Dose-and Gender-Specific Effects of Resistance Training on Circulating Levels of Brain Derived Neurotrophic Factor (BDNF) in Community-Dwelling Older Adults

BACKGROUND: BDNF is known to induce neuroplasticity and low circulating levels have been related to neuronal loss in older persons. Physical exercise is thought to trigger BDNF-induced neuroplasticity, but conflicting observations have been reported regarding the effects of resistance training on circulating BDNF in the elderly. These conflicting observations might reflect dose-and gender-specific differences.

METHOD: Fifty-six apparently healthy elderly (68±5years) participants were randomized to 12weeks of resistance training (3x/week) at either high-resistance (HIGH, 8Males, 10Females, 2x10-15 repetitions at 80%1RM), low-resistance (LOW, 9Males, 10Females, 1x80-100repetitions at 20%1RM), or mixed low-resistance (LOW+, 9Males, 10Females, 1x60repetitions at 20%1RM followed by 1x10-20repetitions at 40%1RM).Serum was collected for BDNF assay at baseline and after 12weeks (24h-48h after the last training).

RESULTS: 12weeks of LOW+ exercise significantly increased BDNF levels in male (from 34.9±10.7ng/mL to 42.9±11.9ng/mL, time x group interaction p=0.013), but not in female participants. No significant change was observed in HIGH or LOW, neither in male nor female subjects.

CONCLUSION: Our results show that only the mixed-low-resistance training program with a very high number of repetitions at a sufficiently high external resistance was able to increase circulating BDNF in older male participants. Training to volitional fatigue might be necessary to obtain optimal results. Additional studies are needed to unravel the underlying mechanisms, as well as to confirm the observed gender difference.