Use of a heart rate-to-ground contact time index to monitor and predict middle-distance running

The purpose of the present study was to determine if field-based variables associated with cardiovascular and neuromuscular stress could be used to accurately monitor and predict middle-distance running. Eleven middle-distance runners (age 21.3±1.6 years) completed three trials of steady-state running at 11, 13, and 15 km · h ^-1, and test performance was compared with competitive performance (personal best times converted to standardized Mericer scores). Oxygen uptake, heart rate (HR), and stride characteristics (ground contact time [Ct], flight time, step length, and step frequency) were monitored during treadmill running with the ratio of HR:1/Ct calculated. Heart rate and stride characteristics were significantly altered (all P<0.05) with increased running speed, while the HR:1/Ct index was unchanged. Stride characteristics, heart rate, and the HR:1/Ct index were reliable measures with no mean bias and low levels of random variation. The HR:1/Ct index was strongly related to competitive performance (r=-0.80 to 0.88, P<0.01). This was primarily attributed to the association between heart rate and Mercier scores (r=-0.81 to 0.87, P<0.01), whereas ground contact time was only moderately related to competitive performance at the fastest running speed (r=-0.60, P<0.05). Simple measures associated with cardiovascular and neuromuscular stress can be reliably monitored in middle-distance runners. A HR:1/Ct index provides a stable measure at any given submaximal running speed and may provide a useful tool for monitoring and predicting middle-distance running.