Locomotor and diaphragm muscle fatigue in endurance athletes performing time-trials of different durations

Purpose: Fatigue in leg muscles might differ between running and cycling due to inherent differences in muscle activation patterns. Moreover, postural demand placed upon the diaphragm during running could augment the development of diaphragm fatigue. Methods: We investigated quadriceps and diaphragm fatigue in 11 runners and 11 cyclists (age: 29±5years; $\dot{V}$ O2,peak: 66.9±5.5mlmin−1kg−1) by assessing quadriceps twitch force (Q tw) and transdiaphragmatic twitch pressure (P di,tw) before and after 15- and 30-min time-trials (15TT, 30TT). Inspiratory muscle fatigue was also obtained after volitional normocapnic hyperpnoea (NH) where postural demand is negligible. We hypothesized that running and cycling would induce different patterns of fatigue and that runners would develop less respiratory muscle fatigue when performing NH. Results: The reduction in Q tw was greater in cyclists (32±6%) compared to runners (13±8%, p0.05). Conclusion: Different levels of leg muscle fatigue in runners and cyclists could in part be related to the specific muscle activation patterns including concentric contractions in both modalities but eccentric contractions in runners only. Diaphragm fatigue likely resulted from the large ventilatory load which is characteristic for both exercise modalities and which was higher in 15TTs than in 30TTs (+27%, p<0.01) while postural demand appears to be of less importance

Is there a direct chloride cofactor requirement in the oxygen-evolving reactions of photosystem II?

The dark incubation at room temperature of photosystem II (PS II) membrane fragments in a chloride-free medium at pH 6.3 slowly leads to large chloride-restorable and non-restorable O evolution activity losses with time as compared with control samples incubated in the presence of 10 mM NaCl. The chloride requirement in O evolution generated under these conditions reveals a complex interplay among various experimental parameters, including the source of the plant material, the times of incubation, the sample concentration, the chloride concentration, as well as those treatments which are believed to specifically displace chloride from PS II such as alkaline pH pretreatment and NaSO addition. The results indicate that secondary, structural changes within the PS II complex are an important factor in determining the influence of chloride on the O evolution activity and raise the question whether or not chloride ions actually play a direct cofactor role in the water-oxidizing reactions leading to O evolution

Changing role of coral reef marine reserves in a warming climate

Coral reef ecosystems are among the first to fundamentally change in structure due to climate change, which leads to questioning of whether decades of knowledge regarding reef management is still applicable. Here we assess ecological responses to no-take marine reserves over two decades, spanning a major climate-driven coral bleaching event. Pre-bleaching reserve responses were consistent with a large literature, with higher coral cover, more species of fish, and greater fish biomass, particularly of upper trophic levels. However, in the 16 years following coral mortality, reserve effects were absent for the reef benthos, and greatly diminished for fish species richness. Positive fish biomass effects persisted, but the groups of fish benefiting from marine reserves profoundly changed, with low trophic level herbivores dominating the responses. These findings highlight that while marine reserves still have important roles on coral reefs in the face of climate change, the species and functional groups they benefit will be substantially altered