High-density exercise involves either high intensity for short periods or moderate intensity for longer periods.

A very high intensity exercise for a short interval (e.g., a sprint or a low-repetition, very-high-weight weightlifting exercise) is high density.

A moderate-intensity exercise for a moderately long interval (e.g. moderate-weight weightlifting exercise repeated to failure or nearly to failure) is also high density.

(A low-intensity exercise for a very long interval is simply an endurance exercise.)

The classic high-density workout is the 8x8 routine. The participant uses a weight approximately half of his or her one-rep maximum, doing 8 sets of 8 repetitions each, with rest intervals of 15 to 30 seconds between sets. The routine targets slow-twitch and fast-twitch A muscle fibers.

Weight training