Trainlow

Train-low refers to a training approach in endurance and high-performance sport where athletes perform workouts with low carbohydrate availability, typically by depleting glycogen stores or limiting carbohydrate intake around training. The goal is to elicit metabolic adaptations thought to enhance fat oxidation and mitochondrial efficiency, and to potentially improve long-term endurance capacity. In practice, train-low protocols vary and may include fasted sessions, sessions after a carbohydrate-restricted diet, or the so-called sleep-low approach in which an evening workout is followed by overnight glycogen depletion and a morning session.

Supporters argue that training with low glycogen can increase enzymes involved in fat metabolism, improve mitochondrial adaptations, and promote greater metabolic flexibility. The evidence for consistent improvements in performance is mixed; some studies show heightened fat oxidation and certain performance benefits in some athletes, while others report no advantage or potential decrements in high-intensity work. Train-low is often used as part of carbohydrate periodization, where athletes alternate low- and high-carbohydrate days or sessions to balance adaptations with the ability to sustain quality workouts.

Cautions: training with low carbohydrate availability can raise perceived exertion and may temporarily reduce training quality, particularly for high-intensity or technical sessions. There is also concern about immune function, muscle protein balance, and overall recovery if not properly managed. As such, train-low approaches are typically tailored to an athlete's training cycle, diet, and goals, and are often supervised by sports nutrition professionals.

History: The concept emerged from research on fat oxidation and metabolic flexibility in endurance training and has been discussed since the early 2000s, gaining public attention with athlete case studies and reviews in sports nutrition literature.