It’s All Connected: How Strength Levels Affect Work Capacity and Body Composition

Obviously strength helps you lift more weight, but how does it affect body composition and work capacity?

Every now and then, you come across research that gets back to the basics. A recent study in the Journal of Strength and Conditioning Research did just that. In the study, participants were divided into two groups: the strong (top fortieth percentile in bench press and leg press) and the not-as-strong (bottom fortieth percentile). The researchers collected data from participants at each of these levels in the following areas.

Assessing Strength

First, the researchers found that overall strength can be determined by any basic strength test in novices. However, this was not the case as strength levels increased. For stronger individuals, coaches should perform a greater number of strength tests.

The Effects of Age

Perhaps surprisingly, age was not a significant factor in strength or work capacity. There is, unfortunately, a lack of data on how the researchers recruited the subjects, but considering the participants were men with a background in resistance training, I would guess there’s some selection bias going on here. Indeed, the average age was around 25 years old, and the oldest participant was in his early thirties, so it’s hardly surprising that age wasn’t a factor in this case.

Determining Work Capacity

The researchers confirmed what many experienced lifters already know: leg exercises are capable of more work at a given percentage of max, regardless of level. In this case, at 80% of max, the leg press had double the reps of the bench press at the same percentage. However, it’s always good to reiterate this point for beginners who look at rep max charts and try to base their workouts on how many reps a chart says they can do. When more muscles are involved, work capacity tends to increase.

Strength and Body Composition

Strength level, which probably was a result of previous experience, had an interesting effect in this study. Work capacity was the same, regardless of strength. The only significant, consistent difference between the strong and the rest, outside of what I have already mentioned, was higher muscle mass in the stronger group. While not at all surprising, one thing to note was that total fat levels were roughly the same in both groups. This reinforces the point that fat loss needs to begin with diet, with strength training as an adjunct. Another fascinating tidbit was that high strength levels did seem to mitigate the effects of fat on strength, probably due to a higher relative strength despite the fat levels.

So there you have it. Some new, and some not-so-new information on what it means to be strong. It’s always good to be reminded of what’s important when hitting the weights, especially at a time when the landscape of fitness is rapidly changing.


1. Chad Kerksick, et. al., “Factors Which Contribute To and Account For Strength and Work Capacity in a Large Cohort of Recreationally Trained, Adult Healthy Men with High and Low Strength Levels,Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0000000000000389

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