Effects of Increasing or Decreasing Cadence on Metabolic, Cardiopulmonary and Biomechanical Responses During Downhill Running

Abstract

PURPOSE: Running races are becoming popular in geographic areas with hilly terrain. This study compared the collective metabolic, cardiopulmonary and biomechanical responses during acute downhill and level running. METHODS:This study used a repeated-measures, crossover design in healthy runners (N=30; 28.6±8.6yrs, 21.6±1.9kg/m2). Each runner completed six conditions including level running at self-selected cadence, and downhill running (-6% grade) at five cadences (self-selected, ±5% and ±10%). A portable gas analyzer and heart rate monitor collected energy cost, minute ventilation (Ve), rate of oxygen use (VO2), heart rate (HR). 3D motion analysis and an instrumented treadmill were used to determine temporalspatial parameters, peak ground reaction forces (GRF) and lower extremity joint powers. RESULTS: During the downhill conditions, Ve increased (61.1 to 65.6 L/min; p=.017) and HR increased (141 to 151 bpm; p=.010) from fastest cadence to slowest cadence, with no difference in energy cost or VO2 among the conditions (both p>.05). As cadence increased among the downhill conditions, step length decreased and step width increased (both p<.05). GRF values progressively increased in the downhill conditions from fastest to slowest cadence (16.7 to 17.5 Nm; p=.029). Among ankle, knee and hip powers, knee power values increased from fastest to slowest cadence (9.5 to 12.2 Watts; p=.023). CONCLUSIONS: When compared to the control condition, running downhill with a progressively faster cadence increases cardiopulmonary and biomechanical responses, but not metabolic responses. The findings suggest that runners maintain energetic cost among different cadence conditions by making adjustments to muscle activation patterns when running downhill. This muscle recruitment concept could be tested using similar cadence conditions described here during flat, uphill and downhill running.