The technique of brushing
Curling is a team sport; every shot is a team shot. Each shot requires co-operation by all four players: the skip to call the line, the thrower to throw the stone at the broom, and the sweepers to place the stone at exactly the right point on the sheet. But brushing, while being critical to making many shots, is arguably the most under-coached technique in curling.
At the Team Glenn Howard fantasy camp in October 2010, attendees were treated to a session by Jim Waite of the CCA where Jim described the most efficient brushing technique known, validated by a study performed by Dr. Thomas Jenkyn and his colleagues in the Faculty of Engineering at the University of Western Ontario. Subsequently, Paul Webster of the CCA posted an article detailing the optimal body position for the most effective sweeping. It is this position that you’ll often see the world’s top curlers use; for example, here is a photograph of Team Martin executing a shot against Randy Ferbey’s rink at the 2009 Canada Cup:
Here, notice the body position of Team Martin second player Marc Kennedy on the left:
- Marc’s back is flat and perpendicular to the ice surface.
- The lower hand is positioned very close to the head of the brush, perhaps six inches (fifteen centimeters).
- Marc is sweeping in a Closed position (see below).
- Marc’s head is directly over the head of the brush.
- His feet are outside (behind) his hips, which means that the majority of his body weight is being transferred through his arms to the head of the brush, maximizing the brush’s pressure on the ice.
While the technique illustrated above is acknowledged as the most effective way to brush a curling stone, it is not the only technique. Moreover, keep in mind that Marc Kennedy is an Olympic-caliber athlete, and it is Marc’s strength and conditioning that enables him to brush in this position through an entire game, and through an entire Brier.
Qualities of effective sweeping
To be effective, sweeping requires the optimization and balance of the following factors:
- Downward pressure
- Brushing technique:
- Orientation of the broom
- Brush-head speed
- Length of brushing stroke
- Proximity of the brush to the stone
- Orientation of the two sweepers, both to maximize effect and minimize the risk of touching any stone
- Weight judgment
- Communication amongst all four players
- Being able to keep up with the stone, even if thrown with peel weight
- Negotiating around guards while still sweeping
- Effective footwork in both the closed and open positions
The Open position
At left is the sweeping position commonly taught to beginners, particularly children, called the “Open sweeping position”. On the left, Laurier varsity player Joel Waters illustrates brushing in the open position: weight is balanced between the arms and the legs, but the real advantage for beginners is two fold: one, while sweeping the curler faces the skip – here, you can see Joel looking up at his skip for directions – and two, the hips and feet are facing forward, making forward movement easy. Moving down the ice in this position uses a leg motion similar to cross-country skiing where the feet shuffle forward, knees bent, while the head and shoulders should stay relatively level.
If sweeping on the other side of the stone, the sweeper must switch hands to stay in the Open position. In the next photograph, both Fraser Reid at left, and Aaron Squires at right, are brushing in the open position. With Aaron, note that his right hand is closest to the brush head. In either case, the hands hold the brush such that the hands are approximately 1/3 of the distance from each end of the brush. Also note that in either case the brush handle is in front of the sweeper’s chest.
A point to stress is that the Open position easily permits effective brushing when wearing a gripper on both feet. Hence the Open position is arguably the preferred sweeping position from a safety standpoint, which is why it is so frequently taught to beginners.
Sweeping is by far more effective if the two brushers are on alternate sides of the stone (see the Team Martin picture above). In this way they are able to sweep as close to the stone as possible, without being in each other’s way as they travel down the sheet.
The Closed position
In sweeping, as in many other sports such as hockey, baseball, or golf, everyone has their favorite side. If one is used to having their left hand lower on the brush handle, but needs to sweep on the right side to accommodate a teammate, what could one do? The answer is to utilize the closed position, which reverses the hands but also has other subtle implications.
In the closed position, the arm farthest from the stone goes across the chest and grips the brush at the lower end of the handle. In the next photograph, Cheryl Kreviazuk (at left) and Sarah Wilkes (at right) of the Laurier Golden Hawks brush in the closed position. With Cheryl, notice that her right hand is closest to the brush head, but her left shoulder is closest to the stone. Some curlers prefer this position at the outset, at least for the hands. But there are three issues with the Closed position:
- The brush is no longer entirely in front of the body.
- By bringing the outside arm across the chest, the brusher is no longer able to easily face the direction of travel down the ice. To look at the skip for direction during the shot, the brusher must twist both their head and their torso (see Cheryl in the next photograph). This twist has the potential to cause issues with the lower back with some players, mentioned by Russ Howard in his book Curl to Win.
- The feet can no longer directly point in the direction of travel. Hence, rather than the forward cross-country skiing motion of the Open position, the sweeper must resort to more complicated footwork often involving a side-to-side “shuffle”. This can be more awkward when using grippers on both feet.
Many curlers sweep in either the Open or the Closed position to ensure that their favorite hand is the lower on the brush handle, if paired with a teammate who favours the same side.
Sweeping in the Closed position is arguably more difficult than sweeping in the Open position because the feet are naturally sideways – the footwork is more complex, as is stepping around and/or over stationary stones once the delivered stone has crossed the far hog line. However, once the footwork is mastered, brushing effectiveness can be gradually improved by creating more pressure on the brush head. The key to the footwork is to make sure the hips are angled forward as much as possible, with the leg drive coming mostly from the rear leg, the front leg providing stability during the sweeping motion.
Applying additional pressure on the brush head can be accomplished in two ways:
- further lowering the lower hand to be closer to the brush head; and
- keeping at least one foot, if not both, outside the line of the hips at all times – so that the maximum amount of force can be transferred to the brush head.
However, applying that amount of force takes a fair degree of both upper- and lower-body strength: in the torso, it requires significant strength in the triceps (arms), deltoids (shoulders), and pectoral muscles (chest), and in the lower body it requires strength in the abdomen and the hip flexors to stabilize the motion. It is rare to find the kind of strength and agility in younger players, both boys and girls. Consequently, under the advice of Scott Taylor of Balance Plus, and Bill Tschirhart, former National Training Center coach for the Canadian Curling Association, we will continue to teach the Open position for beginners, including Little Rockers. The Closed position, which permits the greatest amount of force applied to the ice surface, can be taught once the curler has achieved some mastery of brushing technique, particularly the footwork, and can handle the physical demands of the Closed position.
Finer points of effective sweeping
While attending the Level 3 Technical coaching course in Napanee the last weekend in October, Brian Savill gave us a one-hour “Sweeping Update”, summarizing the latest research undertaken at the University of Western Ontario on the mechanics of brushing and its best practices. I’d like to summarize Brian’s remarks here. There is some other online material available about the UWO study, including a useful article by Scott Arnold.
The UWO study, commissioned by the Canadian Curling Association, studied a wide variety of variables from the points listed above, with both club curlers and highly-skilled curlers from Tour events. The study noted – unsurprisingly – that there exists a strong correlation between the frequency of the brushing stroke and the amount of heat generated. Also, shorter brush strokes tend to be counterproductive because shorter strokes often lead to other adjustments by the player that alters the overall amount of effort put into it.
One of the more interesting variables analyzed in the UWO study was the orientation of the brush head. The two extremes are (a) holding the brush so that the head is perpendicular (across, or 90 degrees) to the line of travel and (b) holding the brush so that the head is parallel to the line of travel.
If the brush is held so that the head is perpendicular to the line of travel, the UWO researchers found that the brush warms the ice to a slightly higher temperature, and it permits the inside brusher to hold the brush head slightly closer to the stone. However, the disadvantage of this orientation is that the brush warms the ice in a “zig-zag” pattern (see the diagram at right) leading to inconsistent warming of the entire path in front of the stone. Moreover, the research team found that the stroke width is much harder to control with the perpendicular orientation.
A parallel orientation, on the other hand, raises the ice temperature a fraction of a degree less than the perpendicular orientation, but offers greater consistency and much better control of the width of the stroke.
The UWO study concluded that in their experiments the most effective orientation for two sweepers is as follows: the inside sweeper brushes next to the stone with the brush head parallel to the line of travel; and the outside sweeper, brushing on the opposite side, holds their brush at a 45-degree angle to the line of travel. Where the ice has some amount of frost, the use of a hair brush by the outside sweeper (again, at a 45-degree angle) is the most effective.
Newer brush heads make a difference
Another assessment performed by the UWO team was on particular types of brush heads. In the past year, these new heads, originally designed and manufactured by Balance Plus and now also offered as Goldline “HE” heads, require less effort to achieve the same efficiency, and are waterproof – a problem with regular nylon heads is that, once wet, they are much less efficient than when they are dry.
The new heads are slightly more expensive than regular nylon, but tend to last much longer.
In the past, both the World Curling Federation and the Canadian Curling Association mandated that brushing had to involve strokes that took the brush head completely across the running path of the stone. In the parlance of the day, “snowplowing” and “corner sweeping” – sweeping only a partial path – were illegal. These rules were changed a few years ago and now “anything goes” except that one must not purposefully stop their brush in front of a stone with the intent to “dump” debris in front of the stone to slow it down.
With “corner sweeping”, there are two orientations: “low-side” and “high-side”. The “low-side” is that part of the stone closer to the direction of curl; the “high-side” is, of course, the opposite side. The UWO study found that corner sweeping on the “low-side” of a stone tended to make the rock go straighter, but since the brushing effect was not on the entire running path of the stone, the stone would not carry down the sheet as far. Conversely, “corner sweeping” on the “high-side” would cause the stone to carry further than with “low-side”, and in addition cause the stone to curl more than when brushing across the complete running path of the stone.
“Corner sweeping” is now used by teams on Tour quite deliberately. Its impact when attempted by younger players is unknown, but anecdotal evidence suggests that corner sweeping can make an impact even with the reduced downward pressure applied by younger players.
Instrumented Curling Brooms
The Golden Hawks Curling HPC has purchased a PT-2 Smart Broom from Canada Curling Tools for use in brushing performance assessments. Background information about instrumented brooms can be found in this article, written by HPC coach Glenn Paulley, that describes the two commercial instrumented brooms available in Canada and some of the research behind the creation of instrumented prototypes.