Investigation of Deltoid Muscle Activation From Different Angles in Body Building Athletes.

Objectives: It is known that bodybuilders suffer from shoulder injuries frequently. Therefore, it is important to determine the most appropriate form of movement during shoulder exercises. For this reason, this study was carried out to determine the most accurate form of movement by examining the deltoid muscle activation of bodybuilders from different angles.

Methods: The survey model, one of the quantitative research techniques, was used in this study. 53 athletes (44 men, 9 women) with an age of 25.77±9.13 years, height of 177.07±8.40 cm, body weight of 78.06±14.16 kg, and body mass index of 24.78±3.43 kg/m² who regularly attended bodybuilding gyms were included in the study. The deltoid activations of the participants was measured, while the glenohumeral joint is at 90°, the cubital joint is in abduction at 180°, 150° and 120°. surface electromyography (sEMG) biofeedback was determined using the Neurotrac Myoplus Pro device. Joint angles were determined with a goniometer. Statistical analyses of the study were performed using the SPSS 25 package program. It was found that the data were normally distributed and the Repeated measures Anova test was applied for comparisons.

Results: As a result of statistical analysis, in male participants, mean deltoid sEMG values and maximum voluntary contraction (MVC [%]) significantly decreased with decreasing angle size (p<0.05). In female participants, the average sEMG and MVC (%) values did not change at different angles (p>0.05).

Conclusion: According to the research results, shoulder sEMG activations decrease in direct proportion to the angle in bodybuilders. When the glenohumeral joint is 90° and the cubital joint is 180°, the activation of the medial deltoid muscle is highest. It is suggested that bodybuilders should consider the results of our study when performing exercises to hypertrophy the deltoid muscle.