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. 2017 Oct 9;4(4):420-428.
doi: 10.1080/23328940.2017.1368877. eCollection 2017.

Performance in complex motor tasks deteriorates in hyperthermic humans

Jacob F Piil  1 , Jesper Lundbye-Jensen  1 , Steven J Trangmar  2 , Lars Nybo  1
Affiliations

Performance in complex motor tasks deteriorates in hyperthermic humans

Jacob F Piil et al. Temperature (Austin). .

Abstract

Heat stress, leading to elevations in whole-body temperature, has a marked impact on both physical performance and cognition in ecological settings. Lab experiments confirm this for physically demanding activities, whereas observations are inconsistent for tasks involving cognitive processing of information or decision-making prior to responding. We hypothesized that divergences could relate to task complexity and developed a protocol consisting of 1) simple motor task [TARGET_pinch], 2) complex motor task [Visuo-motor tracking], 3) simple math task [MATH_type], 4) combined motor-math task [MATH_pinch]. Furthermore, visuo-motor tracking performance was assessed both in a separate- and a multipart protocol (complex motor tasks alternating with the three other tasks). Following familiarization, each of the 10 male subjects completed separate and multipart protocols in randomized order in the heat (40°C) or control condition (20°C) with testing at baseline (seated rest) and similar seated position, following exercise-induced hyperthermia (core temperature ∼ 39.5°C in the heat and 38.2°C in control condition). All task scores were unaffected by control exercise or passive heat exposure, but visuo-motor tracking performance was reduced by 10.7 ± 6.5% following exercise-induced hyperthermia when integrated in the multipart protocol and 4.4 ± 5.7% when tested separately (both P < 0.05). TARGET_pinch precision declined by 2.6 ± 1.3% (P < 0.05), while no significant changes were observed for the math tasks. These results indicate that heat per se has little impact on simple motor or cognitive test performance, but complex motor performance is impaired by hyperthermia and especially so when multiple tasks are combined.

Keywords: cognition; cognitive test; core temperature; heat strain; heat stress; hyperthermia; motor performance; task complexity; visuo-motor tracking.

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Figures

Figure 1.
Figure 1.
Illustration of the motor-math protocol of the present study. e.g. to the left an illustration of the visuo-motor tracking task (VMT), where the 5 boxes/targets appears on the screen 1 s before the 12 s tracking begins. The cursor (green line) moves from left to right over the screen (fixed velocity) and the subject is instructed to adjust force on the strain gauge transducer to keep the cursor within the designated box. In the “separate protocol”, this task then repeats 40 times with the position of the boxes randomly changed from trial to trial, whereas in the multipart protocol, the VMT alternates with the MATH_type, MATH_pinch or TARGET_pinch tasks. During VMT, MATH_pinch and TARGET_pinch, subjects used the strain gauge, whereas in the MATH_type the number pad was used (bottom pic, right).
Figure 2.
Figure 2.
VTM during thermoneutral (CON_baseline and CON_norm) and heat (HEAT_baseline and HEAT_hyper) for both separate and multipart protocol. Values are means plus SD for each condition. * Significant different from baseline and CON_norm conditions.
Figure 3.
Figure 3.
MATH_type, TARGET_pinch and MATH_pinch during thermoneutral (CON_baseline and CON_norm) and heat (HEAT_baseline and HEAT_hyper). Values are means plus SD for each condition. * Significant lower task score within condition, $ significant different form CON_norm, ¤ significant different from all baseline and CON_norm.
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