  The motion of the golf club is measured using two accelerometers mounted at
different points along the shaft of the golf club, both sensitive to
acceleration along the axis of the shaft. The resulting signals are resolved
into differential and common mode components. The differential mode, a measure
of the centripetal acceleration of the golf club, is a reasonable proxy for
club speed and can be used to understand details of tempo, rhythm, and timing.
The common mode, related to the acceleration of the hands, allows insight into
the torques that generate speed in the golf swing. This measurement scheme is
used in a comparative study of twenty-five golfers in which it is shown that
club head speed is generated in the downswing as a two step process. The first
phase involves impulsive acceleration of the hands and club. This is followed
by a second phase where the club is accelerated while the hands decelerate.
This study serves to emphasize that the measurement scheme yields a robust data
set which provides deep insight into the tempo, rhythm, timing and the torques
that generate power in the golf swing.
