Date on Master's Thesis/Doctoral Dissertation

3-2016

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Bioengineering

Committee Chair

Quesada, Peter

Committee Co-Chair (if applicable)

Bertocci. Gina

Committee Member

Bertocci. Gina

Committee Member

Magnuson, David

Committee Member

Holman, Grady

Author's Keywords

bioengineering; muscle activity; body allignment

Abstract

The mechanics of the running stride was altered around the 1970s when shoes were released with an elevated heel (McDougall 2009). At this point in time a heel strike running style became increasingly common and has remained the popular pattern when running in traditional shoes. In fact, the exact same person has been seen to alter their stride when running in a traditional shoe where they heel strike verses barefoot where they take on a forefoot strike (Lieberman 2010).

When an individual heel strikes, the ground reaction force is greater and contains an initial peak which is void in a forefoot strike. During a heel strike, a lot of force is generated in the knee (Kulmala 2013). In fact, it has been recommended to alter a stride from heel strike to forefoot strike if an individual is experiencing knee pain. However, Kulmala identified an increase in stress on the Achilles tendon when an individual utilizes a forefoot strike which leads to a different set of injuries. Another common problem identified while performing a forefoot strike is an increase in the activation time of the gastrocnemius muscles (Ahn 2014).

The first aim of this study was created to identify the difference in muscle activity occurring during a heel strike pattern and a forefoot strike pattern. The second aim is designed to vii identify if adding a forward body tilt while performing a forefoot strike will alter the muscles activated in hopes of reducing the amount of activation at the calf.

To assess the aims, a 3D motion capture analysis system as well as an EMG system were utilized. The EMG system was used to monitor tibialis anterior, medial gastrocnemius, lateral gastrocnemius, vastus lateralis, rectus femoris, semitendinosus, and biceps femoris muscle activity. Each of the 10 subjects underwent a testing period in which four different strides were assigned individually. Prior to data capture of each stride, the subject was allotted time to familiarize with the stride followed by two and a half minutes of running on the treadmill in which the last 15 seconds were recorded (EMG and motion capture). The motion capture data were processed to ensure the assigned stride was correctly performed. The EMG data was processed by a full wave rectification followed by a root mean square 50 ms moving window average and then normalized.

During terminal swing, the three forefoot strike conditions had higher gastrocnemius, hamstring, and quadriceps muscle activity compared to the heel strike condition. During late stance, the forefoot strike (FF), forefoot strike with an upright body position (FFU) and heel strike (HS) patterns had greater gastrocnemius activity compared to the forefoot strike with a forward body lean (FFL) condition. During initial swing, the gastrocnemius and hamstring muscles had a greater amount of activity in the FF conditions compared to the HS condition. Throughout early stance, midswing and terminal swing phases, the tibialis anterior had an increase in muscle activation when a HS was performed verses one of the three FF conditions. The tibialis anterior muscle demonstrated the least amount of variance due to its sole responsibility of dorsiflexion which had a greater need in the HS condition consistent with the viii results presented. The three FF conditions relied on plantarflexion to land toe first which resulted in increased gastrocnemius activity beginning in the initial swing phase and proceeded throughout terminal swing. A greater amount of hip extension in the three FF conditions resulted in an increased amount of activation of the hamstring muscles during terminal swing. Increased activation in the gastrocnemius and hamstring muscles for the FF conditions in terminal swing consequently created a tendency of knee flexion which resulted in an increased amount of activation for the quadriceps muscles for knee extension to occur.

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