Self-paced cycling performance and recovery under a hot and highly humid environment after cooling.

AIM: This study investigated the effects of pre- and post-cooling on self-paced time-trial cycling performance and recovery of cyclists exercising under a hot and highly humid environment (29.92 °C-78.52% RH). METHODS: Ten male cyclists performed a self-paced 20-min time trial test (TT20) on a cyclo-ergometer while being cooled by a cooling vest and a refrigerating headband during the warm-up and the recovery period. Heart rate, power output, perceived exertion, thermal comfort, skin and rectal temperatures were recorded. RESULTS: Compared to control condition (222.78 ± 47 W), a significant increase (P<0.05) in the mean power output during the TT20 (239.07 ± 45 W; +7.31%) was recorded with a significant (P<0.05) decrease in skin temperature without affecting perceived exertion, heart rate, or rectal temperature at the end of the TT20. However, pace changes occurred independently of skin or rectal temperatures variations but a significant difference (P<0.05) in the body's heat storage was observed between both conditions. This result suggests that a central programmer using body's heat storage as an input may influence self-paced time-trial performance. During the recovery period, post-cooling significantly decreased heart rate, skin and rectal temperatures, and improved significantly (P<0.05) thermal comfort. CONCLUSION: Therefore, in hot and humid environments, wearing a cooling vest and a refrigerating headband during warm-up improves self-paced performance, and appears to be an effective mean of reaching skin rest temperatures more rapidly during recovery.

[Mechanical properties of collagen membranes used in guided bone regeneration: a comparative study of three models]. / Propriétés mécaniques des membranes de collagène.

OBJECTIVES: The peroperative rupture of a collagen membrane is a potential cause of complications and loss of effectiveness. The purpose of our study was to determine experimentally the mechanical properties (Young modulus, stress-strain curve, tensile strength) of three collagen membranes used in guided bone regeneration. These properties and isotropy were compared on dry and damp samples. METHODS: Standardized samples were tailored in three different membranes (Biomend Extend(®) [Zimmer Dental™], Bio-Gide(®) [Geitslich™] Neonem(®) [TBR™]) in two orthogonal orientations. They were then anchored on an ElectroForce(®) 3230 Instrument (Bose™) traction machine in a dry and wet state (soaking during 10 minutes in saline at 37°C). The strain curves were analyzed to obtain the various mechanical values. RESULTS: No anisotropy was observed. The Biomend Extend(®) membranes were significantly more resistant in dry and damp states than others. DISCUSSION: The mechanical properties of collagen membranes are very different from one to another. Moistening of the membranes, unavoidable in vivo, considerably alters their mechanical properties. This data should be taken into consideration when choosing a membrane.