The Science Behind Normill's High-Performance Treadmills

A treadmill used for measurement has a different job from one used for training. The number that matters is not top speed but how far the belt drifts from the speed you set, under load, over an hour. Normill frames weigh 800 kg on the XC-3000 and 1250 kg on the XC-3300. The mass is there to keep the deck still: vibration at the deck shows up as noise in force and gait data. Drive is 3.3 kW (4.5 hp) on the XC-3000 range and 6.6 kW (9 hp) on the XC-3300, sized so that belt speed holds when a heavy runner loads the deck at each footstrike rather than sagging and recovering. Each machine is run in and calibrated before it ships. Speed is held to ±1.4% on the XC-3000 and ±0.7% on the XC-3300; incline to ±0.3% and ±0.15%. Those tolerances are what let a protocol run in March be compared with the same protocol in October.