“Float First:” Trapped Air Between Clothing Layers Significantly Improves Buoyancy on Water After Immersion

Approximately 450,000 people drown annually worldwide. The capacity of immersed adults and children to float in clothing is less well understood, but it is possible that air trapped between clothing layers increases buoyancy. Study 1 (n = 24) quantified this buoyancy and the consequence of any buoyancy by measurement of airway freeboard (mouth to water level distance). Study 2 examined the capability of children (n = 29) to float with freeboard used as the outcome measure and is expressed as a percentage of occasions that freeboard was achieved. Buoyancy (Newtons; N) was provided for winter clothing as 105 [+ 12], Autumn/Spring 87 [+ 13], Summer 68 [+ 11]N. Average freeboard was 63 (+ 2) % for winter clothing, 62 (+ 2) % for autumn/spring clothing, 66[+ 2] % for summer clothing, and 15[+ 1] % for the control condition. Children were more buoyant, 95 [+ 17] % freeboard), irrespective of gender, than adults. “Float first” should be advocated

“Float First:” Trapped Air Between Clothing Layers Significantly Improves Buoyancy on Water After Immersion

Approximately 450,000 people drown annually worldwide. The capacity of immersed adults and children to float in clothing is less well understood, but it is possible that air trapped between clothing layers increases buoyancy. Study 1 (n = 24) quantified this buoyancy and the consequence of any buoyancy by measurement of airway freeboard (mouth to water level distance). Study 2 examined the capability of children (n = 29) to float with freeboard used as the outcome measure and is expressed as a percentage of occasions that freeboard was achieved. Buoyancy (Newtons; N) was provided for winter clothing as 105 [+ 12], Autumn/Spring 87 [+ 13], Summer 68 [+ 11]N. Average freeboard was 63 (+ 2) % for winter clothing, 62 (+ 2) % for autumn/spring clothing, 66[+ 2] % for summer clothing, and 15[+ 1] % for the control condition. Children were more buoyant, 95 [+ 17] % freeboard), irrespective of gender, than adults. “Float first” should be advocated

The effects of direct current stimulation on exercise performance, pacing and perception in temperate and hot environments

Background. Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique and has previously been shown to enhance submaximal exercise by reducing rating of perceived exertion (RPE). The present study examined the effects of tDCS on high-intensity self-paced exercise in temperate conditions and fixed followed by maximal exercise in the heat; it was hypothesised performance and RPE would be altered. Methods. Two separate studies were undertaken in which exercise was preceded by 20-minutes of sham tDCS (SHAM), or anodal tDCS (TDCS). Study 1: six males completed a 20-km cycling time trial, on two occasions. Power output (PO), RPE, O2 pulse, and heart rate (HR) were measured throughout. Study 2: eight males completed fixed intensity cycling exercise at 55% of a pre-determined maximal power output (PMax) for 25-minutes before undertaking a time to exhaustion test (TTE; 75% PMax) in hot conditions (33°C), on two occasions. Test duration, heart rate, thermal and perceptual responses were measured. Study specific and combined statistical analyses was undertaken and effect sizes established.. Results. Study 1: mean PO was not improved with the tDCS (197 ± 20 W) compared to SHAM (197 ± 12 W) and there were no differences in pacing profile HR, O2 pulse or RPE (p > .05). Study 2: TTE duration (SHAM 314 ± 334 s cf 237 ± 362 s tDCS), thermal, heart rate and perceptual responses were unchanged by tDCS compared to SHAM (p > .05). When combined, performance in the SHAM trial tended to better than the tDCS. Conclusion. tDCS did not influence cycling performance (study 1) exercise tolerance (study 2) or perception (studies 1&2). tDCS does not appear to facilitate high intensity exercise performance or exercise performance in the heat

Psychophysiology of survival : the impact of psychological strategies on the physiological responses to thermal environments

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Early change in thermal perception is not a driver of anticipatory exercise pacing in the heat

Aim Initial power output declines significantly during exercise in hot conditions on attaining a rapid increase in skin temperature when exercise commences. It is unclear whether this initial reduced power is mediated consciously, through thermal perceptual cues, or is a subconscious process. The authors tested the hypothesis that improved thermal perception (feeling cooler and more comfortable) in the absence of a change in thermal state (ie, similar deep-body and skin temperatures between spray conditions) would alter pacing and 40 km cycling time trial (TT) performance. Method Eleven trained participants (mean (SD): age 30 (8.1) years; height 1.78 (0.06) m; mass 76.0 (8.3) kg) completed three 40 km cycling TTs in standardised conditions (32°C, 50% RH) with thermal perception altered prior to exercise by application of cold-receptor-activating menthol spray (MENTHOL SPRAY), in contrast to a separate control spray (CONTROL SPRAY) and no spray control (CON). Thermal perception, perceived exertion, thermal responses and cycling TT performance were measured. Results MENTHOL SPRAY induced feelings of coolness and improved thermal comfort before and during exercise. Skin temperature profile at the start of exercise was similar between sprays (CON-SPRAY 33.3 (1.1)°C and MENTHOL SPRAY 33.4 (0.4)°C, but different to CON 34.5 (0.5)°C), but there was no difference in the pacing strategy adopted. There was no performance benefit using MENTHOL SPRAY; cycling TT completion time for CON is 71.58 (6.21) min, for CON-SPRAY is 70.94 (6.06) min and for MENTHOL SPRAY is 71.04 (5.47) min. Conclusion The hypothesis is rejected. Thermal perception is not a primary driver of early pacing during 40 km cycling TT in hot conditions in trained participants

Responses to sudden cold-water immersion in inexperienced swimmers following training

BACKGROUND When suddenly immersed in cold water, humans typically exhibit the cold shock response, although training can attenuate hyperventilation. This study extends previous findings by considering the influence of physical activity to maintain buoyancy and subsequent swimming performance. METHODS Six inexperienced swimmers (three men and three women; mean age 22.8) received 1 wk of cold-water head-out immersions (10 x 3 min at 15 degrees C) alongside mental skills training to improve their treading water technique and to control hyperventilation upon immersion. Six inexperienced control swimmers (four men and two women; mean age 21.8) received immersions in temperate water (27 degrees C). Ventilation, brain blood flow velocity, and blood oxygenation were measured during a physiological test in which participants trod water for 150 s. In a subsequent simulated survival test, performance (swimming duration and distance) and perception of effort were recorded. All the tests were in 10 degrees C water with the head out. RESULTS There were significant improvements in the intervention group's ability to suppress rapid increases in respiratory frequency; 62 +/- 24 breaths x min(-1) to 33 +/- 12. The drop in brain blood flow was smaller and more transient than that previously reported due to the hypertensive response associated with treading water. DISCUSSION Inexperienced swimmers could benefit from cold-water habituation combined with mental skills training in order to improve voluntary control over the respiratory portion of the cold shock response as part of learning to tread water. This may improve survival prospects in a real-life emergency scenario such as an overturned boat