Figure 2.

(A) Morphological changes in an athlete’s heart compared with a non-athlete’s heart. The normal heart of a 24-year-old librarian (left) is compared with that of a 23-year-old professional cyclist (right). Note the difference in scale such that the non-athlete’s ventricle is ~10 cm in length (circled in red), whereas the 10-cm mark reaches only halfway along the ventricle of the athlete. Note that all cardiac chambers are enlarged and that increases in wall thickness are relative to dilation. Taken with permission from La Gerche et al. [4]; (B) Morphological changes in a working dog’s (English Springer Spaniel) heart. The non-working dog (66 months old, 19 kg) (left) is compared with that of a Field trials champion (58 months old, 15.3 kg) (right). End diastolic volume in the non-working dog is 47 mL and 58 mL in the field trials champion.