Labview: Data Acquisition and Analysis for the Movement Sciences.

LabVIEW: Data Acquisition and Analysis for the Movement Sciences

McDonough AL. Upper Saddle River, NJ 07458, Prentice-Hall Inc, 2001, spiral-bound, 251 pp, illus, ISBN: 0-13012847-3, $64, includes CD-ROM.

The author originally developed this book as a laboratory manual for graduate courses in motor learning at Teachers College, Columbia University. Written for students, educators, and researchers who are studying human motion, the purpose of this book is to provide programming "essentials" for LabVIEW. The book defines the procedures for using LabVIEW for data collection and analysis of human movement performance, in which signals are recorded from muscles and force, torque, and angle transducers. The book was reviewed by 6 content experts in physical therapy and biomedical engineering.

LabVIEW (National Instruments, Austin, Tex) is a graphical programming language which uses "virtual instruments" (VIs) to simulate hardware devices. LabVIEW is used to acquire and analyze digital electrical signals that are sent to the computer through an analog-to-digital (A/D) converter, which is plugged into one of the computer slots. LabVIEW programs run on both PCs and Macintosh computers. This book discusses LabVIEW version 5.1 (although the most recent version of software is 6i with Internet interactive capacity). Versions 5 and 6 work on Windows NT/98/95 or Mac OS.

The book contains 3 chapters and an index. The first 2 chapters introduce the reader to the LabVIEW programming language and the measurement of laboratory signals. The third and main chapter is on programming techniques. There are 20 subsections in chapter 3: the basic elements of LabVIEW, the "front panel," block diagrams, sample programs to build and run VIs and subVIs (programing subroutines), program structure and feedback loops, and other programming functions for data display and data and statistical analysis. The final section contains information about the sample data files provided on the CD-ROM. The appendix includes a directory and descriptions of the VIs and subVIs on the CD-ROM. Unfortunately, the CD-ROM is not a stand-alone--it requires that you have a working version of LabVIEW installed on your computer. File compatibility with LabVIEW versions after version 5.1 will need to be verified by the user.

Chapter 2 reviews the basic principles of signal measurement, including how an A/D converter works, sampling rates, signal ranges, signal resolution, noise, and synchronization of signals. The descriptions provided by the author are concise but may sometimes be misleading. For example, to minimize the risk of aliasing, the sampling rate should be at least twice the rate of the highest frequency of the signal being recorded (including noise), not just the signal of interest as suggested by the author. In a second example, the discussion of resolution of the A/D converter is limited to 12- or 16-bit A/D boards; this may be adequate for use with the data sets provided on the CD-ROM, in which signals are in the range of [+ or -] 10 volts. The rationale that would help the researcher design a data collection system for signal voltages in the range of [+ or -] 1 volt or less is absent. These are few of many examples in which this book may be adequate for the student laboratory, but where it lacks the breadth and depth needed in the clinical research laboratory. For more complete and accurate descriptions of signal measurement principles, readers should consult the LabVIEW resource books and manuals that accompany the software.

At the beginning of chapter 3, the author reviews newer features of LabVIEW version 5.1. Although a bit wordy and written for people who are experienced with previous versions of LabVIEW, the book's narrative does contain some important tips and useful information. Its references to computer features and characteristics, however, seem a bit passe (ie, 386 PC); this is surprising because this book was published in 2001. However, this information may be useful for academic or clinical settings where older computers are still in use.

The narrative format and attention to detail in chapter 3 are user-friendly and effectively introduce the novice user to LabVIEW for data acquisition and analysis. Use of computer screen displays facilitates the step-by-step implementation of programming with VIs. This book is not a "stand-alone" or a replacement for LabVIEW reference books. The utility of the book would be improved by citing links with LabVIEW's resource books.

The laboratory exercises are practical applications for students studying human movement, with exercises provided at increasing levels of complexity. The user may import real data from an A/D converter or use data files from the CD-ROM, which includes single channels of electromyographic (EMG) or torque data of 1 to 8 seconds, torque or force data with up to 3 channels of EMG, and 5 seconds of force data with an event marker. These data sets may be adequate for the student laboratory environment; however, the voltages and frequency ranges are limited and may not represent the full range of signal characteristics encountered in a research laboratory.

In summary, this book can serve as a laboratory book for students who have access to LabVIEW and who seek a guided instruction in programming with VIs. The unique feature of this book is that the programming design, exercises, and sample data files are specifically designed to aid data acquisition and analysis in human movement studies. Written for use with LabVIEW version 5.1, the compatibility with the current software 6i is unknown. The clinical researcher will need more comprehensive material than this book provides.

Barbara M Myklebust, PT, PhD
The George Washington University
Washington, DC

Dr Myklebust is Director of the Program in Physical Therapy where she teaches physiology. Her clinical research interests are in the area of human motor control, including age-related changes in sensorimotor performance, developmental changes in the neurophysiology of healthy infants and children with cerebral palsy, and limb prosthetics.