Purpose: To assess energy and carbohydrate (CHO) availability and changes in blood hormones in 6 professional male cyclists over multiple single-day races. Methods: The authors collected weighed-food records, power-meter data, and morning body mass measurements across 8 d. CHO intakes were compared with contemporary guidelines. Energy availability (EA) was calculated as energy intake minus exercise energy expenditure, relative to fat-free mass (FFM). Skinfold thickness and blood metabolic and reproductive hormones were measured prestudy and poststudy. Statistical significance was defined as P = .05. Results: Body mass (P = .11) or skinfold thickness (P = .75) did not change across time, despite alternate-day low EA (14 [9] vs 57 [10] kcal/kg FFM/d, race vs rest days, respectively; P < .001). Cyclists with extremely low EA on race days (<10 kcal/kg FFM·d; n = 2) experienced a trend toward decreased testosterone (-14%) and insulin-like growth factor 1 (-25%), despite being high EA (>46 kcal·kg-1 FFM/d) on days between. CHO intakes were significantly higher on race versus rest days (10.7 [1.3] vs 6.4 [0.8] g/kg·d, respectively; P < .001). The cyclists reached contemporary prerace fueling targets (3.4 [0.7] g/kg·3 h CHO; P = .24), while the execution of CHO guidelines during race (51 [9] g/h; P = .048) and within acute (1.6 [0.5] g/kg·3 h; P = .002) and prolonged (7.4 [1.0] g/kg·24 h; P = .002) postrace recovery was poor. Conclusions: The authors are the first to report the day-by-day periodization of energy and CHO in a small sample of professional cyclists. They also examined the logistics of conducting a field study under stressful conditions in which major cooperation from the subjects and team management is needed. Their commentary around these challenges and possible solutions is a major novelty of the article.
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