Strength training: the true cost of a break

One of the key principles of fitness training is something known as ‘reversibility’. So long as you train, you can maintain and (hopefully) build your fitness levels. However, stop training and your fitness levels will steadily decline – a process known as detraining. This principle of reversibility can be very frustrating for athletes who are prevented from training, either because of injury, illness or because of unexpected events in life that crop up and disrupt our normal routines. However, understanding the process of detraining also informs a successful pre-competition tapering strategy; athletes need to ensure enough rest for maximal recovery, but not so much that detraining begins to occur, which then saps performance.

The speed of reversibility

We know it takes many weeks or months of training to produce measurable gains in fitness, especially once a good fitness base has already been established. So how quickly does reversibility kick in? There’s actually surprisingly little published research on fitness losses during an extended period of detraining (see this article for a more general discussion of detraining). This is perhaps to be expected; after all, it’s very hard to recruit athletes who take training seriously and then ask them to stop training for a month or more! Most of the research that has been carried out on detraining has looked at aerobic fitness losses, which can plummet by 7% in less than two weeks (see figure 1)⁽¹⁾. To compound matters further, the ability to work at a high percentage of maximum aerobic capacity also declines, making the impact on performance even greater.

Figure 1: Typical % decline in aerobic fitness over 84 days of inactivity