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

Abstract

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": 1) 15 sedentary individuals, <2 sessions/wk; 2) 25 casual exercisers, 2-3 sessions/wk; 3) 24 committed exercisers, 4-5 sessions/wk; and 4) 13 competitive Masters athletes, 6-7 sessions/wk, plus regular competitions. Absolute (L/min) and relative (mL/kg/min) V̇o_2peak were higher with increasing exercise "dose" (P = 0.0005 and P < 0.0001, respectively). Hemoglobin concentration, hematocrit, and absolute tHbmass and blood compartment volumes were not significantly different between groups (all, P > 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 P < 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 P < 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, P < 0.0340) and tHbmass and erythrocyte volume were also higher in Committed compared with Casual exercisers (both, P < 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.NEW & NOTEWORTHY 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.

Keywords: blood volume; habitual exercise; hemoglobin; oxygen carrying capacity; oxygen uptake.

Graphical abstract

Figure 1.

The effect of exercise dose on absolute and relative total hemoglobin mass (tHbmass; A–C), blood volume (D–F), erythrocyte volume (G–I), and plasma volume (J–L). Females and males are shown in closed and open symbols, respectively. Data were compared via either ANOVA [tHbmass and erythrocyte volume (EV)] or Kruskal–Wallis tests [plasma volume (PV) and blood volume (BV)]; the main effect is shown in the bottom right of each panel and is bold if P < 0.05, with post hoc analyses (Tukey) shown above the data if there was a significant main effect. Only significant P values are shown from post hoc comparisons. CAS, casual exercisers (n = 25); COM, committed exercisers (n = 24); COMP, competitive exercisers (n = 13); SED, sedentary individuals (n = 15).

Figure 2.

The relationships between body composition, total hemoglobin mass (tHbmass; A–C) and blood volume (D–F). Females and males are shown in closed and open symbols, respectively. Note: The break in the data is primarily mediated by a sex-based difference in absolute blood volume, when scaled to body or fat-free mass the break in the data is not present. CAS, casual exercisers (n = 25); COM, committed exercisers (n = 24); COMP, competitive exercisers (n = 13); SED, sedentary individuals (n = 15).

Figure 3.

The relationships between [Hb] and total hemoglobin mass (tHbmass) with maximal oxygen uptake. A–C: the relationships between [Hb] (g/dL) and V̇o_2max (L/min), tHbmass (g) and V̇o_2max (L/min) as well as, tHbmass (g/kg) and V̇o_2max (L/min), whereas D–F show the same relationships but with V̇o_2max expressed relative to body mass (kg). Females and males are shown in closed and open symbols, respectively. [Hb], hemoglobin concentration; V̇o_2max, maximal oxygen uptake. CAS, casual exercisers (n = 25); COM, committed exercisers (n = 24); COMP, competitive exercisers (n = 13); SED, sedentary individuals (n = 15).