The Effect of Isolated and Combined Application of Menthol and Carbohydrate Mouth Rinses on 40 km Time Trial Performance, Physiological and Perceptual Measures in the Heat

The current study compared mouth swills containing carbohydrate (CHO), menthol (MEN) or a combination (BOTH) on 40 km cycling time trial (TT) performance in the heat (32 °C, 40% humidity, 1000 W radiant load) and investigates associated physiological (rectal temperature (Trec), heart rate (HR)) and subjective measures (thermal comfort (TC), thermal sensation (TS), thirst, oral cooling (OC) and RPE (legs and lungs)). Eight recreationally trained male cyclists (32 ± 9 y; height: 180.9 ± 7.0 cm; weight: 76.3 ± 10.4 kg) completed familiarisation and three experimental trials, swilling either MEN, CHO or BOTH at 10 km intervals (5, 15, 25, 35 km). The 40 km TT performance did not differ significantly between conditions (F2,14 = 0.343; p = 0.715; η2 = 0.047), yet post-hoc testing indicated small differences between MEN and CHO (d = 0.225) and MEN and BOTH (d = 0.275). Subjective measures (TC, TS, RPE) were significantly affected by distance but showed no significant differences between solutions. Within-subject analysis found significant interactions between solution and location upon OC intensity (F28,196 = 2.577; p < 0.001; η2 = 0.269). While solutions containing MEN resulted in a greater sensation of OC, solutions containing CHO experienced small improvements in TT performance. Stimulation of central CHO pathways during self-paced cycling TT in the heat may be of more importance to performance than perceptual cooling interventions. However, no detrimental effects are seen when interventions are combined.

Effects of frost on shaded and exposed spruce and pine seedlings planted in the field

Spruce (Piceaabies L.) and pine (Pinussylvestris L.) seedlings were planted at different positions relative to artificial tree shades. Two sites in northern Sweden known as difficult to regenerate owing to frosts during the growing season were used. No deficiency of soil water was recorded during the growing season and all seedlings experienced similar temperature conditions during night frosts. Exposed seedlings received on clear days 7 h more of direct solar radiation than did shaded seedlings. After the first severe night frost in August, discoloration of needles and a decrease in chlorophyll concentration as well as lowered photosynthetic rates were more pronounced for the exposed seedlings. This was more obvious for spruce than pine seedlings. The differences in radiant load seem to be of ultimate importance for the results observed. It is proposed that photoinhibition and subsequent photooxidation of planted seedlings occur in the field when severe night frosts are followed by clear days with high irradiance.