handicapped children, ages 7 to 14 years, with heterogeneous impairments were evaluated before and after riding. For measures of sitting balance and coordination, and hand, hip, knee, and ankle strength, marked improvements were noted for most children. Clinical impressions of therapists and parents suggested concomitant progress in characteristics such as self-confidence and interaction with others. Results from this pilot study appeared to support the use of the apparatus in that field setting.

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Criterion and Construct Validity of Prosthesis-Integrated Measurement of Joint Moment Data in Persons With Transtibial Amputation

Goeran Fiedler, Brooke Slavens, Roger O. Smith, Douglas Briggs, and Brian J. Hafner

Prosthesis-integrated sensors are appealing for use in clinical settings where gait analysis equipment is unavailable, but accurate knowledge of patients’ performance is desired. Data obtained from load cells (inferring joint moments) may aid clinicians in the prescription, alignment, and gait rehabilitation of persons with limb loss. The purpose of this study was to assess the accuracy of prosthesis-integrated load cells for routine use in clinical practice. Level ground walking of persons with transtibial amputation was concurrently measured with a commercially available prosthesis-integrated load cell, a 10-camera motion analysis system, and piezoelectric force plates. Ankle and knee flexion/extension moments were derived and measurement methods were compared via correlation analysis. Pearson correlation coefficients ranged from 0.661 for ankle pronation/supination moments to 0.915 for ankle flexion/extension moments (P < .001). Root mean squared errors between measurement methods were in the magnitude of 10% of the measured range and were explainable. Differences in results depicted differences between systems in definition and computation of measurement variables. They may not limit clinical use of the load cell, but should be considered when data are compared directly to conventional gait analysis data. Construct validity of the load cell (ie, ability to measure joint moments in-situ) is supported by the study results.