Heat strain at high levels does not degrade target detection and rifle marksmanship.
BACKGROUND
A recent investigation found no degradation in rifle marksmanship due to mild heat strain (up to a 1 degrees C increase in core temperature) even though the subjective sensation of discomfort was significant. The present study was conducted to determine if, and at what level of heat strain would degradation in both target detection and marksmanship (TD&M) occur.


OBJECTIVE
Degradation in TD&M performance is expected in individuals who reach a level of high heat strain.


METHODS
There were 11 subjects (mean +/- SD of 28.9 +/- 6.0 yr, 177 +/- 10 cm, and 81.2 +/- 18.8 kg) who participated in 3 counterbalanced trials: control (CN); heat with hydration (HH); and heat without hydration (HD). Core temperature was increased through a combination of exercise and passive heating over 4 h. Measures of shooting performance every half hour included target detection and engagement times, friend-foe discrimination, and shooting accuracy using a small arms trainer.


RESULTS
All physiological measures and indices indicated that a significantly elevated heat strain was attained during HH and HD compared with CN. Mean heart rates and core temperatures approached 150 bpm and 39 degrees C, respectively, at the end of the heated trials. Aside from minor differences in target detection and identification owing to target type, no detrimental impact on TD&M due to heat strain, whether hydrated or dehydrated, was observed.


CONCLUSIONS
High levels of heat strain do not adversely affect target detection and rifle marksmanship performance, at least for a period of time not exceeding 4 h in a non-threatening environment.
Tikuisis
Peter
P
Human Modelling Group, SMART, Defence R&D Canada-Toronto, Toronto, ON, Canada. Peter.Tikuisis@drdc-rddc.gc.ca
Keefe
Allan A
AA
D000328:Adult; D001831:Body Temperature; D005260:Female; D005389:Firearms; D006339:Heart Rate; D018882:Heat Stress Disorders / Q000150:complications; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D013647:Task Performance and Analysis