Rajagopal I. Effects of Gender Difference and Circadian Rhythm on Systolic Blood Pressure in Volleyball Players. JEPonline 2011;14(2):46-54. The purpose of the study was to determine if there are differences in gender and circadian rhythm that affect the systolic blood pressure (SBP) of volleyball players. Thirty volleyball players (15 men and 15 women) between 19 and 22 years of age were selected as subjects. The two independent variables of gender and circadian rhythm and the dependent variable of SBP were evaluated. The experimental design used was a static group factorial design. The SBP data were collected at 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours during the academic year of 2009-2010. The data were statistically analyzed using a two-way factorial (2 x 6) Analysis of Variance (ANOVA) and Cosinor analysis.There was no difference between genders, significant difference at different times of the day and insignificant circadian rhythmicity exists on SBP. However, there were significant differences at different times of the day. But, given that the size of the differences in mm Hg is very small (4mm Hg), it is reasonable to conclude that the variation in SBP at

different times of the day would have little to no effect on the performance of athletes or others planning to improve sports skills.