The effect of 1,3-butanediol and carbohydrate supplementation on running performance

ObjectivesIngested ketogenic agents offer the potential to enhance endurance performance via the provision of an alternative exogenous, metabolically efficient, glycogen-sparing fuel (i.e. ketone bodies). This study aimed to assess the impact of combined carbohydrate and 1,3-butanediol (CHO-BD) supplementation on endurance performance, blood beta-hydroxybutyrate (βHB) concentration and glycolytic activity, in comparison to carbohydrate supplementation alone (CHO).DesignEleven male runners (age 38 ± 12 years, mass 67.3 ± 6.5 kg, height 174.5 ± 5.0 cm, ${\dot{\mathrm{V}}}_{{\mathrm{O}}_{2\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}}$ 64.2 ± 5.0 ml⋅kg⁻¹⋅min⁻¹) performed two experimental trials in a randomised crossover design.MethodsEach trial consisted of 60 min of submaximal running, followed by a 5 km running time-trial (TT), and was performed following the ingestion of an energy matched ∼650 ml drink (CHO-BD or CHO).ResultsThere was no difference in TT completion time between the trials (CHO: 1265 ± 93, CHO-BD: 1261 ± 96 s; p = 0.723). However, blood βHB concentration in the CHO-BD trial was at least double that of the CHO trial at all time points following supplementation (p < 0.05). While blood lactate concentration was lower in the CHO-BD versus CHO trial after 30 min submaximal exercise (CHO-BD: 1.46 ± 0.67 mmol⋅L⁻¹, CHO: 1.77 ± 0.46 mmol⋅L⁻¹, p = 0.040), it was similar at other time points. Blood glucose concentrations were higher post-TT in the CHO-BD trial (CHO-BD: 5.83 ± 1.02 mmol⋅L⁻¹, CHO: 5.26 ± 0.95 mmol⋅L⁻¹, p = 0.015).ConclusionsAn energy matched CHO-BD supplementation drink raised βHB concentration and acutely lowered blood lactate concentration, without enhancing 5 km TT running performance.     

Effect of astaxanthin on cycling time trial performance

We examined the effect of Astaxanthin (AST) on substrate metabolism and cycling time trial (TT) performance by randomly assigning 21 competitive cyclists to 28 d of encapsulated AST (4?mg/d) or placebo (PLA) supplementation. Testing included a VO2max test and on a separate day a 2?h constant intensity pre-exhaustion ride, after a 10?h fast, at 5% below VO2max stimulated onset of 4?mmol/L lactic acid followed 5?min later by a 20?km TT. Analysis included ANOVA and post-hoc testing. Data are Mean (SD) and (95% CI) when expressed as change (pre vs. post). Fourteen participants successfully completed the trial. Overall, we observed significant improvements in 20?km TT performance in the AST group (n=7; -121?s; 95% CI, -185, -53), but not the PLA (n=7; -19?s; 95% CI, -84, 45). The AST group was significantly different vs. PLA (P<0.05). The AST group significantly increased power output (20?W; 95% CI, 1, 38), while the PLA group did not (1.6?W; 95% CI, -17, 20). The mechanism of action for these improvements remains unclear, as we observed no treatment effects for carbohydrate and fat oxidation, or blood indices indicative of fuel mobilization. While AST significantly improved TT performance the mechanism of action explaining this effect remains obscure.     

Placebo effect of carbohydrate feedings during a 40-km cycling time trial

PURPOSE: The placebo effect, a favorable outcome from belief that one has received a beneficial treatment, may be an important phenomenon in athletic performance. We have therefore investigated the placebo effect of a carbohydrate supplement on endurance performance. METHODS: Forty-three competitive endurance cyclists (2 female, 41 male) performed two simulated 40-km time trials on an air-braked ergometer. In the first trial they ingested water to establish baseline performance (mean power 265 +/- 46 W for 58 +/- 4 min, mean +/- SD). For the second trial 6-8 d later they were randomized to two groups: one group ingested 16 mL x kg(-1) of a drink containing 7.6 g x 100 mL(-1) carbohydrate; the other ingested an indistinguishable noncaloric placebo drink. Cyclists in each group were further randomized to three subgroups according to whether they were told the drink contained carbohydrate, placebo, or either (not told). RESULTS: Changes in mean power in the second trial were: told carbohydrate, 4.3 +/- 4.8%; told placebo, 0.5 +/- 5.8%; and not told, -1.1 +/- 8.5%. The difference between the told-carbohydrate and told-placebo groups was 3.8% (95% likely range 7.9 to -0.2%). The change in performance in the not-told group was more variable than that of the told groups by a factor of 1.6 (2.6 to 1.0). The real effect of carbohydrate was a slight reduction in power of 0.3% (4.4 to -3.8%). CONCLUSIONS: (a) The placebo effect of a potentially ergogenic treatment during unblinded laboratory time trials lasting approximately 1 h is probably a small but worthwhile increase in endurance power. (b) Blinding subjects to the treatment increases individual differences in endurance effort, which may reduce precision of performance outcomes in controlled trials.     

High dose Nitrate ingestion does not improve 40 km cycling time trial performance in trained cyclists

ABSTRACT

This study evaluated the chronic effects of nitrate (NO₃^?) ingestion over three days, on 40 km TT performance in 11trained cyclists (VO_2max: 60.8 ± 7.4 ml.kg^?1.min^?1; age: 36 ± 9 years; height: 1.80 ± 0.06 m; body mass: 87.2 ± 12.0 kg). Utilising a double-blind randomised cross-over design, participants completed three 40 km TT on a Velotron® ergometer following the ingestion of either a 140 ml of “BEET It sport®” NO₃^? shot containing 12.8 mmol or 800 mg of NO₃^?, a placebo drink or nothing (control). Performance, oxygen consumption (VO₂), blood bicarbonate (HCO3-), pH and lactate (BLa) and ratings of perceived exertion (RPE) were measured every 10 km throughout the TT. The present findings show that NO₃^? ingestion had no effect on TT performance (NO₃^?: 4098.0 ± 209.8 vs. Placebo: 4161.9 ± 263.3 s, p = 0.296, ES = 0.11), or VO₂ (p = 0.253, ES = 0.13). Similarly, blood lactate and RPE were also unaffected by the experimental conditions (p = 0.522, ES = 0.06; p = 0.085, ES = 0.30) respectively. Therefore, these results suggest that a high dose of NO₃^? over three days has limited efficacy as an ergogenic aid for 40 km TT cycling performance in trained cyclists.     

The effect of 1,000 km nonstop cycling on fat mass and skeletal muscle mass

We evaluated the change in body mass including fat mass and skeletal muscle mass in one ultracyclist whilst cycling 1,000 km in 48 hours at a constant intensity of ～48% VO(2)max, corresponding to a heart rate frequency of ～105 ± 5 bpm. A 1 kg fat mass decrease resulted, with the largest decrease occurring between the 12th and the 24th hour. No steady state in metabolism was observed and no regular decrease of subcutaneous adipose tissue resulted. This result is backed up by the nuclear magnetic resonance (NMR) urine analysis. Body water increase with simultaneous dehydration is possibly due to endocrine-induced renal water retention, in order to maintain metabolism processes that are required for energy supply and blood flow during very prolonged exercise. Both applied methods, the anthropometric and the bioelectrical impedance analysis, analyse fluid accumulation--especially in the skinfolds of the lower extremities--apparently incorrectly as an increase in body mass and not as an increase in fluids.     

Predictive validity of ventilatory and lactate thresholds for cycling time trial performance

PURPOSE: To determine which laboratory measurement best predicts 40 km cycling time-trial (TT) performance. METHODS: Fifteen male cyclists performed lactate-threshold (LT), ventilatory-threshold (VT), 5 km and 40 km TT. Key variables of interest were Watts at thresholds. For VT determination we used: breakpoint of ventilatory equivalent of oxygen (VE/VO2); breakpoint of ventilatory equivalent of carbon dioxide (VE/VCO2); V-slope; respiratory exchange ratio (RER)=1 and 0.95. For LT we used Stegmann's individual anaerobic threshold; the stage preceding the second 0.5 mmol L(-1) increase (Baldari); 4 mmol L(-1); 1 mmol L(-1) increase in 3 min; the stage preceding the first 1 mmol L(-1) increase as criterion methods (<1 mmol). Analyses also included peak power during the incremental threshold tests (MaxVT(watts), MaxLT(watts)) and 5 km performance (5K(avgwatts)). RESULTS: Regression analyses between VT variables and 40K(avgwatts) were significant for V-slope (r2=0.63), VE/VO2 (r2=0.64), RER(0.95) (r2=0.53), RER1 (r2=0.57), and MaxVT(watts) (r2=0.65). Regressions between LT variables and 40K(avgwatts) were significant for Baldari (r2=0.52), 4 mmol L(-1) (r2=0.36), <1 mmol (r2=0.35), Keul (r2=0.34), and MaxLT(watts) (r2=0.51). Regressions between 5K variables and 40K(avgwatts) were significant for 5K(avgwatts) (r2=0.58). Paired t-tests between these variables and the 40K(avgwatts) indicated that absolute power outputs at VE/VO2 (P=0.33), RER(0.95) (P=0.93), and 4 mmol L(-1) (P=0.39) were not significantly different from 40K(avgwatts). CONCLUSION: We conclude that VT-based variables are generally superior to LT variables relative to predicting 40K(avgwatts), the simplest of several valid measures appears to be VE/VO2.     

Physiological and electromyographic responses during 40-km cycling time trial: relationship to muscle coordination and performance.

The purpose of this study was to compare the oxygen uptake (VO(2)), respiratory exchange ratio (RER), cadence and muscle activity during cycling a 40-km time trial (TT), and to analyse the relationship between muscle activity and power output (PO). Eight triathletes cycled a 40-km TT on their own bicycles, which were mounted on a stationary cycle simulator. The VO(2), RER and muscle activity (electromyography, EMG) from tibialis anterior (TA), gastrocnemius medialis (GA), biceps femoris (BF), rectus femoris (RF) and vastus lateralis (VL) of the lower limb were collected. The PO was recorded from the cycle simulator. The data were collected at the 3rd, 10th, 20th, 30th and 38th km. The root mean square envelope (RMS) of EMG was calculated. The VO(2) and PO presented a significant increase at the 38th km (45.23+/-8.35 ml kg min(-1) and 107+/-7.11% of mean PO of 40-km, respectively) compared to the 3rd km (38.12+/-5.98 ml kg min(-1) and 92+/-8.30% of mean PO of 40-km, respectively). There were no significant changes in cadence and RER throughout the TT. The VL was the only muscle that presented significant increases in the RMS at the 10th km (22.56+/-3.05% max), 20th km (23.64+/-2.52% max), 30th km (25.27+/-3.00% max), and 38th km (26.28+/-3.57%max) when compared to the 3rd km (21.03+/-1.88%max). The RMS of VL and RF presented a strong relationship to PO (r=0.89 and 0.86, respectively, p<0.05). The muscular steady state reported for cycling a 30-min TT seems to occur in the 40-km TT, for almost all assessed muscles, probably in attempt to avoid premature muscle fatigue.     

The availability of task-specific feedback does not affect 20 km time trial cycling performance or test-retest reliability in trained cyclists

ObjectivesThis study examined the influence of the availability of task-specific feedback on 20 km time trial (20TT) cycling performance and test-retest reliability.DesignThirty trained, club-level cyclists completed two 20TT’s on different days, with (feedback, FB) or without (no-feedback, NFB) task-specific feedback (i.e., power output, cadence, gear and heart rate [HR]). Elapsed distance was provided in both conditions.MethodsDuring trials, ergometer variables and HR were continuously recorded, and a rating of perceived exertion (RPE) was collected every 2 km. Data were analysed using linear mixed-effects models in a Bayesian framework, and Cohen’s d was calculated for standardised differences. The reliability of finish time and mean power output (PO) was determined via multiple indices, including intraclass correlations (ICC).ResultsPerformance, pacing behaviour, and RPE were not statistically different between conditions. The posterior mean difference [95% credible interval] between TT1 and TT2 for FB and NFB was 10 s [−5, 25] and −2 s [−17, 14], respectively. In TT2, HR was statistically higher (∼8 b min⁻¹) in FB compared to NFB after 13 km (d = 2.08–2.25). However, this result was explained by differences in maximal HR. Finish time (FB: ICC =  0.99; NFB: ICC = 0.99) and mean power output (FB: ICC = 0.99; NFB: ICC = 0.99) in each condition were substantially reliable.ConclusionsThe availability of task-specific information did not affect 20TT performance or reliability. Except for elapsed distance, task-specific feedback should be withheld from trained cyclists when evaluating interventions that may affect performance, to prevent participants from recalling previous performance settings.     

Effects of music on work-rate distribution during a cycling time trial

Previous research work on the ergogenic effects of music has mainly involved constant power tests to exhaustion as dependent variables. Time trials are more externally valid than constant power tests, may be more reliable and allow the distribution of self-selected work-rate to be explored. We examined whether music improved starting, finishing and/or overall power during a 10-km cycling time trial, and whether heart rate and subjective responses to this time trial were altered by music. Sixteen participants performed two 10-km time trials on a Cybex cycle ergometer with, and without, the presence of a form of dance music known as "trance" (tempo = 142 beats x min (-1), volume at ear = 87 dB). Participants also completed the Brunel music rating inventory (BMRI) after each time trial in the music condition. The mean +/- SD time to complete the time trial was 1030 +/- 79 s in the music condition compared to 1052 +/- 77 s without music (95 % CI of difference = 10 to 34 s, p = 0.001). Nevertheless, ratings of perceived exertion were consistently (0.8 units) higher throughout the time trial with music (p < 0.0005). The interaction between distance and condition was significant for cycling speed measured during the time trial (p = 0.007). The largest music-induced increases in cycling speed and heart rate were observed in the first 3 km of the time trial. After completion of the BMRI, participants rated the "tempo" and "rhythm" of the music as more motivating than the "harmony" and "melody" aspects. These results suggest that music improves cycling speed mostly in the first few minutes of a 10-km time trial. In contrast to the findings of previous research, which suggested that music lowers perceived exertion at a constant work-rate, the participants in our time trials selected higher work-rates with music, whilst at the same time perceived these work-rates as being harder than without music.     

Effects of alterations in dietary carbohydrate intake on running performance during a 10 km treadmill time trial.

OBJECTIVE: To examine the influence of a seven day diet manipulation on performance during a 10 km treadmill time trial in trained runners. METHODS: Six trained runners ran two 10 km time trials on a treadmill set at a constant 4% gradient, each after a 7 d period of dietary manipulation. The two experimental diets were a low carbohydrate (CHO) diet (40% CHO by total energy) to be consumed for 7 d, and a high CHO diet containing 55% CHO for the first 4 d followed by 70% CHO for the remaining 3 d. Blood samples were obtained before and immediately after each run. Expired gases were collected and heart rate monitored. RESULTS: Performance time following the high CHO [48.6(SD 2.7) min] and low CHO [48.6(2.3) min] diets was not different (P = 0.72), nor were there any differences in running speed between conditions. No significant differences were found between conditions in any of the metabolites measured (blood lactate, glucose, glycerol, and plasma free fatty acids). The rate of CHO oxidation was greater on the high CHO diet compared to the low CHO diet (P < 0.05). Heart rate was not different between conditions. CONCLUSIONS: The results of this study indicate that moderate changes in the composition of the diet do not affect 10 km running performance in trained subjects.     

Effect of intermittent hypoxic training on 20 km time trial and 30 s anaerobic performance

This study aimed to verify whether the “live low, train high” approach is beneficial for endurance and/or anaerobic cycling performance. Sixteen well‐trained athletes completed 90 min of endurance training (60–70% of heart rate reserve), followed by two 30‐s all‐out sprints (Wingate test), daily, for 10 consecutive days. Nine subjects [intermittent hypoxic training (IHT) group] trained with an F_IO₂ set to produce arterial oxygen saturations of ～88–82%, while seven subjects (placebo group) trained while breathing a normal gas mixture (F_IO₂=0.21). Four performance tests were conducted at sea level including a familiarization and baseline trial, followed by repeat trials at 2 and 9 days post‐intervention. Relative to the placebo group, the mean power during the 30‐s Wingate test increased by 3.0% (95% confidence limits, CL ± 3.5%) 2 days, and 1.7% (± 3.8%) 9 days post‐IHT. Changes in other performance variables (30 s peak power, 20 km mean power and 20 km oxygen cost) were unclear. During the time trial, the IHT participants' blood lactate concentration, respiratory exchange ratio, and SpO₂, relative to the placebo group, was substantially increased at 2 days post‐intervention. The addition of IHT to the normal training program of well‐trained athletes produced worthwhile gains in 30 s sprint performance possibly through enhanced glycolysis.     

The effect of a preexercise meal on time to fatigue during prolonged cycling exercise

PURPOSE AND METHODS: Seven subjects exercised to exhaustion on a bicycle ergometer at a workload corresponding to an intensity of 70% maximal oxygen uptake (VO2max). On one occasion (FED), subjects consumed a preexercise carbohydrate (CHO) containing breakfast (100 g CHO) 3 h before exercise. On the other occasion (FASTED), subjects exercised after an overnight fast. Exercise time to fatigue was significantly longer (P < 0.05) when subjects consumed the breakfast (136+/-14 min) compared with when they exercised in the fasted state (109+/-12 min). RESULTS: Pre- and post-exercise muscle glycogen concentrations, respiratory exchange ratio, carbohydrate and fat oxidation, and lactate and insulin concentrations were not significantly different between the two trials. Insulin concentrations decreased significantly (P < 0.05) from 4.7+/-0.05 microIU.mL(-1) to 2.8+/-0.4 microIU.mL(-1) in FED and from 6.6+/-0.6 microIU.mL(-1) to 3.7+/-0.6 microIU.mL(-1) in FASTED subjects and free fatty acid concentrations (FFA) increased significantly (P < 0.05) from 0.09+/-0.02 mmol.L(-1) to 1.4+/-0.6 mmol.L(-1) in FED and from 0.17+/-0.02 mmol.L(-) to 0.74+/-0.27 mmol.L(-1) in FASTED subjects over the duration of the trials. CONCLUSIONS: In conclusion, the important finding of this study is the increased time to fatigue when subjects ingested the CHO meal with no negative effects ascribed to increased insulin concentrations and decreased FFA concentrations after CHO ingestion.     

The effect of extrinsic motivation on cycle time trial performance

PURPOSE: Athletes occasionally follow pacing patterns that seem unreasonably aggressive compared with those of prerace performances, potentially because of the motivation provided by competition. This study evaluated the effect of extrinsic motivation on cyclists' time trial performance. METHODS: Well-trained recreational cyclists (N=7) completed four 1500-m laboratory time trials including a practice trial, two self-paced trials, and a trial where a monetary reward was offered. Time, total power output, power output attributable to aerobic and anaerobic metabolic sources, VO2, and HR were measured. RESULTS: The time required for the second, third, and last (extrinsically motivated) time trials was 133.1 +/- 2.1, 134.1 +/- 3.4, and 133.6 +/- 3.0 s, respectively, and was not different (P>0.05). There were no differences for total (396 +/- 19, 397 +/- 23, and 401 +/- 17 W), aerobic (253 +/- 12, 254 +/- 10, and 246 +/- 13 W), and anaerobic (143 +/- 14, 143 +/- 21, and 155 +/- 11 W) power output. The highest VO2 was not different over consecutive time trials (3.76 +/- 0.19, 3.73 +/- 0.16, and 3.71 +/- 0.22 L x min(-1)). When ranked by performance, without reference to the extrinsic motivation (131.9 +/- 2.4, 133.4 +/- 2.4, and 135.4 +/- 2.5 s), there was a significant difference for the first 100 m and from 100 to 300 m in power output, with a larger total power (560 +/- 102, 491 +/- 82, and 493 +/- 93; and 571 +/- 94, 513 +/- 41, and 484 +/- 88 W) and power attributable to anaerobic sources (446 +/- 100, 384 +/- 80, and 324 +/- 43; and 381 +/- 87, 383 +/- 90, and 289 +/- 91 W) for the fastest trial. CONCLUSION: Extrinsic motivation did not change the time trial performance, suggesting that 1500-m performance is extremely stable and not readily changeable with simple external motivation. The results suggest that spontaneous improvement in performance for time trials of this duration is attributable to greater early power output, which is primarily attributable to anaerobic metabolic sources.     

Effect of the glycaemic index of a pre-exercise meal on metabolism and cycling time trial performance

This study investigated the effects of low or high glycaemic index (GI) foods consumed prior to a 40 km time trial (TT) on metabolism and subsequent endurance performance. Ten male cyclists consumed high GI or low GI meals, providing 1 g kg^?1 body mass of carbohydrate, 45 min prior to the TT. The TT performance was significantly (p = 0.009) improved in the low (93 ± 8 min) compared to the high GI trial (96 ± 7 min). Low GI carbohydrate oxidation rate (2.51 ± 1.71 g min^?1) was higher (p = 0.003) than the HGI carbohydrate oxidation rate (2.14 ± 1.5 g min^?1). Fat oxidation rate was significantly higher (p = 0.002) for the high (0.27 ± 0.17 g min^?1) than the low GI trial (0.16 ± 0.14 g min^?1). Insulin rose significantly following the high compared to the low GI meal (p = 0.008) but dropped significantly to similar values throughout the TT. No significant differences in either TGA or FFA concentration were observed between the trials. The low GI meal led to an increase in the availability of carbohydrate and a greater carbohydrate oxidation throughout the exercise period, which may have sustained energy production towards the end of exercise and led to the improved TT performance observed.     

The relationship between peak fat oxidation and prolonged double-poling endurance exercise performance

The peak fat oxidation rate (PFO) and the exercise intensity that elicits PFO (Fat_max) are associated with endurance performance during exercise primarily involving lower body musculature, but it remains elusive whether these associations are present during predominant upper body exercise. The aim was to investigate the relationship between PFO and Fat_max determined during a graded exercise test on a ski-ergometer using double-poling (GET-DP) and performance in the long-distance cross-country skiing race, Vasaloppet. Forty-three healthy men completed GET-DP and Vasaloppet and were divided into two subgroups: recreational (RS, n = 35) and elite (ES, n = 8) skiers. Additionally, RS completed a cycle-ergometer GET (GET-Cycling) to elucidate whether the potential relationships were specific to exercise modality. PFO (r² = .10, P = .044) and Fat_max (r² = .26, P < .001) were correlated with performance; however, was the only independent predictor of performance (adj. R² = .36) across all participants. In ES, Fat_max was the only variable associated with performance (r² = .54, P = .038). Within RS, DP (r² = .11, P = .047) and ski-specific training background (r² = .30, P = .001) were associated with performance. Between the two GETs, Fat_max (r² = .20, P = .006) but not PFO (r² = .07, P = .135) was correlated. Independent of exercise mode, neither PFO nor Fat_max were associated with performance in RS (P > .05). These findings suggest that prolonged endurance performance is related to PFO and Fat_max but foremost to during predominant upper body exercise. Interestingly, Fat_max may be an important determinant of performance among ES. Among RS, DP , and skiing experience appeared as performance predictors. Additionally, whole-body fat oxidation seemed specifically coupled to exercise modality.     

Effect of induced alkalosis on performance during a field-simulated BMX cycling competition

Objectives

The aim of the present study was to test the effect of sodium bicarbonate (NaHCO₃^?) ingestion on performance during a simulated competition on a Bicycle Motocross (BMX) track.