Continuous Glucose Monitoring In Daily Life Of Female Long-distance Runners

Continuous glucose monitoring (CGM) may assist in optimizing fuel strategies and capturing energy deficiencies in athletes. Previous studies have used CGM to monitor interstitial glucose levels during competitions, and a high incidence of hypoglycemia indicates the energy deficiency status of athletes. However, energy deficiency can occur in the daily lives of athletes, even outside of competitions. PURPOSE: This study aimed to clarify the characteristics of glucose fluctuations in athletes using CGM under real-life conditions. METHODS: This study included nine female long-distance runners (age; 22 ± 2 years) from a business team in Tokyo, Japan. The participants worked five days weekly from 9 a.m. to 3 p.m. and trained six days weekly. Data were collected over seven consecutive days. A real-time glucose monitor was used for CGM, and the hypoglycemic level was defined as <70 mg/dL. Exercise energy expenditure (EEE) was measured using a triaxial accelerometer, and energy and macronutrient intakes were assessed using dietary records. The data were categorized into three groups according to life patterns: working and training days (working days), non-working and training day (non-working day), and non-working and non-training day (rest day). RESULTS: The daily incidence of hypoglycemia had no significant difference among the groups (working days; 2.6 ± 4.5%, non-working day; 3.5 ± 7.8%, rest day; 5.1 ± 11.7%, p = 0.248). Although EEE on rest day was significantly lower than that on working days (116 ± 119 kcal/day vs.1,225 ± 362 kcal/day, p = 0.007), some cases of hypoglycemia were observed on rest day. Energy (2,039 ± 309 kcal/day vs. 2,409 ± 322 kcal /day, p = 0.005) and carbohydrate intakes (293.9 ± 39.7 g/day vs. 376.4 ± 48.8 g/day, p = 0.019) were significantly lower on rest day than on working days. Hypoglycemia due to a lack of energy intake was observed on rest day following training days. CONCLUSION: Our study found that hypoglycemia can occur even on rest day because the energy status of the body can be affected by training and carbohydrate intake before rest day. This finding suggests the importance of consuming meals to meet energy needs on rest day as well as training days.