Click for next page ( 11


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 10
10 CHAPTER 3 STRATEGIES AND TECHNIQUES TO COUNTER FATIGUE Transportation industries of all modes continue to search and, in some of the stages, the brain is often very active. A typ- for ways to prevent or counter the effects of operator fatigue. ical night's sleep consists of cyclic sleep stages. The only way Fatigue countermeasures are identified in one of three gen- that the different stages are easily recognizable is through the eral approaches: (1) individual personal actions (e.g., care- use of electroencephalography (EEG), a physiological record- fully monitoring one's diet, obtaining plenty of rest, and ing means that measures changes in the electrical brainwave avoiding some medications), (2) managerial (e.g., scheduling potentials on the surface of the scalp. With the possible excep- and assignments and company policies), and (3) technological tion of rapid eye movement (REM) sleep, merely observing (e.g., in-vehicle operator monitoring devices and road and an individual asleep will not identify the various sleep stages. highway design features). A fourth approach, of course, is reg- Lengthy bouts of human sleep consist of several 90-minute ulatory and pertains mostly to HOS considerations as briefly cycles of brainwave stages. Each sleep cycle consists of sev- described earlier in this report. eral sleep stages, some deeper than others and not all of them The McCallum et al. (2003) report addresses 20 fatigue conducive to dreaming. The basic stages of sleep are as fol- countermeasures. The authors organized the 20 counter- lows: measures into four categories based on the results of varied amounts of research. Some of the countermeasures are known Stage 1 occurs as we drift off to sleep. This is a relaxed, to be effective; some might be effective but are still being half-awake state of "falling asleep" or light sleep. studied; others require medical or other professional supervi- Stage 2 sleep begins as relaxation proceeds and the heart sion; and some simply do not work or may even have harmful rate slows. During this period, body movement ceases health effects. A second major information source for this dis- and muscle tension eases. cussion is TCRP Report 81: Toolbox for Transit Operator Stages 3 and 4, often referred to as slow-wave sleep, are Fatigue (Gertler et al., 2002). characterized by different brain activity levels. These are deep states of sleep, which are more difficult to awaken COUNTERMEASURES THAT CLEARLY WORK from and, along with sleep, constitute the stages of sleep that are truly restful and restorative. The countermeasures described in this category are effec- REM sleep, usually occurs last after a cycle or two of tive as shown by research data and operational experience. Stages 1 through 4 sleep have been obtained. REM They encompass both the prevention of fatigue by getting sleep, as the name suggests, is characterized by rapid eye enough sleep and the mitigation of fatigue through counter- movements and generally occurs at the end of each 90- measures applied when one is getting tired. Individual minute cycle. This part of the sleep cycle is character- countermeasures may need to be combined, based on spe- ized by significant brain activity, electrophysiologically, cific operational circumstances. Countermeasures included almost as if the brain were actively awake, but only the in this category are as follows: eyes are moving behind the eyelids. During REM sleep there is a lack of muscle tone, thus preventing the indi- Obtaining adequate sleep, vidual from "acting out" dreams. Napping, Anchor sleep, During the night, sleep behavior may systematically alter- Caffeine, nate between the slow wave and REM stages. As the night pro- Trip planning, and gresses, REM periods lengthen so that sometimes the last one Good sleeping environment. before awakening may comprise almost one-half of the sleep cycle. Sleep specialists agree that adults need an average of 7.5 Obtaining Adequate Sleep to 8 hours of sleep every night to perform in a maximally alert fashion on the job. However, there are exceptions. Some indi- Historically, the medical community believed the brain viduals can function normally on as little as 6 hours of sleep, was inactive during sleep, but research over the past half cen- while others require 9 hours. To be most restful and recupera- tury demonstrated sleep actually consists of several stages tive, sleep stages should proceed through all the sleep cycles.

OCR for page 10
11 This is why eight 1-hour naps do not provide the restorative lowing the nap. Research showing a benefit to napping rest of a longer continuous sleep period. placed the nap right before the work start time while research reporting a performance decrement due to napping allowed Understanding one's individual sleep pattern is crucial for napping to occur throughout the day as desired. This illus- taking the steps to ensure sufficient restorative sleep. People trates the complexity of napping. Both the length and timing can determine their optimum sleep amount by recording their of a nap are co-dependent on each other and may affect one's sleep start and stop times on their third consecutive day off performance and alertness differently depending upon their when they are not using an alarm clock to wake up. level. While many research questions still remain with regard to The amount of sleep needed should be enough to feel naps, when used appropriately napping is a viable strategy for refreshed and healthy the next day, but not more--this will supplementing an inadequate main sleep period and as such usually be between 7.5 and 8.5 hours. Based on the amount can improve on-the-job alertness. Since napping is a primary of sleep needed, people should establish a habitual time for self-prescribed fatigue countermeasure, often without regard going to sleep and waking up, and then maintain this sched- to appropriate usage and potential negative consequences, providing information on effective napping strategies can ule whether or not it is a workday. Additionally, daily exer- help the workforce to be more alert on the job. (Gertler et al., cise helps to promote sounder sleep. 2002, pp. 2223) Getting good sleep depends on knowing what to avoid prior to sleeping. It is especially important to avoid caffeine, Anchor Sleep a widely used stimulant compound--it should be avoided within 4 to 6 hours of going to sleep, since caffeine effects Anchor sleep refers to a regular sleep period of at least can last that long. It is also important to avoid drinking alco- 4 hours' duration, obtained at the same time each day. The hol within 3 hours of bedtime, because alcohol fragments anchor sleep period is supplemented by additional sleep peri- sleep and makes it less restorative. Cutting down or elimi- ods (e.g., naps) taken when the schedule allows. nating nicotine is important for promoting good sleep. Drink- Employing an anchor sleep and taking supplemental naps ing fewer fluids before going to sleep will reduce awakenings should be used as a coping mechanism for situations where to use the bathroom. one cannot get a full continuous eight hours of normal sleep. While split sleep periods may give one a sufficient amount of Napping sleep on a short-term basis, getting a full sleep allotment in a single episode is preferred. Napping is one of the most popular coping mechanisms for Anchor sleep periods have the advantage of stabilizing a those working nontraditional hours. Although science is split person's circadian physiological rhythm to a 24-hour as to the benefits and consequences of napping, there is signif- period, so that a motorcoach operator does not constantly icant evidence of the value of supplementing the primary sleep feel "out of synch" with the clock. He or she can time the period with a nap. In recent years both railroads and airlines anchor sleep period so that the circadian rhythm high and have instituted policies that permit napping during work hours. low points correspond to work and sleep periods. Research An excellent description of the value and strategy of napping data indicate that it is important to have the anchor sleep can be found in Gertler et al. (2002) and is quoted below. period occur at a constant time every day. If a driver is going to use anchor sleep, the driver and the company must Research has shown that subjective sleepiness and sleep qual- make sure his or her schedule allows this. (Minors and ity seem to be a function of the total sleep over the course of the day, and not a function of the number or lengths of the naps. Waterhouse, 1981, 1983) In other words, napping can be effective for meeting the daily Anchor sleep is not a substitute for getting a full 8 hours' sleep requirements, but the length of the nap determines sleep during any 24-hour period. Instead, it is a coping mech- whether or not it significantly adds to a short main sleep period. anism meant to keep one's circadian rhythm synchronized to A nap of less than 90 minutes, or one that does not go through a daily schedule. It is important to supplement anchor sleep an entire sleep cycle of slow wave and REM sleep, will not sig- with naps that are sufficient to provide the complete sleep nificantly add to a short main sleep period and may not prevent the onset of fatigue. While a nap of up to 20 minutes may not allotment that we need on a daily basis. This countermeasure compensate for inadequate daily sleep, it may eliminate the per- anchors the sleep cycle. formance manifestations of fatigue for a short period of time. This type of nap is usually unscheduled and results from an uncontrollable sleep pressure or need to sleep. As such, this Caffeine "emergency" nap should be reserved for infrequent use and not be a regular component of an individual's sleep schedule. Our bodies gradually build up a tolerance to repeated con- Scheduled naps of appropriate timing and duration, well inte- sumption of high levels of caffeine (e.g., 5+ cups of coffee per grated into the worker's sleep management program are a bet- day). A frequent coffee drinker may need a higher dose of caf- ter course of action. With all naps the issue of sleep inertia or feine to obtain the same "boost" effect of the more casual cof- hangover is a factor, just as it is with main sleep periods. Nap placement may be key to the consequences of nap- fee drinker. Therefore, workers who wish to benefit from the ping. The timing of a nap rather than its length has more of alerting effects of caffeine should consume caffeine sparingly an effect on an individual's alertness or performance fol- and "save the boost effect" until they really need it (e.g., during