Metabolic, hormonal and performance effects of isomaltulose ingestion before prolonged aerobic exercise: a double-blind, randomised, cross-over trial

Pre-exercise ingestion of a low glycaemic index rice-based mixed meal increases fat oxidation and endurance running performance in a hot-humid environment

Relative to exercise in a thermoneutral environment, there is only limited evidence demonstrating that a low glycaemic index (LGI) pre-exercise meal can enhance endurance exercise performance in a hot-humid (HH) condition. Also, previous studies predominantly utilised Western-based and single food items, with minimal focus on Asian-based mixed meals. This study aimed to investigate the impact of pre-exercise LGI and high glycaemic index (HGI) rice-based mixed meals on endurance performance among acclimatised trained athletes in HH condition (32 °C, 65% relative humidity). Twelve native-born endurance-trained male runners (age 22.0 ± 5.8 years; peak oxygen consumption (V̇O2peak) 64.2 ± 5.5 mL kg-1 min-1) completed two trials consisting of 45 min steady-state (SS) run at 70% V̇O2peak followed by 10 km performance run (TT10km). Three hours before exercise, participants consumed an isocaloric rice-based mixed meals containing either LGI (GI value = 47) or HGI (GI value = 80), providing 1.3 g of carbohydrate (CHO) per kg of body mass. Participants ran faster during TT10 km after consuming the LGI meal compared to the HGI meal (LGI: 55.18 ± 1.22 vs. HGI: 57.03 ± 2.25 min, p = 0.010). End rectal temperature did not significantly differ between trials (LGI: 39.16 ± 0.74 vs. HGI: 38.95 ± 0.46 °C, p = 0.352). Fat oxidation was higher during the SS run in the LGI compared to the HGI trial (LGI: 0.19 ± 0.05 vs. HGI: 0.13 ± 0.19 g min-1, p = 0.001). This study demonstrated that, relative to HGI, consuming a pre-exercise LGI rice-based mixed meal enhanced endurance performance in HH environment among acclimatised trained male athletes.

Trehalose Improved 20-min Cycling Time-Trial Performance After 100-min Cycling in Amateur Cyclists

Carbohydrate (CHO) supplementation during endurance exercise can improve performance. However, it is unclear whether low glycemic index (GI) CHO leads to differential ergogenic and metabolic effects compared with a standard high GI CHO. This study investigated the ergogenic and metabolic effects of CHO supplementation with distinct GIs, namely, (a) trehalose (30 g/hr), (b) isomaltulose (30 g/hr), (c) maltodextrin (60 g/hr), and (d) placebo (water). In this double-blind, crossover, counterbalanced, placebo-controlled study, 13 male cyclists cycled a total of 100 min at varied exercise intensity (i.e., 10-min stages at 1.5, 2.0, and 2.5 W/kg; repeated three times plus two 5-min stages at 1.0 W/kg before and after the protocol), followed by a 20-min time trial on four separated occasions. Blood glucose and lactate (every 20 min), heart rate, and ratings of perceived exertion were collected throughout, and muscle biopsies were taken before and immediately after exercise. The results showed that trehalose improved time-trial performance compared with placebo (total work done 302 ± 39 vs. 287 ± 48 kJ; p = .01), with no other differences between sessions (all p ≥ .07). Throughout the 100-min protocol, blood glucose was higher with maltodextrin compared with the other supplements at all time points (all p < .05). Heart rate, ratings of perceived exertion, muscle glycogen content, blood glucose, and lactate were not different between conditions when considering the 20-min time trial (all p > .05). Trehalose supplementation throughout endurance exercise improved cycling performance and appears to be an appropriate CHO source for exercise tasks up to 2 hr. No ergogenic superiority between the different types of CHO was established.

Effects of ingesting beverages containing glycerol and sodium with isomaltulose or sucrose on fluid retention in young adults: a single-blind, randomized crossover trial

We evaluated changes in hyperhydration and beverage hydration index (BHI, a composite measure of fluid balance after consuming a test beverage relative to water) during resting, induced by the consumption of beverages containing glycerol and sodium supplemented with fast-absorbing sucrose or slow-absorbing isomaltulose. In a randomized crossover, single-blinded protocol (clinical trials registry: UMIN000042644), 14 young physically active adults (three women) consumed 1 L of beverage containing either 7% glycerol + 0.5% sodium (Gly + Na), Gly + Na plus 7% sucrose (Gly + Na + Suc), Gly + Na plus 7% isomaltulose (Gly + Na + Iso), or water (CON) over a 40 min period. We assessed the change in plasma volume (ΔPV), BHI (calculated from cumulative urine output following consumption of water relative to that of the beverage), and blood glucose and sodium for 180 min after initiating ingestion. Total urine volume was reduced in all beverages containing glycerol and sodium compared to CON (all P ≤ 0.002). The addition of isomaltulose increased BHI by ∼45% (3.43 ± 1.0 vs. 2.50 ± 0.7 for Gly + Na, P = 0.011) whereas sucrose did not (2.6 ± 0.6, P = 0.826). The PV expansion was earliest for Gly + Na (30 min), slower for Gly + Na + Suc (90 min), and slowest for Gly + Na + Iso (120 min) with a concomitant lag in the increase of blood glucose and sodium concentrations. Supplementation of beverages containing glycerol and sodium with isomaltulose but not sucrose enhances BHI from those of glycerol and sodium only under a resting state, likely due to the slow absorption of isomaltulose-derived monosaccharides (i.e., glucose and fructose).