BRAIN-DERIVED NEUROTROPHIC FACTOR CONCENTRATIONS AFTER EXERCISE IN WHEELCHAIR RUGBY ATHLETES

PURPOSE: The purpose of this study was to investigate the influence of a graded exercise test (GXT) of wheelchair rugby athletes with a tetraplegical spinal cord injury (SCI) on acute changes in serum concentrations of brain-derived neurotrophic factor (BDNF). BDNF plays a major role in terms of neurogenesis and neuroplasticity and can be increased by physical activity (Knaepen et al., 2010). Rojas Vega et al. (2008) demonstrated increasing BDNF values after moderate handcycling activities in paraplegic athletes.
METHODS: Nine male elite wheelchair rugby athletes (age: 30.7 ± 3.77 years; height: 180 ± 0.05 cm; weight: 76.7 ± 7.33 kg; wheelchair rugby since 4.11 ± 3.33 years) with a tetraplegic SCI (C5-C7) were recruited for this study. The subjects completed a graded exercise test (GXT) with an initial load of 10 W increased by 10 W every two minutes until exhaustion. Venous blood samples were taken at rest and following the GXT. BDNF concentration was measured using an enzyme immunoassay ELISA kit. In addition blood lactate concentration (mmol/l), oxygen uptake (VO2, absolute [l∙min-1] and relative [ml∙kg-1∙min-1]), respiratory quotient (RQ) and heart rate (HR [b∙min-1]) were measured.

RESULTS: At rest the BDNF concentration was 39.30 ± 24.88 ng/ml and after the GXT 56.54 ± 25.45 ng/ml. Here, no significant differences could be found. The subjects completed the incremental stage test while reaching a maximal power of 73.33 ± 24.49 W. According to this maximal power peak HR was 126.9 ± 23.57 b∙min-1 and maximal lactate concentration 5.1 ± 1.74 mmol/l. The peak VO2max of 1,52 ± 0.64 l∙min-1 (19.8 ± 8.35 ml∙kg-1∙min-1) was found during a maximal RER of 1.01 ± 0.07.

CONCLUSIONS: There is no positive influence of a GXT for wheelchair rugby athletes with a tetraplegical SCI on serum BDNF concentration. Effects of physical activity in terms of increased BDNF levels for humans without a spinal cord injury and for paraplegic athletes depend on exercise intensity and duration (Rojas Vega et al., 2008; Zoladz & Pilc, 2010). In comparison to able-bodied subjects the current BDNF concentrations at rest were about 5-8-fold higher. According to these results further studies should examine the possible increase of BDNF levels in tetraplegic spinal cord injured subjects at different types, durations and intensities of exercise.