Table 2

Estimated linear velocity of the digitised helmet points including the change in head velocity of cases 1–7 (nine impacts), and estimated angular velocity of cases 1, 2, 4 and 7 (five impacts) ±SD of the three trials. Negative linear velocity refers to downward movement (towards the slope) in the normal to slope direction, while positive velocity refers to a rebound (upward) movement. Negative angular velocity refers to a head rotation towards extension while positive angular velocity refers to a head rotation towards flexion. A negative velocity change in the along slope direction indicates a decrease in velocity from preimpact to postimpact, while a positive along slope velocity change indicates a velocity increase

Case numberAnalysed frame rate (Hz)Preimpact velocity (±SD)Postimpact velocity (±SD)Change in velocity (±SD)
Normal to slope velocity (m/s)
 1—impact 160−8.4 (0.6)−0.9 (0.4)7.5 (0.7)
 1—impact 260−10.4 (0.7)3.1 (0.6)13.5 (1.3)
 250−8.3 (0.4)0.4 (0.3)8.7 (0.1)
 350−1.9 (0.8)3.3 (1.0)5.2 (1.1)
 450−5.6 (0.1)3.1 (0.1)8.7 (0.1)
 550−8.2 (1.1)0.0 (0.9)8.2 (1.9)
 6—impact 150−7.7 (0.7)3.5 (2.2)11.2 (2.1)
 6—impact 250−10.1 (0.6)−1.8 (0.3)8.3 (1.0)
 750−12.1 (0.4)0.4 (0.4)12.5 (0.3)
Along slope velocity (m/s)
  1—impact 16014.8 (0.7)17.7 (0.3)+2.9 (0.7)
 1—impact 26014.8 (0.2)15.1 (0.4)+0.3 (0.3)
 2501.9 (0.4)0.0 (0.3)−1.9 (0.4)
 35018.7 (1.1)15.8 (0.8)−2.9 (1.5)
 45027.9 (1.3)27.4 (0.9)−0.5 (0.6)
 55016.9 (0.8)16.6 (0.3)−0.3 (0.7)
 6—impact 15010.2 (0.1)6.5 (0.8)−3.7 (0.7)
 6—impact 25014.9 (0.5)13.9 (0.7)−1.0 (0.5)
 75017.6 (0.2)13.4 (0.5)−4.2 (0.7)
Angular velocity (rad/s)
 1—impact 160−10.5 (3.7)18.0 (3.2)28.5 (3.5)
 1—impact 260−42.1 (0.5)22.1 (2.9)64.2 (3.0)
 250−42.8 (0.3)15.8 (0.9)58.6 (1.0)
 450−18.5 (1.2)2.7 (2.1)21.2 (1.5)
 750−24.3 (4.8)19.6 (1.2)43.9 (5.6)