Marathons are run at about 80% VO2 max. 5Ks at about 95%. 64% is jogging. They know that. The study is a fraud.
“Methods: Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses.”
Fair enough. <50g carbs per day may not be optimal for athletic performance at >70% VO2 max. Personally, I still see no harm in athletes and scientists experimenting with it.
Re-Examining High-Fat Diets for Sports Performance: Did We Call the 'Nail in the Coffin' Too Soon?During the period 1985-2005, studies examined the proposal that adaptation to a low-carbohydrate (<25 % energy), high-fat (>60 % energy) diet (LCHF) to increase muscle fat utilization during exercise could enhance performance in trained individuals by reducing reliance on muscle glycogen. As little as 5 days of training with LCHF retools the muscle to enhance fat-burning capacity with robust changes that persist despite acute strategies to restore carbohydrate availability (e.g., glycogen supercompensation, carbohydrate intake during exercise). Furthermore, a 2- to 3-week exposure to minimal carbohydrate (<20 g/day) intake achieves adaptation to high blood ketone concentrations. However, the failure to detect clear performance benefits during endurance/ultra-endurance protocols, combined with evidence of impaired performance of high-intensity exercise via a down-regulation of carbohydrate metabolism led this author to dismiss the use of such fat-adaptation strategies by competitive athletes in conventional sports. Recent re-emergence of interest in LCHF diets, coupled with anecdotes of improved performance by sportspeople who follow them, has created a need to re-examine the potential benefits of this eating style. Unfortunately, the absence of new data prevents a different conclusion from being made. Notwithstanding the outcomes of future research, there is a need for better recognition of current sports nutrition guidelines that promote an individualized and periodized approach to fuel availability during training, allowing the athlete to prepare for competition performance with metabolic flexibility and optimal utilization of all muscle substrates. Nevertheless, there may be a few scenarios where LCHF diets are of benefit, or at least are not detrimental, for sports performance.https://www.ncbi.nlm.nih.gov/pubmed/26553488Impact Of Ketogenic Diet On Athletes: Current Insights2019 Nov 15Whether nutritional ketosis yields any tangible performance benefits to athletes is a contentious subject within nutrition science. This academic debate has brought about several investigations in an array of athletes, including endurance athletes, resistance-trained athletes, and CrossFit trainees.
The impact of a ketogenic diet (KD) (<50 g/d carbohydrate, >75% fat) on athletic performance has sparked much interest and self-experimentation in the past 3–4 years. Evidence shows 3–4-week adaptations to a KD in endurance-trained athletes were associated with maintenance of moderate (46–63% VO2max) and vigorous intensity (64–90% VO2max) endurance exercise, while at intensities >70% VO2max, increases in fat oxidation were associated with decreased economy (increased oxygen consumption), and in some cases, increased ratings of perceived exertion and heart rate. Two investigations in recreationally active endurance athletes noted no vigorous intensity exercise decrement following 3- and 12-week adaptations. Moderate (70–85% one repetition maximum) and near-maximal to maximal intensity (>85% 1RM) strength performance experienced no decrement following a 3-12-week KD adaptation. Beneficial effects were noted for 2000 m sprint and critical power test completed for short duration at vigorous intensity, while two additional tests noted no decrement. For sprint, near-maximal exercise (>91% VO2max), benefit of the KD was observed for six-second sprint, while no decrement in performance was noted for two additional maximal tests. When protein is equated (grams per kilogram), one investigation noted no decrement in muscle hypertrophy, while one noted a decrement. One investigation with matched protein noted the KD group lost more body fat. In conclusion, moderate-to-vigorous intensity exercise experiences no decrement following adaptation to a KD. Decreases in exercise economy are observed >70% VO2max in trained endurance athletes which may negate performance within field settings. Beneficial effects of the KD during short duration vigorous, and sprint bouts of exercises are often confounded by greater weight loss in the KD group.
With more athletes pursuing carbohydrate-restricted diets (moderate and strict (KD)) for their proposed health benefits, more work is needed in the area to address both performance and health outcomes.Short-Duration Vigorous Intensity (64–90% VO2max, >30 s)Evidence suggests
no decrement to short-duration vigorous-intensity exercise
following 3–12 weeks of a KD within trained and recreationally trained athletes.
Findings are contrary to sports nutrition guidelines, which recommend carbohydrate availability to enable vigorous performance.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6863116/
