Sloth
The sloth has elevated energy conservation to an art form. Burning a mere 0.1 calories per minute during peak activity, it accomplishes in twenty-three hours of sleep what most creatures require several meals to achieve. The Bristol Centre for Metabolic Excellence notes that a sloth expends less energy thinking about moving than a tennis player uses blinking between points.
Their muscles have evolved to function at roughly the same pace as continental drift, which, whilst unhelpful for escaping predators, proves remarkably economical.
Tennis
Tennis players burn approximately 600-900 calories per hour whilst engaged in their curious ritual of chasing a fuzzy yellow sphere. The sport demands explosive movements, rapid direction changes, and the emotional energy required to argue line calls with increasing desperation.
Professional matches can extend beyond five hours, during which participants consume enough electrolytes to desalinate a small pond.
VERDICT
From a pure efficiency standpoint, the sloth achieves existence using 0.02% of the energy tennis requires. The Edinburgh School of Biological Economics calculates that a single Wimbledon final expends enough calories to power a sloth for approximately fourteen months.