Thursday, November 20, 2008

CONTACT STRENGTH (PART 1)

Each time we grasp a hold, we have to do enough strength to support our body weight. But what is contact strength?

Contact strength forces are the forces that occur between objects, and they can be resolved in two components: the force that acts perpendicular to the contact objects (hand – hold) surfaces and the component that acts parallel to that surfaces (friction). (McGinnis 1999)

Climbers main motor force is the first component, and friction allows the climber to exert that motor force.

Friction between two bodies doesn’t depend on the size of the contact surfaces (hand – hold), but depends on the nature of both surfaces.

Magnitude of friction forces is proportional to the Normal between both bodies; that means more force we apply, more friction we generate. When friction acts between two surfaces that are not moving, it is referred to as static friction, and when your hand is sliding from the hold is referred to as dynamic friction. Each time we grasp a hold we want a static friction, so we have to apply a higher force than dynamic friction.


Well, now we know that we have to apply enough force (strength) to catch a hold, and if we analyze a little more, to get more friction force we’ve to apply even more strength.

As sport performance increase, conditions to apply force worsen: the climber will have less time to apply strength, since the same action will be done with greater velocity. So time to apply force is reduced with the increase in sport mastery, and the only solution to this is to improve the force-time curve, that means apply more strength in less time (Badillo y Serna 2002).

As the climber’s level increases, routes are steeper, and hold needs more friction force. But we have to apply the greater force as possible in a short period of time, since if we don’t apply enough force in the precise instant we contact the hold, the force generated by our body weight (gravity) will be enough to impede grasp the hold.


In the force time graphic, we will see that an athlete can apply his maximum strength (100%) in 0,4 sec, An excessive time if we calculate the necessary time to grasp a hold that needs a lot of friction; on the other hand, in less than 0,2 sec the athlete can apply 50% of his maximum strength. That means that the useful strength of this athlete is 50% of his maximum strength, thinking on apply strength as fast as possible.


In the left graphic, we can se how two athletes with different maximum strength con grasp the same hold if the required force is 400 Newton in 200 ms. On the other hand, in the right graphic two athletes with same maximum strength, but in 200ms the continuous line athlete can exert higher strength, so he might have better possibilities grasp holds that requires higher strength levels in lesser time.





This video (extract from Fanatic Search) shows how contact strength fails.

That’s why finger maximum strength and power (strength/time) or climbing specific contact strength has to be one of the main goals of a climbing specific training program.

Next article I’ll show some ways to train contact strength, using climbing, fingerboard and campus board.

Prof. Juan Martín Miranda

Bibliography

Badillo & Serna. 2002 . Programación del entrenamiento de la fuerza. Ed.INDE. Barcelona. España.

McGinnis P. 1999. Biomechanics of sport and exercise. Ed. Human Kinetics. Estados Unidos
Zatsiorsky V. 1995. Science and practice of strength training. Human Kinetics. Estados Unidos.