The science behind kicking a field goal gives soccer style an advantage
By Brian Palmer,
Paradigm shifts in sports fascinate me, in part because they’re virtually always unscientific. Everyone is doing things one way, then a pioneer realizes that another technique simply feels better. While athletes can immediately choose between the old and the new, scientists spend years deciding whether the new technique is truly an advancement.
Consider the Fosbury flop. Prior to the 1968 Olympics, almost all high jumpers went straight at the bar, throwing one leg and their head over at the same time. When Dick Fosbury came along with his backward, head-first, facing-the-sky technique, Time magazine referred to it as “preposterous.” Even Fosbury’s own coach told the magazine, “I wouldn’t advise anybody else to try it.” That was right before Fosbury won gold and set an Olympic record. Four years later, most of the competitors used the Fosbury flop. It took researchers years to figure out the physics of why the flop worked so well.
Now that football is in full swing, I’ve been thinking about the scientific explanation for another paradigm shift. Beginning in the 1960s, the “soccer style” of placekicking began to take over professional football. Younger sports fans might not remember the old straight-on style. The kicker stood directly behind the ball, creating a straight line connecting him, the football and the uprights. The holder placed the ball straight up, perpendicular to the ground. The kicker took a short step, then a full step as he swung his kicking leg straight back, then snapped it forward. His ankle locked, keeping his foot in an extreme flexed position as he walloped the ball with his toes.
Virtually everything about this technique is different from that employed by today’s soccer-style kickers. They approach the ball from the side, the holder tilts the football, and they strike the ball with the instep rather than the toes.
While the two styles of kicking coexisted for the better part of two decades, the soccer-style kickers won out.
Let’s take a look at the biomechanics of kicking, to see how and why the soccer style has taken over and whether the straight-on style has anything to say for itself.
First off, it’s not surprising that straight-on kickers could match, and sometimes exceed, their soccer-style colleagues.
“In a foot/ball collision, the ball goes off at about 20 percent faster than the foot is traveling,” according to Adrian Lees, a professor of biomechanics at Liverpool John Moores University in the United Kingdom. “However, this percentage can be increased or reduced depending on how rigid or flexible the foot is.”
Straight-on kickers lock their ankles, with the foot approximately perpendicular to the leg, which enables them to transfer the kinetic energy of the swinging leg to the ball very efficiently. Soccer-style kickers hold their foot at a more obtuse angle at the moment of impact, which means some of the leg’s energy is absorbed by the flexing ankle joint. Soccer-style kickers use a couple of tactics to overcome this disadvantage.
If you watch the Redskins’ Graham Gano or the Ravens’ Billy Cundiff, you’ll see that their hips swivel during the windup and follow-through of their kick.
“The angled approach allows players to rotate their body segments in more than one axis, not only in one plane, and this seems to make them a bit faster,” says Eleftherios Kellis, a professor of sports science at Aristotle University of Thessaloniki in Greece.
Soccer-style kickers also can decrease the dampening effect of that flexed ankle by striking the ball high up on the foot. Impacting the ball on the instep means more of the leg’s energy is transferred to the ball because the ankle doesn’t bend as much upon impact. (Shoes also absorb some of the force of impact, which is why many kickers used to kick barefoot. Improvments in shoe technology — partially combined with an aversion to pain — have virtually eliminated barefoot kicking)
But striking the ball with the laces introduces an additional complication: The kicker must contact the ball at its center. For most people, trying to smack the center of the ball with the laces of his kicking shoe risks dragging the toe along the ground. So the kicker has to drop his body down slightly when approaching the ball. Studies have suggested that the optimal angle from which the kicker should approach the ball is between 43 and 45 degrees, as measured against the straight line that runs between the ball and the goalposts.
The biggest benefits of the soccer style seem to come in accuracy. The non-kicking leg of a soccer-style kicker is in a better position to control his movements. His bent non-kicking knee absorbs the impact of landing rather than transferring an enormous jolt through the body. Stability through the moment of impact is crucial to making the ball go where you want it to. Research presented at a 2009 conference by Lees showed that muscles around the non-kicking leg of a placekicker are highly engaged during the moments before the ball is struck, which helps the kicker keep the rest of his body stable.
Also, the laces area provides a larger area of contact than the toe, further improving the kicker’s accuracy. While there are no scientific data as yet on this, the practical evidence is suggestive: Some modern kickers make field goals at a higher rate than their counterparts converted simple extra points 30 years ago.
Three men share the NFL record for longest field goal, at 63 yards. One of them, Tom Dempsey, was a straight-on kicker born with no toes on his kicking foot. Dempsey wore a special shoe with a squared-off end, which created a far greater impact area than the toe on an ordinary shoe.
While researchers believe the soccer style of kicking has an accuracy advantage, it’s not necessarily better in all scenarios than the straight-on style, which has undeniable power benefits. When the Skins are stuck on the 50-yard line with one second left on the clock, they just might be better off with their old kicker Mark Moseley, the last great straight-on NFL kicker, than today’s soccer stylists.