Extreme endurance athletes will converge in Salado this spring and fall for an Ultra 520K event.

The spring event April 29-May 1 is billed as the Ultra Underground extreme training camp and clinic.

The first day of the Ultra Underground will have a 3.5 mile open water swim, followed by a 67 mile bike ride. The second day will be a 134 mile boke ride. The third day will be a run from 6.2 to 20 miles in distance.

Registration is online at active.com, keyword Salado Ultra520K.

Athletes can sign up to do one of the races or all three of the races, or any combination in between.

There will be nutrition classes during the three-day event.

Corpåorate sponsorships are available as well by contacting event organizers at gojoendure@gmail.com.

The three-day event will be a preview of the fall 520K Ultra Endurance event on Oct. 21-23. That event will include a 6.2 mile open water swim in Stillhouse Hollow Lake followed by a 93 mile bike ride. Day Two will be a 172 mile bike ride. Day Three will be a 52.4 mile run (back-to-back marathons!).