Glycaemic Effects of a 156-km Ultra-trail Race in Athletes: An Observational Field Study.
Level 4 - case-series / case-control
Prospective observational field study (single-cohort repeated-measures design without an unexposed control group).
PubMed 38555307 · doi:10.1007/s40279-024-02013-4
What was done
Fifty-five athletes (78% male, mean age 43.7 ± 9.6 years) competing in a 156-km ultra-trail race (six 26-km laps, 6000 m total elevation) wore masked continuous glucose monitoring (CGM) sensors from 1 day pre-race to 10 days post-race. Blood draws were conducted at rest, at refueling stops after each lap, and 24 hours post-race. Researchers used linear mixed models and logistic regressions to assess the relationship between continuous glycaemia, running intensity (% heart rate reserve), performance (lap times), psychological stress, behavioural alertness, and metabolic/muscle damage biomarkers.
What was found
Active exercise phases during the race showed no increased risk of hypo- or hyperglycaemia compared with resting baseline. Laps with higher time at maximal aerobic intensity were associated with more time > 180 mg/dL (P = 0.021). Post-race recovery (first 48 hours) showed a significant increase in hyperglycaemia risk versus baseline (P < 0.05), with 31.9% of participants recording glucose levels > 180 mg/dL compared to 5.5% at rest. Creatine phosphokinase increased exponentially and remained 43.6 times higher than resting values at 24 hours post-race (P < 0.001), while lactate dehydrogenase was 1.8 times higher (P < 0.001). Glycaemic metrics did not correlate with physical performance or behavioural alertness.
Why it matters
This study demonstrates that the primary glycaemic perturbation associated with ultra-endurance running occurs not during active exertion, but during the 48-hour recovery window, likely linked to severe muscle damage and acute inflammation.
Limits
The study had a relatively small sample (n = 55) that was predominantly male (78%), limiting generalizability to female runners. There was no unexposed control group, dietary intake during refueling and recovery was not strictly standardized, and the trial was registered retrospectively.
Cited by
- context Working out, particularly for individuals who are fat-adapted, can trigger blood glucose spikes above 140 mg/dL.