High rates of fat oxidation are maintained after the sleep low approach despite delayed carbohydrate feeding during exercise

Abstract

Training with low carbohydrate availability enhances endurance training adaptations but training volume may be compromised. We explored whole body metabolism and performance with delayed carbohydrate feeding during exercise undertaken following acute sleep low training. We hypothesised this strategy would not suppress fat oxidation and would maintain exercise performance. The study involved 3 experimental trials and included 9 men and 1 woman (V O 2 peak=58.8±5.5 mL • kg -1 • min -1 ). Each trial started in the afternoon with an exhaustive cycling protocol. The following morning 1-h of steady state cycling (SS) was followed by a time trial (TT).Carbohydrates (CHO) were not ingested in recovery from exhaustive exercise or during next day exercise in the Placebo trial (PLA); CHO were not ingested during recovery but were fed (15g every ~15-min) from 30-min into SS and continued during the TT in the delayed feeding trial (DELAY); CHO were provided during recovery (1.2 g/kg/h for 7 hours) and next day exercise (as in DELAY) in a third condition (CHO). Exercise metabolism was assessed using indirect calorimetry and blood sampling. Fat oxidation rates during SS were similar in PLA (0.83±0.17 g/min) and DELAY (0.78±0.14 g/min) (p>0.05) and higher than CHO (0.57±0.27 g/min) (p<0.05). There were no significant differences in TT performance (49.1±10.7, 43.4±7.6, 41.0±7.9 min in PLA, DELAY and CHO, respectively; p>0.05). Delayed carbohydrate feeding could be a strategy to maintain high fat oxidation rates typically associated with exercise undertaken after the sleep low approach to training but the acute performance effects remain inconclusive.

Comparable Exogenous Carbohydrate Oxidation from Lactose or Sucrose during Exercise

“…The highest average 30 s of V̇O 2 was considered to be V˙O 2peak . W max was calculated as the power output from the final stage completed, combined with the fraction of the time spent in the following stage, multiplied by 30 W, as previously described ( 17 ).…”

Three weeks of a home-based “sleep low-train low” intervention improves functional threshold power in trained cyclists: A feasibility study

“…Evidence from our laboratory has shown that the provision of a CHO-free sweet placebo drink could partially restore exercise capacity during a “sleep low-train low” approach [ 89 ]. Progressing this further, providing exogenous CHO ingestion during exercise under low CHO conditions does not impair fat oxidation during exercise [ 90 , 91 ] and therefore, providing a moderate dose of CHO may serve to improve exercise capacity by preventing hypoglycaemia during exercise and recovery. However, in our study, since HR data during LIT sessions were similar between SL and CON, we can hypothesise the intensity was sufficiently difficult for SL despite a reduction in power output.…”

New Horizons in Carbohydrate Research and Application for Endurance Athletes

“…Whether training adaptation can be enhanced with this approach has not been studied. More recently, building on previous work [157], the effects of delayed carbohydrate feeding in a glycogen depleted state (i.e., liver and muscle) on whole body metabolism and performance have been investigated [158]. While performance outcomes were unclear, delayed carbohydrate feeding enabled maintenance of stable blood glucose concentrations without suppressing fat oxidation rates and thus created a favorable metabolic response.…”