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The present study aimed to identify the features of movement involved in a quick change of backward direction (COD) in response to a light stimulus. Thirteen male soccer players performed the Reactive Agility Test (RAT) involving a light stimulus and sprint running. For this analysis, the players were classified into 2 groups according to RAT time: fast and slow. Sprint time, step parameters, and various kinematic variables were compared between the 2 groups. In terms of sprint time, no significant inter-group difference was observed, but in terms of RAT time, the fast group showed significantly greater speed from 0 to 3 m, from 5 to 13 m including the COD, and from 0 to 13 m, than the slow group. Among step parameters before and after the COD, the fast group showed a significant increase in step frequency before the COD, and the time until the COD foot contact and the time until the lowest point of the velocity of the center of gravity were significantly shorter. In the movements before and after the COD, the fast group tilted the body backwards while maintaining a low center of gravity and performed a recovery action of the swing leg by bending the hip joint of the COD foot in the pre COD phase. In the COD phase, the knee joint of the COD foot was considered the flexion position, and the angular displacement of the knee was small, the body tilting inwards and forwards. Furthermore, the body and the shank tilted forwards in after COD phase. Therefore, it was clarified that deceleration occurred and ended early, and that the movement for deceleration was initiated before COD in order to perform it quickly. The findings of this research can be considered basic knowledge for training in order to improve COD performance and to create new indicators for evaluating it.

Sorghum [Sorghum bicolor (L.) Moench] pigments are associated with resistance to leaf diseases and grain deterioration. As a defence response, tan sorghum produces flavones (apigenin and luteolin), whereas wild-type sorghum produces additional 3-deoxyanthocyanidins (apigeninidin and luteolinidin). The dominant leaf colour gene P (Sb06g029550) controls 3-deoxyanthocyanidin production; the loss of its function results in tan leaves. We investigated the polymorphism of the P gene alleles and found that 11 of 327 lines from sorghum core collections had tan phenotype due to the loss of Sb06g029550 function. Six alleles (with insertions 1–4, a deletion and a point mutation) were found in tan sorghum, most of them in African landraces. This distribution suggests that the tan phenotype arose independently in different geographical locations and was selected several times during sorghum domestication. As plants with white seed without tannin often have tan leaves, the polymorphism of the transcription factor genes Y1 (for white seeds) and Tan1 (for seed tannin) was analysed. The grain coloration was affected by these transcription factors as previously reported but the leaf coloration by wounding was not affected by them.