There is plenty of work showing that physical endurance increases after extended periods on keto. Athletes have carefully tracked their performance numbers day by day and demonstrated real changes.
And as someone who participates in activities that require large amounts of endurance, I know on keto my ability to perform for extended periods of time is higher. These aren't "I think" numbers, they are "polar heart rate monitor strapped to my chest" numbers.
The very nature of keto leads to improved endurance, fat is a much more plentiful energy source than glucose, it may be less efficient (lifting heavy on keto is a well known problem), but it /never/ runs out. If someone is doing an activity that doesn't cause excessive lactic acid build up or complete muscle fatigue, then a keto will give an endurance advantage.
And as someone who participates in activities that require large amounts of endurance, I know on keto my ability to perform for extended periods of time is higher. These aren't "I think" numbers, they are "polar heart rate monitor strapped to my chest" numbers.
The very nature of keto leads to improved endurance, fat is a much more plentiful energy source than glucose, it may be less efficient (lifting heavy on keto is a well known problem), but it /never/ runs out. If someone is doing an activity that doesn't cause excessive lactic acid build up or complete muscle fatigue, then a keto will give an endurance advantage.