Effect of warm-up and precooling on pacing during a 15-km cycling time trial in the heat

PURPOSE:The best way to apply precooling for endurance exercise in the heat is still unclear. Therefore, we analyzed the effect of different preparation regimes on pacing during a 15-km cycling time trial in the heat.METHODS:Ten male subjects completed four 15-km time trials (30°C), preceded by different preparation regimes: 10 min cycling (WARM-UP), 30 min scalp cooling of which 10 min cycling (SC+WARM-UP), ice slurry ingestion (ICE), and ice slurry ingestion + 30 min scalp cooling (SC+ICE).RESULTS:No differences were observed in finish time and mean power output, although power output was lower for WARM-UP than for SC+ICE during km 13-14 (17±16 and 19±14 W, respectively) and for ICE during km 13 (16±16 W). Rectal temperature at the start of the time trial was lower for both ICE (~36.7°C) than both WARM-UP (~37.1°C) conditions and remained lower during the first part of the trial. Skin temperature and thermal sensation were lower at the start for SC+ICE.CONCLUSIONS:The preparation regime providing the lowest body heat content and sensation of coolness at the start (SC+ICE) was most beneficial for pacing during the latter stages of the time trial, although overall performance did not differ

Patching in reversed-phase high-performance liquid chromatographic materials studied by solid-state NMR spectrometry

The distribution of silane chains over the silica gel surface in reversed-phase high-performance liq. chromatog. (RP-HPLC) phases was studied with special attention being paid to surface homogeneity: there might be areas with high coverage and areas with low coverage of silane chains, hence clustering or patching of the silane chains can occur. Two RP phases were studied before and after well conditioned aging, together with 4 silylated silica gels (serving as models). Two solid-state NMR techniques (e.g.,1H-29Si dipolar dephasing 29Si cross-polarization magic angle spinning NMR and 13C spin-lattice relaxation in the rotating frame) were used. For the 4 model compds. with varying degrees of coverage, only differences in the NMR time consts. were obsd. between the maximally covered phase and the 3 less densely covered silica gels. This proves that silane chains on an RP phase with max. coverage are restricted in their mobilities with respect to the less densely packed materials. For the 2 non-aged RP phases, the silane chains are probably homogeneously distributed over the silica gel surface. Further, the non-aged RP phases were compared with their counterparts, aged under well defined exptl. conditions. After aging, no differences were found between the original and the aged phases, now indicating however, that patching had developed upon agein

Telemetry pill versus rectal and esophageal temperature during extreme rates of exercise-induced core temperature change

Core temperature measurement with an ingestible telemetry pill has been scarcely investigated during extreme rates of temperature change, induced by short high-intensity exercise in the heat. Therefore, nine participants performed a protocol of rest, (sub)maximal cycling and recovery at 30 °C. The pill temperature (

Wind cooling during a self-paced cycling time trial

Introduction Wind has been shown to be an effective cooling method during fixed-paced exercise in the heat, decreasing thermal strain and increasing time to fatigue. However, it has been scarcely investigated in what way these observations translate to self-paced performance. So the aim of this experiment was to study how wind cooling affects thermal strain, thermal perception, pacing and performance during a 15 km cycling time trial in strenuous climatic conditions. Methods Ten male subjects performed two 15 km cycling time trials in a climatic chamber set at 28°C and 80% relative humidity. In one of the time trials, a wind tunnel unexpectedly provided head wind (~4 m/s) during the middle part of the race (3-12 km). Conditions (control: CO and wind: WI) were offered in balanced order with at least two days in between. Measurements included rectal temperature (Tre), average skin temperature (Tsk), heart rate (HR), fluid loss, rate of perceived exertion (RPE, each km), thermal sensation (TS, each 5 km), thermal comfort (TC, each 5 km), power output (PO) and finish time. Results WBGT was similar at the start of both trials (26.5±0.08°C) and dropped when wind was applied to 26.0±0.04°C. Overall, subjects had a higher PO in the WI-trial than the CO-trial (246±11 vs. 235±9 W; P<0.01), leading to a 75±24 s faster finish time. Per kilometer, PO differences between conditions were detected from km 4 to 14. These differences were largest in km 4 and km 11-14 (14-19 W). Tre was similar for CO and WI during each kilometer of the trial. However, wind application induced a clear difference in Tsk from km 4 to 15, being maximally 1.98±0.16°C lower for WI than for CO (km 12). This was reflected in lower RPE values during km 5-13 and improved TS and TC values at the 5 and 10 km mark of the WI-trial. HR was lower during km 10-15 of WI (about 4-6 bpm). No differences in fluid loss and fluid ingestion were observed. Discussion Despite a nearly similar WBGT value, wind application during self-paced exercise in a warm humid environment substantially reduced thermal strain and improved performance. Wind instantly induced a decrease in Tsk, attenuation of RPE and increase in power output. The higher PO was maintained throughout the wind interval at similar or lower Tre and HR values than during the CO-trial, with subjects feeling less exerted, cooler and more comfortable. This may have led to the slightly increased power profile the last 5 km of the WI-trial (even though wind stopped blowing at 12 km), while PO in the CO-trial was not increased until the final kilometer. In conclusion, wind is an effective tool to provide immediate and constant benefits in thermal perception and performance during self-paced exercise in the heat

Effects of wind application on thermal perception and self-paced performance

Physiological and perceptual effects of wind cooling are often intertwined and have scarcely been studied in self-paced exercise. Therefore, we aimed to investigate (1) the independent perceptual effect of wind cooling and its impact on performance and (2) the responses to temporary wind cooling during self-paced exercise. Ten male subjects completed four trials involving 15 min standardized incremental intensity cycling, followed by a 15-km self-paced cycling time trial. Three trials were performed in different climates inducing equivalent thermal strain: hot humid with wind (WIND) and warm humid (HUMID) and hot dry (DRY) without wind. The fourth trial (W3-12) was equal to HUMID, except that wind cooling was unexpectedly provided during kilometers 3–12. Physiological, perceptual and performance parameters were measured. Subjects felt generally cooler during the WIND than the HUMID and DRY trials, despite similar heart rate, rectal and skin temperatures and a WBGT of ~4 °C higher. The cooler thermal sensation was not reflected in differences in thermal comfort or performance. Comparing W3-12 to HUMID, skin temperature was 1.47 ± 0.43 °C lower during the wind interval, leading to more favorable ratings of perceived exertion, thermal sensation and thermal comfort. Overall, power output was higher in the W3-12 than the HUMID-trial (256 ± 29 vs. 246 ± 22 W), leading to a 67 ± 48 s faster finish time. In conclusion, during self-paced exercise in the heat, wind provides immediate and constant benefits in physiological strain, thermal perception and performance. Independent of physiological changes, wind still provides a greater sensation of coolness, but does not impact thermal comfort or performance

Limitations of temperature measurement in the aural canal with an ear mould integrated sensor

Aural canal temperature measurement using an ear mould integrated sensor (

Non-invasive continuous core temperature measurement by zero heat flux

Reliable continuous core temperature measurement is of major importance for monitoring patients. The zero heat flux method (ZHF) can potentially fulfil the requirements of non-invasiveness, reliability and short delay time that current measurement methods lack. The purpose of this study was to determine the performance of a new ZHF device on the forehead regarding these issues. Seven healthy subjects performed a protocol of 10 min rest, 30 min submaximal exercise (average temperature increase about 1.5 °C) and 10 min passive recovery in ambient conditions of 35 °C and 50% relative humidity. ZHF temperature (

Patching in reversed-phase high-performance liquid chromatographic materials studied by solid-state NMR spectrometry

The distribution of silane chains over the silica gel surface in reversed-phase high-performance liq. chromatog. (RP-HPLC) phases was studied with special attention being paid to surface homogeneity: there might be areas with high coverage and areas with low coverage of silane chains, hence clustering or patching of the silane chains can occur. Two RP phases were studied before and after well conditioned aging, together with 4 silylated silica gels (serving as models). Two solid-state NMR techniques (e.g.,1H-29Si dipolar dephasing 29Si cross-polarization magic angle spinning NMR and 13C spin-lattice relaxation in the rotating frame) were used. For the 4 model compds. with varying degrees of coverage, only differences in the NMR time consts. were obsd. between the maximally covered phase and the 3 less densely covered silica gels. This proves that silane chains on an RP phase with max. coverage are restricted in their mobilities with respect to the less densely packed materials. For the 2 non-aged RP phases, the silane chains are probably homogeneously distributed over the silica gel surface. Further, the non-aged RP phases were compared with their counterparts, aged under well defined exptl. conditions. After aging, no differences were found between the original and the aged phases, now indicating however, that patching had developed upon agein