A Qualitative Analysis of Running

Introduction: A Qualitative Analysis of Running

In the 1970's, thousands of people took to the road with a new trend of exercise----running. It was fairly easy; just put one foot in front of the other as fast as you can and go as far as you can. Feel the burn in your chest? The sweat trickling down your face? The throb in your knees as your foot pounds into the ground with every step? Well then, you're exercising! You're running! Since then, running has become a dominant factor in sports and fitness; a factor so prevalent that the number of musculoskeletal injuries due to running has also increased over the last quarter century. These chronic injuries are usually due to overuse, improper training techniques, or a combination of the two. By using the results of other biomechanists' studies, one can extrapolate an idea of what running should look like and what muscles are utilized during the activity. Consequently, changes in technique, strength training, and flexibility training can be made in order to decrease the potential for injury.

Article Summaries

Before analyzing the mechanics of running, it is important to accumulate some of the vast research available for this activity. The following are brief summaries of research articles that study various factors on running.

DeVita (1994) noted the gait cycle is measured in two ways: swing-stance-swing or stance-swing-stance. In this study, EMG activity of six muscles was obtained from four subjects while walking and running. The data was collected while the subjects performed a consecutive swing, stance, swing period of each gait. From this, the swing-to-stance and stance-to-swing period of each gait could be measured. The EMG results showed greater activation levels for 5/6 muscles during the swing-to-stance period. Results concluded that the subjects needed to prepare for the initiation of stance and the application of relatively large external forces and momentums. Therefore, when assessing the human gait, it is best to observe stance-swing-stance.

Jacobs, Bobbert, VanIngen, and Schenau (1993) analyzed the function of mono- and biarticular leg muscles during the stretch-shortening cycle of running at 6 m/s. Kinematics, ground reaction forces and EMG activities were recorded for a single stance phase. First of all, estimates of muscle force were correlated with origin-to-insertion velocity (VOI). Second, a model of the soleus and gastrocnemius was used to find the active state and internal muscle behaviors. High correlations were found between the muscle forces and the VOI time curves for the monoarticular hip, knee and ankle extensor muscles. However, the correlations for the biarticular muscles were low. The results from the model concluded that the active state of the gastrocnemius was high during the stretch phase; the active state of the soleus started out low during the stretch phase, but reached a higher plateau as the stretch phase ended and the shortening phase began. Therefore, the difference in stimulation is a compromise between minimizing energy dissipation and optimal use of the stretch-shortening cycle.

Nig, DeBoer, and Fisher (1995) did a comparison of treadmill and overground running. Twenty-two subjects ran on four different surfaces: overground and three treadmills, each varying in size and power. Each subject was filmed in the sagittal and frontal (posterior) plane. Body landmarks were placed on the superior border of the greater trochanter, the lateral femoral epicondyle, the lateral malleolus, and the head of the fifth metatarsal of the right leg. Subjects ran at four different speeds varying from 3.0-6.0 m/s. It was concluded that the subjects systematically planted their feet in a flatter position on the treadmill than overground. Therefore, using a treadmill for running assessment can lead to inadequate conclusions about overground running.

Anatomical Analysis

According to Thordarson (1997), running can be analyzed by measuring the gait cycle, or the initial contact of one foot to the following initial contact of the same foot, which is broken down into two phases: stance and swing. The stance phase constitutes approximately 40% of the running gait cycle, depending on the velocity of the runner. Moreover, it consists of initial contact of the heel with the ground, the shifting of the body's weight, and bringing the toe off the ground; therefore, the stance phase can be divided into two subphases, absorption and propulsion, which are separated by midstance. The swing phase, approximately 60% of the gait cycle, begins with the toe leaving the ground, the lower extremity decelerating upward, and then accelerating downward. This phase is also divided into two subphases, initial swing and terminal swing, which are separated by midswing. Figure 1 below shows the breakdown of the running gait cycle.

Although the lower extremity is the major variable when studying running, it is important to consider the role of the arms, for they assist in stabilizing the body by creating a force couple with the lower extremity. A couple is defined as "a pair of equal, oppositely directed forces that act on opposite sides of an axis of rotation to produce torque" (Hall, 1999). The understanding of a force couple is based on Newton's third Law of Motion, the Law of Reaction, which states, "for every action, there is an equal and opposite reaction"