This paper uses world records by age in running, swimming, and rowing to estimate a biological frontier of decline rates for both men and women. Decline rates are assumed to be linear in percent terms up to a certain age and then quadratic after that, where the transition age is estimated. For both men and women decline rates are smallest for rowing, followed by swimming and then running.
Decline rates for women are roughly the same as those for men for the short swimming events. They are slightly larger for the longer swimming events and for the rowing events. They are largest for running, more so for the longer events than the shorter ones. The age at which there is a 50 percent decline from age 40 ranges from 70 to 90, an optimistic result for humans. The estimated decline rates can be used by non physically elite people under the assumption that their decline rates in percentage terms are similar to those of the elite athletes.