Birkie Stats

Longitudinal Analyses

Skier performance, as measured by pace, was evaluated for ages 20 to 75. The peak age (age at fastest pace) was determined for each gender and each technique. Pace at all ages was graphed as pace relative to the peak age reference point. The shaded areas reflect the 95% confidence interval about the graphed line. Click on the individual graphs below for more detailed comment.

Summary

Among repeat American Birkebeiner competitors aged 20-75, long-distance cross-country ski performance followed a nonlinear age trajectory with fastest pace reached in the early-to-mid 40s. The estimated peak ages were 42 for both males and females in the freestyle event. The peak ages for the classic event were 46 for males and 44 for females. Performance generally improved from the 20s and 30s toward these reference ages, deteriorated moderately thereafter, and declined increasingly rapidly during the 60s and early 70s.

Based on the longitudinal analyses, males and females had broadly similar performance aging patterns, with the possible exception that males reached their peak performance at a later age in the classic event.

The divergence between longitudinal and cross-sectional estimates at younger ages demonstrates that population age-group differences can differ fundamentally from within-person aging patterns. In a sub-analysis it was determined that If skiers had slower-than-expected performances, they tended to have lower subsequent participation at later ages, confirming an important selection effect among repeat competitors. Repeat competitors perform at a more elite level.

There are many other studies of age-related performance in endurance sports. Take a look at these references if you are interested.