Effects of Incremental Loading on the Center of Mass Velocity in Male Athletes'Underwater Dolphin Kick—Based on Statistical Parametric Mapping Analysis
Objective:To evaluate the load-velocity profile(LVP)of the underwater dolphin kick(UDK),and applies the statistical parameter mapping(SPM)method to analyze the effects of in-cremental load on the horizontal velocity of the center of mass of the underwater dolphin kick.Methods:Eight college swimmers were recruited to participate in 7 rounds of UDK test by us-ing the semi-tethered swimming method.The loads for each round were 21 N,33 N,45 N,57 N,69 N,81 N,93 N,respectively.The least square method was used to fit subjects'personal-ized LVP,and a mixed linear model or SPM was used to analyze the differences between dis-crete variables(average center of mass horizontal velocity)and continuous variables(horizontal velocity of center of mass)across various load levels.Results:The LVP of UDK exhibited a reli-able linear relationship(R2=0.896±0.057,SEE=0.069±0.035).As the load increased,there was a linear decrease in average center of mass horizontal velocity(ES=2.24～7.65,P＜0.01).The SPM method revealed a non-linear effect of incremental load on horizontal velocity of center of mass.Notably,when the load exceeded 57 N,there was a significant decrease in horizontal veloci-ty of center of mass(difference time range:11%～63%),particularly during the up-kick phase.Conclusions:The LVP is an effective tool for evaluate UDK performance of swimmers.When designing in-water resistance training programs,coaches and athletes should carefully consider the continuous influence of incremental loading on swimming technique,and select the individual load levels suitable for athletes based on the analysis of both discrete and continuous variables.
underwater dolphin kickload-velocity profilesstatistical parameter mappingcen-ter of mass velocitysemi-tethered swimming
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