This week, we explore how daily carbohydrate manipulation can enhance endurance training adaptations in trained cyclists.
More specifically, can cyclists increase their FTP (functional threshold power) by eating the same amount of daily carbohydrate, but timing intake differently?
The concept of ‘train low’ has been around for a little while: The depletion in muscle glycogen during exercise whilst withholding carbohydrate post.
It’s been shown that a reduction in muscle glycogen can activate certain adaptive pathways associated with enhanced endurance adaptations.
A hallmark measure of enhanced adaptation is through having greater amount/efficiency of mitochondria in the muscle. This is where fat utilisation takes place. Therefore, during prolonged, sub-maximal cycling, the cyclist can use a greater proportion of fat for fuel. In return, sparing muscle glycogen.
In theory, this can improve higher intensity performances during more intense phases of a ride/race when under normal fuelling conditions.
That being said, RPE and training quality during sessions may worsen due to training under low carbohydrate availability.
However, poorer training quality could be an acceptable compromise for the enhanced molecular adaptations to the muscle.
Although this sounds very promising, the translation of these enhanced adaptations to ‘real world’ race day performances remains limited.
Bennett et al (2021) investigated the nutritional impact of ‘train low-sleep low’ (TLSL) in trained cyclists. This consisted of three phase:
1) Complete a high intensity ride at 105% FTP in the evening to deplete muscle glycogen.
2) Withhold carbohydrate post to ‘sleep low’ to enhance adaptation (not recovery).
3) Perform a lower intensity fasted ride in the morning at 75% FTP under low carbohydrate availability.
This protocol was a home-based training protocol performed three times a week on consecutive days for three weeks in total. Therefore had a more ’real-world’ practical application to cyclists (turbos + Training Peaks).
Pre + post-tests included: FTP, 1 min, and 5 min power. The control group and TLSL were provided a 6g/kg carbohydrate diet (but actually ate ~5g/kg).
The control group evenly distributed their carb intake throughout the day, where the TLSL group followed the below schedule:
– LIS fasted cycle
– 2g/kg breakfast
– 2g/kg lunch
– 2g/kg snack
– HIT cycle
– 0g/kg dinner
Following the 3 week training study, the cyclists retested their FTP. Both groups improved with the TLSL protocol having superior results:
Control = 272W pre to 275W post (1.3%)
TLSL = 271W pre to 282W post (5.5%)
Despite RPE being consistently higher in the TLSL, 5 min power improved in both groups to the same extent; however 1 min power plateaued in the TLSL, where it improved in the control.
Based on these findings, a ‘train low-sleep low’ protocol may be something worth considering to enhance the efficiency of your training and gain greater adaptations. Assuming this protocol complies with your food preferences and levels of food focus at meal times, I would recommend exploring this option.

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