One year of endurance exercise training improved aerobic capacity without improving vascular function in non-trained limbs in previously untrained but healthy individuals.
Key Findings
Results
One year of supervised cycling training did not improve forearm vascular function at any time point during the 12-month period.
Twelve healthy young adults (25 ± 4 years) participated in a 12-month supervised cycling program
Seven participants completed the full 12-month protocol
No change in endothelium-dependent vasodilation (acetylcholine) or endothelium-independent vasodilation (sodium nitroprusside) was observed (p > 0.05)
Flow-mediated dilation (FMD) also showed no significant change across the training period
Vascular assessments were made at baseline and after 1, 4, 6, and 12 months of training
Results
VO2max increased substantially during the first 6 months of training but showed no further improvement from 6 to 12 months.
Baseline VO2max was 40.3 mL·min⁻¹·kg⁻¹ compared to 50.8 mL·min⁻¹·kg⁻¹ at 6 months (p = 0.001)
VO2max at 12 months was 51.3 mL·min⁻¹·kg⁻¹, not significantly different from the 6-month value (p > 0.05)
The improvement in aerobic capacity occurred in the absence of any corresponding improvement in forearm vascular function
Discussion
Vascular adaptations to endurance training appear to be region-specific, confined to limbs actively engaged in exercise.
Forearm vascular function was assessed using intra-arterial infusions of acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent), as well as FMD
The cycling training program engaged the lower limbs but not the upper limbs, making the forearm a non-trained vascular territory
The authors interpret the null findings as supporting the hypothesis that 'vascular remodeling is confined to actively engaged limbs and thus undetectable in vascular territories not directly involved in exercise training'
Background
The study investigated previously untrained but healthy young individuals, a population in which baseline vascular health was not impaired.
Participants were described as 'sedentary but healthy young individuals' at baseline
The authors note that improvements in vascular function from exercise training are 'particularly relevant for populations with impaired vascular health,' suggesting healthy individuals may show a different response
The study was supervised and ran for 12 months, representing a prolonged adherence to endurance training
What This Means
This research suggests that a full year of endurance cycling exercise, while highly effective at improving aerobic fitness, did not improve blood vessel function in the arms of healthy young people who were previously inactive. The researchers measured how well blood vessels in the forearm could dilate—both through their own internal signaling (endothelium-dependent) and in response to a directly acting drug (endothelium-independent)—at multiple points over the 12-month training period. Despite a roughly 25% improvement in aerobic capacity (VO2max) within the first 6 months, none of the vascular measures in the forearm changed significantly at any time point.
The key implication is that vascular benefits from exercise training appear to be localized to the limbs that are actually doing the work. Because the participants were cycling, their legs were the active limbs, and the forearm—used as a non-exercising 'control' limb—showed no improvement. This supports the idea that the mechanical forces of blood flow during exercise, which are highest in the exercising muscles, drive vascular remodeling in those specific regions rather than producing a whole-body effect.
This research matters because it refines our understanding of how and where exercise improves cardiovascular health. For people with healthy vascular function, simply doing one form of endurance exercise may not broadly improve blood vessel health throughout the body. It also raises questions about whether exercise type or variety might be important for achieving vascular benefits across different body regions, though further research would be needed to explore that.
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Rocha M, Sejersen C, Fischer M, Tamariz-Ellemann A, Bonne T, Bejder J, et al.. (2026). One Year of Endurance Exercise Training Does not Improve Vascular Function in Non-Trained Limbs in Healthy Individuals.. Scandinavian journal of medicine & science in sports. https://doi.org/10.1111/sms.70354