Sports Bra Pressure: Effect on Body Skin Temperature and Wear Comfort

Sports bras are an essential apparel for active women, but may exert excessive pressure that negatively affects thermoregulation, thermal comfort and wear sensation. This study measures skin temperature changes during short durations of exercise on a treadmill with different bra pressures. The results based on 21 female subjects (age: 27.2 ± 4.5 years old) show that bras with more pressure at the underband or shoulder straps do not cause statistically significant skin temperature changes during exercise (p > 0.05). Nevertheless, compared to the optimal bra fit, significant differences in bra-breast skin temperature are found during running, cooling down and sitting when the bra pressure is increased (p < 0.05), particularly under bra cup (T1) in this study. The FLIR thermal images can visualize the skin temperature changes at abdomen throughout the four activity stages. Subjective sensations of bra thermal comfort, pressure and breast support are assessed. Despite the increased pressure on the shoulders and chest wall, perceptions towards thermal comfort remain unchanged. The perceived pressure comfort and support sensation amongst the 4 bra conditions are comparable. Interestingly, positive sensations of pressure comfort and breast support are perceived with a tight-fitting sports bra during treadmill exercise. High pressures induced by sports bras (>4 kPa) that habitually considered harmful to the human body may not lead to wear discomfort but enhance bra support sensation and a sense of security to the wearers.

Adding sleep restriction to the equation: impact on wildland firefighters' work performance and physiology in hot conditions

PURPOSE

To examine the effects of sleep restriction on firefighters' physical task performance, physical activity, and physiological and perceived exertion during simulated hot wildfire conditions.

METHODS

31 firefighters were randomly allocated to either the hot (n = 18, HOT; 33 °C, 8-h sleep opportunity) or hot and sleep restricted (n = 13, HOT + SR; 33 °C, 4-h sleep opportunity) condition. Intermittent, self-paced work circuits of six firefighting tasks were performed for 3 days. Firefighters self-reported ratings of perceived exertion. Heart rate, core temperature, and physical activity were measured continuously. Fluids were consumed ad libitum, and all food and fluids consumed were recorded. Urine volume and urine specific gravity (USG) were analysed and sleep was assessed using polysomnography (PSG).

RESULTS

There were no differences between the HOT and HOT + SR groups in firefighters' physical task performance, heart rate, core temperature, USG, or fluid intake. Ratings of perceived exertion were higher (p < 0.05) in the HOT + SR group for two of the six firefighting tasks. The HOT group spent approximately 7 min more undertaking moderate physical activity throughout the 2-h work circuits compared to the HOT + SR group.

CONCLUSION

Two nights of sleep restriction did not influence firefighters' physical task performance or physiological responses during 3 days of simulated wildfire suppression. Further research is needed to explore firefighters' pacing strategies during real wildfire suppression.

Effects of pressure exerted on the skin by elastic cord on the core temperature, body weight loss and salivary secretion rate at 35 degrees C

Effects of pressure exerted on the skin by elastic cord on the core temperature, body weight loss and salivary secretion rate were studied under conditions of ambient temperature of 35 degrees C and a relative humidity of 60%. Twelve healthy females, aged 18-23 years, served as subjects. The subjects entered a bioclimatic chamber and rested quietly in a chair for 80 min. Then, skin pressure was exerted by applying elastic cord (8.5 mm wide) to six different skin areas, such as axilla, under-bust, waist, inguines, thighs and ankles. The values of skin pressure by elastic cord ranged from 11.9 to 33.3 g/cm(2). In the control experiment, wrapping with an elastic cord was loosely performed without any skin pressure. Rectal and skin temperatures, body weight loss by sweating and salivary secretion rate were measured throughout the 160 min experimental period. Core temperature increased more significantly under pressure exerted on the skin. Body weight loss by mainly sweating and salivary secretion rate were significantly suppressed under pressure exerted on the skin. We discussed the physiological mechanisms in terms of suppression of central nervous activity as to why significant increase of core temperatures, inhibition of body weight loss mainly by sweating and of salivary secretion rate occurred, and furthermore practical significance of these findings for impairment of digestion, swallowing, vocalizing, defense against disease bacteria and sport activity.