24 hours

Photo from Wikimedia Commons
Most Pull-ups in 24 Hours
An extraordinary endurance record of over 7,600 pull-ups/Human Records & Feats
The Guinness World Record for most pull-ups in 24 hours is 7,715, set by Brandon Tucker in 2023. That averages out to about 5.4 pull-ups per minute, sustained for an entire day. Assuming an average body mass of about 80 kg and a pull distance of roughly 0.5 meters per rep, the total mechanical work performed is approximately 30 million joules, not counting the metabolic inefficiency of human muscles. The actual caloric expenditure is estimated at several times that. Tucker reportedly took only brief rest breaks throughout, which redefines what most people consider a 'long workout.'
Measurements
Based on ~7,700 reps at ~80 kg over ~0.5 m