CHO Condition Research Articles

Acute Carbohydrate Restriction During Recovery From Prolonged Exercise Enhances Intramuscular Triglyceride Resynthesis

Intramuscular triglyceride (IMTG) is an important substrate during moderate-intensity exercise, but providing a high carbohydrate (CHO) diet following exercise impairs IMTG resynthesis. Restricting CHO intake in the post-exercise period may augment the adaptive response to exercise, but whether this strategy enhances IMTG resynthesis is not known. Furthermore, because the lipid droplet (LD)-associated perilipin (PLIN) proteins promote IMTG storage, their distribution and interaction with LD may determine their role in post-exercise IMTG resynthesis. PURPOSE: To determine the effect of acutely restricting CHO during recovery from prolonged exercise on IMTG resynthesis and PLIN protein dynamics. METHODS: 14 male triathletes (27±1 y, 66.5±1.3 ml.kg-1.min-1) completed 4 h of cycling at ~56% VO2max. In the initial 4 h period following exercise 7 participants consumed a high CHO diet whereas 7 participants consumed only water. For the remaining recovery period (20 h) all participants received the same CHO-rich diet. Muscle samples collected pre and post-exercise, and 4 and 24 h post-exercise were analysed using confocal immunofluorescence microscopy to determine muscle fibre type-specific IMTG content and PLIN localisation to LDs. RESULTS: Exercise reduced IMTG content in type I fibres (-53%, P<0.05), with LD both associated and not associated with PLIN2, PLIN3, and PLIN5 being used. During recovery, IMTG content tended to increase in type I fibres after 4 h in the water condition only (+63%, P=0.076), and at 24 h IMTG content was similar to pre-exercise levels (P=0.987). Despite no change in PLIN protein content, the number of LD with PLIN2 or PLIN3 associated tended to increase during recovery in type I fibres only (P=0.08), and to a similar extent between conditions, whereas the number of LD with PLIN5 associated only increased in the CHO condition (P=0.002). CONCLUSION: Acute restriction of CHO during recovery from prolonged exercise has a tendency to initially enhance IMTG resynthesis, although a CHO-rich diet does not impair overall IMTG resynthesis 24 h later. A redistribution of PLIN proteins appears to support post-exercise IMTG resynthesis, but the predominant PLIN isoform supporting post-exercise IMTG storage may be dependent on post-exercise CHO availability.

Liver and muscle glycogen oxidation and performance with dose variation of glucose\u2013fructose ingestion during prolonged (3 h) exercise

PurposeThis study investigated the effect of small manipulations in carbohydrate (CHO) dose on exogenous and endogenous (liver and muscle) fuel selection during exercise.MethodEleven trained males cycled in a double-blind randomised order on 4 occasions at 60% dot {V}{{text{O}}_{2;hbox{max} }} for 3 h, followed by a 30-min time-trial whilst ingesting either 80 g h−1 or 90 g h−1 or 100 g h−1 13C-glucose-13C-fructose [2:1] or placebo. CHO doses met, were marginally lower, or above previously reported intestinal saturation for glucose–fructose (90 g h−1). Indirect calorimetry and stable mass isotope [13C] techniques were utilised to determine fuel use.ResultTime-trial performance was 86.5 to 93%, ‘likely, probable’ improved with 90 g h−1 compared 80 and 100 g h−1. Exogenous CHO oxidation in the final hour was 9.8–10.0% higher with 100 g h−1 compared with 80 and 90 g h−1 (ES = 0.64–0.70, 95% CI 9.6, 1.4 to 17.7 and 8.2, 2.1 to 18.6). However, increasing CHO dose (100 g h−1) increased muscle glycogen use (101.6 ± 16.6 g, ES = 0.60, 16.1, 0.9 to 31.4) and its relative contribution to energy expenditure (5.6 ± 8.4%, ES = 0.72, 5.6, 1.5 to 9.8 g) compared with 90 g h−1. Absolute and relative muscle glycogen oxidation between 80 and 90 g h−1 were similar (ES = 0.23 and 0.38) though a small absolute (85.4 ± 29.3 g, 6.2, − 23.5 to 11.1) and relative (34.9 ± 9.1 g, − 3.5, − 9.6 to 2.6) reduction was seen in 90 g h−1 compared with 100 g h−1. Liver glycogen oxidation was not significantly different between conditions (ES < 0.42). Total fat oxidation during the 3-h ride was similar in CHO conditions (ES < 0.28) but suppressed compared with placebo (ES = 1.05–1.51).Conclusion‘Overdosing’ intestinal transport for glucose–fructose appears to increase muscle glycogen reliance and negatively impact subsequent TT performance.

Carbohydrate Mouth Rinsing Does Not Prevent the Decline in Maximal Strength After Fatiguing Exercise.

Black, CD, Schubert, DJ, Szczyglowski, MK, and Wren, JD. Carbohydrate mouth rinsing does not prevent the decline in maximal strength after fatiguing exercise. J Strength Cond Res 32(9): 2466-2473, 2018-Carbohydrate (CHO) rinsing has been shown to attenuate the decline of maximal voluntary contractions (MVCs) after fatiguing exercise-perhaps through a central mechanism. This study sought to determine the effect of a CHO rinse on MVC, voluntary activation, and contractile properties after fatiguing exercise. Thirteen adults participated in a double-blind, cross-over study. Maximal voluntary contraction of the dominant knee extensors was assessed, and voluntary activation (%VA) was determined using twitch interpolation. Participants then held 50% of MVC until volitional fatigue followed by a 20-second rinse with a solution of 8% maltodextrin (CHO) or placebo (PLA). Maximal voluntary contraction and %VA were reassessed immediately and 5 minutes after exercise. Maximal voluntary contraction did not differ between the CHO and PLA conditions initially (230 ± 90 vs. 232 ± 90 N·m; p = 0.69). Maximal voluntary contraction declined after exercise (p ≤ 0.01), but no differences were found between the CHO and PLA conditions (p ≥ 0.59). %VA did not differ between conditions (91.9 ± 2.9% vs. 91.5 ± 3.8%; p ≥ 0.11) nor did it change after exercise (p = 0.57). Twitch torque, rate of torque development, and rate of torque relaxation were reduced after exercise (p ≤ 0.05) but were unaffected by CHO rinsing (p > 0.05). Unlike a previous study, a CHO rinse did not preserve MVC after fatiguing exercise. This was likely due to a lack of central fatigue induced by the exercise protocol (as %VA was unaffected) as the CHO rinse is thought to work through a central mechanism.

Impact of a Carbohydrate Mouth Rinse on Motor Performance and Corticospinal Motor Excitability

Application of a carbohydrate (CHO) mouth rinse (MR) prior to exercise has been shown to improve physical performance and facilitate corticospinal motor excitability. It is unclear if different forms of CHO impact this phenomenon. PURPOSE: The purpose of this investigation is to determine the effects of different forms of a CHO MR on muscular performance and corticospinal motor excitability. METHODS: Ten normal healthy subjects (5 females, 5 males; 25±1 years; 1.71±0.03 m 73±5 kg) completed 4 trials each separated by at least 48 hours. A different MR condition was applied during each trial (Placebo (PLAC), 6.4% glucose (GLU), 6.4% maltose (MAL), 6.4% maltodextrin (MDX)). Maximal voluntary contraction (MVC) of the right knee extensors and motor-evoked potential (MEP) of the right vastus medialis was determined pre (10 min before), immediately after, and post (10 min after) application of the MR. MEP was precipitated by applying transcranial magnetic stimulation (TMS) during muscle contraction (50% of MVC). The MR was held in the mouth for 20 sec and MR treatments were applied using a Latin square design. RESULTS: No differences were found in the change of MEP from pre to immediately after the MW across the conditions (PLAC=1.5±4.4%; GLU=-6.2±11.2%; MAL=3.9±3.4%; MDX=8.9±7.9%). In contrast, the increase in MEP was greater at the post time point in CHO conditions (GLU=-11.3±14.7%, p=0.01; MAL=12.9±7.9%, p=0.07; MDX=28.0±14.4%, p=0.02) as compared to PLAC (PLAC=-14.3±7.8%). MVC was similar at pre (PLAC=260±26 Nm; GLU=241±19 Nm MAL=245±21 Nm; MDX=248±25 Nm), after (PLAC=269±26 Nm; GLU=249±18 Nm MAL=257±19 Nm; MDX=250±23 Nm), and 10 min after (PLAC=262±28 Nm; GLU=256±17 Nm MAL=269±25 Nm; MDX=253±21 Nm) the MW. CONCLUSIONS: CHO MR increased corticospinal motor excitability 10 min after application; however, the form of CHO used did not influence this response. The increase in corticospinal motor excitability did not translate into an improvement in motor performance.

Select Skeletal Muscle mRNAs Related to Exercise Adaptation Are Minimally Affected by Different Pre-exercise Meals that Differ in Macronutrient Profile.

Background: Substantial research has been done on the impact of carbohydrate and fat availability on endurance exercise adaptation, though its role in the acute adaptive response to resistance exercise has yet to be fully characterized.Purpose: We aimed to assess the effects of a pre-resistance exercise isocaloric mixed meal containing different amounts of carbohydrates and fat, on post-resistance exercise gene expression associated with muscle adaptation.Methods: Thirteen young (age 21.2 ± 1.6 year), recreationally trained (VO2max 51.3 ± 4.8 ml/kg/min) men undertook an aerobic exercise session of 90-min continuous cycling (70% VO2max) in the morning with pre- and post-exercise protein ingestion (10 and 15 g casein in a 500 ml beverage pre- and post-exercise, respectively). Subjects then rested for 2 h and were provided with a meal consisting of either 3207 kJ; 52 g protein; 51 g fat; and 23 g carbohydrate (FAT) or 3124 kJ; 53 g protein; 9 g fat; and 109 g carbohydrate (CHO). Two hours after the meal, subjects completed 5 × 8 repetitions (80% 1-RM) for both bilateral leg press and leg extension directly followed by 25 g of whey protein (500 ml beverage). Muscle biopsies were obtained from the vastus lateralis at baseline (morning) and 1 and 3 h post-resistance exercise (afternoon) to determine intramuscular mRNA response.Results: Muscle glycogen levels were significantly decreased post-resistance exercise, without any differences between conditions. Plasma free fatty acids increased significantly after the mixed meal in the FAT condition, while glucose and insulin were higher in the CHO condition. However, PDK4 mRNA quantity was significantly higher in the FAT condition at 3 h post-resistance exercise compared to CHO. HBEGF, INSIG1, MAFbx, MURF1, SIRT1, and myostatin responded solely as a result of exercise without any differences between the CHO and FAT group. FOXO3A, IGF-1, PGC-1α, and VCP expression levels remained unchanged over the course of the day.Conclusion: We conclude that mRNA quantity associated with muscle adaptation after resistance exercise is not affected by a difference in pre-exercise nutrient availability. PDK4 was differentially expressed between CHO and FAT groups, suggesting a potential shift toward fat oxidation and reduced glucose oxidation in the FAT group.

Carbohydrate dose influences liver and muscle glycogen oxidation and performance during prolonged exercise.

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% V˙O2max 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.

Carbohydrate mouth rinse reduces rating of perceived exertion but does not affect performance and energy systems contribution during a high-intensity exercise

ABSTRACT Aim The study aimed to verify the effect of carbohydrate (CHO) mouth rinse on time to exhaustion, energy systems contribution and rating of perceived exertion (RPE) during a high-intensity exercise. Methods Fourteen men performed an incremental exercise test to determine their maximal oxygen uptake and peak power output (PPO) and two time-to-exhaustion tests at 110% of PPO. Participants rinsed their mouth with 25ml of 6.4% of CHO or placebo (PLA) solution immediately before the time-to-exhaustion test, using a crossover design. The contribution of the energy systems was calculated using the free software GEDAE-LaB®. Results Time to exhaustion was similar between the conditions (CHO:174.3±42.8s; PLA:166.7±26.3s; p=0.33). In addition, there was no difference between the CHO and PLA condition for aerobic (CHO:135.1±41.2kJ and PLA:129.8±35.3kJ, p=0.34), anaerobic lactic (CHO:57.6±17.1kJ and PLA:53.4±15.1kJ, p=0.10), and anaerobic alactic (CHO:10.4±8.4kJ and PLA:13.2±9.2kJ, p=0.37) contribution. Consequently, total energy expenditure was similar between conditions (CHO:203.2±46.4kJ and PLA:196.5±45.2kJ, p=0.15). However, CHO mouth rinse reduced the RPE at the moment of exhaustion (CHO:18.2±1.0units and PLA:19.1±1.1units; p=0.02). Conclusion CHO mouth rinse neither increased time to exhaustion nor altered energy systems contribution during a high-intensity exercise, but reduced the perceived effort at the exhaustion.

Alterations in Exogenous Carbohydrate, Liver and Muscle Glycogen Oxidation with Different Doses of Glucose and Fructose ingestion during Prolonged Cycling

PURPOSE: To investigate the effect of three CHO doses on fuel selection during exercise, in particular exogenous and endogenous (liver and muscle) CHO oxidation. METHODS: Eleven trained male cyclists (V[Combining Dot Above]O2max: 60.0 ± 4.3 ml/kg/min) cycled on 4 occasions at 60% V[Combining Dot Above]O2max for 3 hours after an overnight fast. From 15 min into exercise and every 15 min thereafter, either 80 g.h-1 (LOW), 90 g.h-1 (MED), 100 g.h-1 (HIGH) of GF (all 2:1 ratio) or a placebo (PLA) was ingested in a double-blind randomised order. The formulations contained 13C isotope tracers and were designed to span the reported saturation levels for SGLT1 and GLUT5. Total, exogenous, endogenous (muscle and liver) CHO oxidation, and total fat oxidation were computed using indirect calorimetry and isotope ratio mass spectrometry. RESULTS: Total CHO oxidation was elevated, and total fat oxidation suppressed in all CHO conditions relative to PLA (CHO range 94.0-125.0 g higher, Fat 29.7-34.3 g lower: both ES > 1.05). Exogenous oxidation in the final hour was greatest in HIGH (91.1 g.h-1), a moderate effect to LOW (81.6 g.h-1, ES = 0.64, P = 0.10) and MED (82.9 g.h-1, ES = 0.70, P = 0.39) a moderate increase from the second hour in all conditions (ES = 1.38-2.00, P < 0.014). However, increasing GF dose beyond intestinal saturation increased muscle glycogen utilisation in the final hour (101.6 ± 16.6 g.h-1 in HIGH; 6.2, -23.5 to 11.1 g.h-1 higher [95% CI] vs. LOW, ES = 0.47, P = 0.61 & 16.1, 0.9 to 31.4 g.h-1 [95% CI]) higher vs. MED, ES = 0.68, P = 0.16), and second hour (ES = 0.51 & 0.48, P > 0.05). A small, non-significant reduction was seen in liver glycogen oxidation with HIGH in the last hour compared with LOW (-2.6, -5.6 to 0.4 g.h-1, ES = 0.40) and MED (-2.6, -6.8 to 1.6 g.h-1, ES = 0.42). CONCLUSIONS: Increasing CHO ingestion beyond previously reported saturation rates produces higher exogenous oxidation, but results in an increased reliance on muscle glycogen. Ingestion of 90 g.h-1 GF can attenuate the rate of muscle glycogen oxidation by the end of 3 hours prolonged exercise, but recommendations should remain in the region of 80 to 90 g.h-1.

Effect of Carbohydrate Intake on Maximal Power Output and Cognitive Performances.

The present study aimed to assess the beneficial effect of acute carbohydrate (7% CHO) intake on muscular and cognitive performances. Seventeen high levels athletes in explosive sports (fencing and squash) participated in a randomized, double-blind study consisting in series of 6 sprints (5s) with a passive recovery (25s) followed by 15 min submaximal cycling after either maltodextrine and fructose (CHO) or placebo (Pl) intake. Cognitive performances were assessed before and after sprint exercise using a simple reaction time (SRT) task at rest, a visual scanning task (VS) and a Go/Nogo task (GNG) during a submaximal cycling exercise. Results showed a beneficial effect of exercise on VS task on both conditions (Pl: −283 ms; CHO: −423 ms) and on SRT only during CHO condition (−26 ms). In the CHO condition, SRT was faster after exercise whereas no effect of exercise was observed in the Pl condition. According to a qualitative statistical method, a most likely and likely positive effect of CHO was respectively observed on peak power (+4%) and tiredness (−23%) when compared to Pl. Furthermore, a very likely positive effect of CHO was observed on SRT (−8%) and a likely positive effect on visual scanning (−6%) and Go/Nogo tasks (−4%) without any change in accuracy. In conclusion acute ingestion of 250 mL of CHO, 60 min and 30 min before exercise, improve peak power output, decrease muscular tiredness and speed up information processing and visual detection without changing accuracy.

A multi-ingredient containing, proteins, carbohydrate and creatine does not attenuate humoral immune response or performance decrease compared to carbohydrate during resistance training

Background: Nowadays, only carbohydrate has shown to be an effective countermeasure to exercise-induced immune dysfunction while the effect of protein remains controversial. The purpose of this study was to investigate the acute effects of a commercially available multi-nutrient supplement on performance and salivary markers of humoral immunity, following a bout of circuit resistance training in young athletes. Methods: Twelve recreationally resistance-trained males (age: 22 ± 1.4 years; body mass 79 ±9.78 kg; 1.81 ± 0.07 m height) volunteered to participate in the study completing 2 randomised controlled circuit resistance training sessions (CT). Participants ingested 2 doses of 500ml of water mixed 60g of a multi-ingredient (MTN) containing whey proteins, carbohydrate, creatine, HMB and sodium bicarbonate or maltodextrin (PL). Beverages were consumed (3 doses of ~166ml) during and after the workout (1 × 500ml). Both MTN and PL looks the same colour and flavour and provide a similar amount of calories (~230 per serving). CT involved three rounds of 7 resistance exercises (CMJs, Bench Press, Parallel-Squat, Upright row, Alternate Lunges, Dead Lift, Push-press, Abdominals) followed by 1 min rest. Participants performed 12 repetitions at 70% 1RM in each of the exercises with no rest in between (only the time to change from one exercise to the next). Measurements included pre and post (30 min and 60 min) salivary markers of humoral immune response: Antimicrobial Peptide, Alpha Defensins (HNP 1-3). The total kg lifted per exercise and in the overall workout was considered as indicator of performance. ANOVA design and Cohen d effect sizes (ES) were used to analyse potential differences between times and treatment conditions. Results: No significant differences were observed between the total weight (kg) lifted per exercise or for the entire session (p > 0.05). HNP 1-3 showed a strong trend (p = 0.06) with a moderate effect size (d = 0.53) at 30 min for the CHO condition [2.001 (1.95) vs 3.037 (2.49) ng/mL], nevertheless, no significant differences were observed at 60 min with respect to the values measured at both pre [3.825 (3.21) vs 2.001 (1.95) ng/mL] and 30 min [3.825 (3.21) vs 3.037 (2.49) ng/mL]. On the other side, HNP 1-3 did not increase at either 30 min [2.464 (3.31) vs 3.656 (3.22) ng/mL] or 60 min [2.464(3.31) vs 2.387 (2.46) ng/mL] post workout for the MTN treatment condition. No differences were observed between the two tested treatment conditions for the three analysed times points (pre, post 30 min and post 60 min). Conclusion: Ingesting both MTN and CHO supplements during and after a circuit resistance-training workout, resulted in no impact on performance. However, even when both nutritional interventions were effective to attenuate the increase of antimicrobial peptide alpha-defensins, MTN showed a stronger effect to blunt exercise-induced immune-dysfunction. These results did not support the notion that only carbohydrate with no added proteins is the only effective nutritional countermeasure against the transient post exercise immunosuppression.

Mouth Rinsing With Carbohydrate Solutions at the Postprandial State Fail to Improve Performance During Simulated Cycling Time Trials.

Mouth rinsing with carbohydrate (CHO) solutions during cycling time trials results in performance enhancements; however, most studies have used approximately 6% CHO solutions. Therefore, the purpose of this study was to compare the effectiveness of mouth rinsing with 4, 6, and 8% CHO solutions on 1-hour simulated cycling time trial performance. On 4 occasions, 7 trained male cyclists completed at the postprandial period, a set amount of work as fast as possible in a randomized counterbalanced order. The subjects rinsed their mouth for 5 seconds, on completion of each 12.5% of the trial, with 25 ml of a non-CHO placebo and 4, 6, and 8% CHO solutions. No additional fluids were consumed during the time trial. Heart rate (HR), ratings of perceived exertion (RPE), thirst (TH), and subjective feelings (SF) were recorded after each rinse. Furthermore, blood samples were drawn every 25% of the trial to measure blood glucose and blood lactate concentrations, whereas whole-body CHO oxidation was monitored continuously. Time to completion was not significant between conditions with the placebo, 4, 6, and 8% conditions completing the trials in 62.0 ± 3.0, 62.8 ± 4.0, 63.4 ± 3.4, and 63 ± 4.0 minutes, respectively. There were no significant differences between conditions in any of the variables mentioned above; however, significant time effects were observed for HR, RPE, TH, and SF. Post hoc analysis showed that TH and SF of subjects in the CHO conditions but not in the placebo were significantly increased by completion of the time trial. In conclusion, mouth rinsing with CHO solutions did not impact 1-hour cycling performance in the postprandial period and in the absence of fluid intake. Our findings suggest that there is scope for further research to explore the activation regions of the brain and whether they are receptive to CHO dose, before specific recommendations for athletic populations are established. Consequently, mouth rinsing as a practical strategy for coaches and athletes is questionable under specific conditions and should be carefully considered before its inclusion. Emphasis should be focused on appropriate dietary and fluid strategies during training and competition.

The impact of intensified training with a high or moderate carbohydrate feeding strategy on resting and exercise-induced oxidative stress.

This study investigated the impact of intensified training (IT) and carbohydrate (CHO) supplementation on resting and exercise-induced oxidative stress. Male cyclists (n = 13, mean ± SD: age 25 ± 6 years; [Formula: see text] 72 ± 5 ml/kg/min) undertook two 9 day periods of endurance-based IT. In a counter-balanced, crossover and double-blinded study design, participants completed IT whilst ingesting high (H-CHO) or moderate (M-CHO) CHO beverages before (H-CHO: 24 g vs. 2 g), during (H-CHO: 60 g/h vs. 20 g/h) and after training sessions (H-CHO: 44 g vs. 10 g). Participants completed fasted performance trials without CHO on days 2, 6 and 10. Blood samples were taken before and immediately after exercise to assess plasma oxidative stress. Resting thiol (-SH) and catalase (CAT) activities decreased following 6 days of IT, independent of CHO condition [-SH (μM oxidised NADPH): H-CHO-14.0 ± 18.8, M-CHO-20.4 ± 20.3 and CAT (nmol/min/ml): H-CHO 12.5 ± 12.5, M-CHO 6.0 ± 4.5; all p < 0.05]. Resting total antioxidant capacity (TAC) was reduced after IT in M-CHO. All exercise bouts elicited significant increases in CAT, TAC, protein carbonylation (PC) and lipid hydroperoxides (LOOH), independent of CHO condition (p < 0.05). The magnitude of increase in PC and LOOH was greater on days 6 and 10 compared to day 2 in both conditions. Short-term IT caused reductions in resting antioxidant capacity in trained cyclists. Exercise-induced increases in PC and LOOH were exaggerated as a result of IT; however, these responses were independent of carbohydrate intake before, during and after the preceding IT sessions.

Fructose–Maltodextrin Ratio Governs Exogenous and Other CHO Oxidation and Performance

Fructose coingested with glucose in carbohydrate (CHO) drinks increases exogenous-CHO oxidation, gut comfort, and physical performance. This study aimed to determine the effect of different fructose-maltodextrin-glucose ratios on CHO oxidation and fluid absorption while controlling for osmolality and caloricity. In a crossover design, 12 male cyclists rode 2 h at 57% peak power then performed 10 sprints while ingesting artificially sweetened water or three equiosmotic 11.25% CHO-salt drinks at 200 mL·15 min, comprising weighed fructose and maltodextrin-glucose in ratios of 0.5:1 (0.5 ratio), 0.8:1 (0.8 ratio), and 1.25:1 (1.25 ratio). Fluid absorption was traced with D2O, whereas C-fructose and C-maltodextrin-glucose permitted fructose and glucose oxidation rate evaluation. The mean exogenous-fructose and exogenous-glucose oxidation rates were 0.27, 0.39, and 0.46 g·min and 0.65, 0.71, and 0.58 g·min in 0.5, 0.8, and 1.25 ratio drinks, representing mean oxidation efficiencies of 54%, 59%, and 55% and 65%, 85%, and 86% for fructose and glucose, respectively. With the 0.8 ratio drink, total exogenous-CHO oxidation rate was 18% (90% confidence interval, ±5%) and 5.2% (±4.6%) higher relative to 0.5 and 1.25 ratios, respectively, whereas respective differences in total exogenous-CHO oxidation efficiency were 17% (±5%) and 5.3% (±4.8%), associated with 8.6% and 7.8% (±4.2%) higher fructose oxidation efficiency. The effects of CHO ratio on water absorption were inconclusive. Mean sprint power with the 0.8 ratio drink was moderately higher than that with the 0.5 ratio (2.9%; 99% confidence interval, ±2.8%) and 1.25 ratio (3.1%; ±2.7%) drinks, with total- and endogenous-CHO oxidation rate, abdominal cramps, and drink sweetness qualifying as explanatory mechanisms. Enhanced high-intensity endurance performance with a 0.8 ratio fructose-maltodextrin-glucose drink is characterized by higher exogenous-CHO oxidation efficiency and reduced endogenous-CHO oxidation. The gut-hepatic or other physiological site responsible requires further research.

Geographical heterogeneity of the relationship between childhood obesity and socio-environmental status: Empirical evidence from Athens, Greece

Childhood obesity (ChO11ChO: Childhood Obesity; OLS: Ordinary Least Square; GWR: Geographically Weighted Regression; SES: Socio-Economic Status; GIS: Geographic Information Systems; AICc: corrected Akaike Information Criterion.) has been recognized as an epidemic in many developed and developing countries. The understanding of the spatial relationships between ChO and socio-environmental status is critical in order to control this epidemic. In this paper, we investigate these relationships and consider empirical evidence from Athens, Greece. We examine the association between ChO and socioeconomic status (education level, family income) and living conditions (population density, land cover of green and recreational areas) by using both global and local statistical analyses. For this purpose, we used survey obesity data collected in 2007 from 18,296 students in the primary schools of Athens. Moreover, we investigated the significance and spatial inequalities of the association between ChO and socio-environmental conditions of the study area. The results from global statistical modeling showed that education level is the most significant predictor of ChO. Furthermore, local Geographically Weighted Regression (GWR) modeling revealed that areas characterized by low educational level, high population density, low family income and limited coverage of green/recreation zones constituted an “obesogenic” environment. The findings of the proposed analysis promote our understanding of the factors influencing childhood obesity and may prove beneficial for the development of policies that target ChO.

Nutritional Strategies to Prevent Hypoglycemia at Exercise in Diabetic Adolescents

Studies on nutritional strategies to prevent exercise-induced hypoglycemia in adolescents with type 1 diabetes are scarce. This study aimed to compare the effect of two food strategies on blood glucose (BG) during and after 60 min of moderate-intensity exercise. Subjects performed exercise 120 min after breakfast in three conditions: 1) standardized breakfast + preexercise placebo beverage (PL), 2) standardized breakfast + preexercise CHO beverage (8 mg of CHO·kg of body weight·min of exercise; CHO), or 3) protein-supplemented breakfast (8 mg of protein·kg of body weight·min of exercise added to the standardized breakfast) + preexercise placebo beverage (PROT). As soon as BG falls <4 mmol·L or symptomatic hypoglycemia occurred during exercise, the session was stopped and CHO tablets were provided to correct hypoglycemia. Ten subjects (age = 14.0 ± 1.5 yr) participated in all conditions. BG decreased by 6.0 ± 1.9, 1.0 ± 3.1, and 4.6 ± 1.9 mmol·L in PL, CHO, and PROT conditions, respectively (P < 0.05). The proportion of subjects reaching hypoglycemic values or sensations of hypoglycemia was significantly different between conditions with 4/10, 1/10, and 0/10 in the PL, CHO, and PROT conditions (P < 0.05). The preexercise CHO beverage induced the least dramatic BG decrease during exercise. The PROT breakfast induced an overall similar BG drop compared to PL, a larger BG drop compared to CHO, but a similar rate of hypoglycemia compared to CHO. Our results suggest that taking CHO supplement before unplanned exercise is still the best strategy to prevent exercise-induced hypoglycemia in an adolescent population. However, a protein supplement strategy may also have some benefits in limiting the rate of hypoglycemia during and immediately after exercise.

The Effect of Adding Caffeine to Postexercise Carbohydrate Feeding on Subsequent High-Intensity Interval-Running Capacity Compared With Carbohydrate Alone

The aim of this study was to test the hypothesis that adding caffeine to postexercise carbohydrate (CHO) feedings improves subsequent high-intensity interval-running capacity compared with CHO alone. In a repeated-measures design, 6 men performed a glycogen-depleting exercise protocol until volitional exhaustion in the morning. Immediately after and at 1, 2, and 3 hr postexercise, participants consumed 1.2 g/kg body mass CHO of a 15% CHO solution, a similar CHO solution but with addition of 8 mg/kg body mass of caffeine (CHO+CAFF), or an equivalent volume of flavored water only (WAT). After the 4-hr recovery period, participants performed the Loughborough Intermittent Shuttle Test (LIST) to volitional exhaustion as a measure of high-intensity interval-running capacity. Average blood glucose values during the 4-hr recovery period were higher in the CHO conditions (p < .005) than in the WAT trial (4.6 ± 0.3 mmol/L), although there was no difference (p = .46) between CHO (6.2 ± 0.8 mmol/L) and CHO+CAFF (6.7 ± 1.0 mmol/L). Exercise capacity during the LIST was significantly longer in the CHO+CAFF trial (48 ± 15 min) than in the CHO (32 ± 15 min, p = .04) and WAT conditions (19 ± 6 min, p = .001). All 6 participants improved performance in CHO+CAFF compared with CHO (95% CI for mean difference = 1-32 min). The study provides novel data by demonstrating that adding caffeine to postexercise CHO feeding improves subsequent high-intensity interval-running capacity, a finding that may be related to higher rates of postexercise muscle glycogen resynthesis previously observed under similar feeding conditions.

Influence of Banana Versus Sports Beverage Ingestion On Phagocytic Cell Responses To 75-Km Cycling Time Trials

PURPOSE: The purpose of this project was to compare the acute effect of ingesting bananas (BAN) versus a 6% carbohydrate sports drink (CHO) on phagocytic cell responses to 75-km cycling in cyclists. DESIGN: Trained cyclists (N=14, age 37±1.9 y, Wattsmax 379±12.5) completed two 75-km cycling time trials (3 weeks apart, randomized, crossover) while ingesting BAN or CHO. Subjects ingested 0.4 gm/kg carbohydrate from BAN or CHO, and then cycled on CompuTrainers (RacerMate Inc., Seattle, WA) for 75-km at the fastest pace possible while ingesting 0.2 gm/kg carbohydrate from BAN or CHO every 15 min. Blood samples were taken pre-exercise, immediately following and 1-h post-exercise, and analyzed for granulocyte and monocyte phagocytosis (PHAG) and oxidative burst activity (OBA) using a flow cytometric procedure with FITC-labeled bacteria (Staphylococcus aureus; Molecular Probes, Eugene, OR) and hydroethidine (HE; Molecular Probes). All blood samples were prepared at the same ratio of eight bacteria per phagocytic cell. RESULTS: The time to complete the 75-km cycling trials did not differ between BAN and CHO (2.41±0.06 and 2.36±0.05 h, respectively, P=0.258). Exercise caused significant increases (P<0.001) above baseline levels in granulocyte PHAG (25% immediately- and 41% 1-h-post-exercise) and monocyte PHAG (50% and 72%, respectively), with no differences between BAN and CHO trials (interaction effects, P=0.215 and 0.191, respectively). Granulocyte and monocyte OBA did not differ between BAN and CHO trials and did not change with exercise (interaction effects, P=0.697 and 0.810, respectively). CONCLUSIONS: Bacterial phagocytosis but not OBA by blood granulocytes and monocytes was strongly increased following 75-km cycling time trials, with no differences between BAN and CHO conditions. The increase in phagocytosis with unchanged OBA reflects an inflammatory response to the physiologic stress of heavy exertion. Supported by a grant from Dole Foods, Inc.

Is acute supramaximal exercise capable of modulating lipoprotein profile in healthy men?

This study examined the effects of acute supramaximal exercise (approximately 115% VO(2max)) on the blood lipid profile for three different carbohydrate (CHO) storage levels (control, low and high). Six male subjects were randomly divided into three different groups: control, low CHO and high CHO. These groups differed in the diet to which the subjects were submitted before each exercise session. The lipid profile [triglycerides (TG), very low-density lipoprotein (VLDL), high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, TG/HDL-C ratio and total cholesterol) was determined at rest, immediately after exercise and 1 h after exercise bouts. The time to exhaustion was lower in the low CHO condition compared with the control and high CHO condition (3.59 +/- 0.72; 2.91 +/- 0.56; and 4.26 +/- 0.69 min; P < 0.05). The energy expenditure (control: 251.1 +/- 56.0 kJ; low CHO: 215.2 +/- 28.6 kJ; and high CHO: 310.4 +/- 64.9 kJ) was significantly different between the low and high CHO conditions (P < 0.05). There were no significant changes in the lipid profile for any of the experimental conditions (control, low and high; P < 0.05). Glucose and insulin levels did not show time-dependent changes in any of the conditions (P > 0.05). These results indicate that a supramaximal exercise session has no significant effects on lipid metabolism.

Influence of macronutrient intake and anthropometric characteristics on plasma insulin after eccentric exercise

To increase understanding of the interaction between macronutrients and insulin resistance (IR), this study sought to determine the influence of macronutrient intake and anthropometric differences on IR and inflammation responses to eccentric resistance exercise. Men and women (n = 12, 19-36 years old) participated in a crossover study and completed 6 sets of 10 unilateral maximal eccentric contractions of the elbow flexors and extensors followed by controlled diet conditions for the first 8 hours postexercise of carbohydrate/fat/protein proportions of either 75%/15%/10% (CHO) or 6%/70%/24% (FAT/PRO). Fasting glucose, insulin, homeostatic model assessment (HOMA) variables, and interleukin (IL)-1 β were measured preexercise and 23 hours postexercise (additional measures of glucose and insulin 1 hour after meals consumed 0.5, 3, and 7 hours postexercise). Insulin increased more ( P < .01) in the CHO compared with the FAT/PRO condition at 1.5, 4, and 8 hours postexercise. Insulin, HOMA-IR, and HOMA- β-cell function increased 23 hours postexercise in both conditions, whereas IL-1 β increased 23 hours postexercise only in the CHO condition. Magnitude of change (Δ) for these variables associated positively with body mass index (BMI) and waist to hip ratio (WHR) in the CHO and inversely in the FAT/PRO condition; that is, r = 0.53 ( P = .10) and r = −0.82 ( P < .01) for BMI vs Δ insulin in CHO and FAT/PRO conditions, respectively. The Δ IL-1 β associated with BMI ( r = 0.62, P < .05) and WHR ( r = 0.84, P < .01) in the CHO condition. The CHO enhanced IR and inflammation as BMI and WHR increased, whereas fat and protein enhanced IR as BMI and WHR decreased. Thus, BMI and WHR may need to be taken into account in the development of nutritional strategies to prevent IR.

Effects of Carbohydrate Supplementation on the RPE-Blood Lactate Relationship

To examine the effects of carbohydrate (CHO) ingestion on the RPE-blood lactate relationship during incremental and constant-effort exercise. Six male and three female subjects (mean age = 27.2 +/- 8.2 yr, height [ht] = 174.5 +/- 13.5 cm, weight [wt] = 68.9 +/- 12.5 kg, body fat = 18.5 +/- 8.3%), completed two incremental cycling lactate threshold (LT)/(.)VO2peak tests followed by two 45-min production trials. Two hundred and forty milliliters of either carbohydrate or placebo (PL) was ingested before and every 15 min during exercise. No differences were observed between conditions at LT, 2.5 and 4.0 mM, and peak. Within the CHO condition: V O2 = 25.0, 32.6, 37.5, 47.2 mL x kg x min(-1); power output = 123.3, 170.7, 200.1, 241.7 W; RPE = 12.8, 15.4, 17.2, 19.3; and HR = 137.4, 156.8, 168.7, 187.7 beats x min(-1) at LT, 2.5 mM, 4.0 mM, and peak, respectively. Within PL: V O2 = 24.7, 32.5, 36.8, 45.7 mL x kg x min(-1); power output = 130.0, 175.4, 201.9, 240.0 W; RPE = 12.1, 15.0, 17.0, 19.3; and HR = 134.9, 157.9, 169.6, 187.2 beats x min(-1), respectively. In the CHO condition, blood glucose was higher (P < 0.001), and a trend was observed for lower RPE over time (P = 0.07). During the production trials (RPE of 16) in the CHO condition, higher blood glucose area under the curve (AUC) (PL: 204.1 +/- 79.3 mM; CHO: 220.6 +/- 18.5 mM; P = 0.039) and a trend for greater total work (PL: 448.5 +/- 73.8 kJ; CHO: 470.5 +/- 65.6 kJ; P = 0.089) were observed. We conclude that 1) CHO ingestion does not alter the blood lactate-RPE relationship during incremental LT/(.)VO2peak cycling; and 2) carbohydrate supplementation during exercise, eliciting high RPE, may increase work output during training sessions.