Physiological Determinants of V̇O 2max Increase with Endurance Training in a Group Including Older and Young Adults.
Level 3 - non-randomized controlled study
Uncontrolled prospective pre-post interventional cohort study
PubMed 40173327 · doi:10.1249/MSS.0000000000003707
What was done
Fourteen healthy adults (7 older: 68 ± 7 years, 7 young: 26 ± 7 years; 9 males, 5 females) completed a 12-week vigorous endurance cycling training program consisting of 45-minute sessions, three times weekly at approximately 70% V̇O₂max. Researchers evaluated pre- to post-training changes in V̇O₂max, central cardiac function (maximal cardiac output [Q̇max], maximal stroke volume [SVmax], maximal heart rate [HRmax]), peripheral oxygen extraction (arteriovenous O₂ difference [a-vO₂ diff]), muscle fiber dimensions (cross-sectional area [CSA], perimeter), muscle capillarization indices (capillary-to-fiber ratio [C:Fi], capillary-to-fiber perimeter exchange index [CPFE], capillary contact [CC], capillary density [CD]), and mitochondrial aerobic enzyme activity (citrate synthase [CS] activity).
What was found
Across all participants, V̇O₂max increased by 20% ± 8% (P < 0.05). Significant increases (all P < 0.05) occurred in Q̇max (+15% ± 11%), SVmax (+14% ± 12%), a-vO₂ diff (+4% ± 6%), muscle fiber CSA (+17% ± 21%), perimeter (+7% ± 9%), CS activity (+144% ± 175%), C:Fi (+32% ± 17%), CPFE (+30% ± 15%), CC (+38% ± 20%), and CD (+22% ± 17%). HRmax showed no significant change (-1% ± 4%, P = 0.448). Changes in V̇O₂max were significantly correlated with changes in Q̇max (r = 0.830, P < 0.001), SVmax (r = 0.655, P = 0.011), CD (r = 0.546, P = 0.043), and CS activity (r = 0.630, P = 0.021). No significant correlations were found between V̇O₂max changes and changes in HRmax, a-vO₂ diff, CSA, perimeter, CC, C:Fi, or CPFE (all P > 0.05).
Why it matters
This study demonstrates that endurance training-induced increases in V̇O₂max across young and older adults are primarily driven by central adaptations (stroke volume and cardiac output) alongside specific peripheral adaptations in capillary density and mitochondrial enzyme activity.
Limits
The study had a very small sample size (n = 14 total; 7 per group) and lacked a non-exercising control group. All primary numerical outcomes and correlations were pooled across young and older adults without separate subgroup comparisons reported in the abstract.
Cited by
- supports An increase in stroke volume is the primary physiological adaptation responsible for improvements in VO2 max.