Functional laterality – that is, handedness, footedness, and ocular dominance, are important physical characteristics in many team sports, such as ice hockey and baseball, or in racquet sports such as tennis, squash, and badminton. Handedness is often less of an issue in other sports, particularly individual sports, such as darts, or golf.
Handedness, in particular, has been studied extensively [1,2]. Handedness refers to an individual’s preferential use of one hand over the other due to strength, quickness, or dexterity. The preferential hand is commonly referred to as the dominant hand. About 10% of the human population is left-handed, though this proportion does vary slightly by gender (males 10.5%, females 8.7%) [1,2], with 1% of the population being ambidextrous, having an equal ability with both hands.
Taylor Stremick of Team Ashley Thevenot of Saskatoon being tested on a CurlSmart instrumented brush at the Sutherland Curling Club.
To a significant degree, in many sports the advantage for a left-handed athlete is simply that their opponents are often unfamiliar with competing against someone who is left-handed. This is certainly true in combat sports such as boxing [3] and fencing [4]. In contrast, in golf there really is no real advantage to left- or right-handedness, but interestingly in golf the number of left-handed players on the PGA Tour is only 5%, half of the population average. The stated reason for this is the historical, and continued, lack of availability of left-handed clubs – which is the reason my brother Gordon, who is left-handed, plays golf right-handed.
In football (soccer) you might believe functional laterality doesn’t play a role since a player other than the keeper can only touch the ball on a throw-in. But in football the trait of importance is footedness, and what’s interesting is that, in a 2016 study, researchers at Nova Southeastern University found that while 98% of right-handed people are right-footed, only 67% of left-handed people are left-footed, making a left-footed striker an even rarer discovery.
It is certainly the case that athletes can adapt their handedness to suit a particular sporting situation; ice hockey is one example, and it is really interesting reading about how the coaching of the sport has changed over time. A left-handed goalie has the advantage of being the rare opponent, with their catching hand on the opposite side to a right-handed player. But handedness at the other positions is important as well. Decades ago it was clear that left-wing and left-defencemen should shoot left in order to take passes on their forehand, and so that their stick was closest to the boards to stop the puck; similarly for right-wingers and right-defencemen. A 2017 study of NHL players found that 62% shoot left; left-handed sticks outsell right-handed sticks 2:1. However, while the typical Canadian youngster will pick up a hockey stick and use their strongest hand as the bottom hand on the shaft, American coaches are frequently getting young athletes to use their dominant hand on the bottom, not their strongest hand.
Mixed-handedness
Our ability to adapt our handedness to suit specific tasks is termed mixed-handedness, mixed laterality, or cross-dominance, to differentiate the adaptation from true ambidextrousness. Adaptability comes with training, though specific preferences depend on a variety of factors including whether the person is cross-lateral with their hands and feet, amongst a range of other variables [5]:
…the quality of human hand movements may be influenced not only by central information processing (hemispheric specialisation) but also by other structures and processes of motor control, such as central pattern generators (CPGs) and biomechanical factors. [5]
… We consider that both theories are correct; laterality is conditioned both by genetic factors, as well as by educational, social, cultural and environmental factors. The process of physical and sports training aims at a balanced development of the upper limbs, the lower limbs, and, implicitly, the two sides of the body: left and right. [6]
Baseball is the Best!
Perhaps there is no other sport where the issue of functional laterality plays a role than in baseball, and Major League Baseball enjoys more than a century of detailed player and pitcher statistics with which to make analyses, on everything from pitching matchups to batting averages.
In baseball, the colloquial term for a left-handed ball player is “southpaw“, though that term is usually reserved for pitchers. Left-handed players are much more prevalent in the major leagues than in the general population: 31% of hitters and 29% of pitchers are southpaws. Interestingly there is a strong bias against left-handed catchers: only 30 left-handed players have caught at least one inning in the major leagues. Ever.
From the viewpoint of mixed-handedness, what is more interesting in baseball is the frequency of “switch hitters”, who bat at different sides of the plate depending on the handedness of the pitcher. About 13% of major leaguers are switch-hitters, even though 95% of those players are right-handed. The ability of a player to hit a 100 mph fastball when batting on the opposite side of the plate requires significant training, and there are other variables, such as ocular dominance, that can come into play. Nevertheless, statistics indicate that left-handed batters enjoy an advantage in baseball, though arguments and research continue:
Batters who adopt a left-handed stance enjoy a range of potential benefits3: the limited experience opponents have pitching to left-handers, an increased likelihood of “off-handed” match-ups against right-handed pitchers, the direction of the bat-swing moving momentum toward first base (to which the batter already stands closer), potential asymmetries in the location of fielders and their skill level, and a possible tendency to be selected on a team to allow a more flexible strategy.4 We speculate that players who throw right-handed and bat left-handed enjoy an additional biomechanical advantage, with the dominant (throwing) hand being placed further from the hitting end of the bat, providing a longer lever with which to hit the ball (potentially at the expense of bat control5). Given these sport-specific explanations, our findings argue against any advantage due to hemispheric lateralization. [7]
So what about curling?
To my knowledge there is no study that has looked at functional laterality in the sport of curling. Since equipment (shoes) are readily available for left-handed players, one can reasonably expect that the frequency of left-handed dominant players would follow the general population: roughly 10%.
In brushing the lower hand supports most of the player’s body mass, with the upper hand assisting to a limited degree (how much is an outstanding research question). Consequently one could imagine that most curling athletes, particularly front-end players, would position their strongest arm lower on the handle, as is commonly the case for ice hockey players. That is the case for me personally: while I am right-handed, my left arm is significantly stronger than my right, so I shoot left in hockey and use my left hand lower on the brush.
In brushing, grip strength certainly plays a role. One study [8] found that only 10.9% of right-handed people have stronger grip strength in their left hand. Interestingly, the figure is 33.3% for left-handed people, although the sample size of left-handed dominant subjects was considerably smaller. Based on grip strength alone, one would think that the majority of curlers would use their dominant hand as their low hand on the brush.
It turns out that’s actually not the case. In my experience in assessing athletes of all LTCD stages over the past 11 years, it is true that most players have a strong preference to which hand is low on the brush. In a sample of 260 unique right-handed athletes, taken from primarily the Learn to Compete (U18) and Train to Complete (U21) LTCD stages, there exists a near-equal distribution of left- and right-hands in the low position on a handle. (Aside: the number of left-handed players in this database is too small to be statistically significant – but I’m working on increasing this sample size).
It’s unclear why the distribution is so even for this sample of right-handed players. Mixed laterality will certainly play a role for some of these athletes, as it does for me and my son Ryan. I note that there are players on Tour that have trained hard at mixed laterality and can switch hand positions depending on the circumstances. In Ontario, Emma Miskew and Katie Cottrill; in Manitoba, Connor Njegovan; and in Saskatchewan, Dustin Mikush, Brittany Tran and Kaylin Skinner are examples of athletes who are equally adept at brushing with either (low) hand, permitting them to brush in the closed stance on both sides of the stone and significantly aiding their respective teams in their versatility with their brushing. However, in my coaching experience this skillset is rare. Out of the several hundred athletes that I’ve worked with over the past decade, only a small handful, less than a dozen, have acquired this level of skill.
I close with mentioning my research colleague at Dalhousie University, Michel Ladouceur, who is starting up a project in Dalhousie’s School of Health and Human Performance to look at shoulder loadings and biomechanics in brushing (and is currently recruiting graduate students in Kinesiology for this work). My hope is that Michel’s research will shed light on the optimal biomechanical position(s) for brushing and recommend ways to mitigate or reduce the incidence of brushing-related injuries. And, possibly, the role of functional laterality in brushing.
References
[1] Scharoun SM, Bryden PJ (2014). “Hand preference, performance abilities, and hand selection in children”. Frontiers in Psychology. 5 (82): 82. doi:10.3389/fpsyg.2014.00082.
[2] Papadatou-Pastou, Marietta; Ntolka, Eleni; Schmitz, Judith; Martin, Maryanne; Munafò, Marcus R.; Ocklenburg, Sebastian; Paracchini, Silvia (June 2020). “Human handedness: A meta-analysis”. Psychological Bulletin. 146 (6): 481–524. doi:10.1037/bul0000229.
[3] Richardson, Thomas; Gilman, R. Tucker (28 October 2019). “Left-handedness is associated with greater fighting success in humans”. Scientific Reports. 9 (1). Nature Portfolio: 15402. doi:10.1038/s41598-019-51975-3.
[4] Harris, Lauren Julius (January 2010). “In fencing, what gives left-handers the edge? Views from the present and the distant past”. Laterality. 15 (1–2): 15–55.
[5] Olex-Zarychta, Dorota & Raczek, Joachim. (2008). The relationship of movement time to hand–foot laterality patterns. Laterality. 13. 439-55. 10.1080/13576500802134623.
[6] Badau, Dana & Badau, Adela. (2022). Optimizing Reaction Time in Relation to Manual and Foot Laterality in Children Using the Fitlight Technological Systems. Sensors. 22. 8785. 10.3390/s22228785.
[7] David L Mann, Florian Loffing, and Peter M. Allen (2017). The Success of Sinister Right-Handers in Baseball. New England Journal of Medicine 377(17), 1688-1690. doi: 10.1056/NEJMc1711659
[8] Nurgul Arinci Incel, Esma Ceceli, Pinar Bakici Durukan, H Rana Erdem, Z Rezan Yorgancioglu (2002). Grip Strength: Effect of Hand Dominance. Singapore Medical Journal 43(5), 234-237. http://www.smj.org.sg/sites/default/files/4305/4305a3.pdf.