It should have been my peak training week for my next race. But I was sidelined, first by Plantar Fasciitis and then by a nasty cold. All hopes of maintaining fitness with cross-training were thwarted. I was basically stuck on the couch for two weeks.
Runners have to hang up their shoes for a variety of reasons: work and life overload, injury or illness, endless winter weather and physical or mental burnout. But how long can we take root as couch potatoes before our fitness declines? After my training was put on pause, I looked into how quickly a runner loses aerobic fitness when they’re forced to stop running.
There are two kinds of fitness: our aerobic fitness, or endurance, and structural fitness, the ability of your muscles, bones, tendons and ligaments to withstand the impact of running. Both are important but decline at different rates.
The amount of time your endurance endures depends on your regimen. Aerobic fitness starts declining for most runners in about seven to fourteen days. You first lose the gains you’ve made in the last several months of training. So if you’re a lifelong runner, you’ll retain much of your aerobic fitness for several months of no activity.
It appears that the better shape you’re in, the more fitness you retain when you’re not running. When University of Texas Professor Edward Coyle studied seven experienced endurance athletes who halted training, he saw their fitness drop off after twelve days. The enzyme levels in their blood, which correlate with endurance performance, decreased by 50 percent. Concurrently, their VO2 max dropped by seven percent. However, capillary density, the number of small blood vessels that grow deep into the muscles, didn’t seem to be affected. Coyle concluded that well-trained athletes are less susceptible to fitness loss than people new to physical training.
Consistency seems to be the key to keeping fit when your training’s interrupted. Since running is as much a lifestyle as it is a sport, runners retrain aerobic fitness for months after weeks on the couch.
Structural fitness is more complicated, unfortunately. And it’s absolutely critical. Structural fitness helps absorb the impact of running. Neglecting it risks long-term injuries.
After time away from running, the muscles, tendons and bones that absorb the shock of your stride begin to weaken. When you run again, your aerobic system is more fit than your structural system, which heightens the risk of injuries especially when you’ve maintained aerobically fitness through cross-training,
During inactivity, small amounts strength work can help maintain your body’s ability to withstand running’s impact. Once you understand that your endurance is lost at a slower pace than your structural strength, you can begin to slowly add miles back in and eventually build back to high-level training.
Even though we lose fitness quickly during rest, you’ll return to your initial fitness faster than you think. In a study undertaken by the University of Alberta’s School of Physical Education’s Elizabeth Ready and Arthur Quinney, subjects whose fitness decreased 40 percent over nine sedentary weeks regained fitness faster than they lost it.
If you have to take time away from running, don’t panic. While you’ll lose much of your fitness, and you lose it fairly quickly, your losses will taper off after several weeks and you retain a much of your initial fitness levels for a long time. And when you resume training, fitness will quickly return. As long as you build slowly and safely, you’ll be back running consistently in no time.