Pedal force feedback training to reduce bilateral asymmetries

Borut Fonda Research Review

In their study, Bini et al. (2016) aimed to examine the pedal force asymmetries before and after sessions of pedalling retraining focused on reducing bilateral asymmetries in pedal forces. They recruited trained cyclists and triathletes (n =20) who were firstly asked to complete an incremental test to exhaustion, with intensity increments in a ramp profile. Following a 30 min passive rest, they completed three 1-min sets at 70 % of their corresponding maximal power. During these trials, forces at the pedals were measured using a two-dimensional pedal dynamometer. Asymmetry index was calculated from the peak total force.
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Figure 1: Real-time pedal force feedback can be used to improve pedal force asymmetry. (Figure taken from www.forped.eu)


Cyclists who exhibited a peak pedal force asymmetry greater than 20 % were asked to complete another 12 sets of pedalling sessions with a provided visual feedback on peak pedal force from each pedal. Cyclists were also instructed to increase the force at their weaker side and to reduce the force at their stronger side. After completion, they completed 3 additional trials without visual feedback. The averages of the first three and the last three were taken into further analysis.

Results showed that the index of asymmetry from asymmetrical cyclists was reduced after 12 feedback trials to values similar to those observed for symmetrical cyclists (< 20 %). A negative correlation was observed between pre-training asymmetry index and percentage changes in asymmetry indices in asymmetrical cyclists. That indicates that cyclists with larger asymmetries present a greater chance for reduction in bilateral asymmetries using force feedback training.

The findings of their study are novel and important for practice, especially from a point that asymmetric cyclists in producing pedal forces can use sessions of retraining to reduce their asymmetry when visual and verbal feedback of pedal forces is provided. The major drawback of the study is that we cannot relate the effects of asymmetry retraining to cycling performance. It would be interesting to see those cyclists with asymmetry index above 20 % to undergo a longer period of retraining and see how their cycling performance would change. The second question that remains unanswered in this study is the source of those asymmetries. The later can occur due to muscle strength imbalances, flexibility or pedalling technique. I believe that only the last can be temporarily improved by pedalling retraining.

In conclusion, an interesting study by a great cycling biomechanics scientist Rodrigo Bini. The results highlight the importance of evaluating pedal forces in everyday practice. It is however worth noting that measures of left and right power is not equivalent to pedal force measurement and margin of error is much higher.
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Bini, Rodrigo R., Tiago C. Jacques, Felipe P. Carpes, and Marco A. Vaz. 2016. “Effectiveness of Pedalling Retraining in Reducing Bilateral Pedal Force Asymmetries.” Journal of Sports Sciences, August, 1–6. doi:10.1080/02640414.2016.1215505.



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