Investigation of rifle marksmanship on simulated targets during thermal discomfort

Marksmanship has been reported to deteriorate during exposure to heat or cold, yet the effect of the resultant thermal strain in isolation of the inflicting thermal stress is not entirely clear. In most studies, the debilitating effects on marksmanship are confounded by an evolving thermal strain (in terms of body heat storage/debt).

Thermal strain (hot and cold) should degrade marksmanship, more with moving targets than with conventional pop-up targets that are deemed less challenging.

The 12 rifle-trained military reservists (7 men and 5 women) were tested on their marksmanship skills using a small arms simulator. Subjects conducted three trials in an environmentally controlled chamber, 1 wk apart in a counter-balanced order. Trial conditions were neutral (N; 22 degrees C), hot (H; 35 degrees C), and cold (C; 5 degrees C), and all were preceded with an immersion in water to chest level to establish thermal strain (for H and C) or to maintain thermal neutrality prior to shooting. Subjects fired a C7 rifle at various targets during sixteen 5-min engagements over 2 h. Targets were presented either as moving in an urban setting or as pop-ups in a lane setting. Body temperatures, heart rate, saliva cortisol concentration, subjective ratings, and measures of marksmanship accuracy and precision were recorded and analyzed using a repeated measures design.

Mean +/- SD of the rectal temperature during the shooting were 36.9 +/- 0.2 degrees C, 37.7 +/- 0.3 degrees C, and 36.8 +/- 0.6 degrees C for N, H, and C, respectively (H > N, C). Corresponding hand temperatures were 31.5 +/- 1.2 degrees C, 35.2 +/- 0.7 degrees C, and 19.4 +/- 3.0 degrees C (H > N > C). These body temperatures were consistent with the subjective indices of heat illness, cold discomfort, and muscle discomfort. Cortisol concentration and perceived exertion were higher during H. Surprisingly, thermal strain did not degrade marksmanship. Instead, some aspects of precision (horizontal displacement) and accuracy (shooting error) were poorer during N compared with H and C.

Deep body temperatures not higher than approximately 37.9 degrees C and not less than 36.4 degrees C (accompanied by hand temperatures of not less than 19 degrees C) do not negatively affect rifle marksmanship performance, even if significant respective sensations of heat and cold are present.