Tempo runThreshold run

A tempo run is a continuous effort held at 'comfortably hard' — roughly the pace you could hold for about an hour in a race, which for most runners sits close to lactate threshold. Typical sessions run twenty to forty minutes at that effort, sometimes broken into a few long blocks.

It matters because threshold is the most trainable of the endurance variables and the one that most directly sets race pace over middle and long distances. Raising it means a higher speed becomes sustainable rather than merely survivable.

In practice the commonest error is running tempos too fast, which turns them into interval sessions with none of the intended adaptation and all of the fatigue. The effort should feel controlled throughout, and you should finish believing you could have continued.