Below is an excerpt from an interview with David Epstein, author of The Sports Gene. He discuses how Olympic Marathon record holder Paula Radcliffe’s VO2 max hasn’t changed much since she was a teenager despite her improvement over the many years. This just goes to show that following heart rate is more of a predictive factor in cardiac improvement then your VO2 max. While a high VO2 max can be a predictor of your body’s ability to better transport and utilize oxygen, it can be genetic in that you can’t really improve it.
Paula is way taller than a lot of the people she runs against. She’s not extraordinarily tall, but she is for a marathoner. [Physiologist] Andrew Jones has tested her since she was a teenager, and he suggested that that was actually one of her advantages. She already had a VO2 max of 72 when she was a teenager without hardly training—close to as high as women get. Over the next decade of her training, her VO2 max didn’t really improve, but her running economy got better year after year after year. Part of that Jones attributed to her legs being longer while her body weight stayed basically the same.