In my opinion, one of life’s injustices is how quickly all the effort we put into an exercise program begins to unravel during a period of prolonged inactivity. This was front and center in my mind recently, when I experienced a hip injury. I could no longer lift the weight I was accustomed to, and my running program was completely sidelined. I could barely walk, let alone run, and the expression “use it or lose it” loomed constantly. Before discussing how our bodies become “unfit,” we need to talk about how we become fit in the first place.
In a nutshell, whether our goal is to improve musculoskeletal strength, cardiovascular fitness, or both, our exercise program must exceed what is referred to as “habitual load“. Put simply, this means you have to do more than the activity levels your body is used to.
We become more and more fit as our bodies adapt and become accustomed to these increased levels of activity.1 This produces a good kind of stress on our muscles and bones, (especially when introduced gradually and consistently over time), and is exactly what leads to higher fitness levels. The result is that we no longer get sore, or feel particularly tired after a workout. Most times, we actually feel good, both physically and psychologically after exercising.
The time it takes to get to that higher fitness level depends on factors such as your pre-existing fitness level, your age, and how intense you train. For example, the more out of shape you are when you begin, the longer it will take to see those gains. Similarly, improvements will come more slowly the older you are at the onset of the program. However, for those persistent exercisers, the undeniable improvements in strength and endurance can be empowering, and motivate us to keep us plugging away.
Nevertheless, there will inevitably be times, as John Lennon once said, when “life is what happens to you while you are busy making other plans.” An injury, an illness, or any unexpected life event can put us on the sidelines. Then what?
The bad news is that we begin to lose cardiovascular fitness and strength within 48 hours of stopping. In both women and men, these effects are generally not felt for at least 2-3 weeks for cardiovascular fitness, and in about 6-10 weeks for strength.2 The evidence shows that for the average person, 12 weeks without training causes a significant decrease in the amount of weight they can lift. The reason for this is we are no longer putting our muscles and bones under that “good stress” I discussed above. We become deconditioned, and a condition called sarcopenia gradually develops, where muscle mass and strength decline. Sarcopenia is to muscles what osteopenia/osteoporosis is to bones, and they are intricately connected.
But here comes the good news – regular readers of my blogs know that there is always at least some good news!
The fitter you are, the slower you’ll lose the gains you worked so hard to achieve. Additionally, you will very likely recover more quickly from your injury if you have higher pre-existing fitness levels. The downslide you experience as you are sidelined, however long, can be gradually recovered. In fact, we humans are very resilient creatures. As stated in one study of the effects of stopping and restarting exercise programs in older adults:
“An occasional missed exercise session or temporary cessation of habitual exercise should not be a cause for distress in exercising older adults. Instead, they should realize the case with which they may restart their exercise program and also appreciate the generalized fitness benefits that can be ascribed to becoming more active.” 3
As for me, I’m gratefully back in the saddle, as they say, and I’m as determined as ever to stay strong.
- Landi F, et al. Impact of Habitual Physical Activity and Type of Exercise on Physical Performance Across Ages in Community Living People. PLOS ONE 2018; 13(1): e0191820.
- Martínez-Aldao D, et al. Impact of a Five-month Detraining Period on the Functional Fitness and Physical Activity Levels on Active Older People. Archives of Gerontology and Geriatrics 2020 July;91:104191.
- Sforzo GA, et al. Resilience to Exercise Detraining in Healthy Older Adults. Journal of the American Geriatric Society 1995 March;43(3):209-215.