The Triathlete's Holy Grail: Part II
Application is the best way to understand biomechanics, so I'd like to present three practical examples for each sport of how to use the torque/lever arm relationship to your advantage. Logically progressing, I'll start with the swim. Next week, in Part 3 of this series, I'll be moving on to the run and the bike.
The Kick: There are three centers of rotation in the kicking action: the hip, the knee, and the ankle. Due to the weight of the leg and the surface area of the lever arm sticking out from it (i.e. the entire leg), the most torque is produced in the hip. This is why the muscles around the hip joint are the some of the strongest in the body, and the most well equipped to produce a resistive torque against the downward force of the leg sinking in the water and the drag from the water itself, as well as the upward force against the weight of the water. Technically, the lever arm of the hip is longest when the knee is completely straight, so in this scenario, the hip could produce the most torque. But remember that the idea is not to necessarily produce the most torque, but to produce optimal torque to gain the greatest speed while minimizing fatigue. A slight bend in the knee will accomplish two objectives: 1) incorporation of assistive knee musculature, which can help delay hip fatigue and 2) decreased lever arm length, to reduce torque production at the hip, again delaying hip fatigue.
The bonus is that by decreasing the lever arm, you also decrease resistance to angular momentum. This means that the hip not only experiences less fatigue with a slightly bent knee, but the leg actually gains the ability to travel faster in the water, allowing for an increased kick cadence.
Another lever arm involved in the hip is that of the foot. The fastest swimmers in the world just happen to have very flexible ankles, which means they can achieve a greater toe point angle than their less speedy counterparts. A large amount of extension in the ankle increases the lever arm at the hip (hip to foot distance), the knee (knee to foot distance), and the ankle (ankle to foot distance). Therefore, by simply extending the foot, you greatly increase the amount of torque you are able to produce with the entire leg, without having to kick harder or through a greater range of motion. Does this cause greater fatigue in the leg musculature? Anyone who has done a fin workout will respond with a definitive yes. However, the increase in speed and the reduction in drag that results from this small biomechanical adjustment will outweigh the increased muscular demand.
While any drill that focuses primarily on kicking will improve your kick efficiency, I recommend incorporating fin drills. By automatically increasing your lever arm, kicking with fins will force you to kick from the hip with a slight knee bend, while also extending your ankles. Try a few front and side swimming kick sets in at least one workout of the week.
Let's move on to the pull, or what many coaches refer to as the insweep, which is the portion of the stroke in which the arm is pulling under and across the body. With the arm completely extended, the lever arm is as long as possible, and maximum torque is produced in the shoulder joint. Remember, however, that the water is pushing just as hard against the swimmer as the swimmer pushes against the water, so this maximum torque can prematurely fatigue the shoulder joint. By bending the elbow, and thus shortening the lever arm, less torque is produced in the shoulder (similar to bending the knee in the kick) and the torque is redistributed among the chest, upper back, and forearm muscles (the lever arm actually increases with respect to these muscles). Just like bending the knee in the kick incorporates the assistive knee musculature, bending the elbow in the swim allows for use of the these assistive muscles. In addition, bending the elbow allows the arm to move faster through the water (decreased resistance to angular momentum) and puts the hand in a position that is perpendicular to the direction of travel, which actually allows the swimmer to grab more water. Forearm angle should be at 20-40 degrees (low angles for tall, lanky swimmers, high angles for short, stocky swimmers).
One of the best drills to encourage a bent forearm is the fist-swimming only drill, in which the hands are kept closed. By keeping the hands from providing the primary propelling force, a swimmer is forced to bend the elbows in order to increase surface area of the forearm that is exposed to the water, as well as increase torque application from the accessory upper body muscles, to assist the shoulder.
Finally, consider the lever arm with respect to the recovery portion of the swim phase, in which the arm is removed from the water after finishing the pull stroke, in preparation to be thrust in front of the body for the next stroke. There are two ways that torque is increased in this situation: 1) the greater the angle of the elbow, the longer the lever arm, and the greater the torque in the shoulder; 2) the greater the angle at which the arm is extended away from the body (a “diagonal” reach), the greater the torque in the shoulder. This is a common scenario in swimmers who windmill (swimming with a straight-arm recovery), or swimmers who do not reach forward in a streamlined position (reach at an outward angle instead). Either way, the increased torque in the shoulder is useless, as it simply fatigues the shoulder without achieving any additional pull against the water (your arm is in the air). Therefore, when the arm is withdrawn from the water, the elbow should be bent, as if a string were attached from the elbow to the ceiling, pulling it straight out of the water. In addition, when reaching forward to initiate the pull-phase of the next stroke, the arm should be thrown forward directly in front of the body, with the head tucked between the shoulders, as opposed to reaching at an angle away from the body. If you think about it, reaching more directly forward (similar to an 11am/1pm clock position) is a direct result of having a bent elbow removed from the water, because a straight arm must swing through a greater (i.e. longer) arc, and therefore enter the water sooner if speed is to be maintained (at more of a 10am/2pm clock position).
A great drill to incorporate more elbow flexion at water removal is the shark fin/zipper drill. As the arm is removed from the water and the hips are rotated to initiate the breath, the swimmer zips up an imaginary zipper that extends along the side of the body, then holds the elbow in a bent shark fin position for a brief 1 count, before continuing into the front swimming position.
Whew! Time to take a break. We'll continue next week by considering how lever arms and torque can be used to improve speed and conserve energy in the run and the bike.
Until next time, train smart,
Ben Greenfield