A large capacity of the heart to transport oxygen to the exercising muscles must be matched by an equivalent capacity of those muscles to absorb a large blood flow (requiring a large capillary network) and to extract oxygen at high rates from the blood stream.
(A large capacity of the heart to transport oxygen to the exercising muscles; must be matched; by an equivalent capacity of those muscles)
A large capacity of the heart to transport oxygen to the exercising muscles
must be matched
by an equivalent capacity of those muscles