Research

Mixed

Training twice every second day with low muscle glycogen during the second session enhances mitochondrial enzyme activity and fat oxidation markers compared to daily training with normal glycogen, but does not improve 1-hour endurance performance.

If you are an endurance athlete, splitting your daily training into two sessions on alternate days (training low on the second session) may boost your mitochondrial enzymes and fat-burning capacity. However, do not expect this to make you faster in a 1-hour race compared to training daily with normal glycogen. In fact, your high-intensity session quality may suffer initially. Prioritize recovery and glycogen replenishment if performance is your primary goal.

GoodQualifiesHIGH confidence
We conclude that compared with training daily, training twice every second day compromised high-intensity training capacity. While selected markers of training adaptation were enhanced with twice a day training, the performance of a 1-h time trial undertaken after a 60-min steady-state ride was similar after once daily or twice every second day training programs.
Wee Kian Yeo et al. · Journal of Applied Physiology · 2008

Why this rating

Randomized controlled trial with well-trained subjects, clear protocols, and statistically significant biochemical markers, though small sample size (n=7 per group).

Source

Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens

Wee Kian Yeo et al. · Journal of Applied Physiology · 2008

DOI 10.1152/japplphysiol.90882.2008

rct · n=18Cited 286×
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DOI resolved against Crossref · corpus check 2026-06-10

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