Effect of slope angle on muscle activity during variations of the Nordic exercise

This study investigated the muscular activity of the lower muscles during variation of Nordic exercises following changes of the Nordic angles and the base slope angles. Twenty-one healthy participants were participated in this study. Participants performed six variations of Nordic exercises including two Nordic angles positions and three base slope angles. Each Nordic exercise defined as Nordic angle 10°, 15° and base slope angle 0°, 10°, 15°. During the Nordic exercises, erector spine, gluteus maximus, biceps femoris, gastrocnemius activities and subjective difficulties (Borg RPE score) were measured. The activities of all muscles and subjective difficulties were significantly greater with the 15° of Nordic exercise compared to the 10° of Nordic exercise, regardless of base slope angles. There were significant differences in gluteus maximus, biceps femoris, gastrocnemius, and the Borg RPE score between three base slope conditions (P<0.05). The Borg RPE score and activities of the gluteus maximus were increased with the increases of base slop angles from 0° to 15°. Conversely, the activities of the gastrocnemius and biceps femoris were decreased with the increases of base slop angles from 0° to 15°. Present study indicates that application of the greater Nordic angle during the Nordic exercise is advantageous for activating lower extremity muscles. Using the base slopes during the Nordic exercise could be used for selective activation of the lower muscles. High base slope angles inducing greater knee flexion could maximize the exercise effects for activating gluteal muscles rather than lower leg muscles such as biceps femoris and gastrocnemius.