With a larger left ventricle, the heart rate can decrease and still maintain a level of cardiac output necessary for the body. Therefore, athletes with AHS commonly have lower resting heart rates than nonathletes.The heart becomes enlarged, or hypertrophic, due to intense cardiovascular workouts, creating an increase in stroke volume, an enlarged left ventricle (and right ventricle), and a decrease in resting heart rate along with irregular rhythms. The wall of the left ventricle increases in size by about 15–20% of its normal capacity. No decrease of the diastolic function of the left ventricle occurs. The athlete may also experience an irregular heartbeat and a resting pulse rate between 40 and 60 beats per minute (bradycardia).The level of physical activity in a person determines what physiological changes the heart makes. The two types of exercise are static (strength-training) and dynamic (endurance-training). Static exercise consists of weight lifting and is mostly anaerobic, meaning the body does not rely on oxygen for performance. It also moderately increases heart rate and stroke volume (oxygen debt). Dynamic exercises include running, swimming, skiing, rowing, and cycling, which rely on oxygen from the body. This type of exercise also increases both heart rate and stroke volume of the heart. Both static and dynamic exercises involve the thickening of the left ventricular wall due to increased cardiac output, which leads to physiologic hypertrophy of the heart. Once athletes stop training, the heart returns to its normal size.
: 86 In conjunction with increased end levels of IGF, it is likely that perspiration and friction may be necessary predeterminants for lesions, since the level of insulin is usually not enough to activate IGF receptors across the body. Diagnosis
Acanthosis nigricans is typically diagnosed clinically. A skin biopsy may be needed in unusual cases. If no clear cause is obvious, it may be necessary to search for one. Blood tests, an endoscopy, or X-rays may be required to eliminate the possibility of diabetes or cancer as the cause. : 87 On biopsy, hyperkeratosis, epidermal folding, leukocyte infiltration, and melanocyte proliferation may be seen. : 979 : 87

Differential diagnosis
Acanthosis nigricans should be distinguished from the casal collar appearing in pellagra. Classification
Acanthosis nigricans is conventionally divided into benign and malignant forms, although may be divided into syndromes according to cause:: 506 
Benign This may include obesity-related, hereditary, and endocrine forms of acanthosis nigricans. Malignant. This may include forms that are associated with tumour products and insulin-like activity, or tumour necrosis factor.An alternate classification system still used to describe acanthosis nigricans was proposed in 1994. It delineates acanthosis nigricans syndromes according to their associated syndromes, including benign and malignant forms, forms associated with obesity and drugs, acral acanthosis nigricans, unilateral acanthosis nigricans, and mixed and syndromic forms. Treatment
People with acanthosis nigricans should be screened for diabetes and, although rare, cancer. Controlling blood glucose levels through exercise and diet often improves symptoms. Topical fade creams (normally used for eliminating age spots) can lighten skin cosmetically in less severe cases.