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PROTRACK » Coaching & Training » Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance

Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance

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Tim W. Dorn, Anthony G. Schache and Marcus G. Pandy
J Exp Biol 215, 1944-1956

Abstract:

Humans run faster by increasing a combination of stride length and stride frequency. In slow and medium-paced running, stride length is increased by exerting larger support forces during ground contact, whereas in fast running and sprinting, stride frequency is increased by swinging the legs more rapidly through the air. Many studies have investigated the mechanics of human running, yet little is known about how the individual leg muscles accelerate the joints and centre of mass during this task. The aim of this study was to describe and explain the synergistic actions of the individual leg muscles over a wide range of running speeds, from slow running to maximal sprinting. Experimental gait data from nine subjects were combined with a detailed computer model of the musculoskeletal system to determine the forces developed by the leg muscles at different running speeds. For speeds up to 7 m s–1, the ankle plantarflexors, soleus and gastrocnemius, contributed most significantly to vertical support forces and hence increases in stride length. At speeds greater than 7 m s–1, these muscles shortened at relatively high velocities and had less time to generate the forces needed for support. Thus, above 7 m s–1, the strategy used to increase running speed shifted to the goal of increasing stride frequency. The hip muscles, primarily the iliopsoas, gluteus maximus and hamstrings, achieved this goal by accelerating the hip and knee joints more vigorously during swing. These findings provide insight into the strategies used by the leg muscles to maximise running performance and have implications for the design of athletic training programs.


Discussion:

A study by Matt Brughelli that came out a couple of years ago really turned some heads in terms of learning which muscles and forces really contribute to top-end speed development. In Brughelli’s landmark study, it was found that when moving from a jog to a sprint, the horizontal forces increase markedly, but the vertical forces increased by fairly little. Bottom line of the study, train the muscles responsible for horizontal force development if you want breakaway speed! These muscles would be the glutes and hamstrings.

In this study, the researchers took a new approach to determining how changing from a jog to a sprint changes muscle and force contributions, and also threw in the aspect of the ankle performance. This study used an actual track in which to collect the data, along with computer modeling, so many of the “haters” of prior studies (which were done on treadmills) may have less to criticize regarding this study and it’s relevance. Instrumentation in this study included a 3d motion capture system and reflective markers (near and dear to my heart), force plates spaced out on the track, and EMG.


The results of this study found similar results to Brughelli’s treadmill study. In going from 3.5m/s to 7.0m/s all muscle groups increased in force production and EMG activity. The transition from 7.0m/s to 9.0m/s was where things transitioned to the dominance of horizontal force at this speed. Vertical support forces in this study increased by around 33% when making the jog (3.5m/s) to light sprint (7.0m/s) transition, but those forces did not increase at all when moving to an near maximal sprint at 9.0m/s. The gastroc, soleus and vasti muscles of the quads were found to provide 75% of the vertical support forces during sprinting.


The action of the horizontal forces when moving from 7.0m/s to 9.0m/s were a different story! When calculating the force production of the glute and hamstring, both muscles force output doubled when moving from the light sprint to near-maximal effort. The hamstring muscle was taxed the most, working at a force of 9x bodyweight at the high speed sprint! The researchers also found the strength of the iliopsoas muscle group to be of massive importance during the swinging action of the leg during sprinting. No wonder sprinters like Asafa Powell have such huge hip flexor muscles! If you have read Jimson Lee’s report on Jamaican sprinting, you will find that they often end their workouts with running high knees for extended distances, assisting with the strength of their hip flexors, so important for sprint speed.

The researchers conclusion of the study was that maximal sprint velocities rely heavily on the glutes, hamstrings, and hip flexors; not the quads or calves. If you want to get blazing speed, you need to be paying attention to your posterior chain and hip flexors in your strength development. My new favorites, as I have stated before are the hip thrust and glute bridges. Although running high knees is old school, I recommend those as well, based on this study.


Comparing Iliopsoas groups between an elite sprinter (Asafa Powell) and a mere mortal

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