Improving Putting Accuracy with Electrical Muscle Stimulation Feedback Guided by Muscle Synergy Analysis

Research Background and Issues

• Problem Identification and Challenges:
  The authors point out that while muscle synergy analysis is valuable for quantifying differences in muscle usage between experts and novices, methods for applying it to practical feedback remain underdeveloped. This study seeks to address how to provide clear guidance for sports training based on the results of muscle synergy analysis. Additionally, due to significant individual variability, selecting appropriate expert reference data for novices poses a challenge.

• Significance of the Problem:
  Muscle synergy is critical for improving athletic performance, especially for high-complexity movements such as golf putting, which require the coordination of multiple muscle groups. Optimizing muscle usage can enhance performance and reduce the complexity of movements. Furthermore, putting accounts for approximately 40% of golf swings, making improvements in putting accuracy highly valuable for overall golf performance.

• Research Motivation and Related Work:
  The authors aim to overcome the limitations of traditional muscle synergy analysis, which only quantifies muscle usage differences, by integrating electrical muscle stimulation (EMS) to provide targeted training feedback. Existing studies have demonstrated the significant effects of EMS in motor learning and complex movement training, but the systematic integration of muscle synergy analysis with personalized feedback methods remains unexplored.

Proposed Solution

• Methodology and Innovations:
  A golf putting training system is proposed, combining muscle synergy analysis with EMS feedback. The system employs non-negative matrix factorization (NMF) to extract users' muscle synergy patterns and uses optimal transport distance (OTD) to calculate the similarity between users' and experts' synergy patterns. Based on the differences in muscle synergy, EMS is applied to key target muscles to guide users' attention.

• Innovations:

  1. Using OTD to evaluate muscle synergy similarity instead of traditional Pearson correlation coefficients, providing a more biomechanically relevant assessment.
  2. Offering personalized muscle synergy guidance through expert data matching, rather than relying on a uniform model.
  3. Addressing individual differences by diversifying expert data selection and implementing targeted EMS feedback for more precise motor learning guidance.

• Implementation Steps:

  1. Users wear EMG sensors to record muscle activity during putting.
  2. NMF is applied to the user data for muscle synergy analysis, decomposing it into spatial synergy vectors and temporal activation coefficients.
  3. OTD is used to calculate the similarity between the user's muscle synergy and those of multiple experts, selecting the most similar expert data.
  4. Differences in muscle weights between the user and the expert are identified to determine target muscles for activation.
  5. EMS parameters are adjusted, and electrical stimulation is applied to target muscles to guide muscle usage during practice.

Research Outcomes

• Key Findings:
  In experiments, participants using the system improved their putting success rate by an average of 15%, significantly outperforming the control group's 7% improvement. The results demonstrate the system's effectiveness in enhancing novices' motor learning capabilities.

• Advantages over Existing Solutions:
  The study introduces a personalized muscle synergy analysis feedback mechanism, addressing the limitations of traditional methods that overlook individual variability. Unlike the Pearson correlation coefficient, OTD incorporates biomechanical considerations, enabling more precise expert data matching. Additionally, EMS allows targeted training of specific muscles, enhancing the focus and effectiveness of user training.

• Experimental and Evaluation Results:

  1. Comparison of Success Rate Improvements: The experimental group's success rate improvement was significantly higher than that of the control group, validated through independent t-tests with medium to large effect sizes.
  2. Comparison of OTD and Pearson Correlation Coefficient: OTD more effectively captures differences in human muscle synergy, providing better expert data matching for personalized training.
  3. Personalized Feedback: Each participant in the experimental group received EMS stimulation tailored to their muscle synergy differences, achieving targeted guidance.

• Limitations and Future Directions:

  1. Current limitations include the system's open-loop feedback design. Future work could incorporate closed-loop control for real-time monitoring and adjustment of muscle synergy.
  2. The cost matrix design could be further optimized, for instance, by leveraging advanced neuroscience data to enhance precision.
  3. Long-term testing of the system's effectiveness and exploration of its application to other sports (e.g., swimming, baseball) are needed.

Conclusion

This study innovatively combines muscle synergy analysis with personalized EMS feedback to improve golf putting accuracy. The results demonstrate that the system significantly enhances novices' motor skills and highlights the broad potential of muscle synergy analysis in motor learning. Future research will expand the system's applicability to a wider range of sports and optimize feedback algorithms to improve user experience and training outcomes.