Monitoring Metabolic Status Predicting Decrements in Physiological and Cognitive Performance (2004) / Chapter Skim
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3 Monitoring Overall Physical Status to Predict Performance
3 Monitoring Overall Physical Status to Predict Performance
Pages 53-84
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From page 53... ...
This chapter describes some of the physiological measures used to indicate overall physical status, such as vital signs and temperature, while more specific surrogate measures for muscle fatigue, bone health, and renal and immune function are described in Chapter 4. Although measuring overall physical status in the field presents a challenge, the importance of measuring total daily energy expenditure as an indication of energy intake needs cannot be overemphasized.
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From page 54... ...
Although the normal range is useful in the practice of clinical medicine because there are other opportunities to make judgments about a patient's condition, a more rigorous approach may be needed for a system monitoring the vital functions of a combat service member. A biomarker is a surrogate marker for an important outcome and therefore the choice of biomarkers will have a significant impact on the types and design of the devices and systems that will be needed.
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From page 55... ...
. When disease is present, measures of conventional physiological parameters, such as vital signs (e.g., pulse, temperature, blood pressure, and respiratory rate)
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From page 56... ...
Despite the limitations mentioned above, some conventional measures are valuable for monitoring the physical status of combat service members in field operations; however, more research is needed to validate these measures. The following sections review current physiological monitoring methods and suggest potential uses of these conventional measures for monitoring in the field.
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From page 57... ...
. It also includes the energy cost of involuntary muscular activity, such as shivering and fidgeting (also called spontaneous physical activity)
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From page 58... ...
However, some field devices are based on the direct calorimetry principle and use changes in body heat to predict total energy expenditure. Under basal conditions, both direct and indirect calorimetry give identical results, but due to the cyclical changes in body temperature throughout the day, direct calorimetry cannot be used to assess heat production for periods of less that 24 hours (Jequier and Schutz, 1983)
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From page 59... ...
Subjective Measures. These measures include the direct observation of physical activity by a trained observer or the recording of daily physical activity by the subject.
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From page 60... ...
These measures use some type of mechanical or electronic device (e.g., pedometers, heel- or foot-strike monitors, accelerometers, heart-rate monitors, heat-flow sensors) that measures changes in body movement, heart rate, or body temperature.
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From page 61... ...
Based on a review by Schutz and colleagues (2001) , measuring the total daily energy expenditure of combat service members at the accuracy required by the military will require the development of a motion sensor that is inexpensive and is more convenient and reliable than current pedometers or accelerometers.
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From page 62... ...
Overall Vital Signs With the measurement of pulse rate, respiratory rate, and core body temperature, one could potentially design algorithms to distinguish the following conditions: moderate activity, more intense activity, cold exposure affecting performance, sleep, and systemic inflammatory response (usually due to infection under battlefield conditions if the soldier is otherwise unaware of injury) (see Table 3-1~.
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From page 63... ...
High (> 160) Respiratory Rate Increased Core Body Temperature Normal Intense activity Cold exposure Sleep Systemic inflammatory responses Elevated for a prolonged period Normal to low Lower than awake pulse rate > 90, but usually < 120 Normal to low Lower than awake pulse rate Elevated, but less than intense activity Prolonged elevated respiratory rate may lead to increased core body temperature Low Slightly lower to nonnal Higher Ambient Temperature Although ambient temperature is not a vital sign, it is included here because environmental temperature can have a dramatic effect on the body's ability to maintain physiological stability, especially during exercise (Cheung et al., 2000)
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From page 64... ...
~ . L~m~tec exercise Suspend exercise rapid heart rate, nausea, chilling, headache, and decreased coordination)
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Therefore, a number of physiological parameters may need to be measured to assess thermal strain on the combat service member. Core Body Temperature.
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From page 66... ...
are being used to assess total energy expenditure or physical activity. They also measure a variety of temperature-related variables, such as heat flux, skin temperature, near-body ambient temperature, and galvanic skin response (see Table 3-3~.
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From page 67... ...
based on rectal temperature and heart rate two physiological parameters that adequately depict the combined strain reflected by the cardiovascular and thermoregulatory systems (Moran et al., 1998b)
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In addition to conventional measures, self-assessments have the potential for use as indicators of physical status in the field. Self-assessment measures include: perceived exertion, muscle soreness, muscle pain, ratings of sleep quality, and mood states.
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From page 69... ...
Physiological variables (e.g., heart rate, blood pressure, and cortisol, epinephrine, norepinephrine, muscle and blood lactate, glycogen, oxygen uptake, and ventilatory minute volume) and individual variables (e.g., gender, training state, personality structure, and mood state)
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From page 70... ...
However, since perceptual ratings have some advantages and some studies have showed that they may be more accurate than some physiological measures in predicting performance, a case can be made for developing and employing perceptual models in efforts to monitor distress during training and special operations. Perceived Exertion as a Predictor of Physical Strain and Physical Endurance Although heart rate may be easy to measure, the case has been made that ratings of perceived exertion may be a better measure of the whole physiological situation of an individual.
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From page 71... ...
This case study supports the theoretical views advanced by Borg (1973, 1998) that ratings of perceived exertion are more accurate in predicting endurance performance than measures of heart rate and rectal temperature.
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In the first experiment, 26 healthy male volunteers completed a test of VO2max on one day, and were retested at 80 percent of VO2max on two subsequent days in the walking and running modes. Heart rate, VO2, VC02, minute ventilation, end tidal CO2, and RPE were obtained throughout the exercise.
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From page 73... ...
While most of this research has been carried out with trained athletes, there is no reason to believe that combat service members cannot be trained to perform prolonged efforts in a steady state. There is research evidence that perception of effort, the key component of steady-state energy expenditure, can be an effective tool in applications with military personnel engaged in physical efforts (Horstman et al., 1979; Morgan, 1977, 1981; Morgan et al., 1983; Patton et al., 1977; Soule and Goldman, 19734.
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From page 74... ...
Preferred Intensity Indirect support for the use of perceptual monitoring is offered by Pollock and colleagues (19724. These investigators evaluated the influence of aerobic training in 22 men ranging in age from 30 to 45 years who were randomly assigned to one group that trained at 90 percent of maximum heart rate or a second group that trained at 80 percent of maximum heart rate.
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From page 75... ...
Examples of the physiological changes associated with overtraining include: . · elevated heart rate and blood pressure; · elevated cortisol, creatine kinase, epinephrine, and norepinephrine at rest, along with greater increases in these values following a standard exercise stimulus; and decreased glycogen stores (Costill et al., 1988; Kirwan et al., 1988; Morgan et al., 1987, 1988; O'Connor et al., 1989, 1991; Wilmore and Costill, 19944.
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From page 76... ...
SUMMARY The overall physical status of service members in the field can be evaluated by analyzing either objective physiological measurements or subjective measurements of self-assessments (or assessments by peers)
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From page 77... ...
This may be one of the reasons why studies have shown that self-assessment measurements, such as rating of perceived exertion, are better indicators of physical performance than a single physiological measurement. Whether physiological measurements or self-assessments are used to measure performance, it is critical that before implementation in the field, the biomarker is validated not only in the laboratory, but also in the field.
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From page 78... ...
Med Sci Sports Exerc 32:S442-S449. Horstman DH, Morgan WP, Cymerman A, Stokes J
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From page 79... ...
Med Sci Sports Exerc 35:S284. Knaus WA, Draper EA, Wagner DP, Zimmerman JE.
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Psychophysiology of self-awareness during vigorous physical activity. Res Q Exerc Sport 52:385-427.
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From page 81... ...
Med Sci Sports Exerc 20:408-414. Murray R
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From page 82... ...
Med Sci Sports 5: 128- 131. Sutton JR.
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From page 83... ...
Med Sci Sports Exerc 32:S489-S497. Wilmore JH, Costill DL.
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