Benign Premature Ventricular Contractions (PVCs): This is the most common cause of palpitations during exercise. PVCs are extra heartbeats that originate in the ventricles, causing the heart to contract prematurely. They are often harmless and can be triggered by physical activity, stress, or caffeine.

Supraventricular Tachycardia (SVT): A condition characterized by an abnormally fast heart rate that originates above the ventricles. Exercise can trigger episodes of SVT, leading to palpitations.
Anxiety or Stress: Anxiety and stress can cause palpitations, especially during physical activity. The body's "fight or flight" response can lead to an increased heart rate, which may be perceived as palpitations.
Dehydration or Electrolyte Imbalance: Dehydration or an electrolyte imbalance, particularly potassium or magnesium deficiency, can disrupt heart rhythm, leading to palpitations during exercise.

Hypertrophic Cardiomyopathy (HCM): A condition where the heart muscle becomes thickened, which can lead to obstructed blood flow and increased risk of sudden cardiac death during exercise. Although less common, it is crucial to consider due to its potential severity.
Wolff-Parkinson-White (WPW) Syndrome: A rare condition where an abnormal electrical pathway in the heart can cause rapid heart rates, potentially leading to life-threatening arrhythmias during exercise.
Long QT Syndrome: A disorder of the heart's electrical activity that can cause sudden, uncontrollable, dangerous arrhythmias, particularly during physical activity or stress.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): A rare heart condition where the muscle in the right ventricle is replaced by fatty tissue, leading to abnormal heart rhythms, which can be exacerbated by exercise.
Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT): A rare genetic disorder that can cause life-threatening arrhythmias during physical activity or emotional stress due to an abnormal response to adrenaline.