Science Friday: The Strength Training Debate

Are these counterproductive?

Advice from the running community (coaches, magazines, books) always includes the plea to supplement your running with strength training. It can help correct muscle imbalances, prevent injuries, and improve your running economy. But most runners are resistant. We run because we love running, not hanging out in gyms heaving weights around. We sneak our runs into our already busy schedules, early in the morning, on our lunch break, after work while others are out enjoying social lives. Do we really need to make time for strength training also?

But when I stumbled upon an article about combining endurance training and strength training, I found that the scientific community seems to think the opposite. Since endurance training and strength training target two opposing mechanisms, it may be counterproductive to do both.  (Endurance training increases mitochondria in your muscles, while strength training increases growth of muscle cells, or hypertrophy.) The research seems to suggest strength training will interfere with the effects of our endurance training. (For example, the resources needed to increase mitochondria might be used up trying to increase muscle size.) Could it be true? Could we get away with skipping the weights? Would we have a scientific excuse to do so?

The short answer, unfortunately for all you running purists, is no, we can’t skip the weights just yet. While most of the articles I read mentioned this interference, their findings showed it didn’t really hold up.

One article was a recent meta-analysis (basically a combination of all previous data, reexamined for large trends) that compared groups that did strength training only, endurance exercise only (running or biking), or a combination. As expected, they did find some interference. Tests of power were the most striking: people who only strength trained had greater power than those who strength trained and did endurance work. This fit with their hypothesis: by supplementing running, weight lifters may sacrifice some power. But to us runners, what we care about is the endurance group compared to the strength + endurance group. In that comparison, people who did both strength and endurance training had improved power versus those that only did endurance training. (See figure below.) More importantly, adding strength training did not affect VO2 max, so lifting weights doesn’t interfere with all our work done on the roads. Additionally, body fat measures were lowest in the strength + endurance groups, and lower for runners than bikers. (Take that cyclists!) As a side note, high intensity exercise increased body fat loss the most, consistent with other research. (So keep up with those intervals if that’s what you’re looking for.)

For us runners, we are most concerned with the comparison between endurance training alone (checkered bars) and endurance training + strength training ("concurrent," horizontal lined bars.) In all categories, adding strength training either helps or doesn't hurt.

So it seems like it’s not as bad as some research would imply. But does it help? What does it mean practically, and why should we bother?

Another group did a review of the literature (the difference from a meta-analysis is they didn’t reanalyze any data.) They found improved endurance capacity (measured by time trials or time to exhaustion) when there was a combination of strength and endurance training. This was true for both short trials (less than 15 minute time trials) and longer trials (over 30 minutes.) They also found that sprinting at the end of the trial (the finishing kick) was improved with strength training. Interestingly, they found that these improvements were made without increasing hypertrophy. The authors speculate that in this case the interference might be a good thing, because it prevents hypertrophy while still allowing for some improvements. So while strength training is helping, it’s not causing you to bulk up, something most runners will be happy to hear. (This article says that lots of reps of heavy weights are best, although I’ve read just the opposite elsewhere. That will have to be a story for another day.)

So here is what the advice for runners is built on: if you strength train, you can run faster over shorter distances, longer distances, have a better finishing kick, and not fatigue as quickly. And no, you won’t bulk up.

Crap, the coaches/magazines/books were right. Time to hit the weights.

On a completely unrelated note, there was an interesting piece this week about changing the way we sell exercising. In a world fueled by a desire for instantaneous results, it seems long term benefits of exercising (living longer and healthier) aren’t enough to encourage people to start exercising. So if you are trying to convince friends and family to develop healthy habits, you might want to emphasize how awesome you feel after a run or from being a runner, rather than how awesome it will be to live longer and healthier. (Good luck selling them on the lifting.)

Dream big,

Teal