Bryan Johnson promotes 4×4 interval training for cardiorespiratory fitness

On 25 August 2026, Bryan Johnson posted a Norwegian 4×4-style interval prescription. He recommends more than 3 workouts per week for 8 weeks. Each workout has 4 minutes at 90–95% effort, 3 minutes easy, repeated 4 times. He states that the resulting improvement in cardiorespiratory fitness lowers all-cause mortality risk by 11%. The post does not identify the source study, give a sample size, define the mortality estimate’s population, or report his own baseline and follow-up VO2 max. The closest primary exercise literature supports short-term fitness improvements from interval training, but an 8-week personal protocol cannot demonstrate an 11% mortality reduction. A reply from Ryan Williamson, MD, calls 4×4 a well-validated way to improve VO2 max and reduce mortality, while other replies describe the 95% effort intervals as difficult. Those replies are commentary, not outcome data. This entry records a public training recommendation with an n=1 subject context, not a new randomized trial. The practical content is specific enough to reproduce, but the mortality statement is an extrapolation from population associations and prior studies rather than a measured result from Johnson.

Your improved cardiorespiratory fitness is the risk reduction.