Functional and Behavioral Measures of Nutritional Status
PART VIII BEGINS WITH A DISCUSSION in Chapter 23 of the use of involuntary muscle contraction for nutritional assessment. With muscle function analysis (MFA), skeletal muscle function is measured by applying an electrical stimulus at various frequencies and then studying the resulting pattern of involuntary contractions. Studies seem to indicate that lower MFA relaxation rates indicate some nutritional abnormality, such as protein malnutrition. This method is relatively noninvasive and sensitive, but some of its disadvantages (for example, difficulty in locating the ulnar nerve) indicate that more testing is needed to establish its validity.
In Chapter 24 and 25, the focus turns to assessment of cognitive function in the military. As discussed in Chapter 24, the Army's interest in the influence of nutrition on cognitive function has focused on food deprivation in the field, underconsumption of rations, and identification of performance-optimizing ration components. There are limitations in cognitive assessment technology, and assessment has been accomplished largely through the use of observation of behavior, paper-and-pencil tests, and tests of manual dexterity or hand-eye coordination. These tests are being replaced by assessment technologies that make use of computer games or performance tracking devices.
Chapter 25 describes two electronic activity-monitoring devices for psychomotor vigilance testing: the Motionlogger Actigraph, which monitors
sleeping and waking activity and collects data to calculate sleeping and waking time, and the Vigilance Monitor, which combines the aforementioned measurement capabilities with vigilance assessment and intervention capability. The Vigilance Monitor is unobtrusive, has a fairly low cost, and can be programmed to provide data on several variables concurrently while monitoring a number of subjects simultaneously.
Finally, the Iowa Driving Simulator (IDS), as described in Chapter 26, is one possible example of an interface that allows for the use of identical assessment tools in the laboratory and in the field. The IDS is a high-fidelity computational vehicle model set in a fully interactive, virtual environment. Its military applications have included the development of a virtual proving ground based on actual Army test courses, and the design and testing of new Army vehicle prototypes. The different degrees and types of fidelity required for different performance measures can be limiting, as can the extent to which subjects perceive the experience to be real.