Advanced Footwear Technology, But Not Acute Ingestion of a Ketone Monoester, Improves Running Economy in Middle- and Long-Distance Runners

PURPOSE: This study examined the separate and combined effects of advanced footwear technology and acute ingestion of a ketone monoester on running economy (RE), time to exhaustion, and other metabolic and cardiorespiratory parameters. METHODS: In a four-condition, placebo-controlled, randomized crossover design, 18 middle- and long-distance runners (male/female = 10/8, V̇O 2peak = 59.4 ± 7.2 mL·kg -1 ·min -1 ) completed five 8-min stages of submaximal running (male = 10-14 km⋅h -1 , female = 9-13 km⋅h -1 ) on a motorized treadmill, immediately followed by a ramp test to volitional exhaustion. Participants consumed 500 mL of either a 10% carbohydrate solution (CHO) or 500 mg·kg -1 body mass of an (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester with flavored water (KME) 20 min before exercise, and an additional 300 mL of the 10% carbohydrate solution or 250 mg·kg -1 body mass of KME during exercise, while wearing either Nike Pegasus Turbo (PEG) or Nike ZoomX Vaporfly Next% 3 (VAP) running shoes. The four randomized conditions were PEG + CHO, PEG + KME, VAP + CHO, and VAP + KME. RESULTS: RE was significantly improved during the third and the fourth submaximal running stages in VAP + CHO and VAP + KME compared with PEG + CHO and PEG + KME (all P < 0.05, ES = 0.53-0.84). RE was also improved during the fifth submaximal running stage in VAP + KME compared with PEG + CHO, and in VAP + CHO and VAP + KME compared with PEG + KME (all P < 0.05, ES = 0.56-0.66). No differences in RE were found between CHO and KME conditions. Time to exhaustion was significantly longer in VAP + CHO (381 ± 125 s) than PEG + CHO (356 ± 140 s, P = 0.023, ES = 0.18) and PEG + KME (329 ± 131 s, P < 0.001, ES = 0.40) and in VAP + KME (375 ± 125 s) than PEG + KME ( P < 0.001, ES = 0.35). CONCLUSIONS: Advanced footwear technology, but not the acute ingestion of a ketone monoester, improved the RE of trained male and female middle- and long-distance runners at submaximal running speeds.