Comparison of rectal and tympanic thermometry during exercise.

ABSTRACT

Background. Heat-related deaths are among the most preventable injuries in athletics. We sought to examine two methods of monitoring body temperature during exercise as a means of preventing heat-related illnesses.

Methods. Ten adult subjects exercised in hot, humid conditions while body temperature was monitored by rectal (Tre) and tympanic (Tty) thermometry.

Results. Our results indicate that increase in Tty was significantly greater than increase in Tre during exercise. However, rectal temperatures continued to increase after exercise cessation and peak temperatures were not significantly different. Temperature readings of the two devices during exercise had a strong correlation. There was a poor correlation between the two methods of measurement in the recovery phase.

Conclusions. Tympanic thermometry is reliable for monitoring changes in body temperature during exercise. This could be valuable for monitoring individuals during long exercise in an effort to prevent heat exhaustion or heat stoke.

**********

HEAT-RELATED ILLNESS continues to be a major concern for athletes in selected regions of the United States. In fact, heat-related deaths among American football participants occur at a rate of more than 1 death per year (Table 1). (1) These figures do not include other sports such as soccer, track, and wrestling. In an effort to prevent potential catastrophic results from the chain of physiologic events associated with elevated core temperature, sports medicine associations on both the national and state levels have issued position statements and/or guidelines regarding exercise and competition in extreme environmental conditions. (2-6) Athletic deaths attributed to heat-related illness have decreased significantly since the guidelines were introduced in the mid-1970s. (7,8) These preventive measures include close monitoring of ambient temperature and relative humidity, as well as monitoring loss of body weight related to hydration levels. Game and practice schedules are to be altered as conditions dictate t o reduce thermal stress (Table 2). The guidelines also address the role of physical conditioning, acclimatization, and prudent clothing selection in regard to thermoregulation.

Human thermoregulation involves two closely related physiologic dimensions: core temperature and level of hydration. With this in mind, an adjunct to monitoring weather conditions and weight loss may be to monitor changes in body temperature during exercise. This could certainly help to identify individuals who are approaching risk of heat exhaustion or heat stroke. Differentiating between heat stroke and heat exhaustion can be difficult. Symptoms of both conditions include headache, nausea, vomiting, vertigo, and malaise (Table 3). Classic presentation of heat stroke includes warm and dry skin, but many victims of exertional heat stroke will have sweat-soaked clothing and skin. The critical clinical indicators of heat stroke involve acute neurologic disability and core temperature of 42[degrees]C or more. (9) The current standard of core temperature measurement in athletes is rectal temperature, though this technique does not lend itself to casual use during athletic participation. The best method of measuri ng core temperature in an athletic arena has been debated in the literature.

The American College of Sports Medicine recommends the use of rectal thermometry in anyone suspected of having heat illness or hypothermia. (2) Indeed, sports medicine texts concerning heat illness during exercise use rectal temperature as a reference point. (8,10,11) However, because of its invasive nature and long equilibration time, rectal thermometry may not be suited to monitoring temperature in active, unrestrained subjects. Rectal thermometry is generally considered to be safe, though it is not entirely without risks. These risks include perforation, infection, and thermometer breakage. (Electric temperature sensors are preferred to mercury-in-glass thermometers for subjects who are exercising.) In addition, practitioners and/or athletes may refuse to comply because of modesty, lack of privacy, or social customs. (12) Other investigators point to the lag associated with rectal thermometry and suggest that this method is unreliable when monitoring rapidly changing core temperatures. (13-17)

Our study was initiated in an effort to find an alternative to rectal thermometry in athletic participants. We also wanted to identify a reliable method of monitoring body temperature during exercise as a means of preventing heat-related illnesses. Benzinger (18) found that tympanic temperature measurements provide a reliable measurement of core temperature, and tympanic thermometry has proven to be reliable in febrile conditions. (17,19,23) Little information regarding tympanic thermometry and exercise is available in the literature. This study was intended to measure the efficacy of infrared tympanic thermometry in monitoring changes in body temperature in humans during exercise and recovery. Of great interest to us was the correlation between tympanic and rectal temperatures during exercise and during recovery from exercise. We chose to have the subjects exercise in a hot and humid (70% relative humidity) environment in an effort to more closely represent a high-risk athletic environment.

METHODS

Subjects

Ten subjects (6 male, 4 female) participated in this study. The subjects' average age was 28 years (range, 22 to 35), and all were physically active and generally healthy. Potential subjects were rejected if positive for a history of heat illness, recent surgical procedure, exercise-induced asthma, high blood pressure, cardiac related problems, or pregnancy. The institutional review board at Grandview Hospital and Medical Center approved this study on human subjects. Each subject provided written informed consent before testing.

Protocol

A testing room was heated to 32[degrees[C (89.6[degrees]F), and humidity levels were increased to a wet bulb temperature of 27.5[degrees]C (81.5[degrees]F) (relative humidity ~70%). Environmental conditions were monitored with a WibGet Heat Stress Monitor (Rueter-Stokes, Twinsburg, Ohio). Rectal temperatures were monitored throughout the exercise protocol with a Blanketrol Hypo-Hyper Temperature Control Unit (Cincinnati Sub Zero, Cincinnati, Ohio) via a flexible rectal probe inserted 10 cm. The probe was held in place with tape applied to the subject's shorts. Tympanic temperature was measured with the Thermoscan Pro-1 tympanic thermometer (San Diego, Calif) in the rectal equivalent mode. In this mode, the device uses an algorithm to convert tympanic temperature to the "rectal equivalent." A single investigator performed all tympanic measurements during this study with an upward and backward tug applied to the pinna as recommended. (24) Initial body temperature measurements were taken for both Tty and Tre before the exercise protocol was started.

The subject exercised on a stationary stair climber (Stairmaster 4000PT, Kirkland, Wash) at self-selected intensity. (Each subject was encouraged to exercise at an aerobically challenging pace.) Water was provided ad libitum, and temperature measurements were recorded every 5 minutes. The subject continued exercise until Tre increased 1.5[degrees]C. At this point, the exercise was stopped, and the subject remained in the hot environment for an additional 10 minutes. The subject was then moved to a cooler environment (21[degrees]C [69.8[degrees]F]). The rectal probe remained in place for continued monitoring until Tre returned to within 1.0[degrees]C of initial measurement.

Statistical Analysis

Pearson correlation coefficients were used to assess the strength of association between the two temperature measurement methods during and after exercise. Student's t test was used to compare rectal and tympanic temperatures at selected points in the exercise protocol. Measurement of agreement was calculated by plotting the difference against the mean as described by Bland and Altman. (25) Level of significance was set at P<.05.

RESULTS

Each subject completed the test protocol with no adverse affects. The average exercise time was 36.5 minutes, followed by a 10-minute rest period in the hot environment, and an additional rest period in a cool environment (time was [DELTA] Tre dependent). Average time required to complete test protocol was 61 minutes.

Preexercise Tty was 37.3[degrees]C; Tre was 37.3[degrees]C. These temperatures were measured in the test room before initiation of exercise protocol, and at 5-minute intervals during the exercise and recovery periods. The correlation between the two methods of temperature measurement during exercise was strong (r= 0.98; P<. 0001) (Fig 1). During exercise, the Tty increased 1.9[degrees]C, while Tre increased 1.5[degrees]C; this difference was statistically significant (P = .03). However, the difference between peak temperatures (39.2[degrees]C Tty, 38.9[degrees]C Tre) was not significantly different (P> .05). We refer to peak temperature because upon completion of the exercise protocol, the Tty began an immediate decrease, but the Tre continued to increase for 5 to 10 minutes after exercise (average [DELTA] + 0.1[degrees]C). The Tty returned to preexercise levels shortly after the subject was moved to the cooler environment. The Tre failed to show a similar pattern; in fact, the Tre was virtually the same at t he end of the rest period in heat as it was at the end of the exercise period. The Tre did decline more rapidly in the cool environment, dropping 0.5[degrees]C in an average time of 15 minutes. There was no significant correlation between the two methods of measurement during recovery phase (decreasing temperatures) (P>.05).

A plot of the analysis of agreement comparing the difference between infrared tympanic membrane and rectal temperature against the mean change measured by the two methods illustrates the level of agreement (Fig 2). The mean difference was 0.36[degrees]C. The limits of agreement, set at [+ or -] 1.5 SD, ranged from 0.96 to -0.25. The 95% confidence interval was 1.76 to -0.42.

DISCUSSION

Our findings indicate that before exercise rectal and tympanic temperatures are closely correlated. This finding supports several studies that found tympanic thermometry to be reliable for measuring body temperature. (20-24,26) Many of the early tympanic temperature studies were done with thermistors carefully placed on the tympanic membrane. This procedure does have inherent risks involved and is not recommended for use in the field. In the mid-1980s, development of an infrared tympanic thermometer enabled the practitioner to measure energy emitted by the tympanic membrane while avoiding contact with the membrane. This noninvasive method of tympanic membrane temperature measurement is accomplished in about 3 seconds and has been shown to be reliable when done according to manufacturer's standards by an individual trained in its use. (16,24)

We found only two studies that compared tympanic and rectal thermometry during exercise in extreme heat, and one of these was conducted on a sheep model. (23,27) The authors concluded that both rectal and tympanic thermometry are reliable indicators of core temperature during exercise in extreme conditions. Again, our findings support this conclusion, since tympanic and rectal temperatures increased at similar, predictable rates. Our results indicate a strong correlation coefficient for the two methods of measuring temperature changes during exercise. An analysis of agreement demonstrated the relatively small differences between tympanic and rectal temperature measurements during exercise (less than 1[degrees]C). We believe that this difference, when closely correlated with clinical findings, is acceptable for monitoring changes in body temperature during exercise.

Conversely, we found a weak correlation between Tty and Tre during recovery from exercise. The Tre decreased in a predictable pattern, though at a much slower rate than was shown by Tty. This finding is consistent with previous studies of rapidly changing body temperature associated with exercise. In comparisons of esophageal thermometry (Tes) and Tty, Deschamps et al (28) found that Tty declined more slowly than Tes after exercise, and they considered this difference unacceptable when monitoring rapidly changing body temperature. Two earlier studies that compared Tes to Tre and Tty concluded that Tty, while lagging slightly behind Tes, is a more accurate predictor of Tes during recovery from exercise than is Tre. (17,27) Rectal temperature lag phenomenon was discussed in both of these papers (17,27) and was explained by the presence of feces and relatively poor blood supply to the rectum. (27)

Whereas our study was concerned with change in temperature during exercise, postexercise temperature comparisons are more common in sports medicine literature. Three separate investigators comparing postmarathon Tre with Tty noted the potential importance of rectal temperature lag in rapidly changing environmental conditions and the attractiveness of a noninvasive rapid assessment device for measuring body temperature. (3,12,28) In two of the studies, (12,29) investigators found moderate correlation between the two methods of measurement (r= .68, r= .69). Neither study, however, endorsed tympanic thermometry for postmarathon temperature measurement, since Tty was consistently lower than Tre when measured in the recovery tent. (12,29) Conversely, Ash and Brengelmann (30) described the successful use of inner ear canal temperature measurement at a major marathon event for 7 years. Careful measurement, with an emphasis on technique, correlated closely with clinical condition. The authors believed that the phenomenon of rectal temperature lag may deserve more attention.

Ash et al (13,14) noted this rectal lag phenomenon in studies of Tre, Tty, and Tes while moving subjects between warm and cool water baths. Analysis of tympanic thermometry and esophageal temperatures indicates a high correlation during periods of rapid change. Rectal temperatures did not show similar agreement. In fact, the authors reported shivering in subjects undergoing rapid cooling after hyperthermia; this with Tes of 98.4[degrees]F while Tre remained above 101[degrees]F. (13,14) This shivering was attributed to the low Tes, not to a "paradoxical shivering" phenomenon.

This apparent paradox may be observed in a runner who stops running or collapses. Running premises a tremendous increase in the metabolic rate, producing up to 25 times as much heat as when resting. (31) The increased metabolic rate is principally responsible for increases in core temperature. (22) Upon cessation of exercise (or collapse), muscular activity slows, and heat production drops considerably. However, the athlete's wet skin, clothing, and hair continue to allow for significant heat loss through evaporation. (15) The result is a rapidly decreasing core temperature that may not be shown by rectal temperatures because of significant thermal inertia at that site. (17) If rectal temperatures fall to show decreasing core temperatures during rapid cooling, inadvertent hypothermia becomes a risk. (14) Also, elevated rectal temperatures may launch serial treatments when the subject's actual core temperature has returned to an acceptable range.

Heat stroke victims have had temperatures in the range of 40[degrees] to 47[degrees]C, (28,12,13) though not all athletes with 40[degrees]C core temperature have heat stroke. None of our subjects exceeded 39.7[degrees]C by either measurement method; none had collapse with thermoregulatory failure. Thus, the recovery cool-down in our study followed a predictable pattern. Since the subjects in our investigation did not approach thermoregulatory failure, we make no assumptions regarding recovery in individuals who have had thermoregulatory failure.

CONCLUSIONS

Infrared tympanic thermometry is reliable for measuring changes in body temperature during long exercise. Therefore, this device may enable practitioners to accurately monitor changes in body temperature during endurance training and competition. Individuals at risk for heat-related injuries (Table 4) may be identified and monitored to prevent escalation of thermal stress to the point at which heroic measures are necessary. Elevation in body temperature should be closely correlated with clinical findings to reduce episodes of serious heat illness.

Future studies may establish normative data for temperature changes in athletes who are participating in practice or games in various weather conditions. Investigators may also address the efficacy of tympanic thermometry in sideline assessments of athletes with early stages of heat illness.

The limitations of this study are as follows: (1) We measured temperature changes during a long exercise program. We did not examine the performance of the tympanic thermometer during intermittent exercise common to football, soccer, and other sports. (2) We used the tympanic thermometer in the "rectal equivalent" mode. This introduced an algorithm programmed into the device that did not allow us to use raw data for tympanic temperature. This mode was used to provide similar numbers for comparison.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

TABLE 1

Fatalities From Heat Stroke in "American" Football (1, 7)

1964-1973  39
1974-1983  15
1988-1997  12
1998-2001  13
TABLE 2

Guidelines for Exercising in the Heat (2-5, 9, 10)

Dry Bulb *                     Relative              Wet Bulb
Temperature                    Humidity             Temperature

26[degrees]-32[degrees]C         <70%        16[degrees]-19[degrees]C
(80[degrees]-90[degrees]F)                  (61[degrees]-66[degrees]F)


26[degrees]-32[degrees]C         >70%        19[degrees]-22[degrees]C
(80[degrees]-90[degrees]F                   (67[degrees]-72[degrees]F)



32[degrees]38[degrees]C          <70%        23[degrees]-25[degrees]C
(90[degrees]-100[degrees]F)                 (73[degrees]-77[degrees]F)

32[degrees]-38[degrees]C         >70%       [greater than or equal to]
(90[degrees]-100[degrees]F)                       25.5[degrees]C
                                            ([greater than or equal to]
> 38[degrees]C               Regardless of        >25.5[degrees]C
(>100[degrees]F                humidity          (> 78[degrees]F)




Dry Bulb *
Temperature                            WBGT +

26[degrees]-32[degrees]C           <18[degrees]C
(80[degrees]-90[degrees]F)         (64[degrees]F)


26[degrees]-32[degrees]C      18[degrees]-23[degrees]C
(80[degrees]-90[degrees]F    (65[degrees]-73[degrees]F)



32[degrees]38[degrees]C
(90[degrees]-100[degrees]F)

32[degrees]-38[degrees]C      23[degrees]-28[degrees]C
(90[degrees]-100[degrees]F)  (73[degrees]-82[degrees]F)

> 38[degrees]C                28[degrees]-30[degrees]C
(>100[degrees]F              (82[degrees]-87[degrees]F)

                                   31.1[degrees]C
                                   (88[degrees]F)

Dry Bulb *                              Heat
Temperature                             Index

26[degrees]-32[degrees]C
(80[degrees]-90[degrees]F)


26[degrees]-32[degrees]C      30[degrees]-35[degrees]C
(80[degrees]-90[degrees]F    (85[degrees]-95[degrees]F)



32[degrees]38[degrees]C      35[degrees]-40.5[degrees]C
(90[degrees]-100[degrees]F)  (95[degrees]-105[degrees]F)

32[degrees]-38[degrees]C
(90[degrees]-100[degrees]F)

> 38[degrees]C
(>100[degrees]F

                                    >41[degrees]C
                                  (>105[degrees]F)

Dry Bulb *
Temperature                               Comment

26[degrees]-32[degrees]C     Watch overweight/unconditioned
(80[degrees]-90[degrees]F)   athletes closely. Also watch
                             athletes with history of heat
                             illness.
26[degrees]-32[degrees]C     Moderate risk for hyperthermia.
(80[degrees]-90[degrees]F    Constant and careful supervision of
                             athletes. Ten-minute rest in shade
                             every hour with additional water ad
                             libitum.
32[degrees]38[degrees]C      Increasing risk for hyperthermia.
(90[degrees]-100[degrees]F)  Continue close supervision. Provide
                             rest/drinks every 30 minutes.
32[degrees]-38[degrees]C     High risk. Suspend practice until a
(90[degrees]-100[degrees]F)  cooler hour. Shorts and T-shirts
                             only; no football pads, no tights.
> 38[degrees]C               Any activity should be carefully
(>100[degrees]F              controlled. Use extreme caution
                             with these guidelines.
                             Advisable not to participate in any
                             training session or competition.

* Dry bulb must always be regarded in conjunction with relative
humidity.

+ WBGT = Web bulb globe temperature; this combines dry bulb, wet bulb,
radiant heat, and air movement.
TABLE 3

Evaluation and Initial Care of Heat Illness (2-6, 9)

                      Signs and Symptoms

Heat cramps      Painful cramping of abdomen and
                 extremities caused by intense
                 prolonged exercise in the heat.
                 Associated with fluid/electrolyte
                 imbalance.

Heat syncope     Weakness, fatigue, thirst, and
                 fainting due to exercise in heat
                 and fluid/electrolyte imbalance.
                 Predisposes athlete to heat
                 stroke.

Heat exhaustion  Profound weakness, exhaustion,
                 tremendous thirst, nausea,
                 vomiting, headache, dizziness,
                 profuse sweating, elevated body
                 temperature (<40[degrees]C). Also,
                 chills, hyperventilation, loss of
                 coordination, irritability,
                 syncope, confusion. Acute stages
                 may include low blood pressure and
                 elevated pulse rate.

Heat stroke      As in heat exhaustion, but also
                 neurologic disability, signs of
                 central nervous system
                 dysfunction, and elevated body
                 temperature (>41[degrees]C).
                 Contrary to previous beliefs,
                 victims of exertional heat stroke
                 may present with perspiration, not
                 dry skin. Seizure and coma are
                 possible.




                            Treatment

Heat cramps      Stop exercise. Replace fluids and
                 electrolytes orally.




Heat syncope     Stop exercise. Move to cooler
                 environment, begin oral
                 replacement of fluids and
                 electrolytes.


Heat exhaustion  Stop exercise. Move to cooler
                 environment; remove equipment and
                 cool victim with fanning and ice
                 packs/cool water showers. Athlete
                 should not return to activity for
                 remainder of that day (minimum).





Heat stroke      THIS IS A MEDICAL EMERGENCY. DELAY
                 COULD BE FATAL. Remove wet or
                 heavy clothing. Begin whole body
                 cooling with water immersions,
                 vigorous fanning, ice packs
                 applied to neck, groin, and
                 underarm. Do not use methods that
                 inhibit other medical procedures
                 such as cardiopulmonary
                 resuscitation. Continue to monitor
                 body temperature until emergency
                 medical service arrives; do not
                 cool below 39[degrees]C.
TABLE 4

Factors That May Increase Risk of Heat Illness (2,9)

     Behavior Related                Illness/Medical Condition

Obesity                           Previous history of heat stroke
Poor fitness level                Illness including fever, diarrhea,
                                  or vomiting
Poor diet                         Respiratory tract infection
Poor fluid intake                 Cardiovascular disease
Insufficient rest/sleep           Sunburn
Inappropriate clothing selection  Dehydratio
Inappropriate acclimatization
High motivation
Age (elderly/child)
Athlete
Military recruit

     Behavior Related             Medications/Toxins

Obesity                           Diuretics
Poor fitness level                Antidepressants

Poor diet                         Antihistamines
Poor fluid intake                 Salicylates
Insufficient rest/sleep           Ethanol
Inappropriate clothing selection  Hallucinogens
Inappropriate acclimatization
High motivation
Age (elderly/child)
Athlete
Military recruit

References

(1.) Mueller FO, Diehl JL: Annual Survey of Football Injury Research: 1931-2001. Waco, Tex, American Football Coaches Association, 2002. Available at: http://www.unc.edu/depts/nccsi/SurveyofFootballInjuries.htm

(2.) Armstrong LE, Epstein Y, Greenleaf JE, et al: American College of Sports Medicine position stand. heat and cold illnesses during distance running. Med Sci Sports Exerc 1996; 28:i-x

(3.) National Athletic Trainers' Association: Position statement: fluid replacement for athletes. J Athletic Training 2000; 35:2212-2224

(4.) Missouri State High School Athletic Association: Recommended guidelines for avoiding heat-related problems during practice sessions and athletic contests. MSHSAA Sports Med Manual, 1997

(5.) Prevention of heat illness. 1997 NCAA Sports Medicine Handbook. Overland Park, Ks, National Collegiate Athletic Association, 1997, pp 16-17

(6.) Mandatory Regulations. Bulletin FT98-1, Columbus, Ohio High School Athletic Association, 1998

(7.) Murphy R: Heat illness in the athlete. Am J Sports Med 1984; 12:258-261

(8.) Reider B, Belniak R, Miller DW: Heat stroke in football. Sports Medicine: The School Age Athlete. Philadelphia, WB Saunders Co, 3rd Ed, 1996, pp 628-629

(9.) Tek D, Olshaker JS: Heat illness. Emerg Med Clin North Am 1992; 10:299-310

(10.) Arnheim DD, Prentice WE: Environmental considerations. Principles of Athletic Training. St. Louis, McGraw-Hill Co, 10th Ed, 2000, pp 263-271

(11.) Booher JM, Thiobdeau GA The body's response to trauma and environmental stress. Athletic Injury Assessment. St. Louis, Mosby-Year Book Inc, 1994, pp 130-140

(12.) Roth RN, Verdile VP, Grollman LJ, et al: Agreement between rectal and tympanic membrane temperatures in marathon runners. Ann Emerg Med 1996; 2:414-417

(13.) Ash CJ, Cook JR, Homer LD: The use of rectal temperature to monitor thermal injury of marathon runners in temperate weather. Mo Med 1990; 87:298-303

(14.) Ash CJ, Cook JR, McMurry TA, et al: The use of rectal temperature to monitor heat stroke. Mo Med 1992; 89:283-287

(15.) Ash CJ, Kashmeery AMS: Heatstroke: marathons to Mecca. 1995 Yearbook of Intensive Care and Emergency Medicine. Vincent JL (ed). New York, Springer-Verlag, 1995, pp 971-981

(16.) Bricknell MCM: An evaluation of infra-red tympanic thermometry for thermal physiology research. J R Army Med Corps 1997; 143:149-152

(17.) Edwards RJ, Belyavin AJ, Harrison MH: Core temperature measurement in man. Aviat Space Environ Med 1978; 49:1289-1294

(18.) Benzinger TH: Tympanic thermometry in surgery and anesthesia. JAMA 1969; 209:1207-1211

(19.) Cork RC, Vaughan RE, Humphrey LS: Precision and accuracy of intraoperative temperature monitoring. Anesth Analg 1983; 62:211-214

(20.) Chamberlin JM, Grandner J, Rubinoff JL, et al: Comparison of a tympanic thermometer to rectal and oral thermometers in a pediatric emergency department. Clin Pediatr 1991; 30:(suppl 4):24-29

(21.) Doyle F, Sehner WJ, Terndrup TE: The effect of ambient temperature extremes on tympanic and oral temperatures. Am J Emerg Med 1992; 10:285-289

(22.) Milewski A, Ferguson KL, Terndrup TE: Comparison of pulmonary artery, rectal and tympanic membrane temperatures in adult intensive care unit patients. Clin Pediatr 1991; 30:(suppl 4):13-16

(23.) Tayeb OS, Marzouki ZMH: Tympanic thermometry in heat stroke: is it justifiable? Clin Physiol Biochem 1989; 7:255-262

(24.) Pransky SM: The impact of technique and conditions of the tympanic membrane upon infrared tympanic thermometry. Clin Pediatr 1991; 30:(suppl 4):50-52

(25.) Bland JM, Altman DG: Satistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307-310

(26.) Terndrup TE, Milewski A: The performance of two tympanic thermometers in a pediatric emergency department. Clin Pediatr 1991; 30:(suppl 4):18-23

(27.) Minard D, Copman L, Dasler AR: Elevation of body temperature in health. Ann NY Acad Sci 1964; 121:12-25

(28.) Deschamps A, Levy RD, Cosio MG, et al: Tympanic temperature should not be used to assess exercise induced hyperthermia. Clin J Sports Med 1992; 2:27-32

(29.) Briner WW: Tympanic membrane vs rectal temperature measurement in marathon runners (Letter). JAMA 1996; 276:194

(30.) Ash CJ, Brengelmann GL: Rectal temperatures in marathon runners (Letter). Ann Emerg Med 1997; 29:693

(31.) Dickenson JG: History and epidemiology: definitions and groups at risk. Hyperthermic and Hypermetabolic Disorders. Hopkins PM, Ellils FR (eds). Cambridge, Cambridge University Press, 1996, pp 3-19

RELATED ARTICLE: KEY POINTS

* Heat illness continues to be a major concern for sports medicine practitioners.

* Tympanic thermometry is reliable for measuring changes in body temperature during long exercise with a minimally invasive technique.

* A temperature lag associated with rectal thermometry may result in decreased accuracy in rapidly changing environmental conditions.

* Monitoring body temperature during exercise may help to prevent occurrence of heat stroke in athletes.

From the Dayton Sports Medicine Institute, Dayton, Ohio.

Reprint requests to Katherine R. Newsham, MA, ATC, Kent State University, 264-D MACC Annex, Kent, OH 44242.