In college Graham had played tailback, which was the passing position in the single-wing formation used by Northwestern, but in Cleveland, where the T formation was favoured, he played quarterback.
The initial hand position was set to −0.15 m for the leftmost passing positions, 0 m for the central passing position, and to 0.15 m for the rightmost passing position (accounting for the minor offset when using the left and right hand).
Figure 2 illustrates how hand movements depend on the ball's spin direction (i.e., curve) and passing position.
For each passing position, three different spin directions were used (CS; 10 rps), counter-clockwise spin (CCS; 10 rps), and no spin (NS).
To calculate the early bias, we first defined the moment of initiation of the movement in the direction of the ball's passing position; the used (absolute) velocity criterion was the maximum of 0.05 m s−1 and 2% of the first velocity peak in the direction of the passing position exceeding 0.25 m s−1.
For those curved free-kicks that elicited an initial erroneous movement, the early bias increased in magnitude towards the goal centre; for NS free-kicks the early bias was very small and uninfluenced by passing position.
The effects of spin direction and passing position in the novices were analyzed for both variables using a linear mixed model with participant as a random factor (alpha = 0.05).
In light of the time available to move to intercept the free-kick, our participants were faced with a trade-off between starting to move early to reach the passing position in time to stop the ball, and waiting longer to observe a larger part of the ball flight to better anticipate where it might be heading [19].
Note that this Tini is not equal to the one used to quantify the early movement bias, which only referred to the movement component in the direction of the ball's passing position; Tini refers to the entire movement, even if the initial movement was in the wrong direction.
Setting position is different than passing position.
