Tuning the Core

Runners from sprinters to marathoners all benefit from a strong core

BY DR. STUART MCGILL

Professor Emeritus, University of Waterloo, and Chief Scientific Officer, Backfitpro.com, author of four books on spine health and how to eliminate back pain, from Waterloo, ON.

BACKFITPRO

Core stability is a great influencer. It is the driving force for speed in the sprinter and efficiency in endurance runners. Here we explore three basic concepts of core stability for the athlete incorporating stability, mobility, elasticity, and pulsed muscle activation.

Generation And Transmission Of Power

The first concept of core stability involves assisting the transmission of power that is developed in the hips to drive the legs. Here, as the skeleton forms a linkage, proximal stiffness enhances distal athleticism, or specifically, core stiffness produces more speed on the leg side of the hip while unwanted spine bending is arrested in the proximal (pelvis and spine) side. Consider the right leg at foot strike. The hip and thigh muscles are activated to prevent their collapse, followed by the driving force required for the next stride cycle. Now consider the frontal plane where the right hip experiences the decelerating forces on foot strike, and the reaction forces of the unsupported left hip to drop towards the ground. Together with the stressful lateral bending of the spine, this is an inefficient use of energy. While this can be prevented to some degree by the right hip abductors, our work has shown that the left lateral core musculature is essential to hold up the left side of the pelvis to prevent the left hip drop. A similar situation occurs in the sagittal plane. Consider the gluteal musculature and associated fascia that cross the hip joint. The distal connection to the femur creates a very desirable leg extension. However, the proximal connections into the pelvis and associated fascia impose flexion stressors on the spine and a posterior pelvic tilt on the pelvis. Controlling these with a stable core will enhance the sprinter’s speed and the propulsive force in the endurance runner.

Storage And Recovery Of Elastic Energy

The second concept of core stability involves the storage and recovery of elastic energy with each running cycle. The skeletal linkage when bound together with muscles, tendons, and fascia forms a complex elastic system. Two more essential properties of linkage mechanics are introduced:

1. The body uses joint stiffness to control motion;

2. When a muscle contracts it creates both force and stiffness.

Stiffness and elasticity must work together to control the optimal storage and recovery of elastic energy, together with relaxation to facilitate the speed of muscle length changes. Recovery of elastic contributions requires skillful muscle pulses. Tuning the “effective mass” of the core/torso with core stability is the difference between pushing rope and pushing stone. Activating core/torso muscles together creates muscle and fascia slings linking arm motion to leg propulsion. Furthermore, the elastic components of the fascia muscle complex are tuned with posture, for example running “tall” is a trait of success (Benzie: The Lost Art of Running, 2020). The skilled athlete “tunes” both the activation and the elastic contributions.

Breathing Mechanics

The third element of core stability involves breathing and ventilatory mechanics. Some 100-metre sprinters hardly take a breath, or if they do it is a “sip” of air usually at 60 - 70 metres. They have found that allowing loss of air pressure compromises the tuned stiffness through the core, resulting in unwanted eccentric contractions that absorb some of the stored elastic energy, leading to a loss of top-end speed. The endurance athlete, however, coordinates breathing by tuning the core musculature to enhance hydrostatic pressure, movement of visceral contents, and enhanced efficiency of the diaphragm.

HOW SHOULD THE RUNNER EMPLOY THE CONCEPT OF CORE STABILITY AND FASCIAL ELASTICITY?

Over the past 35 years we have measured spine stability, resilience and performance in a wide variety of athletes. Three exercises, which became known as the McGill big three, kept surfacing as a superior way to tune appropriate stiffness and resilience: the bird dog exercise for the back, the side plank for the lateral core, and a modified curl up for the anterior core. Some of the fastest and most successful running athletes use these as foundational exercises to:

• Arrest proximal movements in the running cycle.

• Potentiate the storage in recovery of elastic energy.

• Enhance breathing efficiency.

• Build a higher training capacity for the track and strength and conditioning work.

Progressions of the big three include specific drills to enhance running athleticism. These concepts are detailed in my book, Ultimate Back Fitness and Performance, (2017) that summarizes athletic progressions. For those runners with back pain, they should start by following the self-assessment and pain reduction program first synthesized in my other book, Back Mechanic (2015).

In summary, tuned core stability is essential for the linkage to move. Core stiffness must be tuned “just right” to optimize storage and recovery of elastic energy. Better runners develop cleaner and more precise pulses of muscular force to allow faster muscle length change and speed. They “tune” the stiffened “effective mass” of the torso to assist propulsive elastic efficiency, and “tune” elastic fascial stiffness with tall running posture. Begin training with the big three and progress accordingly to enhance optimal elasticity, and muscular pulsing.