pulmonary reserve: the additional volume of air that the lungs can inhale and exhale when breathing to the limit of capacity in times of stress
reserve: (medicine) potential capacity to respond in order to maintain vital functions
sugar maple: maple of eastern and central North America having three-lobed to five-lobed leaves and hard close-grained wood much used for cabinet work especially the curly-grained form; sap is chief source of maple syrup and maple sugar; many subspecies