AbstractAIM: This study aimed to investigate and compare the physiological, cognitive and cardiovascular responses during explosives ordnance disposal (EOD) type activity in moderate and hot environments whilst wearing an EOD suit and phase change material cooling garments on either the head or torso.
METHODS: Following ethical approval from Coventry University’s Ethical Committee, and after providing informed consent, six healthy, unacclimatised males took part in the study (age: 23 (3) yrs; height: 1.74 (0.05) m; mass: 65.1 (2.0) kg). Each participant underwent 9 sessions performed on separate days consisting of; three pre-trial practice sessions (no EOD suit worn), one trial familiarisation session (light-weight EOD suit worn) and six experimental sessions (consisting of 6 experimental trials; light-weight EOD suit worn), with a week separating the familiarisation and each experimental session. The experimental trials involved six separate conditions, two without cooling (20NC and 40NC), two with head cooling (20HC and 40HC) and two with torso cooling (20TC and 40TC) performed at 20 °C and 40 °C. Conditions were applied in a randomised cross-over type design. Cooling consisted of a phase change material (PCM) scrum cap (head cooling) and PCM vest (torso cooling) donned by the participant prior to wearing a light-weight 3010 Ergotec EOD suit 15 minutes before each trial. Each trial consisted of 6 activity stations; 1. Treadmill walking (4 km·hr-1); 2. Manual loading; 3. Searching and crawling; 4. The postural challenge; 5. Unloaded arm ergometry (60 rev·min-1); 6. The spatial working memory (SWM) test, performed 4 times through to make up 4 cycles lasting a total of 80 minutes per trial.
RESULTS: There was an increase in physiological, perceptual and cardiovascular strain with duration in all conditions. Physiological strain was greater in 40 °C air than in 20 °C air (p<0.001). The heart rate (HR), core temperature (TcP), skin temperature (Tsk), chest temperature (Tc), rate of perceived exertion (RPE), thermal sensation (ThS) and thermal comfort (ThC) responses (excluding Tf) were lowest during the 20TC trial when compared to 20HC and 20NC. At 40 °C, the physiological strain was reduced with both cooling conditions (40HC and 40TC). During 40HC, TcP, Tf, and PhSI, were lowest for upto 60 minutes of activity (3 cycles) when compared to 40NC. 40TC produced the lowest Tsk responses for up to 60 minutes of activity (3 cycles) and Tc responses throughout the 80 minute trial, compared to 40NC and 40HC. The recovery of mean arterial blood pressure (MAP) was not compromised in response to standing at 40 °C, however during both cooling trials within the first cycle at 20 °C MAP did not recover back to the pre-stand response. At 40 °C, HR peaked significantly post-stand and remained greater than that during the pre-stand response. Completion speed of the cognitive spatial working memory test was greatest during the final cycle of activity, (p<0.017).
CONCLUSION: At 20 °C torso cooling created the most benefit when compared to head cooling at reducing the physiological and perceptual strain experienced. At 40 °C, both cooling methods (TC and HC) were effective at lowering the physiological, perceptual and cardiovascular strain when compared to the non-cooling control (40NC). The majority of this benefit was observed within the first hour of activity. It is recommended that the torso cooling garment be used within the light-weight EOD suit to reduce the thermal strain experienced at 40 °C, and that when using the light-weight EOD suit at 20 °C the PCM cooling garments are not required as the physiological strain experienced at this temperature is less than that experienced at 40 °C
|Date of Award||2012|
|Sponsors||NP Aerospace Ltd|
|Supervisor||Doug Thake (Supervisor)|