Continuously Measured Interstitial Glucose Responses Over A 9 Day Training Camp In Female Professional Cyclists

PURPOSE: To characterise the glycaemic changes of professional female cyclists using continuous interstitial glucose monitoring over a 9 day training camp. METHODS: Nine cyclists (age: 26 ± 5 years, height: 168 ± 5 cm, mass 58.5 ± 4.5 kg) were observed using continuous glucose monitoring devices throughout a training camp. Interstitial glucose [iG] data were captured via a continuous glucose monitor paired to smartphone app software. Daily [iG] data were split into distinct time ranges i.e., Overall (24-hourly), day-time (06:00-23:59), night-time (00:00-05:59) and exercise (defined as the data points that fell within the in-ride time-frame). [iG] data were stratified into the percentage of time below range ([TBR] <70 mg/dL), time in range ([TIR] 70-140 mg/dL) and time above range ([TAR] ≥141 mg/dL). Differences in diurnal and nocturnal data were analysed via repeated measures ANOVA and paired t-tests, as appropriate. A p-value of ≤0.05 was accepted as significant. RESULTS: As a group, riders spent 3 ± 1% TAR, 93 ± 2% in range and 8 ± 3% TBR. Mean 24 h [iG] concentration was 92.8 ± 2.3 mg/dL with a CV of 18 ± 1%. There were no diurnal differences in any glycaemic parameter throughout the camp. [iG]mean (day: 95 ± 2.7 vs. night: 86 ± 3.1 mg/dL, p = 0.0001) and [iG]CV (day: 18.3 ± 1.1 vs. night: 9 ± 1% , p < 0.0001) was higher during the day-time hours compared with nighttime. TAR was more evident during the day (day: 3 ± 1 vs. night: 0 ± 0 %, p = 0.0001) but TBR (day: 8 ± 3 vs. night: 10 ± 5 %, p = 0.165) and TIR (day: 89 ± 5 vs. night: 90 ± 5 %, p = 0.364) were similar between day and night-time periods. CONCLUSIONS: These data reveal novel insight into the glycaemic demands of consecutive days of intensive cycle training in professional female cyclists. Cyclists displayed twice the time spent below range than what is recommended by the international diabetes consensus guidelines. The potential health and performance implications of low blood glucose in healthy athletes warrants further investigation.