City 2 Surf is a 14km foot race in Sydney, and attracts over 60,000 runners each year.

My initial guess was that the 20-29 years age group was fastest because I thought that adults in their younger ages are generally fitter.

The data (below) shows otherwise. Based on median finishing time, the 30-39 years age group is fastest, followed by 20-29 years and then 40-49 years.

c2s data

Source: article

Now, when comparing the top two age groups, why might 30-39 year olds perform better than 20-29 year olds? Here are my guesses:

  • Self-selection – people in their 30s are more likely to be married – the average first marital age for men was 29.6 years – and perhaps have greater pressure from their workplace , as they progress into their early to mid careers. Perhaps with greater demands on their time, only the more serious individuals took part in the race. So perhaps the result indicates less which age group is fitter and more reasons about the motivations to participate.
    • And by the same reason of self-selection, perhaps there were just more individuals dressed up as gorillas and super heroes in the 20-29 years age group, which would also affect the median.
  • Experience helps – familiarity with the route, the race conditions and the distance is helpful to improve performance. People in the 30-39 age group are more likely to have participated in the event in the past than their younger counterparts.
  • Endurance takes time to build – Over a running race of 14km in length, speed-endurance is a big advantage. Athletes who have taken the time and effort (years of training) to build up their endurance will be stronger than those with less training.
  • Mental resilience – perhaps people in their 30s are more mentally resilient and have stronger perseverance to pursue short term goals than those in their 20s.

These are all guesses. I enjoyed the  process of thinking this through.

Concrete statue


Food: oranges, gold kiwifruit, bananas, dried figs, bento box (chicken, fish, veges, rice), garlic broad beans.

Workout: ~1.5km running during touch football.