Autonomic Function in Indoor Versus Mountain Bike Riding

Road cycling and cross country mountain biking are common cycling disciplines. Cross country biking creates an adrenaline rush, which causes sympathetic nervous system, stimulation which can increase heart rate. Sympathetic and parasympathetic nervous system activity is analyzed via heart rate variability to determine cardiovascular autonomic function. Chronic stimulation of the sympathetic nervous system has shown to impair autonomic function and lead to sudden cardiac death. The purpose of this study was to assess autonomic function before and after road and cross country mountain biking. Four healthy, experienced, male bikers were recruited. Subjects completed a baseline, pre, and post ride tilt-table test while electrocardiograph and blood pressure data were collected. Subjects performed a stationary, indoor ride to simulate a road ride and cross country mountain bike ride in a randomized fashion. Speculative analysis indicates that after the cross country ride diastolic blood pressure increases compared to before, whereas following the indoor ride, cardiac output is elevated. The cardiac output increase may be from the immediately preceding exercise. The blood pressure increase may result from sympathetic stimulation from the outdoor mountain bike ride. Hence, an outdoor cross country ride may potentially increase sympathetic nervous system activity more than an indoor ride.