You stop riding
Your mood sails south. Within minutes of starting exercise, neural activity lights up your brain like a slot machine on full tilt, which not only builds your brain (literally), but also improves your mood. Brain chemistry researcher J. David Glass of Kent State University reports that the minute lab rats hop on their wheels and start running, they get a 100- to 200-percent increase in serotonin, the same brain chemical antidepressants signal to improve wellbeing and fight depression. Deny your body that fix for even a day and your mood will slump, particularly during a stressful day when you need the release and lift most.Your metabolism stagnates. Riding revs your metabolism five-fold above its resting rate at your desk job. You lose between 400 and 500 calories burned for every hour you skip. That adds up to a pound of fat a week you could have lost but didn’t.… One week later
Your blood pressure rises. Aerobic exercise like cycling prompts your body to release hormones that make your blood vessels more compliant. It also pumps high levels of blood through your system, which helps keep your arteries and veins supple. The effects are swift—when you start and when you stop. Research generally finds that regular cycling can lower your blood pressure about 8 (diastolic) to 10 (systolic) points in a month. It starts rising again after just one week out of the saddle, and you’re back to where you started in just two weeks’ time.
Your blood sugar surges. When you’re riding regularly, your hungry muscles suck up the sugar that enters your bloodstream after you eat to store as energy for later. After just five days of downtime, that post-meal sugar just stays in your blood, which over time can lead to heart disease and diabetes, according to one study published in Medicine & Science in Sports & Exercise. What’s more, the enzymes that mop up fat and sugar in your blood stream start shutting down when you’re sedentary, so both blood cholesterol and blood sugar rise.
… Two to four weeks later
Bye-bye, blood volume… and fitness. Regular cycling builds blood volume and your body’s ability to use the oxygen it carries. After just two to four weeks off the bike, your blood volume plummets nearly 10 percent. Your stroke volume (the amount of blood your heart can push out per beat) drops 12 percent. Your mitochondria, which act as your body’s energy producing furnaces, start to shrink from disuse. The end result: Your V02 max—the benchmark of fitness—declines 6 percent, leaving you off the back from where you were just a few weeks before.
… More than one month later
Your clothes get snug as you grow soft. As your metabolism and muscles’ fat burning activity dwindle, your fat stores rise. A study published in theJournal of Strength and Conditioning Research found that swimmers who stopped training for five weeks put on pounds, increased their waistlines, and bumped up their body fat by 12 percent just five weeks after leaving the pool.
… Years later
Your health declines in major ways. A study on identical male twins who had been physically active found that when one twin stopped exercising regularly for a few years, he differed remarkably in health from his brother. Specifically, he was significantly weaker, had about seven more pounds of body fat, had more insulin resistance, and had even less gray matter (read: his brain was smaller) than his physically-active brother.
The good news is that it doesn’t take much to halt this rapid decline. Research has shown that just going out for a good brisk ride once or twice a week can help you maintain those hard-earned fitness gains. When time is tight, try cross training or high-intensity intervals (tabatas!) to keep your fitness and health from hitting the skids.