NordicAngle app for iPhone and iPad

■Overview■
Nordic Angle is a smartphone application developed in collaboration with S-CADE. Co., Ltd. and Athletic Training Laboratory at Waseda University (instructed by Professor Norikazu Hirose). AI automatically detects landmarks at the hip, knee, and ankle joints. Based on the location information of the detected landmarks, the break-point angle (0° defined as the fully extended knee joint), which is considered to be the initiation point of hamstring relaxation during Nordic hamstringing, is calculated.

Previous studies suggest that individuals with stronger eccentric hamstring strength have a lower risk of hamstring strain injury. Furthermore, it has been reported that the stronger the eccentric hamstring strength, the smaller the break-point angle during Nordic hamstring. Therefore, regular measurement of the break-point angle by the Nordic Angle might assess the risk of hamstring strain injury.

The smaller the break-point angle value, the deeper the upper body tilts forward, which is anticipated to indicate stronger eccentric hamstring strength. On the other hand, the larger the break-point angle value, the shallower the upper body tilts forward, which is anticipated to indicate weeker eccentric hamstring strength. Therefore, regular measurement of the breakpoint angle indicates that a smaller value means a lower risk of hamstring strain injury, and conversely, a larger value means an increased its risk.

■How to use■
1. The device is placed at a distance of about 3 m to the left and right of the subject so that the entire body is captured by the camera.
2. When the subject is ready, record a video at the slow setting (240 fps).
3. The subject leans forward as slowly as possible from a kneeling position, and then leans forward as far as possible.
4. Please change the playback speed to slow at the initial and final parts of the video (※How to support).
5. If the video is long, please trim it short from tthe initial and final parts of the motion of subject.
6. Please select a video.
7. The screen changes and the break-point angle is displayed.

※How to support the playback speed to slow at the initial and final parts of the video
To import slow video in the camera roll into the application, select the video to be imported in advance and tap the "Edit" button that is displayed in the top right corner on the playback screen. The barcode-like white lines displayed at the bottom of the video in the edit screen are narrower on the right and left edges than in the center. The entire playback speed of the video can be changed to slow by increasing the distance between the right and left white lines. If the playback speed is not slow at the initial and final parts of the video, the break-point angle may not be accurately measured.

■Notes■
・Please use a bench that can secure the ankles.
・Please avoid showing anyone other than the subject.
・The entire body of the subject should be shown.
・Loose fitting clothing will reduce detection accuracy.