CHAPTER 21 • GAIT ANALYSIS 129during walking and running, except for the amplitude
which is greater in running (Novacheck, 1998).- Ankle, knee, and hip power patterns during walking
are very similar to those obtained during running;
however, the amplitudes of power absorption and gen-
eration are directly related to the individual speed
(greater powers for higher speeds).
DYNAMIC ELECTROMYOGRAPHY
- Knowledge of the activation phases of the main lower
limb muscles, in association with the joint moment
patterns, can provide an effective description of over-
all gait function. While joint moments provide infor-
mation regarding the effect of action of all the
muscles involved, the knowledge of the activation pat-
terns allows us to discriminate in time the muscle
groups that are responsible for the observed joint
moment (Perry, 1992). - Surface electromyography(EMG) is the most common
method for detecting muscle activity during gait.
Current dynamic EMG systems allow one to detect
EMG signals from up to 16 muscles at a time, which
can be synchronized to both motion analysis systems
and force platforms. - Activation patterns of lower limb muscles during a run-
ning gait cycle are different from those observed during
a walking gait cycle with respect to both timing and
duration of activity. Figure 21-3 illustrates the phases of
muscle activity during running. In general, muscle
activity during running begins earlier in the swing
period and lasts for a relatively longer time during the
stance period. During walking the quadriceps are active
at the end of swing through 25% of the stance period
while during running and sprinting they continue to be
active through 50 to 100% of the stance period.
Similarly, the hamstrings are active earlier in swing
during running and continue nearly to the end of the
stance period while in walking they cease activity early
in stance. The ankle dorsiflexors during walking are
active from late stance until early stance; while during
running they continue to be active through midstance.
During walking the ankle plantarflexors are active only
during stance from loading response or midstance to ter-
minal stance; while in running they are active in termi-
nal swing through mid to terminal stance (Perry, 1992).OXYGEN CONSUMPTION- Measurement of oxygen consumption is typically
obtained with pulmonary gas exchange devices,
which are usually wearable and can be used outside a
laboratory. Respiratory volumes of O 2 and CO 2 can be
monitored during the execution of the motor task. - The measurement of oxygen consumption provides
information regarding the economy of gait. Walking
energy expenditure per unit of distance is highly
dependent on walking speeds. At natural walking
speed, energy expenditure is lower than at both lower
and higher speeds. In running, this dependency is not as
evident. In both running and walking the highest energy
expenditure per distance unit occurs at slower speed.
OVERALL GAIT EVALUATION- Clinically meaningful information can be obtained
from the wealth of data gathered from the measurement
instruments and analysis techniques reported here. By
relating EMG, kinetic, and kinematic patterns, it is
possible to describe and evaluate the function of gait at
a local level (i.e., the joint). By combining CoM time
histories and more complete segmental kinematic
information with oxygen consumption measurements,
an overall evaluation of the energetics of gait at a global
level is possible. - While during walking the total energy (kinetic plus
potential) is almost constant throughout the cycle, in
FIG. 21-3 Solid bars representing the timing of
active muscles in various phases of the gait cycle.
(From Novacheck, 1998).