Tuesday, 21 August 2012

Running and Rotation

Running Form

A post that follows on from a previous post (“Running Posture and Injuries) looking at rotation in the thoracic spine

Thoracic rotation and the low arm drive

Have you seen the distance runner with the low arm action? The runner with a decreased flexion at the elbow hanging around the waist? Is this significant with regards to efficiency? Does it impact on injury? Let’s take a look at the possible effects in the thoracic spine.

Our arms are used as a means of propelling the lower body throughout the gait cycle. The arms play an important role in balance and stability, particularly in the thoracic spine and its subsequent actions in the lumbo-pelvic region. The control of, and action can play a vital role in maintaining lower impact forces.

With a low arm drive the lever is lengthened, creating a need for larger forces to be generated. With this occurring there is an increased distance for the arm (in this case the hand being the distal part) to travel from in front of the body to terminal arm swing (behind the body).  This increased distance takes longer and requires more effort. Often that effort involves the larger muscles of the torso (trunk rotators) as a means of ‘driving’ the arms.

Fig 1. Low arm drive increase rotational forces through thoracic spine. This encourages greater force activation from the larger torso muscles.

This position not only takes longer, it also encourages a kyphotic position of the thoracic spine and increases the rotation demand through the lower thoracic and upper lumbar region. The upper thoracic spine (T1-T6) is better designed to take rotational forces and does so in a more upright (extended) position. In an extended position the facet joints create a better joint axis for rotation to occur.

With rotation coming from lower down the spine it also encourages an increased shoulder rotation travelling in an inferio-lateral direction; that is, as the left leg reaches mid to late swing, the right shoulder drives towards the left and inferiorly. This increased load on the left leg (in this case) results from the rotational drive ‘into the ground’. The opposite side must then return from this position, once again increasing the load on the thoracolumbar spine.

Fig 2. Rotation through the right shoulder will increase loading on left foot strike

Not only does this increase lower limb loading, it also increases energy expenditure for a given speed. With this occurring it would appear to increase ground contact time – the slowest portion of the gait cycle! If you want to be quicker – spend less time on the ground! Further load is appreciated when you consider the calves have to contract concentrically and eccentrically over a longer period of time in preparation for toe off.

Low arm swing may also throw energy in a lateral direction. This creates movements travelling in all sorts of directions, often ‘fighting’ against each other!

If you want to change lower limb loading, starting with a change in the upper limbs. This can be achieved in a two-step process;

1.    Increase the elbow flexion to between 90-110- deg
2.    Extend the upper thoracic spine to allow rotation to occur in the upper thoracic spine

This often aids in a quicker arm swing over a shorter distance and decreases rotation from the thoracolumbar spine.

Rotation in the extended position acts more like a ‘spring’ increasing the efficiency of the posterior chain (thoracolumbar, lats and glutes on the opposite side). Efficiently utilising this system also increases force closure of the SIJ – another stabilisation mechanism during running. 

This is not a ‘one size fits all’ approach, but a position from which to start with rotational forces that are a strong contributing factor to loading and/or injury.

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