Coach recommends interval sprints 70-90%

Vernon Griffith said in a post on X that runners can use short interval sprints at 70% to 90% of top speed for 10 to 30 seconds, followed by walking recovery, as a way to train for speed and muscle. The post, shared on his X account under status ID 1856350568840655026, described the format as an alternative to longer steady efforts. Griffith also tied the running advice to mobility work, writing that mobility can be trained with load and progression. ### What exactly did Griffith recommend runners do? Vernon Griffith’s post described a simple structure: run hard for 10 to 30 seconds at roughly 70% to 90% of top speed, then walk to recover before repeating the effort. The post presented the workout as interval running rather than continuous tempo work. The X post said the goal was to build speed and muscle while using recovery walks to separate the faster efforts. Griffith did not, in the material reviewed, set out a full weekly plan, target mileage or a fixed number of repetitions. ### How did he describe the purpose of the workout? Griffith’s post said the short efforts could be used in place of longer tempo-style runs when the aim is speed gains and anaerobic work. The wording in the source material framed the session around short, harder bouts rather than prolonged sustained running. The post also linked the idea to lab-tested anaerobic capacity claims, according to the source briefing. No separate study citation or named paper was attached in the material available for review. ### What mobility work did he include with the running advice? Griffith’s post included examples of loaded mobility drills, including hip airplane progressions and hip hikes. The source briefing said he framed mobility as a form of strength training when it is progressively loaded. Those examples placed the running advice inside a broader training approach rather than as a standalone sprint prescription. The post did not appear, in the material available, to give set-and-rep prescriptions for each mobility exercise. ### How does the recovery piece fit the session? The recovery element in Griffith’s post was walking, not jogging, between the faster intervals. That detail matters because the session as described alternates brief high-effort running with deliberate downshifts in intensity. Running training guides commonly describe interval sessions in similar work-rest terms, though the exact ratio varies by goal. Outside, in a coaching explainer on interval recovery, said a common rule of thumb is for recovery to last roughly 50% to 100% as long as the work interval, while other run-walk guides describe planned walk breaks as a way to manage fatigue during harder efforts. ### What can be verified from the post itself? The clearest verifiable elements are the account, the topic and the examples included in the source briefing: Vernon Griffith, interval running at 70% to 90% of top speed for 10 to 30 seconds, walk recovery, and mobility examples including loaded hip airplanes and hip hikes. The post is identified as an X post from Griffith’s account with status ID 1856350568840655026. (run.outsideonline.com) The available web fetch did not return readable text from the X page itself, so the wording here relies on the supplied source briefing for the substance of the post and on the live page identifier for confirmation that the post exists at that location. May 24, 2026 is the latest dated context in the supplied briefings, and the next reference point for readers is Griffith’s X account, where the post remains listed under the cited status ID. (x.com)