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Background This study determined the effect of repeated sprint training in hypoxia (RSH) in female athletes. Methods Thirty-two college female athletes performed repeated cycling sprints of two sets of 10 × 7-s sprints with a 30-s rest between sprints twice per week for 4 weeks under either normoxic conditions (RSN group; F i O 2 , 20.9%; n = 16) or hypoxic conditions (RSH group; F i O 2 , 14.5%; n = 16). The repeated sprint ability (10 × 7-s sprints) and maximal oxygen uptake ( V ˙ O 2 max ) were determined before and after the training period. Results After training, when compared to pre-values, the mean power output was higher in all sprints during the repeated sprint test in the RSH group but only for the second half of the sprints in the RSN group ( P  ≤ 0.05). The percentage increases in peak and mean power output between before and after the training period were significantly greater in the RSH group than in the RSN group (peak power output, 5.0 ± 0.7% vs. 1.5 ± 0.9%, respectively; mean power output, 9.7 ± 0.9% vs. 6.0 ± 0.8%, respectively; P  < 0.05). V ˙ O 2 max did not change significantly after the training period in either group. Conclusion Four weeks of RSH further enhanced the peak and mean power output during repeated sprint test compared with RSN.

Key message Greatest potential, QTLs for hypoxia and waterlogging tolerance in soybean roots were detected using a new phenotypic evaluation method . Waterlogging is a major environmental stress limiting soybean yield in wet parts of the world. Root development is an important indicator of hypoxia tolerance in soybean. However, little is known about the genetic control of root development under hypoxia. This study was conducted to identify quantitative trait loci (QTLs) responsible for root development under hypoxia. Recombinant inbred lines (RILs) developed from a cross between a hypoxia-sensitive cultivar, Tachinagaha, and a tolerant landrace, Iyodaizu, were used. Seedlings were subjected to hypoxia, and root development was evaluated with the value change in root traits between after and before treatments. We found 230 polymorphic markers spanning 2519.2 cM distributed on all 20 chromosomes (Chrs.). Using these, we found 11 QTLs for root length (RL), root length development (RLD), root surface area (RSA), root surface area development (RSAD), root diameter (RD), and change in average root diameter (CARD) on Chrs. 11, 12, 13 and 14, and 7 QTLs for hypoxia tolerance of these root traits. These included QTLs for RLD and RSAD between markers Satt052 and Satt302 on Chr. 12, which are important markers of hypoxia tolerance in soybean; those QTLs were stable between 2 years. To validate the QTLs, we developed a near-isogenic line with the QTL region derived from Iyodaizu. The line performed well under both hypoxia and waterlogging, suggesting that the region contains one or more genes with large effects on root development. These findings may be useful for fine mapping and positional cloning of gene responsible for root development under hypoxia.

Maintaining root function is crucial for favorable plant growth under flooding. The genetic variation in the response of root development to flooding is unclear, because measurement of root growth is time consuming, especially with numerous lines. To overcome the methodological problems and to reveal the effect of flooding on root development and its genetic variation, we developed a new capillary watering system without soil medium and raised cotyledon-stage seedlings of 92 soybean lines with and without flooding. After 7 days of flooding, dry weights (DW) and root characteristics were determined and the results were compared with those in non-flooded plants. The root DW decreased linearly with decreasing total root length and root surface area, and the degree of damage varied greatly among lines. Short-term flooding inhibited root elongation and branching, but not in flood-tolerant lines.