David D. Church, PhD, CSCS – Post Doctoral Fellow, University of Arkansas for Medical Sciences
Nicholas Coker, MS, CSCS – Graduate Teaching Associate, University of Central Florida
Matt S. Stock – Assistant Professor, University of Central Florida
David Boffey, MA, CSCS – Graduate Teaching Associate, University of Central Florida
Chad H. Herring, MEd, CSCS – Graduate Teaching Associate, University of Central Florida
Tyler Starich – Master Student, University of Central Florida
PURPOSE: Circulating brain-derived neurotrophic factor (BDNF) has been shown to be important to central (CNS) and peripheral (PNS) nervous system health. Considering the large neural component involved in the production of strength it is plausible that BDNF has a role in strength expression. The purpose of this study was to see if BDNF is related to measures of strength. METHODS: Seventeen males (Age: 23.8 ± 2.4 years; Height: 178.0 ± 6.1 centimeters; Mass: 88.7 ± 16.6 kilograms) volunteered to participate in this study. Assessments of motor unit (MU) recruitment at 50% and 80% of each participant’s maximal voluntary isometric contraction (MVIC), as well as one-repetition maximum (1RM) of the squat (SQT), leg press (LP), and leg extension (LE) were performed. A surface electromyographic (EMG) signal decomposition algorithm was used to decompose the signals into their constituent MU action potential trains. MUs with decomposition accuracy < 91% were not analyzed. Following the decomposition procedure, the recruitment threshold (RT; % MVIC) and mean firing rate (MFR; pulse per second [pps]) of each MU were determined. Linear regression was used to quantify the slope (pps/% MVIC) and y-intercept (pps) of the MFR versus RT relationship for each participant. Blood samples were obtained after a 4-hour fast, and both serum (sBDNF) and plasma (pBDNF) BDNF concentrations were measured via enzyme-linked immunosorbent assays. Pearson product-moment correlations were used to examine selected bivariate relationships. Alpha level was set a priori to p≤0.05 RESULTS: Pearson product-moment correlation analysis revealed that pBDNF was significantly correlated (r = -0.641, p = 0.014) to SQT 1RM, but not LP 1RM (r = -0.464, p = 0.095), LE 1RM (r = -0.405, p = 0.151), or MVIC (r = -0.432, p = 0.141). No significant correlations (p > 0.005) were noted for sBDNF. CONCLUSIONS: Our results indicate that pBDNF, but not sBDNF, concentrations may be related to SQT and LP 1RM strength. It appears the relationship between pBDNF and 1RM is stronger with movement patterns that require greater balance, proprioception, and coordination (SQT > LP > LE). PRACTICAL APPLICATIONS: Our data indicate circulating pBDNF may have a relationship with strength assessements that involve complex movements. Neither sBDNF nor pBDNF were correlated to MU properties; thus, circulating BDNF does not appear to influence MU firing rate characteristics. However, as correlation does not imply causation, our preliminary results should be interpreted carefully.