Background: The Nordic hamstring exercise is a closed-chain exercise that effectively activates all lower extremity muscles, but there is a lack of consideration of ankle joint which affects exercise effectiveness. One of the major advantages of the Nordic exercise have been known as strengthening lower extremity extensors. This manifests the exercise increases activities of the ankle plantar flexors as well as hip extensors. Objectives: To investigated the impacts of changes in ankle position on the lower extremity musculature and subjective difficulties during the Nordic hip extension exercise. Design: Cross-sectional study. Methods: Twenty the healthy male participants participated in this study. Participants perform three variations of the Nordic exercises including three ankle positions. Each Nordic exercise was defined as ankle position (neutral, dorsiflexion and plantar flexion). During the Nordic exercise, erector spine (ES), gluteus maximus (GM), biceps femoris (BF), gastrocnemius (GCM) activities and subjective difficulties (Borg RPE score) were measured. Results: Muscular activities of the biceps femoris and gastrocnemius were significantly different among the three ankle conditions, which showed controversial results (P<.05). The biceps femoris activity was significantly higher with the dorsiflexion condition, compared to the others (P<.05). On the other hand, activity of the gastrocnemius was significantly higher with the plantarflexion position compared to the others (P<.05). Conclusion: Present study suggests the ankle positional changes could affect lower muscular activities during the Nordic exercise. Although it is difficult to affirm the causes due to limited data, selective activation of the biceps femoris might accomplish with ankle dorsi flexion and that of the gastrocnemius might accomplish with the ankle plantarflexion during the Nordic exercises.

INTRODUCTION
SUBJECTS AND METHODS
    Subjects
    Outcome Measures
    Experimental Procedures
    Data and Statistical Analysis
RESULTS
    Changes in muscular activities accordance withankle positions during the Nordic exercise
    Changes in subjective difficulties accordance withankle positions during the Nordic exercise
DISCUSSION
CONCLUSION
ACKNOWLEDGEMENT
REFERENCES

• Sungkwang Ju(PT, Prof., PhD, Department of Physical Therapy, Kaya University, Kimhea, Republic of Korea)
• Seyeon Park(PT, Prof., PhD, Department of Physical Therapy, Uiduk University, Keongju, Republic of Korea) Corresponding author