Study Information

Title: Unilateral Flywheel Training Enhances Eccentric Braking Capacity, Change-of-Direction Performance, and Match Acceleration/Deceleration in Soccer Players
Journal: Published in Applied Sciences (MDPI)
Link to Study: https://doi.org/10.3390/app16042134

Purpose and Background

Soccer athletes regularly perform high intensity decelerations and changes of direction during a match. These actions require rapid eccentric loading of the plant leg during the initial deceleration steps. For that reason, it’s recommended that athletes develop eccentric capacities to help support the execution of these demanding actions within training and competition (1). This study investigated whether flywheel training was an effective method for improving eccentric strength, change of direction performance, and on-field acceleration and deceleration metrics in soccer athletes.  

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Methods

Twenty-four healthy male soccer players (~20 years old, >6 years of experience) from the Beijing Sport University were randomly assigned to either perform unilateral flywheel training group (n=12) or a traditional resistance training control group (n=12). Both groups performed unilateral lower limb 2x/week for 8 weeks, with a progressive increase in loading over time. The main exercises included split squats, lateral squats, and lunges.  

The measurements taken before and after the 8-week training period included:

• Isokinetic testing of the knee extensors and flexors, with metrics including peak eccentric torque, eccentric-to-concentric ratio (EC ratio), and leg asymmetry.  

• Sprinting and Change of Direction (COD) tests such as a 10m linear sprint, the modified 505 COD test, COD deficit (505 COD time – 10m sprint time), and a soccer-relevant dribbling COD test.  

• GPS-derived measures of high intensity accelerations and decelerations during soccer match play (high intensity events were those with > 3 m/s² for accelerations and < -3 m/s² for decelerations).  

Key Results

Eccentric Strength

The flywheel group had statistically significant improvements in eccentric peak torque during knee extension (+0.54 Nm/kg) and flexion (+0.46 Nm/kg), as well as increased EC ratio (+0.13) and lower inter-limb strength asymmetry (-1.95%). In contrast the traditional training group did not have significant changes in any of the eccentric strength measures.  

Field-Based Sprinting and COD Tests

While neither group had significant improvements in the 10m linear sprint test, the flywheel group had significant improvements in the COD measures, including faster 505 COD times for the right (-0.12 s) and left side (-0.09 s) and a reduced COD deficit for the right and left side (indicating they were losing less time due to the COD component of the tests). This translated to faster times in the dribbling-based COD test (-1.13 s). In contrast, the traditional training group did not have statistically significant changes in any of the field-based performance measures.  

Accelerations and Decelerations during match play

The flywheel group had increases in the number of high-intensity accelerations (+6.08) and decelerations (+6.75) performed during match play, after the training program. In contrast, the traditional group did not have significant changes.  

Summary and Key Takeaways

The results of this study found that 8 weeks of unilateral flywheel training increased lower limb eccentric strength and improved performance in field-based COD tests (both with and without dribbling a soccer ball). Importantly, this also translated into significantly higher frequencies of high intensity accelerations and decelerations during soccer match play.  

Notably, the group performing the dumbbell-based traditional program did not have significant improvements in any of the measures, suggesting that the eccentric loading offered by flywheel training may have been particularly useful for change of direction performance in these athletes.  

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References

1. Harper, D., Cervantes, C., Van Dyke, M., Evans, M., McBurnie, A., Dos' Santos, T., ... & Kiely, J. (2024). The braking performance framework: practical recommendations and guidelines to enhance horizontal deceleration ability in multi-directional sports. International Journal of Strength and Conditioning, 4(1).