Getting a Grip: The Role of Traction in Your Training
Surprisingly, the quality of traction influences whether you will achieve the highest levels of sport performance or risk injury. It’s not what you think.
gettingagrip
Various running surfaces combined with footwear offer unique training effects.
How much traction do you have when your foot connects with the ground? Traction, or grip or friction, significantly influences our training, racing, and performance in individual and team sport, not to mention our ability to remain upright and free of injury,

Consider a few examples of the interface between the foot, the shoe, and the ground: We might run across grass wearing an eight-stud rugby cleat, or across a gymnasium floor wearing court shoes. Indoor soccer shoes on turf and running shoes on concrete offer very different experiences of traction. Imagine yourself wearing cross trainers on an outdoor hockey rink. Each example has interesting traction considerations.

How ground reaction forces work

Ground reaction force (GRF) refers to the equal and opposite force the ground has on the foot. GRFs include a vertical component, which refers to the amount of force with which our foot is pushing straight down. GRFs include friction, which stops our foot from slipping. At heel strike or as we first make ground contact our foot is moving forward, and the ground helps to stop the foot via friction. This is best demonstrated by its opposite, when friction is lacking: we’ve all experienced the unfortunate “one-heel squeal” when landing on ice we didn’t anticipate. During the propulsive phase of movement, we need friction to push our body forward. Sprinters, at the extreme end of the traction continuum, use spikes to ensure perfect traction as they push themselves forward.

Another traction consideration is rotation. In most agility-oriented sports we pivot on the ground during cutting maneuvers, swinging golf clubs, swinging racquets, and surprisingly even while walking straight forward.

Why is understanding traction important? The most obvious reason is performance. In no sport, other than curling, is less traction considered a performance enhancer. One of the most important elements of sports shoes is to enhance traction for any transitional movement like stopping, starting, and cutting. So is there any advantage to having less traction? In many circumstances, yes. Less traction can be used for two very important reasons: a training effect and injury prevention.

Training effects

A training effect occurs when a stimulus to our body results in an improved capacity to perform a task, such as running. Altering the traction our foot has with the ground is an excellent way to subconsciously cause a training effect. Consider those fleeting moments as our foot makes initial ground contact. As we land on a high-friction surface, such as brushed concrete, our brain and body know that the foot is not going to slip forward. But if we walk or run on a winter day, we may have to step from concrete to ice, a very different friction scenario. As seasoned Canadians, our brains tell us that the next step will connect our foot with a patch of ice and that because we have experienced this change in the degree of friction in the past, we understand how to alter our gait pattern instantly to accommodate the expected slippery conditions. Brilliant Canadians, eh!

Winter cross-training

My favourite winter cross-training activity involves wind sprints at my local outdoor hockey rink. Yes, armed with my hockey helmet, elbow pads, and wrist guards, I perform wind sprints on the ice. There are a multitude of training effects you get by running or walking on slippery terrain. One is a reduction in overstriding. Overstriding is when your stride length is too long and your stride cadence is too small. Overstriding is next to impossible on slippery terrain. Your brain knows that if you take a big long stride expecting friction to stop your foot’s forward progression, your next vertical ground reaction force might be with your rear end. And so, a “tight” more “stable” gait program is produced. The resulting training stimulus is a fantastic addition to the repertoire of running or gait patterns your body can draw upon to run more efficiently. It will also subconsciously transfer to improve your running patterns when you return to normal running surfaces.

Summer cross-training

In junior high my buddy and I started an activity we called “Kamikaze running.” Basically, after a good rainstorm, we hit the muddy trails with our oldest runners or court shoes. The fun factor was high, the training effect was huge. No marathon shuffle in these conditions. Your brain and body are forced to be extremely vigilant and pay attention. No two steps are the same. This stimulus of ever-changing ground contours and traction teaches your muscles to be more aware of the world under foot. This heightened awareness then helps us adapt faster to future terrain surfaces, including concrete.

Injury prevention

An interesting study was conducted in the Australian Football League (AFL) between 1992 and 1998. The objective was to determine if weather conditions affected the risk of anterior cruciate ligament (ACL) tears in the knee. The researchers concluded that wet fields significantly lower the risk of ACL injuries in AFL footballers. The key reason was speculated to be reduced shoe-surface traction.

Similar findings concerning traction have been observed in American football, soccer, and other sports. A variety of injuries, but especially knee injuries, are significantly higher with better traction.

This poses an interesting dilemma for those trying to perform at their best but who are also concerned about the risk of injury. If you are the only player on the field without cleats, you will be at a performance detriment. If you increase your traction with cleats, you accept a higher potential for injury. My suggestion is to reduce traction for training and practicing. Try using cross-trainers or indoor soccer shoes outside during practices. I would urge coaches of running game sports to encourage their athletes to decrease some amount of grip for practices. For sports on the more “grippy” artificial turfs, coaches might consider taking practices out to the grass.

How about the rest of us “less competitive” athletes? For those of us who run and play sports for fun, participation, and health, increase of injury risk is generally not acceptable. Performance versus injury risk is a personal choice, but you won’t find my old and busted body playing ultimate in cleats. The risk of re-injury due to my history of prior ankle sprains is too high. So now when it’s dry I use basketball shoes. Basketball shoes are great when it comes to lateral support, and the reduction of traction dramatically decreases my chance of re-injuring my ankle. The performance detriment is acceptable, as continued play and participation far outweigh performance.

The aches and pains of golf and running

When your feet are completely fixed to the ground with spikes, the rotational force of a big golf swing puts you at a high risk of injury if the knees or other weak structures in the leg are not able to withstand the force over time. It can lead to mild increases in knee joint wear and tear compounded over hundreds of swings per week. Try removing your spikes from your golf shoes, especially on dry days, as a little less grip allows for minor rotational “slip” and thus can decrease rotational stress within the leg and knee. You may be surprised that your performance isn’t that much worse, if at all! This idea is also beneficial for the walking component of a golf game. Again, if your feet are not fixed to the ground by spikes, your foot will be allowed minor levels of “slip” that can decrease rotational stresses in the leg during normal walking.

Likewise, as we run, there is a small amount of relative movement between the ground and the shoe. Certain individuals move much more than others and certain surfaces allow more relative “slip.” We’re talking millimetres or less, but millimetres count. Two important examples of this slip are at heel strike, where the heel slides into place, and rotation of the shoe relative to the ground. Some people’s bodies work better if a small amount of rotation is allowed to occur between the ground and shoe. The forces on the foot and leg can be significantly altered when you switch from more or less ‘grippy’ surfaces. As far as friction is concerned, concrete really “grips” the shoe, while gymnasium floors, shale paths, dirt, grass, and even most treadmills offer a bit less grip.

About the Author

Lee MacKenzie, B.Sc.Kin., C.Ped (C), CAT (C), is president of Footjax in Calgary, Alberta, a certified pedorthist with the Pedorthic Association of Canada, and a certified athletic therapist with the Canadian Athletic Therapists Association. For more information, see www.footjax.com.
 

1 Comments

  1. KonstantinMiller makes this comment

    Mon 06 Jul 2009 19:23:50 PDT

    You know so many interesting infomation. You might be very wise. I like such people. Don't top writing.

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