Biomechanics of running by Dr. Sachi mevada ( Masters in Physiotherapy of Cardiopulmonary Disorders )

Biomechanics of running , kinetics and kinematics.

1. biomechanics
of
running
BY DR.SACHI MEVADA

2. CONTENTS
Introduction
Explanation
Joint motion
Muscle activity
Kinematics
Rotation through kinetic chain

3. INTRODUCTION
Running is similar to walking in terms of locomotor activity. However,
there are key differences. Having the ability to walk does not mean
that the individual has the ability to run.
Running requires:
Greater balance
Greater muscle strength
Greater joint range of movement

4. RUNNING CYCLE

5. INTRODUCTION
There is a need for greater balance because the double
support period is not present when running.
There is the addition of a double float phase, at the
beginning and end of the swing phase during the
running gait cycle, in which both feet are off the ground.
The amount of time that the runner spends in float,
increases as the runner increases in speed.

6. INTRODUCTION

The muscles must produce greater energy to elevate the
head, arms and trunk (HAT) higher than in normal
walking, and to support the HAT during the gait cycle.
The muscles and joints, must also be able to absorb
increased amounts of energy to control the weight of
the HAT.
As seen, there is an absorption phase and a generation
phase in the stance phase of running. After absorption,
the velocity of the center of mass decelerates
horizontally.

7. INTRODUCTION
After stance phase reversal, the center of mass is
translated upward and forward during stance phase
generation. At swing phase reversal, the next period of
absorption begins.
During the running gait cycle, the ground reaction force
(GRF) at the centre of pressure (CoP) have been shown
to increase to 250% of the body weight.

8. RUNNING CYCLE

9. EXPLANATION
The gait cycle begins when one foot comes in contact with the ground
ends when the same foot contacts the ground again
that refers as initial contact.
Stance ends when the foot is no longer in contact with the ground
Toe off marks the beginning of the swing phase of the gait cycle
The timing of toe off depends on speed

10. EXPLANATION
Double support – when both feet are touching the ground – with
walking, there are two phases of double support, one at the
beginning of the stance phase, and one at the end of the stance
phase
With running, toe off occurs before 50% of the gait cycle (40%),
and double support does not occur - instead double float
occurs, once at the beginning of swing and at the end of swing
As speed increases, time spent in swing increases, stance time
decreases, double float increases, and cycle time shortens

11. DOUBLE SUPPORT
VS
DOUBLE FLOAT

12. EXPLANATION
Ground Reaction Force (GRF) is created between the foot and
the ground, in which the foot and ground exert an equal and
opposite force on each other. The direction and magnitude of
the ground reaction force is determined by the position and
acceleration of the runner’s center of mass.
After maximum velocity is reached, the center of mass moves
backward. Someone who tries to accelerate with their body
upright would fall backward due to the direction of the GRF. A
forward trunk lean and pelvic tilt keep the GRF in a position to
allow forward acceleration.

13. JOINT MOTION
Beginning of stance phase - hip is in about 50°
flexion at heel strike, continuing to extend during
the rest of the stance phase. It reaches 10° of
hyperextension after toe off.
The hip flexes to 55° flexion in the late swing phase.
Before the end of the swing phase, the hip extends
to 50° to prepare for the heel strike.
The knee flexes to about 40° as the heel strikes,
then flexes to 60° during the loading response

14. JOINT MOTION
The knee begins to extend after this, and reaches
40° flexion just before toe-off.
During swing phase and the initial part of the float
period, the knee flexes to reach maximum flexion of
125° during mid swing.
The knee then prepares for heel strike by extending
to 40°
The ankle is in about 10° of dorsiflexion when the
heel strikes, and then dorsiflexes rapidly to 25° of
dorsiflexion.

15. JOINT MOTION
Plantarflexion happens almost immediately, continuing
throughout the rest of the stance phase of running, and as it
enters swing phase also.
Plantarflexion reaches a maximum of 25° in the first few
seconds of swing phase.
The ankle then dorsiflexes throughout the swing phase to
10° in the late stage of swing phase, preparing for heel
strike.
The lower limb medially rotates during the swing phase,
continuing to medially rotate at heel strike.
The foot pronates at heel strike.
Lateral rotation of the lower limb stance leg begins as the
swing leg passes by the stance leg in mid stance position.

16. MUSCLE ACTIVITY
Muscles are most active jus before and just after heel strike.
This is a crucial time for muscle contraction, as opposed to
when the foot is preparing to leave the ground at toe off.
There is a lag of about 50ms between the onset of EMG
activity and the facilitation of muscle contraction. In
addition, there are also instances where EMG activity is has
stopped, while muscles may still be activating.

17. MUSCLE ACTIVITY
Gluteus maximus and gluteus medius are both active at the
beginning of the stance phase, and also at the end of the
swing phase.
Tensor Fascia Latae (TFL) is active from the beginning of
stance, and also the end of swing phase. It is also active
between early and mid swing.
Adductor Magnus is active for about 25% of cycle, from late
stance to the early part of swing phase.

18. MUSCLE ACTIVITY
Iliopsoas activity occurs during the swing phase, for 35-60%
of the cycle.
Quadriceps work in an eccentric manner for the initial 10%
of the stance phase. Their role is to control knee flexion as
the knee goes through rapid flexion. Its activity stops after
the first part of the stance phase, and it remains inactive
until the last 20% of the swing phase. At this point, the
quadriceps change to a concentric action, for the knee to
extend in preparation for heel strike.

19. MUSCLE ACTIVITY
Medial Hamstrings become active at the beginning of the
stance phase (18-28% of stance). They are also active
throughout much of the swing phase (40-58% of initial
swing, then the last 20% of swing). They act to extend the
hip and control the knee through a concentric contraction.
In late swing, the hamstrings act eccentrically to control
knee extension and take the hip into extension again.

20. MUSCLE ACTIVITY
Gastrocnemius muscle activity starts just after loading at
heel strike, remaining active until 15% of the gait cycle (this
is where its activity begins in walking). It then re-starts its
activity in the last 15% of the swing phase in preparation for
heel strike.

21. MUSCLE ACTIVITY
Tibialis Anterior (TA) muscle is active through both stance
and swing phases in running. It is active for about 73% of
the cycle (compared to 54% when walking). The swing phase
when running is 62% of the total gait cycle, compared to
40% when walking, so TA is considerably more active when
running. Its activity is mainly concentric or isometric,
enabling the foot to clear the support surface during the
swing phase of the running gait.

22. KINEMATICS
Sagittal Plane Kinematics - when comparing walking,
running, and sprinting, there is a shift into flexion, as motion
progresses, as well as lowering of the center of mass.
Although a greater amount of pelvic tilt may be expected
with increasing speed, pelvis tilt remains relatively
consistent between the different gait speeds. This occurs to
maintain energy and the efficiency with running or sprinting.
Despite the minimal changes, as speed increases, there is a
forward tilt in the pelvis and trunk, the center of mass is
lowered, and the horizontal force produced in the propulsion
phase is the greatest.

23. ROTATION THROUGH THE KINETIC
CHAIN
The kinetic chain can be described as a series of joint movements,
that make up a larger movement. Running mainly uses sagittal
movements as the arms and legs move forwards. However, there is
also a rotational component as the joints of the leg lock to support
the body weight on each side.
There is also an element of counter pelvic rotation as the chest
moves forward on the opposite side. This rotation is produced at
the spine, which is often referred to as the spinal engine. This is also
linked to running economy . This counter rotation enables the spinal
forces to be dissipated as the foot hits the ground.

24. ROTATION THROUGH THE KINETIC
CHAIN
Runners may complain of a feeling of restriction in hamstrings or
shoulders, however, when examined it may be found that there
is actually limitation in rotation of the pelvis, causing the
problem.

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