Health and Fitness

What time of day should we exercise for best results? This simple question begs additional relevant questions. How hard do you exercise? Does your exercise (or physical labor) involve your spine, whether stretching or lifting? Do you have a “normal” schedule, or do you keep very irregular hours? Do you like lower back pain?

Each question is significant. If our “exercise” is strolling around the block once, it makes little difference when we do it unless it requires great effort due to special circumstances. But if it involves strength, flexibility, or a high activity level, time of day affects the effectiveness and safety of our play, workout, or hard work. If the spine is involved -- and it’s tough to exercise without involving the spine -- our options are limited. And our wake-sleep cycle – our circadian hormonal rhythm -- is heavily involved, too.

Extensive research has established that evening exercise wins. Our bodies are out of the post-slumber slump but short of needing more sleep, they are fed and hydrated, our muscles are warm and loose, and punching the bag beats punching the boss after a hard day in the salt mines. More specifically, research shows the following advantages to an evening session:

  • Our most efficient and effective endurance and strength-building workouts come within three hours of our peak in body temperature and hormone levels, which occur around 6:PM.
  • People can and do pump that iron, lift that bale, or chase that ball harder and with less perception of exertion in the early evening.
  • Exercise helps moderate our appetite, so an early evening workout before supper will leave most people less compelled to stuff themselves. [One would expect this exercise timing would offer a triple boost to our health: 1) it should relieve the workday’s stress, 2) it should lead to a smaller evening meal, and 3) both of those should promote sleep.]

If your evening workout leaves you restless at bedtime, try a little earlier workout, a more prolonged active cool-down, and/or an evening meal with less protein. Or maybe you sleep better with an early evening meal followed by a workout an hour later. Experiment.

Even though evening is the best time physiologically to get your exercise, it may be impossible with your schedule. The other obvious times for people with normal work schedules would be mornings or at lunchtime. Most consistent exercisers get theirs in the morning. The exercise habit develops easier then, largely because morning presents fewer distractions from schedules or other people. Solid morning exercise revs up our cardiovascular system and metabolism for perceived and measurable boosts in our physical and mental abilities, especially useful for slow morning starters. Research has shown that a brisk walk wakes us up quicker and for longer than a light meal, whether early or at midday. For outdoor exercisers, summer mornings are cooler so we can comfortably work or play harder and the morning air is cleaner so we don’t have to chew it before putting it to good use.

The downsides of morning exercise include low body temperature and accompanying lethargy, stiffer muscles which may injure more easily, and the number of people who just hate mornings. Of course, exercise might change the latter.

But recent research has uncovered an even stronger reason not to exercise in the morning, strong enough that it was the inspiration for this month’s column: exercise within a couple of hours after getting out of bed damages our spines over the long haul. As we sleep, the compressive burden of being upright human beings is relieved from our spine’s fluid-filled discs so they inflate with fluid. Bending or loading the spine significantly increases pressure in those fat, juicy discs separating the vertebrae from each other.

Dr. John Dunne, of the Ohio Sports and Spine Institute, puts it bluntly: “NEVER exercise in the first two hours after getting out of bed.” This stern advice from a back specialist and dedicated amateur athlete will upset many morning athletes and their coaches, but most people develop low back pain by middle age and it often becomes chronically debilitating, so pay attention to his explanation, as follows.

Recently published and ongoing spine lab research has demonstrated that the extra disc hydration after a night’s bed rest leaves the spinal discs subject to extreme pressure rises when loaded. Most stresses involving bending or loading the spine increase the pressure in your discs by more than a thousand pounds above what is proven to cause disc herniation. After a couple of upright hours the night’s extra hydration dissipates and the discs are no longer subject to these extreme pressures in ordinary exercise.

So where are the legions of people crippled by this problem? Ask anyone over 50. It’s just now becoming accepted that this type of spinal stress leads to vertical herniation into the vertebrae, not the lateral ruptured or slipped discs we associate with traumatic spinal problems leading to nerve damage. Vertical herniation leads to “Schmorl’s nodes”, which form in the vertebra due to frequent micro-fractures. They are so common that radiologists presumed they were normal and of little concern. They’re just now being recognized as the primary cause of chronic back pain associated with particular positions or activities. They do not heal well and cannot be treated; maybe delaying that workout or gardening until at least mid-morning will help avert or delay chronic back pain. Being upright is all the workout our spines can handle safely until two hours after we get up. Any more exercise contributes to days, then weeks, then maybe years of agony as we grow older.

But there’s another morning exercise threat that may make disc herniation moot: hard exercise early after rising can make even a young athlete’s body react like the body of an old man having a heart attack. Many measurable physiological responses in heart behavior and body chemistry look very similar in both scenarios, and shoveling the driveway before work kills many people who could have done it without impact after work.

For those of us with normal schedules and jobs, that leaves lunchtime exercise if we can’t do our hard work or play after work. Lunchtime exercise advantages include a break from the job, an easy habit to form, maybe a wide choice of exercise partners, beneficial higher body temps and hormone levels than early AM, and a bigger and more prolonged energy boost than a snack. Lunchtime exercise will increase your afternoon productivity and often eradicate your involuntary post-lunch nap attack, but it’s tough to cram the preferable 45-minute walk into a 30-minute break if a short-sighted boss or legitimately rigid schedule won’t allow a longer lunch. If you’re worried about odor if your lunchtime run leaves you sweating after your quick post-run shower, don’t be. It takes bacteria many hours to convert odorless sweat into aromatic bacterial byproducts.

Meal interference with exercise depends a lot on how hard you exercise. Hard, sustained exercise such as running a couple of miles in 12 minutes immediately after a full meal can be dangerous in hot weather for those whose digestive process steals too much blood from the brain. The weightlifting session most people might put in shortly after a full meal isn’t likely to produce a champion, but it probably would allow a sufficient workout to improve one’s health unless it produces heartburn. Your body will quickly tell you how well you tolerate exercise after various types of meals, how long you need to wait, and how well you sleep after either or both. But exercising after a fast, such as waking up and working out without at least a snack to start building some blood sugar, would be pretty uncomfortable and limiting for most people.

Any exercise is better than none, unless it cripples your back in old age or stops your heart in a snowy driveway because too much of it was done early in the morn. Given any choice, later is better.

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