Research objective: Identify contribution percentage of some physiological variables (dimensions and thickness) of heart muscle left and right ventricles in junior swimmers 50m, 100m, 200 m freestyle swimming time .  Predict record level for 50 m,  100 m , and 200 meter freestyle junior swimmers knowing some physiological variables (dimensions and thickness) of heart muscle . Research sample: The study was conducted on (30) swimmers aged 12 years with 3 years swimming training from Kazma club who participated in Arab and international swimming competitions. Time field: 2015 training season. Conclusions: In light of research objectives and sample limits the following could be concluded: 1-     Overall contribution percentage in 50m is 19.4% with one variable only namely: Right ventricle end Systolic dimension (RVESD ) 2- Overall contribution percentage in 100m is 35.9% with two  variable namely: Right and left ventricle end Systolic dimension (RVESD ) with contribution percentage (19.4% and 16.5% respectively) 3-  Overall contribution percentage in 200m is 31.6.% with two  variable namely: Right ventricle end Systolic dimension (RVESD ) and Right Posterior wall thickness in diastole (RPWTD)   with contribution percentage (18.1% and 13.5% respectively) 4- it was arrived to prediction equations of freestyle swimming time using morphological variables