Last week, we looked at how your aerobic fitness declines after you take some time off from running. While of interest to runners taking a break after a marathon or those afflicted with an injury, healthy runners in training fortunately don’t have to worry about this.

Strength training, however, is something many runners do for a while and then abandon because of a busy schedule, soreness, or an upcoming race.

What happens after that? How quickly do you lose some of the strength training gains? And what may be some of the positive after-effects?

To find out, we’ll again have to look at some scientific research.

The research on how taking a break from strength training affect fitness gains

The first study we’ll examine, by Lars Andersen et al. in 2005, is a fairly straightforward analysis of strength training and “detraining.”

A group of 14 sedentary men did lower-leg strength training three to four times a week for three months. They returned to being sedentary again for another three months.1 The subjects had the strength and explosive power of their legs tested at the outset, midpoint, and end.

Unsurprisingly, the subjects added a significant amount of muscular strength. They also lost much or all of it after three months of inactivity.

Interestingly, though, after a short time away from strength training, the subjects’ muscular power under no load increased markedly.

The authors proposed that the men retained some of the strength-training muscular benefits and lost some of the highly specialized adoptions for moving heavy weights. The resulting muscle composition executed less inhibited and more powerful movements.

The detraining results — the improved muscular power and velocity and the loss of slow moving muscle fibers — might be of use for a runner who requires just these characteristics to perform.

But the subjects in this study were sedentary—how does this type of experiment play out in highly trained athletes?

Highly trained athletes

This was the question asked by Tibor Hortobagyi and coworkers at East Carolina University in a 1993 paper.2 Their study looked at changes in strength after 12 highly trained power athletes (power lifters and DI football players) took two weeks of rest.

While they experienced only minor changes in their actual strength (abilities on the bench press, squat, etc.), there were moderate to significant decreases in the size of their highly trained fast-twitch muscle fibers.

Conversely, their hormonal profile became more favorable. The growth hormone and testosterone levels increased, while levels of cortisol, the “stress hormone,” decreased. Hortobagyi suggested that, with careful manipulation, this type of rest could be beneficial and allow athletes to advance their performances.

On the other hand, we need to be cautious not to rest for too long. It appears that the most highly-trained areas of an athlete’s muscular system (the fast-twitch fibers, in this case), are the first to lose their strength.

An expert overview

Finally, a review article by Iñigo Mujika and Sabino Padilla attempts to synthesize some older research that confirms the findings of Hortobagyi, et al., and draws some additional useful conclusions about strength training.3

Within the first two to four weeks away from strength training few changes occur.

Specialized athletes like runners, rowers, and power athletes must continue sport-specific training (like running for runners). Otherwise, they may lose their specialized fitness muscle fibers: In endurance athletes, the size of slow-twitch muscle fibers declines In power athletes, the size of fast-twitch muscle fibers declines



For both groups, the muscular strength fibers appear not to change for up to one month.

Applying the research to the taper process

Anyone thinking about designing a taper for a big race can apply these findings.

From a muscular strength perspective, continuing to lift or do strength exercises until your big race is unnecessary.

From a recovery perspective, it may make sense to intentionally stop strength training for a few weeks before a big competition to retain your muscle power.

This, and the more favorable hormonal profile and reduced highly specific inhibitory mechanisms could help you bring your performance to the next level.

Final thoughts

If you’ve been training with slow-moving weights for a while, you don’t need to be exceptionally good at that on race day. As such, you would rather focus on the specific fitness and strength from your running training.

However, strength exercises that are highly specific to running — bounding, skipping, or other plyometric or sprint-drill style exercises — encourage your body to maintain those running-specific muscular adaptations for the big race. Thus, these should remain in your training up until the week before your goal race.

Keep these guidelines in mind as you plan a tapering strategy. This should give you the best of both worlds: The muscular power gains from strength training and technique and specificity from running training.

If you’re interested, our Strength Training for Runners Guide has prescriptions for how to add running-specific strength work to your training for distances from 5k to the marathon; including how to continually progress your strength work and how to taper. Click here to get your copy.