The effect of chronic habitual exercise on oxygen carrying capacity and blood compartment volumes in older adults.

Absolute total hemoglobin mass (tHbmass) and blood compartment volumes are often considered to be higher in endurance athletes compared with nonathletes, yet little data support a fitness effect in older age. Therefore, we measured tHbmass and blood compartment volumes (carbon monoxide rebreathing) in 77 healthy individuals (23% female; aged, 60-87 yr). Participants were recruited into groups based upon their lifelong (>25 yr) exercise "dose": ) 15 sedentary individuals, <2 sessions/wk; ) 25 casual exercisers, 2-3 sessions/wk; ) 24 committed exercisers, 4-5 sessions/wk; and ) 13 competitive Masters athletes, 6-7 sessions/wk, plus regular competitions. Absolute (L/min) and relative (mL/kg/min) V̇o were higher with increasing exercise "dose" ( = 0.0005 and < 0.0001, respectively). Hemoglobin concentration, hematocrit, and absolute tHbmass and blood compartment volumes were not significantly different between groups (all, > 0.1328). When scaled to body mass, tHbmass (Sedentary, 9.2 ± 1.7 mL/kg; Casual, 9.2 ± 1.3; Committed, 10.2 ± 1.4; Competitive, 11.5 ± 1.4, ANOVA < 0.0001) and blood volume were significantly different between groups [Sedentary, 63.4 (59.2-68.5) mL/kg; Casual, 67.3 (64.4-72.6); Committed, 73.5 (67.5-80.2); Competitive, 83.4 (78.9-88.6), ANOVA < 0.0001], whereby all values were highest in Masters athletes. However, when scaled to fat-free mass (FFM), tHbmass and blood compartment volumes were greater in Competitive compared with Casual exercisers (all, < 0.0340) and tHbmass and erythrocyte volume were also higher in Committed compared with Casual exercisers (both, < 0.0134). In conclusion, absolute tHbmass and blood compartment volumes are not different between groups, with dose-dependent differences only among exercisers when scaled for FFM, with the highest tHbmass and blood compartment volumes in competitive Masters athletes. We observed that absolute oxygen carrying capacity (total hemoglobin mass, tHbmass) and blood compartment volumes were not associated with lifelong exercise dose. However, hematological adaptations associated with lifelong habitual exercise are only present among exercisers, whereby competitive Masters athletes have a greater oxygen carrying capacity (tHbmass) and expanded blood compartment volumes when scaled to fat-free mass.