Speed 101: Ground Contact Time
Ground Contact Time (GCT) is defined as the period of time between the moment an athlete's foot touches the ground to the moment the athlete's foot leaves the ground. GCT plays a critical role in the majority of athletic movements on a field or court, including but not limited to: acceleration, deceleration, maximum velocity, change of direction, and really any other explosive reactive movements.
Naturally, the shorter the ground contact time, the faster the coordination and implementation of the next movement can occur. Understanding the basics of GCT, and implementing drills and techniques to diminish GCT, is foundational to the development of speed, agility, and reactive explosiveness (we will go into this more on our next post about Ground Reaction Force!).
Keys to Optimizing Ground Contact Time
Core Integrity and Dynamic Mobility:
Core engagement is like the ignition switch to athleticism. We often hear our athletes and clients request “core” exercises. When asked to elaborate or define core, they simply state “abs”. Though “core” certainly includes the abdominal muscles, “core” is ultimately so much more. At Altius, we believe core should be understood as any musculoskeletal element within or directly attached to the trunk, as these muscles tie together the majority of any upper and lower extremity movements. Optimally, these muscles work together to stabilize and drive every athletic motion. Our trainers will often refer to a strong core as the 360 degree “pillar” or “seatbelt” for strength and athleticism. The ability to engage and dynamically integrate core over a full range of motion sets up an efficient kinetic chain that not only increases power production, but also greatly decreases the risk for potential injury. The areas of core that we see needing the most work are deep and rotational abdominal muscles, hip flexors and extensors and scapular stabilizers.
Dorsiflexion and Ball-of-Foot Ground Contact:
Dorsiflexion of the ankle joint enhances foot and ankle positioning to maximize ball-of-foot ground strike. Thus optimizes the stretch-reflex characteristics of the foot and the the Achilles’ tendon. Tendons are highly elastic. When anything elastic is put on stretch, it holds high amounts of potential energy (picture a rubber band!). Utilizing stretch-reflex in any movement yields increased output and movement efficiency.
The surface area of ground contact also plays a significant role in GCT. The smaller the surface area of the foot touching the ground, the better the potential for quicker GCT. Vice versa, the greater the surface area of the foot on the ground, the longer the GCT. In the majority of athletic movements, the ball of the foot is ideally the only part of the foot that is weight-bearing and in contact with the ground.
Consider a distance runner vs a sprinter. Which has faster GCT? (This is a rhetorical question as the answer should be pretty obvious). Simply look at the design of the shoes. Distance “running shoes” are often heavily cushioned, especially in the heel and are designed for the sequence of 1) initial heel strike to, 2) mid-foot, and finally, 3) toe-off. The entire surface area of the shoe is designed to touch the ground. This is not a very efficient sequence for true speed, nor is it great for biomechanics and longterm joint health (another conversation for a later time). Now consider the shoe of a sprinter. There is very little if any padding, especially not in the heel. Sprint shoes are designed for ball-of-foot contact to toe-off only. Ball of foot contact utilizes the stretch-reflex capacity of both the aforementioned Achille’s tendon and the foot intrinsics/arch.
When initially teaching GCT, we often use a sequence of drills including GCT sPops, skips and bounds. We always begin our athletes in their shoes, and then ask them to try again barefoot and find that our athletes best learn and feel the difference between quick vs prolonged GCT without shoes. Why? Because they are forced to land on the balls of their feet. Anywhere but ball-of-foot ground contact is uncomfortable without the crutch of highly-padded shoes. The majority of our athletes instantly look and feel more springy. Furthermore, the majority find that their movement feels easier. Success! Anytime our athletic movement feels easier, we are becoming more efficient in our movement.
To elaborate on efficiency within movement, we often refer to Newton’s Laws of physics.
For every action there is an equal and opposite reaction.
An object in motion stays in motion unless acted upon by another outside force.
Energy cannot be created or destroyed.
To summarize how these apply: Every movement carries kinetic energy and this energy can either be absorbed by or reflected into our next movement. Quick GCT is always reflected. Not only is our next movement sequence then faster, but it is easier as we are essentially recycling and reusing the energy from our previous movement. We will further elaborate on these physics in a future blog on Ground Reaction Force.