Oxidation of Solid versus Liquid CHO Sources during Exercise

PFEIFFER, B., T. STELLINGWERFF, E. ZALTAS, and A. E. JEUKENDRUP. Oxidation of Solid versus Liquid CHO Sources during Exercise. Med. Sci. Sports Exerc., Vol. 42, No. 11, pp. 2030-2037, 2010. The ingestion of CHO solutions has been shown to increase CHO oxidation and improve endurance performance. However, most studies have investigated CHO in solution, and sporting practice includes ingestion of CHO in solid (e. g., energy bars) as well as in liquid form. It remains unknown whether CHO in solid form is as effectively oxidized as CHO in solution. Purpose: To investigate exogenous CHO oxidation from CHO provided in either solid (BAR) or solution (DRINK) form during cycling. Methods: Eight well-trained subjects (age = 31 +/- 7 yr, mass = 73 +/- 5 kg, height = 1.79 +/- 0.05 m, (V) over dotO(2max) = 69 +/- 6 mL.kg(-1).min(-1)) cycled at 58% +/- 4% (V) over dotO(2max) for 180 min while receiving one of the following three treatments in randomized order: BAR plus water, DRINK, or water. The BAR and DRINK was delivered glucose + fructose (GLU + FRC) in a ratio of 2: 1 at a rate of 1.55 g.min(-1), and fluid intake was matched between treatments. Results: During the final 2 h of exercise, overall mean exogenous CHO oxidation rate was -0.11 g.min(-1) lower in BAR (95% confidence interval = -0.27 to 0.05 g.min(-1), P = 0.19) relative to DRINK, whereas exogenous CHO oxidation rates were 15% lower in BAR (P G 0.05) at 120, 135, and 150 min of exercise. Peak exogenous CHO oxidation rates were high in both conditions (BAR 1.25 +/- 0.15 g.min(-1) and DRINK 1.34 +/- 0.27 g.min(-1)) but were not significantly different (P = 0.36) between treatments (mean difference = -0.9 g.min(-1), 95% confidence interval = -0.32 to 0.13 g.min(-1)). Conclusions: The present study demonstrates that a GLU + FRC mix administered as a solid BAR during cycling can lead to high mean and peak exogenous CHO oxidation rates (>1 g.min(-1)). The GLU + FRC mix ingested in the form of a solid BAR resulted in similar mean and peak exogenous CHO oxidation rates and showed similar oxidation efficiencies as a DRINK. These findings suggest that CHO from a solid BAR is effectively oxidized during exercise and can be a practical form of supplementation alongside other forms of CHO.