Biomechanics Of Running: All You Need To Know

By December 18, 2020December 22nd, 2020No Comments
Biomechanics of running

Running has become very popular in the last 30-40 years. Thousands of people around the world run on a regular basis, for recreation, pleasure, or competition. Research and surveys show that nearly 75%-80% of the runners suffer from recurring injuries. Though the top most reason for injuries is overtraining, many of these could be avoided through proper running biomechanics. Years of research and studies have gone into figuring out what is the correct running form and it’s still a work in progress.

Numerous innovations have been done around foot placements, foot strikes, running gear (shoes), arm movements etc. Host of opinions, recommendations and facts exist but everything comes back to the same point – “If it feels normal and natural to you and doesn’t hurt, stick to it”. Recreational runners want to run faster and longer without getting injured. But to do so, should we alter anything in our running form? To answer this, understanding and following the science behind running is a good way to start.

What is Running Biomechanics?

Biomechanics of running is basically the study of how our body moves (running kinematics) and the relationship between those movements and the forces that causes them (running kinetics).

Why do we need to understand the biomechanics of running?

If we want a deeper understanding of our running form, or what is causing the running-related injuries (if any) , or if we want to make any improvements in our running economy, runners should have a basic understanding of the biomechanics of running. Once you have this understanding, you will be able to make more sense and appreciate what you read further about running styles, footwear (shod running vs barefoot or minimalist running), running-training programs, running injuries and what causes them, effect of strength and conditioning on the running economy.

Every runner has his/her own unique running style which is predetermined by the individual running biomechanics. Once we understand what a good running form is, the energy saved by doing minor tweaks in our running form can make a big difference. The energy saved by running efficiently can be used for running fast and running long with more ease and less tension.

What is a Gait Cycle and its phases?

Knowing the phases of running with gait analysis aka kinematics and kinetic analysis helps to improve our running. Let us start by understanding the most used term: Stride or a Gait cycle. It is defined as a period when one foot meets the ground to when the same foot gets in touch with the ground again.Biomechanics Of Running: All You Need To KnowEach stride is broken into two phases: The Stance Phase and the Swing Phase.

The Stance Phase

The phase when the entire time one foot is in touch with the ground and the other leg is swinging forward. The periods in the Stance phase are as following:

Loading response begins with initial contact. Imagine your left leg is out in front of you and about to touch the ground. The instant the left foot touches the ground, the stance phase begins with the period known as loading response. Your right foot behind you is in the swing phase during this period.

Midstance or single support phase begins when one leg is directly under the hips taking the maximum load and the body passes over it. The ankle and knee are bent to the maximum. This is the single-limb support phase.

Terminal stance begins when the center of gravity is over the supporting foot (left) and ends when the right foot contacts the ground. Pre-swing begins at the right foot’s initial contact and ends at toe-off which corresponds to the gait cycle’s period of double limb support.

The Swing Phase

The phase when the entire time both feet are off the ground.

The periods in Swing phase are as following:

Initial swing begins at toe-off and continues until maximum knee bend (up to 60 degrees) occurs. The left leg is far behind and the heel starts to lift off.

Mid swing is the period from maximum knee bend until the shin is vertical or perpendicular to the ground.

Terminal swing begins where the shin is vertical and ends at initial contact of right foot. Once one knee crosses from under the hips, the lower leg unfolds. It prepares once again for initial contact marking the end of swing phase.

The following image sums up the biomechanics of running well.

Biomechanics Of Running: All You Need To Know

Forces acting on the body during run

Of both the phases and periods of Gait cycle, the one where the feet are in touch with the ground needs to be focused more. Only one leg bears the body weight, and the impact of the ground reaction forces can lead to injuries and impact running performance, if not done properly. The muscles and tendons store the elastic energy during stance phase which recoils in the swing phase to re-accelerate the body.

Research shows that at least 50% of the elastic energy comes from the Achilles tendons in the foot. This cyclic behaviour permits efficient force production and is critical for avoiding mechanically costly high-energy collisions during foot–ground contact.

The following forces act on the body while running:

Impact force: The impact of the body with the ground.

Drag force, or air resistance: A resistive force against the airflow.

Gravitational pull: When running upright, gravity pulls straight down on the body. When leaning forward, the centre of mass of the runner moves in front of the point of contact. This causes more of the horizontal-forward gravitational pull down and less of the vertical pull on the runner.

Frictional force: The force that opposes motion and allows the runner’s foot or shoe to grip the ground for balance.

Normal force: When a runner’s foot meets the ground, the ground exerts a force upward preventing the runner to fall through. It points up toward a body from the other object or the body it is in contact with.

Biomechanics Of Running: All You Need To KnowMuscles active during running

The biomechanics of running also shows that hip, knee, and ankle joints provides the propulsion to move forward. The lower limb muscles that are activated in each phase are:

Phase of the strideMuscles activated
Early Stance Phase Gluteus (maximus/Medius), Tensor fascia Latae (also known as IT Band), Quadriceps, Hamstring, Gastrocnemius (part of calf muscle), Tibialis Anterior (shin muscle), Erector Spinae (trunk muscles)
Late Stance/ Early SwingIT Band, Adductor Magnus and Gracilis at Inner thighs, Iliopsoas at front Hip, Rectus femoris (Quadriceps muscle), Trunk Muscles
Swing Phase EndGlutes, IT Band, Quadriceps, Hamstrings, Gastrocnemius, Tibialis Anterior

Upper body and arm mechanics

The upper body and the arms action balance the lower limb movements to promote an efficient movement. The upper body works in opposition to the lower limbs.

In the initial contact to midstance, when the body is preparing for braking/de-acceleration, the arms and upper body produce propulsive forces for the body to move forward along with the store elastic energy in the lower limbs’ muscles and tendons.

During midstance to toe-off, the arms and upper body produce a braking force. When the right knee fires through in front of the body, a counterclockwise momentum is created. The left arm and shoulder move forwards to create a clockwise momentum to reduce rotational forces and control the momentum.

Driving the knee through in the swing phase and the forward movement of the arm need to be passive movement. It leads to unnecessary waste of energy which leads to poor running economy if we try to control that.

Propelling your arms up and forward wastes energy and reduces the efficiency of movement. Consciously bringing the arms too far back (or forward) can cause over striding which may lead to excessive braking and injury.

Biomechanics of running downhill

Braking is the highest ground force which occurs when your foot touches the ground ahead of your centre of gravity. Braking forces are maximum in case of downhill running. We land ahead of ourselves (over-stride) and the higher impact forces occur because we try to apply brake.

READ ALSO:  Revisiting History Through 21K Run In Delhi

Tip: Shorten your stride, land under your centre of gravity. This will make running downhill easy and injury-free.

Foot strikes, Pronation and Foot Arch

How a runner land on the foot each time the runner takes a step is called the foot strike. Pronation is a natural movement of the human body which is characterised by the way a person’s foot roll inwards for the impact distribution upon landing phase of running. There is a ligament that runs down to the bottom of the foot between the ball of the foot and the heel which is known as Plantar fascia ligament. Position of that ligament determines the foot type or foot arch.

Pronation can be classified as:

Supination: Supinators land on the outside of the heel with very little or no inwards rolling of foot which puts pressure on the smaller toes on the outside of the feet. They have high foot arch. They are more prone to Plantar fasciitis, shin splints or ankle strains.

Neutral: The foot lands on the outside of the heel but then rolls inwards to absorb the shock and support the body weight which leads to even distribution of weight on the feet. They have normal foot arch. They are not immune but less likely to get injured.

Overpronation: Overpronators lands on the outside of the heel but the foot rolls inwards excessively putting lots of weight on the inner edge of the foot. They have low arches or flat feet. They are more prone to shin splints, plantar fasciitis, bunions, and heel spurs.

Foot strike can be classified as:

Forefoot: In this foot strike, the weight of impact is on your toes and ball of the foot. The heels rarely hit the ground between steps.

Midfoot: In this foot strike, the centre of your foot lands on the pavement to evenly distribute the shock of impact.

Rearfoot: In the rearfoot or heel strike, runners hit the pavement with the back of your foot. It is the most common foot strike among recreational runners.

What is a good running form?

Most runners have no reason to modify the way they run naturally unless something starts hurting. So always keep a note of how you feel during and after the run. Even if it hurts, we do not force ourselves to run differently.

More than often, fixing specific weak (e.g. core strength) or tight muscles ( e.g., shoulders and hip flexors), learning to activate a few muscle groups or evening out muscular imbalances, working on stability and mobility (lower trunk, pelvis, and hips) work for almost all of us.

Flexibility, muscular strength, and muscle memory are key to good running form.

Any change or modification, if needed, should be gradual, otherwise it puts us into the greater risk of injury. Having said this, it is important for all of us to understand what a good running form is. This tailored attention can help us what is and isn’t working for us during the run.

Body Position: Maintain tall upright posture, keeping the head and face relaxed. The alignment of your trunk (balance between far to upright and far too front) is important because that affects your centre of mass.

Running is a motion in straight line, so the body shouldn’t be rotating excessively from side to side. Excessive rotation offsets the end goal of making forward movement. In fact, it costs runner the energy to control and stabilise the movement.

Feet: As soon as the knee comes through and the foot is ready for initial contact, put the foot down underneath you close to centre of the body. When overstriding, the first rule of thumb is to look for the alignment of knee and ankle upon initial contact. The knee should be slightly flexed directly above the ankle when you make the contact. The ankle is ahead of the knee if there is an overstride. The impact of the ground impact forces, and the braking forces is determined by the foot strike in relation to the rest of your body. One foot strike cannot be deemed better than the other if you are not maintaining the right body position.

Cadence: Make a note of your cadence (which is stride frequency or number of steps per minute). The overstride can be reduced if the runner increases his/her cadence. Your best cadence is going to be different from someone, depending upon how tall or short that runner is. The ideal cadence is specific to everyone.

Pelvis: Maintain horizontal movement by minimising any vertical oscillation at hips and by controlling rotation. This leads to optimum force in the forward direction improving the running economy.

Upper body:

  • Pull your shoulder blades together without arching your back.
  • Avoid side to side rotation at the shoulder. Arms control rhythm and provide balance and power as we run. So let arms swing spontaneously and keep them relaxed. Keep the elbows bent and tucked in.
  • Do not dangle them by your sides by pulling them backwards parallel to the body.
  • Don’t clench your fists.
  • Extend the hip and control rhythm and speed through arm stroke and hip extension.
  • Proper arm swing creates the impulse for the legs to move ahead more smoothly and rhythmically.

Why do we need to have a good running form?

During a run

As soon as the left foot touches the ground, body tries to de-accelerate and apply brake to control the landing. The maximum impact peak can be 2 ½-3 times his or her body weight.

If the runner spends less time in stance, cycle time is short. If they are logging mileage, then the total number of steps become very high.

If the runner is placing foot closer to the midline of the body, then the base of support becomes narrow and the lower leg angle changes. This may require additional pronation of the foot.

Body fatigue also sets in during the long run which causes the muscle function to change.

With the cumulation of all the above-mentioned forces, even a slight biomechanical abnormality can create problems. For a long-distance runner, it becomes especially more important to pay heed to the running form and make gradual necessary corrections.

Common strategies to correct biomechanical error

While these following strategies are general, these small changes can help in improving running performance or reduce the chances of running injuries:

1. Pay attention to running shoes.

2. Land gently with your foot under your hips.

3. Strengthen and learn to activate the support muscles (which includes arches and calves also). Research indicates that even three weeks of hip adductor strength training has a significant effect on reducing the chances of knee and hip joint related running injuries like Patellofemoral pain syndrome.

4. Focus on running cadence and foot strike as they affect the running economy. Keep a balance in the stride length. As already mentioned, too high has an associated energy cost and leads to swinging limbs. Too low also has an associated energy cost. Cadence influence the biomechanics and has the inverse relationship with the stride length.

5. Prepare a video of you running on a treadmill and analyse that or run in front of a mirror. The common misalignments are easily identifiable.

The video gait analysis and strength and conditioning exercises improve landing mechanics. An experienced coach familiar with biomechanical principles or a skilled running coach can visually analyse and help you understand your running form.

At the end of the day, every runner is unique and there is not one perfect running form that you should be chasing. It is individualized based on your body. The best thing you can go by is comfort, run freely and enjoy it. If at any point in time, you really want to improve your running performance or reduce the recurring injuries, always remember that running form is just one piece of a bigger puzzle. You need to make sure that you consider the role of other factors in the running performance too.

Jyoti Khera

Jyoti Khera

The writer is a fitness coach from Hyd who has been running for over 15 years now. She is Sports Injury rehab specialist and a Sports nutrition advisor. Instagram @iamjyotikhera

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