Responses to Detraining

Question:

Do you have any new info on detraining, defined as how long one can go without a workout (CV and strength training) without losing fitness level and/or endurance? Last I knew, CV was two to three weeks for endurance and 50 percent loss of strength gained in five to six weeks. Does this still hold true?

Answer:

Many personal trainers are interested in the time course for physiological response to training. They often ask how long will it take to see strength gains or increased cardiovascular endurance. A number of scientific studies have examined various training programs to answer these questions, and we have a good understanding of these responses. As interesting are the responses to reduced training. A trainer is often interested in how long a client can go without a workout before there is an appreciable reduction in strength or endurance.

For the sake of clarity, we will use the following definition: “Detraining is the partial or complete loss of training-induced adaptations, in response to an insufficient training stimulus” (Mujika and Padilla).

The duration of the training cessation is important. Mujika and Padilla describe two main timeframes of short (less than four weeks) and long term (greater than four weeks). It is important to note that this is not a taper or regeneration period, both of which have shown either a maintenance or improvement in physiological responses.

As with all forms of training, individual responses will vary according to a number of factors. The two primary factors associated with detraining is the level and/or the length or training prior to the detraining period. Therefore we should classify our clients as “athletes” or “recently” trained in order to better understand the response patterns of detraining.

From a cardiovascular standpoint, maximal oxygen consumption (VO2max) is the most commonly measured parameter. Table 1 shows the time course reductions in VO2max with an inadequate training stimulus. A reduction in blood volume and stroke volume are primary causes for the decrease in oxygen consumption. In addition to physiological changes, endurance performance is also affected by detraining. For endurance athletes, time to exhaustion tests show a 24 percent reduction in time to exhaustion in less than four weeks of detraining, whereas recently trained individuals show little to no change. On the other hand, long-term cessation for the athlete seems to plateau while recently trained individuals see complete reversal of the training effects.

Table 1.

Changes in VO2max with short- and long-term exercise cessation

*Percentages indicate loss in VO2max

Strength performance tends to be more resilient compared to endurance parameters when training is stopped. In the short term, there seems to be little decline for both trained and recently trained individuals (see Table 2). However, upper body strength declined quite rapidly in untrained individuals, up to 27 percent loss in five weeks. Long-term detraining tends to be more dramatic for the recently trained compared to athletes. The underlying mechanisms are a mix of neural and morphological changes. Neural adaptations tend to decrease more quickly followed by changes in muscle fiber area and characteristics.

Table 2.

Changes in strength with short- and long-term exercise cessation

* Percentages indicate loss in VO2max

In conclusion, the evidence would suggest that short-term detraining has relatively little effect on strength and cardiovascular components, while long term can significantly reduce training adaptations, especially in recently trained individuals. Therefore, if a client, who has been training for a long time at “high” intensities is going on holidays or becomes ill for a short period of time, he will be able to maintain the vast majority of his fitness. However, the client relatively new to training may lose a greater amount, especially if the detraining period is longer.

References

1. Mujika I. and Padilla, S. (2001). Muscular characteristics of detraining in humans. Med Sci Sports Exerc. 33: 1297-1303.
2. Mujika I. and Padilla, S. (2000a). Detraining: loss of training-induced physiological and performance adaptations. Part 1. Short term insufficient training stimulus. Sports Med. 30: 79-87.
3. Mujika I. and Padilla, S. (2000b). Detraining: loss of training-induced physiological and performance adaptations. Part 2. Long term insufficient training stimulus. Sports Med. 30: 145-154.