Loading...
Carbohydrate dose influences liver and muscle glycogen oxidation and performance during prolonged exercise
King, Andy J. O'Hara, John P. Morrison, Douglas J. Preston, Tom King, Roderick F. G. J.
King, Andy J.
O'Hara, John P.
Morrison, Douglas J.
Preston, Tom
King, Roderick F. G. J.
Abstract
This study investigated the effect of carbohydrate (CHO ) dose and composition on fuel selection during exercise, specifically exogenous and endogenous (liver and muscle) CHO oxidation. Ten trained males cycled in a double‐blind randomized order on 5 occasions at 77% urn:x-wiley:2051817X:media:phy213555:phy213555-math-0001 for 2 h, followed by a 30‐min time‐trial (TT ) while ingesting either 60 g·h−1 (LG ) or 75 g·h−1 13C‐glucose (HG ), 90 g·h−1 (LGF ) or 112.5 g·h−1 13C‐glucose‐13C‐fructose ([2:1] HGF ) or placebo. CHO doses met or exceed reported intestinal transporter saturation for glucose and fructose. Indirect calorimetry and stable mass isotope [13C] tracer techniques were utilized to determine fuel use. TT performance was 93% “likely/probable” to be improved with LGF compared with the other CHO doses. Exogenous CHO oxidation was higher for LGF and HGF compared with LG and HG (ES > 1.34, P < 0.01), with the relative contribution of LGF (24.5 ± 5.3%) moderately higher than HGF (20.6 ± 6.2%, ES = 0.68). Increasing CHO dose beyond intestinal saturation increased absolute (29.2 ± 28.6 g·h−1, ES = 1.28, P = 0.06) and relative muscle glycogen utilization (9.2 ± 6.9%, ES = 1.68, P = 0.014) for glucose‐fructose ingestion. Absolute muscle glycogen oxidation between LG and HG was not significantly different, but was moderately higher for HG (ES = 0.60). Liver glycogen oxidation was not significantly different between conditions, but absolute and relative contributions were moderately attenuated for LGF (19.3 ± 9.4 g·h−1, 6.8 ± 3.1%) compared with HGF (30.5 ± 17.7 g·h−1, 10.1 ± 4.0%, ES = 0.79 & 0.98). Total fat oxidation was suppressed in HGF compared with all other CHO conditions (ES > 0.90, P = 0.024–0.17). In conclusion, there was no linear dose response for CHO ingestion, with 90 g·h−1 of glucose‐fructose being optimal in terms of TT performance and fuel selection.
Keywords
Date
2018
Type
Journal article
Journal
Physiological Reports
Book
Volume
6
Issue
1
Page Range
1-17
Article Number
ACU Department
Collections
Relation URI
Source URL
Event URL
Open Access Status
Open access
License
CC BY 4.0
File Access
Open