Aitor Coca

Salivary and serum cortisol levels during recovery from intense exercise and prolonged, moderate exercise

The aim of this study was to compare serum (SERc) and salivary cortisol (SALc) responses during recovery from two different exhaustive exercises to determine peak cortisol sampling time and the agreement between SERc and SALc levels. Twelve healthy men underwent a maximal treadmill graded exercise to exhaustion (MEx) and a prolonged, submaximal cycle exercise in the heat for 90 min (PEx) while SERc and SALc samples were taken in parallel at baseline, end of exercise, and 15 min intervals over one hour of recovery. MEx and PEx significantly increased SERc and SALc levels (p < 0.01) while absolute SERc levels were approximately 7-10 folds higher than SALc. SERc and SALc showed highly positive correlation (R = 0.667-0.910, p < 0.05) at most sampling times and only a few individual values were out of 95% limit of agreement when analyzed by Bland-Altman plots. However, peak SERc levels (MEx: 784.0±147, PEx: 705.5±212.0 nmol · L−1) occurred at 15 min of recovery, whereas peak SALc levels (MEx: 102.7±46.4, PEx: 95.7±40.9 nmol · L−1) were achieved at the end of exercise in MEx and PEx. The recovery trend of SERc and SALc also differed following MEx and PEx. Activity of 11β-hydroxysteroid dehydrogenase type 2 enzymes may be suppressed following MEx compared to PEx. In conclusion, sampling for peak SERc and SALc levels should take into account their evolution and clearance characteristics as well as type of exercise performed, whereas SALc appeared to be a more sensitive marker than SERc for the measurement of cortisol responses during exercise recovery.

Comparison of different cooling regimes within a shortened liquid cooling/warming garment on physiological and psychological comfort during exercise.

The aim of this study was to compare the effectiveness of different cooling regime intensities to maintain physiological and subjective comfort during physical exertion levels comparable to that engaged in during extravehicular activities (EVA) in space. We studied eight subjects (six males, two females) donned in our newly developed physiologically based shortened liquid cooling/warming garment (SLCWG). Rigorous (condition 1) and mild (condition 2) water temperature cooling regimes were compared at physical exertion levels comparable to that performed during EVA to ascertain the effectiveness of a lesser intensity of cooling in maintaining thermal comfort, thus reducing energy consumption in the portable life support system. Exercise intensity was varied across stages of the session. Finger temperature, rectal temperature, and subjective perception of overall body and hand comfort were assessed. Finger temperature was significantly higher in the rigorous cooling condition and showed a consistent increase across exercise stages, likely due to the restriction of heat extraction because of the intensive cold. In the mild cooling condition, finger temperature exhibited an overall decline with cooling, indicating greater heat extraction from the body. Rectal temperature was not significantly different between conditions, and showed a steady increase over exercise stages in both rigorous and mild cooling conditions. Ratings of overall comfort were 30% higher (more positive) and more stable in mild cooling (p<0.001). The mild cooling regime was more effective than rigorous cooling in allowing the process of heat exchange to occur, thus maintaining thermal homeostasis and subjective comfort during physical exertion.

Physiological Evaluation of Cooling Devices in Conjunction With Personal Protective Ensembles Recommended for Use in West Africa

OBJECTIVE Cooling devices (CDs) worn under personal protective equipment (PPE) can alleviate some of the heat stress faced by health care workers responding to the Ebola outbreak in West Africa. METHODS Six healthy, young individuals were tested while wearing 4 different CDs or no cooling (control) under PPE in an environmental chamber (32°C/92% relative humidity) while walking (3 METs, 2.5 mph, 0% grade) on a treadmill for 60 minutes. Exercise was preceded by a 15-minute stabilization period and a 15-minute donning period. RESULTS The control condition resulted in a significantly higher rectal temperature (Tre) at the end of the exercise than did all CD conditions (CD1, P=0.004; CD2, P=0.01; CD3, P=0.000; CD4, P=0.000) with CD1 and CD2 resulting in a higher Tre than CD3 and CD4 (P<0.05). The control condition resulted in a higher heart rate (HR) at the end of exercise than did the CD3 (P=0.01) and CD4 (P=0.009) conditions, whereas the HR of the CD1 and CD2 conditions was higher than that of the CD3 and CD4 conditions (P<0.05). Weight loss in the control condition was higher than in the CD3 (P=0.003) and CD4 (P=0.01) conditions. Significant differences in subjective measurements of thermal stress were found across conditions and time. CONCLUSIONS Use of CDs can be advantageous in decreasing the negative physiological and subjective responses to the heat stress encountered by health care workers wearing PPE in hot and humid environments. (Disaster Med Public Health Preparedness. 2017;11:573-579).

Comparison of Shortened and Standard Liquid Cooling Garments to Provide Physiological and Subjective Comfort During EVA

The shortened liquid cooling/warming garment (SLCWG) developed by the University of Minnesota group was compared with the standard NASA liquid cooling/ventilating garment (LCVG) garment during physical exertion in comfort (24°C) and hot (35°C) chamber environments. In both environmental conditions, the SLCWG was just as effective as the LCVG in maintaining rectal temperature (Tre) in a thermal comfort range; sweat production on the face was less; and subjective perception of overall and local body comfort was higher. The findings indicate that the SLCWG produces the same or greater comfort level as that achieved with the LCVGs total coverage of the body surface.

Informative Value of Temperatures in Different Areas of the Human Body for Correcting Body Thermal Imbalance during Extravehicular Activities

Identification of noninvasive and informative sites on the body reflecting the development of body thermal imbalance during extravehicular activities (EVAs) is highly important for enhancing astronaut safety. Temperature changes were evaluated on several areas of the head (the mastoid fossa (Tmf), the forehead (Tfo), and the cheek (Tch)) and on the fingers (Tfing). Subjects were dressed in a multicompartment liquid cooling/warming garment. Studies I and II consisted of different combinations of hood versus garment cooling or warming imposed across stages; studies III and IV involved sagittally divided cooling or warming regimes with the hood worn (study III) or with the head uncovered (study IV). In studies I and II, Tmf significantly (P < 0.05) differed between stages 2, when the head was cooled and the rest of the body heated, and 3, when the head was heated and the rest of the body cooled. The Tmf changes were consistent with the thermal conditions imposed on the head but not reflective of the developing body heat deficit. In study III, the Tmf at stages 2 and 3 on the right or the left followed the thermal conditions on the ipsilateral side of the body (P < 0.01). In study IV, Tfing showed no significant differences across stages. In studies I–IV, Tfing showed consistent changes across stages (P < 0.05), reflecting the developing body heat deficit. In all studies, there were no significant differences in rectal temperature (Tre) across stages. Tmf and temperatures at other head skin sites did not respond in accordance with the actual intensity of a heat or cold flux from the garment and were not reflective of the overall development of body thermal imbalance. Tfing was a more adequate indicator of initial thermal destabilization and provided information that would be useful for monitoring the thermal balance and comfort during EVAs.