Click name to view affiliation
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  vs 57  kcal·kg−1 FFM·d−1, race vs rest days, respectively; P < .001). Cyclists with extremely low EA on race days (<10 kcal·kg−1 FFM·d−1; 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−1) on days between. CHO intakes were significantly higher on race versus rest days (10.7 [1.3] vs 6.4 [0.8] g·kg−1·d−1, respectively; P < .001). The cyclists reached contemporary prerace fueling targets (3.4 [0.7] g·kg−1·3 h−1 CHO; P = .24), while the execution of CHO guidelines during race (51  g·h−1; P = .048) and within acute (1.6 [0.5] g·kg−1·3 h−1; P = .002) and prolonged (7.4 [1.0] g·kg−1·24 h−1; 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.
Heikura and Burke are with the Mary MacKillop Inst for Health Research, Australian Catholic University, Melbourne, Australia, and Sports Nutrition, Australian Inst of Sport, Canberra, Australia. Quod, Strobel, and Palfreeman are with Mitchelton–Scott (WorldTour Team), UCI, Adelaide, SA, Australia. Palfreeman is also with Aspetar Orthopedic and Sports Medicine Hospital, Doha, Qatar. Civil is with Nottingham Trent University, Nottingham, United Kingdom.