Red cell volume response to exercise training: Association with aging.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of exercise intervention studies.
PubMed 27859711 · doi:10.1111/sms.12798
What was done
Authors conducted a systematic review and meta-analysis of MEDLINE, Scopus, and Web of Science through February 2016 for studies evaluating the effect of normoxic exercise training (primarily lower-limb endurance training, mean duration 15.2 weeks) on red blood cell volume (RBCV) in healthy individuals. The analysis included 30 studies representing 299 participants (mean age 19–71 years; 271 males). Mean differences (MD) between pre- and post-training measurements were calculated overall and stratified by age (<60 years vs. ≥60 years).
What was found
Across all 299 participants, exercise training did not lead to a statistically significant increase in RBCV (MD = 49 mL, 95% CI: -11 to 108, P = 0.11). However, subgroup analysis showed a significant expansion in RBCV among young and middle-aged participants under 60 years old (n = 106, MD = 81 mL, 95% CI: 0 to 162, P < 0.05; I² = 0%), whereas older adults aged 60 and above experienced no meaningful change (n = 110, MD = 13 mL, 95% CI: -76 to 102, P = 0.77; I² = 0%).
Why it matters
These findings suggest that the hematological adaptation of expanding red cell volume in response to endurance exercise is age-dependent and attenuated or absent in older adults. This clarifies conflicting literature on exercise-induced hematological changes across the lifespan.
Limits
The total sample size is modest (299 individuals across 30 studies, averaging ~10 participants per study) and heavily male-dominated (90.6% men), limiting generalizability to women. The pooled studies primarily evaluated within-subject pre-post changes rather than randomized control comparisons, and training protocols across included studies may have differed in intensity and volume.
Cited by
- supports Endurance exercise increases total blood volume and the number of red blood cells in the body.