Effects of Training on Athletes. Sports physiology is the study of the long-and short-term effects of training and conditions on athletes. This specialized field of study goes hand in hand with human anatomy. Anatomy is about structure, where physiology is about function.
Visa and Mastercard always have 16 digits whereas American Express has 15 digits. The short answer is that American Express cards have a different PAN format than Visa, MasterCard and Discover because they offer a different kind of financial service.
For example, the MasterCard system is identified by the number 5, American Express and Diners Club credit card numbers start with the number 3, while Visa and Discover Card systems are identified by the numbers 4 and 6, respectively. Each credit card number has a structure that varies by system. In the MasterCard system, digits two through six are used to identify the bank number, digits seven through 15 designate the account number and digit 16 represents a check digit.