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In their research Hamner, Seth and Delp determined and reported the role of muscles in propulsion and support during running. The authors have demonstrated how the combination of muscles, and the arms and torso motions contribute to the propulsion of the body mass center during running.

In their demonstration, the authors developed a three-dimensional muscle-actuated simulation model from which they analyzed the simulation to quantify the contribution of each of the muscles to the acceleration of the body center mass during the stance and the braking phases of the running gait cycle.

The reason for conducting the study was identification of an existing knowledge gap with regard to the effect of muscles in the propulsion and support of the body mass center, including arm and torso motions during running. The study was conducted because previous studies have focused on the contribution of muscles to propulsion and support of the body mass without taking into account the potential contribution of role of the arm and torso motions (Hamner, Seth & Delp, 2010). As such, the authors sought to determine overall contribution of the muscles including the arm and torso motion to the propulsion of the body mass center during the running cycle.

The demonstration involved development of a three-dimensional muscle-actuated running simulation model including 92 musculotendon actuators which represented about 76 muscles of the lower body and torso (Hamner, Seth & Delp, 2010). Through this model, the authors were able to quantify the contribution of muscles and arms motions to mass center propulsion during the running cycle. The motivation behind this study was to establish whether arm and torso motions have a role to play in the acceleration of the body mass center during running contrary to previous studies which have only identified muscles as the sole contributor to propulsion of the body mass center propulsion in the running cycle.

At the end of the study, the authors were able conclude that indeed the arm and torso motions (specifically the quadriceps and plantarflexors) contribute significantly to the acceleration of the body mass center during running.


The authors wrote a brief and precise abstract capturing all aspects of the study including the objective of the study, a summary of the methodology, findings and the conclusion from the study findings. As such, a reader is able to have a clear overview of the overall research and deduce the key findings of the study without having to go through the entire article. However, it is not clear to pick the motivation behind the need to conduct the study from the abstract. In addition, any reader would need to read through the background information, of which little information is provided in the abstract to understand the findings of the study.


The authors have provided a strong introduction capturing what is known or has been achieved by other researchers. The introduction provides a clear explanation of the muscle activities involved in the running process as demonstrated in other studies. This provides any reader with a strong background to be able to understand the study findings. The authors have reported the findings of related studies and identified some of the shortcomings in those studies as well as the limitations of theoretical framework underpinning the spring-mass model (Hamner, Seth & Delp, 2010). Through this, the reader is able to understand why the authors had to develop the three-dimensional muscle actuated simulation model used in this study.


The methodology section of the article is provided in stepwise format easy to follow every activity carried out during the study. The method used involving a singly healthy male subject to provide the different measurements required for the study was sufficient data to answer the study’s objectives. I believe that comparison of two or three subjects would have provided more credible results that can be generalized among other subjects. However, the authors enhanced the accuracy of the simulation quantifications by comparing the findings to experimental data (Hamner, Seth & Delp, 2010). The authors have also identified the challenges in the analysis of the simulation including difficulties in capturing the rapid changes in acceleration at the foot contact. Clear formulas have been provided to guide the readers on how the different parameters were determined.

The results have been presented in different frequency graphs indicating the different joint moments. This allows any readers to correlate the results with the findings and the discussion. The comparison of the simulation activations from the computed muscle control, the experimental EMG from the subject and the speed-matched experimental EMG are clearly presented in form of line graphs (Hamner, Seth & Delp, 2010). The data section is well detailed and well organized as well as described to make it easy to understand and connect it with the discussion.


The authors have only discussed from their study and not from any other study. This means that the discussion can be inferred to the results. The discussion has also compared the known and the findings of the study. The discussion leads to a better understanding of the contributions of the different muscles to the propulsion of the body mass center during running. The conclusion is also made based on the study findings and not information from other research works.

General Comments and Further Research

The authors of this article have presented a high quality and credible research findings that will go a long way in helping understand the muscle dynamics involved when an individual is running. The presentation of the study findings is brilliant and easy to follow the results and the discussion. As such, the selected paper has played a critical role in helping understand the muscle dynamics involved in the running process. With the limitations associated with the study, future research should focus on creating a new model that would allow better analysis of the effects at the initial foot contact.


Hamner, S., Seth, A & Delp, S. (2010). Muscle contributions to propulsions and support during running. Journal of Biomechanical, 43, 2709-2716.