## 1 Introduction  
Handball is a sport with a high risk of injury due to its intensity and physical contact. Men have the highest injury rates per 1000 h of exposure and the shoulder complex is one of the most susceptible regions to injuries [1]. The shoulder complex of handball athletes presents several adaptations due to the repeated throwing actions at high velocity, such as glenbumeral internal rotation deficit (GIRD) of the throwing shoulder (TS), reduction in the total rotation range of motion (tROM), and limitation of the horizontal adduction (HA) ROM [2; 3; 4; 5]. These adaptations are considered risk factors for pain and injuries when the GIRD is higher than 15\({}^{\circ}\)[6] and the tROM reduction is higher than 10\({}^{\circ}\)[3]. In these cases, the handball athletes present twice the risk of suffering pain and/or injuries in several shoulder structures [3].  
Posterior muscle stiffness seems to be the source of these shoulder adaptations [4; 5; 6; 7; 8; 9]. Specifically, the teres major muscle seems to have a special relationship with the shoulder function. [PERSON] et al. suggested that this muscle promotes glenohumeral stability by resisting inferior displacement of the humeral head with the arm lifted [10]. The mechanical properties, like stiffness and tone, of this muscle have shown to be increased in TS compared to non-TS and non-handball athletes [11]. Therefore, the increase in the stiffness of the teres major muscle may reach the humeral head, favoring GIRD and reductions in tROM and HA. Despite the fact that no study has investigated the correlation between the properties of the teres major muscle and glenohumeral ROM, its treatment immediately improved pain intensity, shoulder ROM restrictions, and extensibility in handball athletes [7].  
The management of the teres major muscle in patients with shoulder pain and ROM restrictions seems to be a promising approach. Dry seedling DN and diacutaneous fibrosis DF are the two most common instrumental techniques used for different shoulder and upper-body dysfunctions [7; 12; 13; 14; 15; 16; 17; 18; 19]. DN is an instrumental invasive technique while DF is a conservative instrumental technique. DN uses stainless single-use acupuncture needles to eliminate or inactivate myofasical trigger points in the soft tissues by eliciting local twitch responses [20]. DF is an instrument-assisted soft tissue technique based on the Cyriax principles that uses a metallic hook to achieve a deeper and more precise application. Both techniques have shown to be effective in decreasing muscle stiffness immediately after the intervention and at 30 m [21] to 72 h of follow-up [22]. Moreover, these techniques have proven to be clinically effective in a wide range of musculoskeletal conditions. But not all patients can tolerate invasive techniques. So, considering that no study has compared the effects of both techniques on the stiffness of the teres major muscle in elite handball athletes, we wanted to investigate if both techniques presented similar changes.  
Thus, the primary objective of this randomized controlled trial was to compare the effects of the DN technique and the DF technique on the stiffness of the teres major muscle; the secondary objective was to compare the effects of both interventions in teres major muscle tone, pain intensity, shoulder ROM, and posterior shoulder extensibility in handball athletes with shoulder pain and GIRD.