When humans approach targets at maximum velocity, speed is traded off for accuracy when confronted with a constraining target. The ability of humans to contact targets in a whole-body activity was explored using an adaptation of Fitts’ (1954) procedure in which the adjustments made to gait when approaching targets of various widths was explored during running. Previous research on the speed/accuracy trade-off has generally been limited to upper limb aiming tasks (eg., Fitts, 1954; Langolf, Chaffin and Foulke, 1976), having only recently being investigated in lower limb tasks with Drury and Woolley’s (1995) study on walking. The importance of investigating speed/accuracy relationships in running is its application to applied settings such as sports like long jumping and gymnastics vaulting, in which maximum speed to contact a target is a prerequisite for successful performance.
Participants (n = 24) sprinted toward and placed their foot within targets of four different widths for 8 m and 12 m approach distances while "running through" the target. A speed/accuracy trade-off (Figure 1) showing a linear relationship (r = 0.976, p<.05) between target widths in the range of 29 cm to 44 cm and approach time was found for the 8 m approach distance. At the 12 m approach distance, target widths in the range of 43 cm to 65 cm did not impose sufficient constraint on lower limb targeting to show a systematic speed-accuracy relationship. An accelerative sub-movement and a later targeting or "homing-in" sub-movement were found in the approach kinematics for both approach distances. Mean approach stride length and velocity and the stride length into the target area increased with the amplitude of the approach. Final stride duration increased and final velocity decreased with a decrease in target width. Approach speeds were significantly faster in the unconstrained approaches (3.57%:8m; 1.91%:12m), revealing the magnitude of slowing in maximal speed approach tasks due to the requirement to contact the target.
Overall the results of this study demonstrate a possible upper limit for target size that will induce a speed/accuracy trade-off, and that within the limits of fatigue, a longer approach distance is less constraining on speed when approaching a target. With regards to applied sporting situations it can be concluded that in tasks such as gymnastics vaulting where the approach velocity and power developed at take-off from the board is important, increasing the size of the "sweet spot" on the take-off board, would decrease the effects of the speed/accuracy trade-off, thus allowing greater power development and improved performance.
Drury, C. G, & Woolley, S. M (1995). Visually-controlled leg movements embedded in a walking task. Ergonomics, 38, 714-722.
Fitts, P. M (1954). The information capacity of the human motor system in controlling the amplitude of movement. Journal of Experimental Psychology, 47, 381-391.
Langolf, Chaffin, Foulke (1976). An investigation of Fitts’ Law using a wide range of movement amplitudes. Journal of Motor Behaviour, 8, 113-128.