Weight training increases resting energy expenditure in older women

You’ve probably heard people say that some forms of exercise “increase your metabolism”. What this often means is that after you’ve done a certain kind of exercise, your body’s energy expenditure — the amount of energy it’s spending on tasks like recovering from whatever crazy thing you’ve done — is temporarily elevated. It might be trying to recover some of the oxygen you burned through while doing that 20-rep squat set. It might be trying to tidy up damaged proteins and rebuild new ones. Etc.

We know that some forms of exercise do this more than others.

Moderate walking, for example, hardly raises post-exercise energy expenditure (EE) at all. But anything high-intensity that demands a lot of energy — such as heavy, high-volume weight training or sprints — can raise EE for hours afterwards. As the study authors point out, mixed endurance/resistance exercise (circuit training) results in significantly greater post-exercise energy expenditure than endurance exercise (treadmill running) alone, while a single bout of resistance exercise has been found to result in greater overall increases in recovery energy expenditure than similar bouts of either cycling or circuit training.

A new study examines this phenomenon in women. This is important for two reasons.

First, as you may have noticed, women’s bodies are often different than men’s. We still don’t know all the ways in which this is true. Some stuff is the same, some isn’t. And it’s not always what you might expect.

Second, the effects of heavy weight training haven’t been as well studied in women as they have been in men. Because, y’know, the lovely ladies are just toning and whatnot.

Anyway, this study identified factors that influence recovery energy expenditure in women after an acute bout of resistance exercise. 17 women participated, which isn’t a huge number but could be suggestive.

What’s interesting here is that the women were older — 40-55. The average age was about 46.

As the authors point out, many of these types of studies are done on younger women, and it’s hard to generalize the results to older women. Older women often assume that the benefits of weight training don’t apply to them.

Methods

The researchers had the women do the following:

• 1 set of 8-12 reps of eight exercises at 50% of one-repetition maximum (1-RM)
• 2 sets of 8-12 reps of the same exercises 80% 1-RM
• Rest 1 minute between sets

The exercises were: chest press, lat pulldown, leg press, shoulder press, seated row, leg extension, triceps pushdown, and biceps curl.

They measured EE by measuring women’s oxygen consumption (VO₂) before and for 120 min after resistance exercise.

Findings

Overall mean recovery energy expenditure was 133±6 kcal. What this means is that there was a noticeable EE effect but it was fairly small.

Folks often convince themselves that weight training makes them calorie-furnace ninjas so they can go and suck down a Jamba Juice with 900 calories of sugar in it. But it doesn’t work that way. Increases are fairly modest, so if fat loss is the goal then you still have to make intelligent dietary choices.

This study found there was no age difference among the women studied, although with a wider range of ages this may have been different. Neither was there an effect of body size: smaller women did the same as larger women. Lean mass (i.e. muscle tissue) did have a slight effect, though.

The factor most consistently related to post-exercise energy expenditure was total exercise volume — how much work the women put in, in terms of how many times they lifted the weights.

Let’s talk for a moment about exercise choice. You’ll notice that most of these exercises are single-joint isolation exercises. Probably most of them were done on machines. Were researchers to use more demanding free weight exercises, such as clean + press or deadlift, they would likely find that post-exercise EE increased much more significantly.

Based on these findings, say the researchers, it is recommended that women be encouraged to lift at higher intensities (70-80% 1-RM) to maximize post-exercise energy expenditure and potentially promote fat loss. In other words, more evidence for lifting heavy!

Benton, Melissa J. and Pamela D. Swan. Influence of resistance exercise volume on recovery energy expenditure in women. European Journal of Sport Science 9 no.4 (July 2009): 213-218.