The aim of this study was to measure the level of agreement of four portable
football velocity and spin rate measurement systems (Jugs speed radar gun, 2-D
high-speed video, TrackMan and adidas miCoach football) against a Vicon
motion analysis system. One skilled male university football player performed
70 shots covering a wide range of ball velocities (12–30 m·s-1
) and spin rates (94–
743 rpm). A Bland-Altman analysis was used to assess the level of agreement.
For ball velocity, the 2-D high-speed video had the smallest systematic error,
followed by the radar gun, TrackMan and miCoach football at 0.2, 0.4, 0.5 and
4.8 m·s-1
, respectively. A similar ranking was also observed for the random errors
(±0.4 m·s-1
, ±1.5 m·s-1
, ±1.9 m·s-1
and ±6.0 m·s-1
95% CIs). The first three
systems all tracked ball velocity in > 90% of shots, while the miCoach football
tracked slightly fewer shots (79%). For spin rate, the miCoach football had a much
smaller systematic error (4 rpm vs 38 rpm) and random error (±24 rpm vs ±355
rpm 95% CIs) compared to TrackMan. The miCoach also successfully tracked
spin rate in more shots than the TrackMan (79% vs 44%). These results indicate
that 2-D high-speed video would be the preferred option for the field assessment
of ball velocity, however, radar gun and TrackMan may also be appropriate. A
minimum of ten frames of 2-D high speed video, captured close to the ball starting
position, was demonstrated to be sufficient in providing a reliable measure of ball
velocity. The miCoach ball is the preferred option for field assessment of ball spin
rat
