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The Art of Running:
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The
image of a distance runner running along may cause one to conjure thoughts of
efficiency, and virtual ease of movement. The fact is that there are many
distance runners who make running appear very easy for them. There are other
runners who look as if they have to work quite a bit harder to maintain pace. In
this case looks are not deceiving, through qualitative analysis an individual
can determine the inefficiencies in a runner's technique. These inefficiencies
could prove to be costly, and limit the performance of the athlete. Unlike other
sports distance runners rarely analyze and try to improve their mechanics. It is
perceivable that a 1 % decrease in the energy cost of running could improve a
marathoners time by nearly two minutes (Costill, 1986). These energy costs due
to biomechanical inefficiencies may cause an individual to work at a higher
level of their maximal oxygen uptake capacity. This study will look at the basic
biomechanics of running with relation to running economy and
VO2 max.
Running is a structured movement pattern or a motor skill. A motor skill
can be defined as a group of simple, natural movements combined toward achieving
a goal (Henatsch & Langer, 1985). Training and technique are very important
in developing or improving a sport skill. Generally as the adaptation to
training takes place, the efficiency of the skill improves. This can be seen in
an improved running style. There are four characteristics that can be observed
as a skilled performer optimizes energy expenditure to achieve a high level of
performance (Martin & Coe, 1991). First there is improved balance and
coordination, therefore reducing postural work. Then unnecessary and exuberant
movements are eliminated. Thirdly necessary movements are refined to ensure that
these occur in proper direction, with optimum quickness to minimize the loss of
kinetic energy. Next the most important muscles for movement, prime movers, are
used effectively. This includes the coordination of agonists, antagonist, and
synergist. This will result in minimum energy used to initiate the movement, and
minimal opposing resistance. These factors can be observed as a novice runner
becomes more efficient through adaptation in the training process. There are
several biomechanical principles that can be related to running (Martin &
Coe, 1991).
The first principle is that force must be applied to change the velocity
of an object in motion. An example of this concept would be a runner who looses
velocity during the airborne phase of each stride, and to maintain continual
motion, force must be applied by the support leg at takeoff. The next principle
is that linear and angular motion need integration to permit optimum performance
of movement patterns. This can be seen with the flexion and extension of the
lower limbs, and how these movements work with the rotation, abduction,
adduction of the hips and spine. All these movements about various planes must
be complementary. The third principle is the longer the length of a lever, the
greater the potential linear velocity at its end. This principle is reversed in
running, where the limbs are shortened to bring them forward with less energy
requirement. The fourth principle is for every action there is a reaction equal
in amount but opposite in direction. This can be observed with every
foot-strike, the landing surface pushes back with a force equal to the impact
force, driving the runner upward and forward in a direction opposite to that of
impact. The running and walking gait cycles are similar to each other.
Running and walking are both fundamental skills, but differ from many
other skills because they are continuous. One foot moves in front of the other,
with the arms moving in the opposite direction synchronously. The trunk should
have minimal forward lean to reduce the stress placed on the postural muscles.
The trunk and head make up 60% of body weight, and should be kept directly over
the point of ground support. The feature that most distinguishes running from
walking is that in running there is a period where the runner is airborne.
There are various phases during the running cycle that can be broken into
two phases: support and forward recovery (Slocum & James, 1968). During
running the support phase can be reduced to as little as 30% of the total cycle
time. On the average the support phase occupies 40% of the running cycle, and
the free-floating forward recovery phase occupies about 60%. The support phase
consists of the periods: foot-strike, mid-support, and takeoff. During forward
recovery there are three periods: follow-through, forward swing, and foot
descent. The follow-through, and foot descent are known as the float period.
The foot-strike is the start of the running cycle. As the foot touches
the ground it will be slightly ahead of the center of mass. This will minimize
the braking effect, and help to carry linear momentum forward. When the foot
contact occurs, several actions take place: the knee flexes, the tibia
internally rotates, the ankle plantar flexes, and the subtalar joint pronates (Miliron
& Cavanagh, 1990). The pronation helps to absorb some of the compressive
shock forces, torque conversion, adjustment to uneven ground contours, and
maintenance of balance. It is necessary to have a certain amount of pronation to
disseminate the energy of the foot-strike. If there is too little or too much
pronation injuries may occur (Edington, Frederick & Cavanagh, 1990). There
are corrective footwear, and orthotics available to correct these biomechanical
problems (Edington et al.). The foot during the
foot-strike should be straight and in line with the direction of linear
motion. If the feet are turned outward it reduces the distance covered, and puts
more stress on the knees and lower extremities (Williams, 1990). The next period
in the running cycle is the mid-support.
The period of mid-support sees the foot transform from a mobile structure into a rigid lever that can support several times the body weight of the runner. This change is due to the position of the subtalor and midtarsal joints of the foot. Much of the rigidity of the foot can be attributed to the shape of the bones, and the tension on the ligaments. The supination of the subtalor joint forms a rigid lever for forward propulsion. This occurs through a series of events including the knee joint extending, the lower extremity rotates externally, the calcaneus inverts, the midtarsal joint locks, and the foot becomes a rigid lever. This allows for the propulsive force to be thrust backward and downward from a combination of hip extension, knee extension, and ankle plantar flexion. The mid-support period ends with the heel rising upward into takeoff.
When the foot leaves the ground, the follow-through period begins. This
is the initial floating period of the forward recovery phase. The next period of
the forward recovery phase is the forward swing. This is achieved through hip
flexion and forward rotation of the pelvis, which cause the thigh to start
moving forward. Hip flexion is assisted by flexion of the knee; this shortens
the lever allowing for greater forward velocity. After maximum hip flexion is
reached, the final float period called foot descent begins. Knee extension
occurs to promote movement of the lower limb. The hamstrings slow the forward
movement of the foot and leg by generating tension. As the next foot strike
occurs, ideally the foot will be moving backward with a velocity equal to the
forward movement of the trunk. Stride length and the stride rate can play a
critical role in the efficiency of a runner.
It has been well documented that humans increase both stride length and
stride frequency as running velocity increases(Cavanagh & Kram, 1990).
Stride length tends to reach its maximum at higher velocities of
running(Cavanagh & Kram). Stride frequency tends to increase more at the
higher velocities. The exact combination of length and frequency at a particular
velocity may differ due to such variables as leg length, hip flexion, breathing
rate, and state of fatigue (Cavanagh & Kram). The optimum stride length for
most runners occurs subconsciously, and is developed with practice over time. A
change in the optimum stride either by
lengthening or shortening can cause energy costs to rise (Cavanaugh &
Williams, 1979). Over-striding can be energy costly due to the foot-strike
deceleration it causes. Along with the stride variables, the upper extremities
also play a key role in the running process.
The arm action in running is compensatory and synchronous with the action
of the legs (Hinrichs, 1990). The arms help the legs in propelling the body
upward, thus providing lift to the runner. The arms also aid in achieving a
constant horizontal velocity, which could lead to a reduction in energy cost (Hinrichs).
Williams (1980) reported that runners who were more economical in terms of
oxygen consumption tended to use less vigorous arm swing. Theoretically arm
swing should increase with running velocity. Also as a runner begins to fatigue
the use of arm swing becomes more important, and helps the runner to maintain
lift and drive. The arms should be
carried low and relaxed, with the hands cupped loosely. This will help the
runner from tightening up in the upper body. In an ideal situation the elbows
should swing forward and backward in a straight line (“Up in Arms,” 1980).
Lateral motion or outward rotation can also hinder efficiency. The angle of arm
flexion should be around 90 degrees. This should not be a fixed angle, but
should allow for some movement on either side of it. This will help to smooth
out the form and avoid robot arm action. The arms due play vital role in running
and are not just merely used for balance. Aristotle once said, “runners run
faster if they swing their arms.” All the different variables in running
produce the running economy of an athlete, which have an impact on the metabolic
energy costs.
It is reasonable to expect mechanics of movement do have an influence on
the metabolic costs of running. There are several studies that suggest
a strong relationship between maximal oxygen consumption and running
performance, there are also indicators that running economy can be an important
factor (Daniels, 1985). It is then logical to assume that an improvement in an
individuals running mechanics would result in less energy costs, and would allow
for better performances (Williams, 1990). An example would be two runners with
similar VO2 max ratings, and compete against each other on a regular
basis at the marathon distance. One of the runners has better mechanics and
continually finishes several minutes ahead of the other
runner. The more efficient runner is able to run at a faster pace with a
lower percentage of their VO2 max being utilized. It cost some
runners more to run at a given speed than it does others with better technique (Costill,
1986). This knowledge would be beneficial for coaches and athletes to understand
the basic concepts of running biomechanics, and how to improve efficiency, which
would ameliorate performance.
Adelaar, R. (1986). The practical biomechanics of running. American
Journal of Sports Medicine, 14, 497-500.
Cavanagh, P., & Kram, R. (1990). Stride Length in Distance Running:
Velocity, body dimensions, and added mass effects. In P.R. Cavanagh (Ed.), Biomechanics
of Distance Running (pp. 35-63). Champaign, IL: Human Kinetics.
Cavanagh, P, & Williams, K. (1979). Should You Change Your Stride
Length?. Runners World, 14 (7), 64.
Costill, D. (1986). Inside Running: Basics of sports physiology.
Muncie, IN: Brown & Benchmark.
Edington, C., Frederick, E.C., & Cavanagh, P. (1990). Rearfoot Motion
in Distance Running. In P.R. Cavanagh (Ed.), Biomechanics of Distance Running
(135-161). Champaign, IL: Human Kinetics.
Henatsch, H.D., & Langer, H.H. (1985). Basic neurophysiology of motor
skills in sport: A review. International Journal of Sports Medicine, 6,
2-14.
Hinrichs, R. (1990). Upper Extremity Function in Distance Running. In P.R.
Cavanagh (Ed), Biomechanics of Distance Running (107-131). Champaign, IL:
Human Kinetics.
Martin, D., & Coe, P. (1991). Training Distance Runners.
Champaign, IL: Human Kinetics.
Milliron, M, & Cavanagh, P. (1990). Sagittal Plane Kinematics of the
Lower Extremity During Distance Running. In P.R. Cavanagh (Ed.). Biomechanics
of Distance Running (65-97). Champaign, IL: Human Kinetics.
Slocum, D.B., & James, S.L. (1968). Biomechanics of running. Journal
of the American Medical Association, 205, 721-728.
Up in Arms. (1980, April). Runners World, 53-57.
Williams, K. (1990). Relationships Between
Distance Running Biomechanics and Running Economy. In P.R. Cavanagh
(Ed.). Biomechanics of Distance Running (271-299). Champaign, IL: Human
Kinetics.
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