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Surf Analysis

Updated: Jun 4, 2021



The "Get Up"


The surf “get up” occurs immediately after the individual has completed the paddle into the wave. After the energy of the wave is felt and enough momentum is created in order to catch the wave, the “get up” skill is performed. Optimal joint range of motion (ROM) and stability must be expressed during this skill in order for biomechanical efficiency to occur. When biomechanical efficiency is achieved stress applied to the joints and soft tissues is reduced, susceptibility to injury is reduced, and performance is enhanced.


Kinematics


There are two main movements in the surf “get up” that require optimal ROM and mobility. These main positions are the plank on hands and the bottom lunge position, or surf stance position. The plank on hands occurs immediately before the surfer sweeps the legs underneath the body to assume the bottom lunge position.


This article will primarily focus its intent on the analysis of the thoracic spine, lumbar spine and hip regions. The athlete movement skill will remain in pure sagittal and frontal plane views for ease of analyzing kinematic and kinetic criteria. The kinematic requirements of the three body regions in plank on hands and bottom lunge requires adequate measure of the thoracic spine, lumbar spine, and hip joint ROM and mobility. For reference, normative values of thoracic flexion are 30-40° and extension 20-25°. The total arc motion for the thoracic spine is between 50-65°. Lumbar flexion is 40-60°and extension 20-30°. Hip flexion is 120° and extension 20°.

Our athlete displays normal ROM values in the plank on hands position. However, a greater amount of global extension through the thoracolumbar spine and hip would allow him to generate greater loading of the fascial system and increasing demand of the stretch-shortening cycle of the abdominal wall and hip flexors. The result of this effect would allow our athlete to sweep his legs underneath him quicker and make the transition to bottom lunge position with greater efficiency.



The ROM and mobility requirements moving from the plank on hands and bottom lunge shift from one side of the joint to the other. While the athlete is in the plank on hands position the thoracolumbar spine and hip need to extend, in contrast to the bottom lunge position the thoracolumbar spine and hip need to flex. So as long as the hip moves well into extension and flexion with sufficient abdominal wall activation and coordination biomechanical sufficiency can be achieved. If, however, the hip does not extend well in plank on hands nor flex well in bottom lunge the repeated stresses of surfing may lead to tissue overload and injury. Some may view this through the lens of the joint by joint, or refer to it as the “tail wagging the dog.”



While meeting the criteria for normative values of hip flexion, our athlete does not achieve the ROM capacity in order to meet the demands of this position. Due to the requirements of the bottom lunge, limitations in ROM capacity will require compensation to get the motion elsewhere. This is evident in the thoracic spine. The lumbar spine demonstrates a reasonable amount of flexion that does not appear to create excessive strain.



Kinetics


The body requires a certain level of internal torque capacity in order to meet the demands of external torque being applied to the body via reactive forces during the “get up” skill.


Plank on hands position requires appropriate muscle timing, activity and balance throughout the kinetic chain. Proper muscle timing is needed to sequence the movement appropriately. Suitable muscle activity leads to the recruitment of necessary muscles that provide stability and joint centration. Good muscle balance leads to optimal length tension relationship of muscle pull on either side of the joint. Excessive activity or muscle pull on one side of the joint can create joint micro-instability leading to movement inefficiency and potential injury. Because the scapula is so linked to kinetic chain involvement of the surfing technique, contributions from the scapular stabilizers and intraabdominal pressure (IAP) create joint moments that aid in spinal uprighting.

We know that through the fascial network system the external obliques are directly connected to the serratus anterior which serve as scapular stabilizing muscles. If the stability of the abdominal wall is compromised, the force cannot be transmitted efficiently through the kinetic chain. Scapular muscle function would therefore decline if they cannot pull from a sturdy proximal attachment. Our athlete appears to demonstrate this task satisfactorily establishing sufficient scapular control in the plank on hands. However, evidence of forward head posture and rib cage elevation may suggest inhibition or weakness of the deep neck flexors, serratus posterior superior and abdominal wall.



The abdominal wall is responsible for providing stability under the current demands of plank on hands position. We should expect to see the abdominal wall control excessive lumbar hyperextension, unload the facet joints, prevent overuse of the lumbar paraspinal muscles, and provide a stable base for the hip flexors and other muscles to act from. We identify our athlete assuming a slight open scissor position. One likely contributing factor for this is the inability of the deep stabilizing systems ability to provide a stable base. Therefore, energy leakage is present as the hip flexors win the tug of war match as they work eccentrically against an unstable proximal base.

In bottom lunge the legs are landing underneath the body to catch and receive the weight of the trunk and torso above it. Just before the amoritization phase (transition from eccentric to concentric muscle activation). The lumbar paraspinals should work in a coordinated manner with the abdominal wall to overcome a trunk flexion moment and to maintain spinal uprighting through hydraulic amplification.

As we take a look from the posterior view, we observe kinetic forces acting on the muscles that control and stabilize the lumbopelvic hip complex in the frontal plane. The gluteus medius acts eccentrically to overcome contralateral pelvic drop. The abdominal wall including the lumbar paraspinals on the left side is shortening while on the opposite right side are lengthening. One might consider the left side as working concentrically, however, in our athlete's case, we find his lack of hip flexion mobility in the sagittal plane that is likely contributing to the frontal plane deviation. The right side abdominal wall is working eccentrically to try to stabilize the pelvis and prevent a drop on that side.



Combined Kinematics and Kinetics


When joint accessory mobility, muscle relative flexibility, and neuromuscular activation are sufficient proper joint centration may be achieved. This prevents susceptibility to movement in specific directions enhancing the point of immediate center of rotation (PICR), optimizing joint function. This reduces the amount of stress on the joint and the surrounding soft tissues. Hereby, we can see the continuum of mobility and stability. Achieving optimal mobility and muscle length give the neuromuscular system a greater advantage to calibrate appropriate timing and activation, in turn enhancing stability of the joint. This is the fascinating part of the human movement system as we watch kinetic and kinematic factors at play to achieve the desired skill at hand.


Athlete Feedback


Plank on hands position needs to achieve greater global extension to improve fascial loading and stretch-shortening cycle “snap” for better leg sweep momentum. In order for this to occur athlete focus should be directed at improving thoracic extension mobility, hip flexor length and IAP retraining. Our athlete could also benefit from a greater amount of hip flexion and IAP retraining during the bottom lunge position.


6/3/21

Jonathan Dickey


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