Investigation of biorhythms in female athletic performance.

Implications for sports performance and athletic injury occurrence have been forcefully insinuated by proponents of a biorhythm theory based on date of birth. The theory postulates that variations in human abilities are governed by three consistently recurring cycles of 23, 28 and 33 day lengths. This study assessed the validity of biorhythms by analysing best performances in 610 top ranked European female track and field specialists over a single competitive season. Chi-square analysis of data found no significant influence of the computed physical, emotional or intellectual cycles on peak performances. It concluded that 'biorhythms' theory has no basis to justify its application to strenuous exercise.