BDNF and paraplegia: Contrastingly, Rojas Vega et al. (13), found that 10 min of low-intensity (54% HR max) handbiking significantly increased serum BDNF compared to rest, whereas BDNF decreased relative to rest following completion of a marathon-distance (42 km) bout of handbiking in 11 elite male athletes with paraplegia (T4-T12).