Sublime

The amount of acid produced up to 20 seconds is still manageable, but the next doubling is over the top: Even a single 30-second sprint spikes the ammonia levels almost five-fold. Why

Your body is unique, as is your history of taking care of it (and failing to take care of it). You may have particular health challenges. You may have tons of family or work responsibilities. You may have more or less money with which to buy time or gear. You may be naturally optimistic or pessimistic.

the metabolic expense associated with each variation in gait.

‘Marathon runners have a reduced experience of pain compared with non-runners,’

Shock absorption is particularly important in marathon running, since the feet of long-distance runners contact the ground an average of 10,000 times per hour, absorbing between two and seven times their body weight with each strike.

I’ve also become semiobsessed with an activity called rucking, which basically means hiking or walking at a fast pace with a loaded pack on your back. Three or four days a week, I’ll spend an hour rucking around my neighborhood, up and down hills, typically climbing and descending several hundred feet over the course of three or four miles.

Both groups’ physical symptoms improved, but the runners improved significantly more on the mental side.

at slow speeds of locomotion, walking was most efficient with the knees relatively stiff and nearly locked (remember the quadriceps are expensive muscles to fuel), while at higher speeds, sprinting with an extended airborne phase was most efficient