How Muscle Action Shifts at Different Sprinting Speeds and the Coaching Implications

Effective sprint training requires an in-depth understanding of the physiological demands sprinters face as they accelerate and maintain high speeds. This deep dive will explore a study by Dorn, Schache, and Pandy (2012) highlighting the muscular strategy shifts that occur as sprinters increase their running speed. This article explores the findings of their study, discusses the key muscular adaptations, and provides practical implications for coaches working with sprinters and distance runners.

Key Findings
Dorn et al. (2012) revealed that as athletes increase their speed, they shift from relying on the ankle plantarflexors (soleus and gastrocnemius) to the hip muscles for achieving further acceleration. This change occurs around the 7 m/s mark, which is particularly relevant for sprinters who race at speeds consistently above this threshold.

1. Below 7 m/s: The Role of Stride Length
   At lower speeds, up to around 7 m/s, increasing stride length is the primary mechanism for improving running velocity. The soleus and gastrocnemius play a significant role in generating vertical ground reaction forces that propel the body upwards and forwards. This action enhances the time the sprinter spends in the air, contributing to a longer stride.
2. Above 7 m/s: The Shift to Stride Frequency
   As speed increases, ground contact time decreases, limiting the effectiveness of the ankle plantarflexors. The force-velocity relationship of muscles means that at higher velocities, the ability of the soleus and gastrocnemius to generate force diminishes. Beyond 7 m/s, the focus shifts to increasing stride frequency, which is achieved through faster leg swing facilitated by the hip muscles—specifically the iliopsoas, gluteus maximus, and hamstrings.

Source

• Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance (Dorn, Schache, and Pandy, 2012)