This week, we look at the potential association of body fat percentage with muscle damage from heavy eccentric exercise

Ultimately, when athletes are exposed to a stimulus they’re unaccustomed to, they’re gonna be sore. As you know, the intensity of competitions isn’t always controlled. Therefore, the large spikes in workload cause higher amounts of muscle damage and soreness.

So, what’s body fat percentage got to do with this?

I recently came across a study by Yoon and Kim (2020) where they investigated the level of muscle damage, soreness and performance after eccentric exercise in individuals with different levels of body fat.

In this study, they recruited thirty healthy males and placed them into a high body fat group (>20% body fat) or a low body fat group (<15% body fat) and did 2 sets of 25 eccentrically loaded preacher curls.

It’s worth noting that these individuals were students who hadn’t lifted for over <6 months. I.e. not athletes. Of interest, the researchers measured two blood markers (creatine kinase (CK) and myoglobin (Mb)) which are released into the bloodstream following damaging exercise.

Therefore, these are typically used as a measure of muscle breakdown/damage.

Unsurprisingly, both groups had elevated blood levels of CK and Mb. However, a far greater increase was found in the high body fat group. So why is this?

It’s been suggested that obesity is a potential factor that weakens cell membranes. The weakened cell membrane on the muscle is therefore more susceptible to damage. Furthermore, individuals with higher fat mass typically have heightened amount of inflammation, which then further disrupts the cell membrane integrity.

And this is potentially why more CK and Mb was leaked into the bloodstream in individuals with higher fat mass – an indication that the muscle is damaged and ‘leaky’.

In contrast, muscle strength and perceived levels of DOMS were similar for both groups…However, how would this translate into more demanding physical challenges on a repeated basis?

Nevertheless, this study shows that body fat percentage *could* play a role in the severity of muscle damaged incurred via eccentric exercise…