Running Gait

To fully understand how and why Core Running can help you become a better runner it's important to understand the biomechanics and muscle actions of the running gait. I'll give you a fairly technical yet simple description of running based on kinesiology studies.

Running is a cyclic motion in which the feet contact and leave the ground in sequence. The running gait cycle has two major phases, the support phase followed by the swing phase.

Each of these phases is broken down into three sub-phases. The cycle begins with ground contact of one foot and continues until the next contact of the same foot.

Phases & Sub-phases of the Running Gait

The support phase occurs when one foot is in contact with the ground. It is divided into foot contact, midsupport and toe-off.

1. Foot contact occurs from initial ground contact until full weight bearing by the foot. The initial ground contact sub-phase is also referred to as the absorption phase. If the landing is too hard excessive braking forces are generated. Proper foot landing minimizes the amount of braking forces and allows the body to efficiently absorb the impact forces of running.
2. Midsupport follows full weight bearing to the beginning of ankle plantar flexion (pointing the toes downward). This is also known as the propulsion phase. The foot, leg and hip recoil elastic energy stored in the muscles and tendons during the absorption phase to propel the body forward. It's important to use most of the recoil energy to push the body forward and not upward.
3. Toe-off starts with ankle plantar flexion and ends when the foot leaves the ground.

Healthy runners show little variation in the support phase with each footfall. Injured runners on the other hand can show a big difference in how they land with each footstrike.

The swing phase occurs when the foot is in the air and consists of the follow-through, forward swing and foot descent.

1. The follow-through occurs after toe-off until maximum hip extension, the point at which the leg is at its maximum extension.
2. Forward swing starts with initial flexing of the hip and ends with maximum hip flexion, where the knee is at its maximum bend and highest point in the air.
3. Foot descent takes place after maximum hip flexion until the foot contacts the ground again.

When running there is a period when one leg is in the support phase while the other is the swing phase. And there are two periods during the swing phase when both feet are off the ground, commonly called double-float.

As running speed increases, the time spent in the support phase decreases while time in the swing phase increases meaning the foot is in contact with the ground for less time.

Injuries occur only when there is ground contact. So if you reduce the ground contact time, you reduce the risk of injury. You can reduce the time your foot is on the ground by running faster as mentioned above or you can increase your cadence.

Differences Between Running & Walking

Double-float and ground impact forces are the main characteristics that differentiate running from walking. Impact forces are much higher during running (reaching up to four times bodyweight) and during walking one foot is always in contact with the ground while during running there is double-float when both feet are off the ground.

Muscle activation patterns are also very different when running. Many people make the faulty assumption that running is just a faster version of walking when in fact, running and walking are two very distinct movements.

Leg & Hip Muscle Activation During Running

The legs work together in an integrated manner during running with various combinations of muscles activated at different parts of the running cycle.

Electromyography (EMG) is a technique researchers use to determine the amount of activity in a muscle during movement. It involves placing electrodes on the muscles which measure the amount of electrical activity in that muscle. More electric activity means the muscle is working harder.

EMG studies on runners have show the co-contraction pattern and changing interaction between different muscle groups at various running speeds.

Researches found the least amount of muscle activity during toe-off and greatest amount of muscle activity during initial foot contact, mid-support, and foot descent.

The tibialis anterior muscle is active for the greatest total time with the hamstrings being the second most activated muscle.

As running speed increases more overall muscle activity occurs with the muscles around the hip joint showing the greatest increase in activity. However there is less activity during the support phase at faster speeds.

Studies have also shown that highly skilled runners exhibit lower muscular activity than poorly skilled runners. This means they are more efficient in using the energy they produce.

Muscles in the calf control pronation and ankle dorsiflexion (lifting toes upward) to provide a stable foot during the early support phase. As a runner lands the gastrocnemieus, soleus, (the two main muscles comprising the calf muscle) and tibialis posterior help to stabilize the foot and ankle.

During the late support phase however, there is little activation in the calf muscles which means that runners do not "push off" from the foot. Rather the large Achilles tendon acts as a spring to return elastic energy to the ground as the foot leaves the ground.

The plantar fascia under the foot also helps with the spring like loading and unloading to propel you forward. Together, the tendons of the foot and the Achilles tendon provide at least half of the elastic energy used to propel the body forward.

Upper Body, Pelvic & Trunk Muscle Activation During Running

There is a slight forward lean of the trunk during the stance phase which helps keep the forward momentum going. The pelvis also tilts slightly downward to help with the absorption of impact forces. The muscles of the trunk (abs and back) work with the glutes and hamstrings to control the trunk and pelvis during the absorption phase.

The leaning of the trunk along with the tilting of the pelvis down toward the front of the body direct energy forward. If this doesn't happen and the trunk is too upright, too much energy is directed upward making for an inefficient running style.

If the muscles of the truck and pelvis are weak or tight, excessive stress is placed onto the legs, spine and/or pelvis, increasing the risk of injury.

You should also have lateral stability in the pelvis as you run. Too much up and down movement between the two sides or even worse, a difference between the movement of each side of the pelvis increases your risk of injury.

The arms and shoulders move in sync with the legs though on opposite sides of the body i.e. left arm swings forward as the right leg is moving forward and vice versa.

This counter movement of the opposing arm and leg creates balance. During the stance phase of the leg, the forward swing of the opposite arm produces forward momentum. Likewise, during the forward swing phase of the leg the backward swing of the opposing arm creates stabilizing forces in the body to control movement.

As the legs and arms move in opposition, the abdominal and back muscles of the trunk need to stabilize the rotational forces that are generated by this movement. They help direct this energy into forward motion. If you over-rotate through the trunk too much energy is wasted so you fatigue quicker and/or you run slower.

Summary

While many runners don't give much thought to such a technical explanation of running, it is a good knowledge to have. You are then better able to understand the importance of proper muscle activation and having a training program that trains the muscles the way they need to function in running.

To summarize the detailed explanation above:

(a) The muscles of the core (hips, abs, and back) are crucial to providing a stable platform for the legs and arms to move from;
(b) the muscles in the upper leg and hips function as primary movers to move the legs forward;
(c) the muscles of the lower leg act more as stabilizers;
(d) the tendons in the legs, especially around the ankle and foot, act as springs to propel the body forward.

The coordination action of all these muscles and joints is important in developing a good running style.

Core Running technique practice and strength-training take into account the way muscles are used during running. Using the methods of the Core Running program you'll become a better, more efficient runner.