Energy or carbohydrate (CHO) intake has been shown to enhance performance for endurance workouts lasting more than 2-hour duration. Impact of carbohydrate intake on shorter durations (~ 1h) even if associated with high intensity effort (≥ 80 % VO2 max), are less clear.

The hypothesis was originally questioned by Jeukendrup, a Dutch nutritionist and exercise physiologist, when he concluded that CHO ingestion will unlikely contribute to energy expenditure, as only around 10-20% will be oxidized within the first hour of exercise. So, what does really enhance the 40km time trial (TT) cycling performance?

The following studies have concluded the following:

- Glucose administered intravenously had no effect on the one-hour cycle TT Performance as suggesting its increased bioavailability and absorption uptake into the tissues. (25)

- A follow up study for the same mentioned group that CHO rinsing only without ingestion has improved performance.

- Rinsing with a 6.4–10% CHO* solution every 5-10 minutes (5-10 seconds of oral cavity contact) in high intensity one-hour rides has shown to improve performance by 2-3%). This has been evidenced in a systemic review.

This comes with a good recommendation for cyclists who want to perform a 40km TT cycling ride that mouth swishing or rinsing can be of value for performance especially if athletes complain from gastrointestinal distress. Longer workouts duration of ~2 h or more should ingest the carbohydrates.

*6.4–10% CHO solution would be equal to 6.4gm – 10gm for every 100ml. That’s around 32gm – 50gm carbohydrate in 500ml

References:

1. Vitale K, Getzin A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients. 2019 Jun 7;11(6):1289.

2. A. Jeukendrup, F. Brouns, A. J. M. Wagenmakers, W. H. M. Saris. Carbohydrate-Electrolyte Feedings Improve 1 h Time Trial Cycling Performance. Int J Sports Med 1997; 18(2): 125-129