Previous Test
Current Test
CSS change
faster 6.0s/100m
Critical speed improved clearly
Previous CSS: 01:56/100m
Current CSS: 01:50/100m
DPrime change: 3.1 m
Theory
CSS improvement means sustainable (aerobic) speed has increased. DPrime is the y-intercept of the critical speed model — an "anaerobic distance capacity" you can spend above critical speed. Dekerle et al. (2002) validated that critical speed from a simple 200m/400m two-point test agrees closely with longer time-trial protocols, making it a practical field test for coaches. If CSS improves but DPrime drops sharply, endurance gains may be coming at the expense of short-distance speed capacity (training skewed aerobic, lacking sprint stimulus). If DPrime rises but CSS stays flat, anaerobic capacity improved but more threshold work is needed to build the aerobic base.