High-dose short-term creatine supplementation without beneficial effects in professional cyclists: a randomized controlled trial.

BACKGROUND: Growing evidence supports the ergogenic effects of creatine supplementation on muscle power/strength, but its effects on endurance performance remain unclear. We assessed the effects of high-dose short-term creatine supplementation in professional cyclists during a training camp. METHODS: The study followed a double-blind, randomized parallel design. Twenty-three professional U23 cyclists (19 ± 1 years, maximum oxygen uptake: 73.0 ± 4.6 mL/kg/min) participated in a 6-day training camp. Participants were randomized to consume daily either a recovery drink (containing carbohydrates and protein) with a 20-g creatine supplement (creatine group, n = 11) or just the recovery drink (placebo group, n = 12). Training loads and dietary intake were monitored, and indicators of fatigue/recovery (Hooper index, countermovement jump height), body composition, and performance (10-second sprint, 3-, 6-, and 12-minute time trials, respectively, as well as critical power and W') were assessed as study outcomes. RESULTS: The training camp resulted in a significant (p < 0.001) increase of training loads (+50% for total training time and + 61% for training stress score, compared with the preceding month) that in turn induced an increase in fatigue indicators (significant time effect [p < 0.001] for delayed-onset muscle soreness, fatigue, and total Hooper index) and a decrease in performance (significant time effect [p = 0.020] for critical power, which decreased by -3.8%). However, no significant group-by-time interaction effect was found for any of the study outcomes (all p > 0.05). CONCLUSIONS: High-dose short-term creatine supplementation seems to exert no consistent beneficial effects on recovery, body composition or performance indicators during a strenuous training period in professional cyclists.

Acute ketone supplementation in the absence of muscle glycogen utilization: Insights from McArdle disease.

BACKGROUND & AIMS: Ketone supplementation is gaining popularity. Yet, its effects on exercise performance when muscle glycogen cannot be used remain to be determined. McArdle disease can provide insight into this question, as these patients are unable to obtain energy from muscle glycogen, presenting a severely impaired physical capacity. We therefore aimed to assess the effects of acute ketone supplementation in the absence of muscle glycogen utilization (McArdle disease). METHODS: In a randomized cross-over design, patients with an inherited block in muscle glycogen breakdown (i.e., McArdle disease, n = 8) and healthy controls (n = 7) underwent a submaximal (constant-load) test that was followed by a maximal ramp test, after the ingestion of a placebo or an exogenous ketone ester supplement (30 g of D-beta hydroxybutyrate/D 1,3 butanediol monoester). Patients were also assessed after carbohydrate (75 g) ingestion, which is currently considered best clinical practice in McArdle disease. RESULTS: Ketone supplementation induced ketosis in all participants (blood [ketones] = 3.7 ± 0.9 mM) and modified some gas-exchange responses (notably increasing respiratory exchange ratio, especially in patients). Patients showed an impaired exercise capacity (-65 % peak power output (PPO) compared to controls, p < 0.001) and ketone supplementation resulted in a further impairment (-11.6 % vs. placebo, p = 0.001), with no effects in controls (p = 0.268). In patients, carbohydrate supplementation resulted in a higher PPO compared to ketones (+21.5 %, p = 0.001) and a similar response was observed vs. placebo (+12.6 %, p = 0.057). CONCLUSIONS: In individuals who cannot utilize muscle glycogen but have a preserved ability to oxidize blood-borne glucose and fat (McArdle disease), acute ketone supplementation impairs exercise capacity, whereas carbohydrate ingestion exerts the opposite, beneficial effect.

Pre-sleep protein supplementation in professional cyclists during a training camp: a three-arm randomized controlled trial.

Background: The effects of pre-sleep protein supplementation on endurance athletes remain unclear, particularly whether its potential benefits are due to the timing of protein intake or solely to an increased total protein intake. We assessed the effects of pre-sleep protein supplementation in professional cyclists during a training camp accounting for the influence of protein timing. Methods: Twenty-four professional U23 cyclists (19 ± 1 years, peak oxygen uptake: 79.8 ± 4.9 ml/kg/min) participated in a six-day training camp. Participants were randomized to consume a protein supplement (40 g of casein) before sleep (n = 8) or in the afternoon (n = 8), or an isoenergetic placebo (40 g of carbohydrates) before sleep (n = 8). Indicators of fatigue/recovery (Hooper index, Recovery-Stress Questionnaire for Athletes, countermovement jump), body composition, and performance (1-, 5-, and 20-minute time trials, as well as the estimated critical power) were assessed as study outcomes. Results: The training camp resulted in a significant (p < 0.001) increase in training loads (e.g. training stress score of 659 ± 122 per week during the preceding month versus 1207 ± 122 during the training camp), which induced an increase in fatigue indicators (e.g. time effect for Hooper index p < 0.001) and a decrease in performance (e.g. time effect for critical power p = 0.002). Protein intake was very high in all the participants (>2.5 g/kg on average), with significantly higher levels found in the two protein supplement groups compared to the placebo group (p < 0.001). No significant between-group differences were found for any of the analyzed outcomes (all p > 0.05). Conclusions: Protein supplementation, whether administered before sleep or earlier in the day, exerts no beneficial effects during a short-term strenuous training period in professional cyclists, who naturally consume a high-protein diet.

Durability in Professional Cyclists: A Field Study.

PURPOSE: To assess durability in professional cyclists, as well as potential associated indicators. METHODS: Twelve male professional cyclists participated in the study (age: 26 [5] y, VO2max: 83.0 [3.6] mL·kg-1·min-1). They performed a 20-minute time trial (TT) on 2 different sessions separated by a 48-hour period: (1) with no previous fatigue (TTFresh) and (2) immediately after a long submaximal ride (approximately 4 h, 40 kJ/kg) (TTFatigue). We then assessed the decay (in percentage) in mean power output (PO) from TTFresh to TTFatigue and its association with different laboratory-based endurance indicators (ventilatory threshold, peak PO, and VO2max) determined through a previous maximal incremental cycling test, as well as with training loads during the 4 weeks preceding the TTs. RESULTS: While no differences were noted in the average heart rate (177 [7] vs 176 [6] beats·min-1, P = .118), there was a significant decay in PO between TTFresh and TTFatigue (386 [29] W vs 375 [28] W [-2.9%], respectively; P = .007), albeit with signs of interindividual variability (range = -8.5% to 1.1%; coefficient of variation = 105%). No significant associations were found between the PO decay and any of the analyzed indicators (all P > .05). CONCLUSIONS: Performance is significantly impaired after a certain amount of work completed (approximately 40 kJ·kg-1) in professional cyclists, and the magnitude of this impairment seems to be not related to "traditional" laboratory-based endurance indicators or to markers of training load. These findings might support the need for specifically assessing durability in cyclists and confirming potential determinants of this parameter.

Comparative analysis of endurance, strength and body composition indicators in professional, under-23 and junior cyclists.

Purpose: To compare endurance, strength and body composition indicators between cyclists of three different competition age categories. Methods: Fifty-one male road cyclists classified as either junior (n = 13, age 16.4 ± 0.5 years), under-23 [(U23), n = 24, 19.2 ± 1.3 years] or professional (n = 14, 26.1 ± 4.8 years) were studied. Endurance (assessed through a maximal incremental test and an 8-minute time-trial), strength/power (assessed through incremental loading tests for the squat, lunge and hip thrust exercises) and body composition (assessed through dual energy X-ray absorptiometry) were determined on three different testing sessions. Results: U23 and, particularly professional, cyclists attained significantly (p < 0.05) higher values than juniors for most of the analyzed endurance indicators [time-trial performance, maximum oxygen uptake (VO2max), peak power output (PPO), respiratory compensation point (RCP), and ventilatory threshold (VT)]. Significant differences (p < 0.05) between U23 and professionals were also found for time-trial performance, PPO and VT, but not for other markers such as VO2max or RCP. Professional cyclists also showed significantly (p < 0.05) lower relative fat mass and higher muscle mass levels than U23 and, particularly, juniors. No consistent differences between age categories were found for muscle strength/power indicators. Conclusion: Endurance (particularly time-trial performance, PPO and VT) and body composition (fat and muscle mass) appear as factors that best differentiate between cyclists of different age categories, whereas no consistent differences are found for muscle strength/power. These findings might help in performance prediction and/or talent identification and may aid in guiding coaches in the design of training programs focused on improving those variables that appear more determinant.