Abstract
Swimming is an extremely popular sport around the world. The streamlined body position is a crucial and foundational position for swimmers. Since the density of lungs is low, the center of buoyancy is always on the cranial side and the center of gravity is always on the caudal side. It has been reported that the greater the distance between the centers of buoyancy and gravity, the swimmer’s legs will sink more. This is disadvantageous to swimming performance. However, the way to reduce the distance between the centers of buoyancy and gravity is yet to be elucidated. Here we show that swimmers with high gliding performance exhibit different abdominal cavity shapes in the streamlined body position, which causes cranial movement of the abdominal organs. This movement can reduce the distance between the centers of buoyancy and gravity, prevent the legs from sinking, and have a positive effect on gliding performance.
Highlights
decreases[6,16]
No significant difference in characteristics with regard to age, height, weight, body mass index (BMI), body surface area (BSA), upper limb length, lower limb length, and shoulder width was noted between participants in the high performance group and those in the low performance group (Table 1)
In the low performance group, the cross-sectional area (CSA) increased significantly only at the upper liver level, and there were no significant changes at the lower lung and umbilical levels (Wilcoxon signed rank test, P = 0.027, P = 0.65, P = 0.25, respectively) (Fig. 3a) (Table 2)
Summary
In the high performance group, CSA increased significantly from the resting to the streamlined body positions at the upper liver and lower lung levels, and decreased significantly at umbilical level (Wilcoxon signed rank test, P < 0.01, P < 0.01, P < 0.01, respectively). In the low performance group, the CSA increased significantly only at the upper liver level, and there were no significant changes at the lower lung and umbilical levels (Wilcoxon signed rank test, P = 0.027, P = 0.65, P = 0.25, respectively) (Fig. 3a) (Table 2). The changes in the CSA were significantly greater in the high performance group than in the low performance group at all three levels: upper liver level, lower lung level, umbilical level (Mann–Whitney U test, P = 0.036, P < 0.01, P < 0.01, respectively) (Fig. 3b–d) (Table 3) These change in abdominal cavity shape can cause cranial side movement of abdominal organs. Swimmers with high performance group (as shown in Case 1) exhibit different abdominal cavity shapes in the streamlined body position compared to low performance group (as show in Case 2), which can cause cranial-side movement of abdominal organs
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