A 6-Week Ketogenic Diet Enhances the Phosphocreatine Energy System Contribution During Intermittent Sprints

Team sports often involve intermittent sprints. During these activities the Phosphocreatine-ATP buffer (ATP-PCr) signifies the major anaerobic energy substrate. While the effects of ketogenic diets (KD) on carbohydrate and fat metabolism during endurance exercise are widely reported, we explored keto-adaptation in ATP-PCr metabolism during intermittent sprint exercise.

Following a within-subject repeated measures design, 15 recreationally active participants (7 men, 8 women, aged 25.1 ± 6.4 years) performed cycle ergometer intermittent sprints (6 × 10 s sprints, 2 min recovery) with VO₂ and blood lactate measurements for energy system calculations. These laboratory tests were performed in alternate weeks; First, twice at baseline on their habitual diet (HD) (35% CHO, 45% fat, 20% protein) and thereafter over a 6-week KD (7% CHO, 66% fat, 28% protein).

Repeated measures ANOVA’s and Bonferroni tests revealed ATP-PCr derived energy increased significantly from HD to KD week 6 (+ 22.0 ± 43.15 J; P = 0.019; ES = 0.47). From HD to KD week 2, anaerobic glycolytic contribution lowered (- 14.4 ± 28.16 J; P = 0.031; ES = -0.10) and peak blood [lactate] reduced significantly (- 2.92 ± 0.851 mmol; P = 0.004; ES = -0.73). There was no statistically significant within-subject change in mean sprint power (P = 0.356).

The 6-week KD did not compromise intermittent sprint performance. The findings suggest that the ATP-PCr energy pathway may be a novel site of metabolic keto-adaptation. This, combined with the lowered blood [lactate] we observed, presents desirable metabolic adaptations for intermittent sprint sport athletes.