What Actually Happens When You Lose Fitness?

If you want to maintain and enhance your fitness, there isn’t any alternative other than training regularly. If you stop training, you’ll lose fitness gradually.  This begs the questions, “How much fitness will be lost if I took a break from training for personal issues or forced to due to an illness or injury? And how rapidly will I lose fitness?”

Before we can answer these queries, we need to realize there are many different components of fitness, which includes muscular endurance, muscular strength, and cardiovascular (heart, lung, circulatory) endurance. If you stop training, the performance of each of these components will decline at varying rates.

Here’s how an amateur cyclist will lose fitness over the period of six months if he/she stops training:

Lose Fitness: The Timeline

Day 0

This is last day of your training. You won’t be training for the next six months. No exercises, no running — nothing. And, yes, store your bike away.

Day 3

It’s been only three days of complete inactivity. You may think that your fitness is starting to decline, but actually, the fall is so low, you won’t feel it. In fact, your cycling fitness is now enhanced as you rested for three days since day 0. The reason is that in those three days of complete rest, your muscles got plenty of time to recover.

Day 7 (Week 1)

After seven days of total inactivity, the body goes through changes that indicate fitness loss. After three days, the blood volume can decrease to 5 percent from 12 percent. This means there’s a decline in the amount of blood your heart can pump. As a result, your heart has to work a little harder for intense riding sessions.

The metabolism will also change, too. After six days of inactivity, muscles tend to become less efficient in absorbing glucose from the bloodstream. Another change the body goes through is that the muscles efficiency to cope with lactate accumulation during extended hard cycling takes a downturn.  This means you’ll soon become tired during strenuous training or cycling sessions.

Weeks 2-3

At this stage, your maximal oxygen uptake or VO2 max will register a decline between 4 to 20 percent. The primary cause is the reduction in cardiac output. This occurs because the muscle chambers of the heart have declined by approximately 20 percent due to three weeks of inactivity.


1 Month

It’s been 30 days since you last exercised and all the physical changes resulting from detraining mentioned above will continue to progress. But the most notable alterations will occur in the muscles. You’ll discover that the muscles capillarization has reverberated to its pre-training stage. The biochemical processes that assist muscles to burn fat for energy have become less effective. As a result, you won’t burn much fat even after intense, longer rides. In addition, your muscles endurance capacity will also be greatly reduced.

2-3 Months

After two months of no training, your heart will be less muscular as its muscles wall that consists of the pumping chambers have shrunk to almost 25 percent.  The muscles mitochondria have also become less effective in using oxygen, which will cause it to produce less energy for the muscles.

After three months of zero activity, you’ll also experience hormonal detraining. This means that more stress hormones will be released when you workout, which will make you tired soon. Your muscle recovery times will also be longer. As a result, you lose fitness.

6 Months

By the end of six months, declines in your fitness levels have almost stabilized. However, the volume of mitochondria per unit volume of muscle is still on the decline. Your body fat has also increased during this time due to slower calorie burn and reduction in overall muscle mass. You may also realize that you’ve become “fatter”, even though your weight scale does not show any signs of weight gains.






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