The control of the cardiovascular system depends on the autonomic nervous system. Heart rate (HR) is primarily controlled by the autonomic nervous system and is a cardiovascular indicator that is often used to assess autonomic function. A balanced sympathetic and parasympathetic nervous systems are indicated by normal HR. Parasympathetic dysfunction is thought to be the primary mechanism linking chronotrophic disorders to a poor prognosis [1]. An unusual delay in HR recovery during exercise can be caused by parasympathetic system dysfunction [[1], [2]].

The reduction in HR from the peak exercise rate in the first, second, third, and fifth minutes following the end of the exercise stress test is known as the heart rate recovery index (HRRI) [3]. A drop of <12 bpm in the resting first-minute HR, which is an independent predictor of all-cause and cardiovascular death, was considered abnormal in previous reports [[4], [5]]. HRRI is an important measure of autonomic nervous system dysfunction and is directly related to parasympathetic activity [5].

Several methods have been used to assess myocardial repolarization, such as the QT interval (QT), corrected QT interval (QTc), and T-wave peak-to-end interval (Tp-e interval). Recent research suggests that the Tp-e interval on an electrocardiogram (ECG) may be a useful predictor of cardiovascular mortality and ventricular arrhythmias because it reflects the overall distribution of repolarization. [5]. Moreover, the QT, QTc, and Tp-e intervals remained unaffected by changes in HR. As a result, a new index known as the Tp-e/QT ratio has been suggested as a more accurate measure of the distribution of ventricular repolarization [[6], [7]].

Anabolic androgenic steroids (AAS) are synthetic variations of the male sex hormone testosterone [8]. Although they are beneficial in certain medical conditions, such as endometriosis, severe trauma, AIDS-related cachexia, neuromuscular dystrophy, anemia with bone marrow failure, and hypogonadism [9,10], they can also cause a variety of health issues when misused or abused.

The use and abuse of AAS have become a growing concern, particularly among athletes and bodybuilders [11]. These synthetic variations of testosterone have gained popularity because of their ability to enhance muscle growth, strength, and athletic performance. Although side effects are rare at therapeutic doses, abusers typically use excessive doses of AAS. Among the most obvious side effects of AAS use are the effects on the cardiovascular system. There are a growing number of alarming reports of sudden death (SD) and malignant ventricular arrhythmias associated with AAS [12].

Chronic AAS use causes sympathovagal imbalance and increases sympathetic nerve activity in the heart, leading to increased sympathetic dominance [13]. The effects of AAS on the cardiac autonomic nervous system of bodybuilders are quite limited, and the results are controversial. We aimed to investigate the effects of AAS abuse on the HRRI and ECG measurements. Our hypothesis was that the use of AAS decreases HRRI during maximal exercise and increases the risk of cardiac arrhythmias and SD.