Researchers investigated the effects of exercise on circulating sex hormone concentrations in older men and found dehydroepiandrosterone (DHEA) has a positive effect on the neuromuscular system. The results were published in GeroScience.

The study included 43 men aged 60 to 85 years who were recruited between 2014 and 2017.

The control group included 18 untrained men, 14 endurance masters athletes, and 11 power master athletes. ‘Masters athletes’ were considered those who regularly competed in their sport, trained for more than 5 hours per week, and had been participating in their sports for an average of 49.8 years since reaching adulthood.


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Total body composition, quadriceps muscles, and serum hormone concentrations were measured at the beginning of the study.  Levels of DHEA, DHEA sulfate (DHEAS), total testosterone (T), dihydrotestosterone (DHT), and total estradiol (E2) from a 10 mL were measured from a fasting blood sample.

Researchers assessed each participant’s physical capacity by measuring voluntary contraction of isometric knee extension, hand grip strength, lower limb vertical jump power, gait speed, balance, and reaction time.  They also visualized motor unit (MU) activity levels within the vastus lateralis using intramuscular electromyography (iEMG), taking measurements at various depths. Additionally, they calculated motor unit firing rate (MU FR) and MU potential.

Power master athletes exhibited larger muscle size than both the endurance athletes and untrained men (P <.05) and greater jump power than endurance athletes (P =.014) with no difference compared to untrained men (P =.134). Both endurance and power master athletes demonstrated faster timed up and go (TUG) times than the untrained men (P <.05).

Endurance athletes had lower  fat mass and MU FR (P <.001) as well as lower E2 levels compared with power athletes (P =.036) and age-matched controls (P =.016).There were no differences in DHEA, DHEAS, T, or DHT levels between groups.

DHEA levels positively correlated with motor unit firing rate (P = .019). Elevated testosterone and estradiol (E2) levels correlated with lower MU potential complexity (P =.006 and P =.019, respectively).

“Compared with nontrained age-matched individuals, masters athletes exhibited larger motor unit potentials, fewer denervated muscle fibers, and increased fiber type grouping,” the researchers said. “There are established benefits of exercise for the ageing neuromuscular system, yet the interactions with circulating sex hormones in these highly active older individuals are unclear.”

Limitations of the study included a sample size limited to a rare elite athlete group. Additionally, the study participants were entirely male. The study authors acknowledged these and other limitations cannot prove causality between circulating sex hormone levels and neuromuscular characteristics.

“Although evident in males only, this work highlights the potential of hormone administration as a therapeutic interventional strategy specifically targeting the human neuromuscular system in older age,” the study authors concluded.

Disclosure: One study author declared affiliations with pharmaceutical and private industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Guo Y, Piasecki J, Swiecicka A, et al. Circulating testosterone and dehydroepiandrosterone are associated with individual motor unit features in untrained and highly active older men. GeroScience. Published online December 3, 2021. doi:10.1007/s11357-021-00482-3