May: Cramming

   Most of us are workout thieves, stealing a run whenever a small window of time is left open. It's stunning what you can accomplish in a pilfered hour; even two short, unplanned workouts a week can propel you to dramatic levels of performance and fitness.

   Trouble brews when you come to count on these extra workouts: when you feel unprepared for a looming race, when impatience from a recovering injury urges you to push your progress, or when you're trying to reassert control over a life besieged by personal problems. Injury is the devil's due for squeezing too many workouts into your week. Regardless of the danger, cramming doesn't work.

   The satisfying burn you feel during a hard sprint tells you that you're building muscle. Alas, it tells you a lie. Hard workouts tear muscle tissue down; only rest makes you stronger. And invariably, rest is the casualty of any hurried training program. The result is over-training, a notoriously elusive syndrome often unrecognized by coaches and physicians alike. Among its symptoms are moodiness, irritability, altered sleep patterns, depression, decreased appetite, weight loss, persistent muscle soreness, a raised resting pulse, clumsiness, and a greater incidence of injury. These are roughly the same symptoms for being cantankerous and alive, so it's no wonder that running coaches often prescribe extra intervals as the remedy.

   Only recently have sports physiologists put rest under the microscope. Its role in building muscle is more complex than anyone imagined. During slow-wave sleep, for example, growth hormone is released from the pituitary gland at the base of the brain, stimulating muscle growth and repair, bone building, and fat burning. This much we know. Human growth hormone is crucial to recovering from grueling workouts. When you cheat yourself of a good night's sleep, lower amounts of the hormone are released, which is why extended sleep loss will eventually hurt your performance.

   The mechanics are only dimly understood. Meanwhile, runners who care more about the stopwatch than biomechanics classes are gaining enormous results from putting calculated periods of rest into their workout routines. Most competitive runners, for example, are well versed in tapering, in which the distance and intensity of workouts are gradually reduced during the week or so before an event. Recent studies have shown that tapering not only improves performance, it increases muscle strength and power; it reduces sleep disturbances as well as stress and fatigue; it lowers perceived rates of exertion as well as heart rates during a workout: it results in an overall brighter mood.

   How does this magic happen? No one really knows. Most of us are driven by a cultural predilection to believe that extra effort alone brings results. After all, perseverance and desire separate runners from, well, non-runners. But this way of thinking ignores half of what your body needs in order to get stronger. So instead of stealing an extra hour for a workout, try stealing an extra hour of sleep.