By: Ergolog

The size of your red blood cells says something about your health. If they are all about the same size then the chance that you’ll develop fatal cardiovascular disease is pretty small. How come this happens? We don’t know. Sports scientists at the University of Mississippi in the US have discovered that resistance training keeps red blood cells pretty much an even size. And how come this happens? We don’t know this either.

Red Blood Cell Width Distribution

The Red Blood Cell Width Distribution – usually abbreviated to RDW – is an indication of the amount of variation in size of a person’s red blood cells. The lower the RDW, the more uniform the red blood cells are in size.

About five years ago American cardiologists at Wayne State University discovered that people with a relatively small RDW are noticeably less likely to die of cardiovascular disease than people with a high RDW. [Circulation. 2011; 124: A12295.] The Red Blood Cell Width Distribution was a stronger factor than the concentration of inflammatory protein C-Reactive Protein [CRP].

Red Blood Cell Width Distribution: another way in which resistance training extends life expectancy

Since then researchers have repeatedly observed that a relatively low RDW increases the survival chances of people in various conditions.

Resistance training

The data used to generate the figures above come from the National Health and National Examination Surveys. The researchers at the University of Mississippi used the same source for their recent publication in Preventive Medicine. The researchers used data on 8257 adults, some of whom did resistance training. And the more often the participants trained, the lower their RDW was.

Every 2 workouts per week reduced the chance of a high RDW by 11 percent. In this group, at least. The researchers suspect that the workouts that fitness fanatics and bodybuilders do have a much stronger effect – as most of the participants in this study did not train hard. Their lean body mass was on average only a miserable 500 g more than average.


“These findings suggest an inverse association between muscle strengthening activities and Red Blood Cell Width Distribution”, the researchers summarised. “Although speculative, these findings suggest that Red Blood Cell Width Distribution may be one potential mechanism through which muscle strengthening activities may reduce an individual’s risk of cardiovascular disease.”

“Further studies are needed to evaluate whether Red Blood Cell Width Distribution does indeed mediate the health benefits related to muscle strengthening activities.”

Prev Med. 2015 Apr;73:130-2.