When Better Running Economy Is Bad News: The Sleep-Loss Paradox

Running economy is usually treated as an unqualified good: use less energy at a given pace, and you should be able to sustain that pace longer, thereby racing faster. A small experiment shows how going without sleep affects economy and time-trial performance in a paradoxical way.

Sixteen healthy recreational runners—seven men and nine women—completed a randomized crossover study after a normal night of sleep and after one night of total sleep deprivation. In each condition, they ran on a treadmill at intensities around the first and second lactate thresholds, ending with an interval to exhaustion at the second lactate threshold.

• After sleep deprivation, runners used a lower cadence, spent longer on the ground, and had a higher duty factor (meaning a greater share of each stride cycle was spent in contact with the treadmill).
• Leg stiffness also fell, and work shifted up the chain, with more force placed on the knee and less on the ankle.
• At the same time, metabolic power was lower, which looks like improved running economy. Yet time to exhaustion at the second lactate threshold fell by 13.2% in the sleep-deprived runners.

This is where the study becomes useful. A lower energy cost at a fixed speed is not automatically a better performance state. Sleep loss changed how the runners organized each stride and reduced their tolerance for hard running even while the metabolic measurement moved in a seemingly favorable direction.

What this means for runners

Do not let a surprisingly comfortable easy pace after a bad night convince you that sleep loss did no harm. The cost may appear when intensity rises, or the effort has to be sustained. If you have flexibility, move a threshold workout or long quality session rather than forcing it solely because the warm-up feels normal.

That being said, one poor night is not a reason to panic before a race. But this experiment reinforces the value of protecting sleep across the week and avoiding the assumption that running economy alone captures how ready you are to run, especially after an all-nighter.