Exercise Intensity and Circulating CD34+ Progenitor Cell Mobilization in Trained Adults

NCT07841561 | Completed

• 1 other identifier: SRG-CD34-EXINT-2026-01
• Study Type: interventional
• Target: 40
• Locations: 1 country
• Sites: 1

Brief Summary

This randomized crossover study investigated whether exercise intensity influences the mobilization of circulating CD34+ progenitor cells when total external work is matched. Forty trained male endurance athletes completed two cycling exercise conditions in randomized order: a higher-intensity condition at 70% of peak work rate (WRpeak) and a lower-intensity condition at 30% WRpeak. Both conditions were performed until 250 kJ of external work had been completed and were separated by a washout period of at least 7 days. Venous blood samples were obtained before exercise, immediately after exercise, and at 15, 30, and 60 minutes of recovery. The primary outcome was the absolute concentration of viable circulating CD34+ cells measured using single-platform flow cytometry. Secondary outcomes included CD34+CD45dim, CD34+CD133+, and CD34+VEGFR2+ cell phenotypes, together with adrenergic, metabolic, chemokine, growth-factor, and cardiovascular responses. The study was designed to determine whether exercise intensity produces distinct progenitor-cell mobilization responses despite identical external work.

Conditions

Exercise-Induced Circulating Progenitor Cell Mobilization

Keywords

Exercise Intensity; CD34+ Progenitor Cells; Circulating Progenitor Cells; Endurance Athletes; Crossover Study; Adrenergic Response; CXCL12

Outcome Measures

Primary Outcomes (1)

• Change From Baseline in Absolute Circulating Viable CD34+ Progenitor Cell Concentration

  Absolute circulating viable CD34+ progenitor cells were quantified in peripheral blood using single-platform flow cytometry with counting beads and expressed as cells/µL. Measurements were obtained before exercise and during recovery after each exercise condition. Change from baseline was calculated for each post-exercise time point and compared between the 70% WRpeak and 30% WRpeak work-matched exercise conditions.

  Baseline, immediately post-exercise, and 15, 30, and 60 minutes post-exercise during each intervention session.

Secondary Outcomes (3)

• Change From Baseline in Circulating CD34+CD45dim Progenitor Cell Concentration

  Baseline, immediately post-exercise, and 15, 30, and 60 minutes post-exercise during each intervention session.

• Change From Baseline in Circulating CD34+CD133+ Progenitor Cell Concentration

  Baseline, immediately post-exercise, and 15, 30, and 60 minutes post-exercise during each intervention session.

• Change From Baseline in Circulating CD34+VEGFR2+ Progenitor Cell Concentration

  Baseline, immediately post-exercise, and 15, 30, and 60 minutes post-exercise during each intervention session.

Study Arms (2)

Sequence AB: 70% WRpeak Then 30% WRpeak

EXPERIMENTAL

Participants first completed a cycling exercise bout at 70% of individual peak work rate (WRpeak) until 250 kJ of external work was achieved. After a washout period of at least 7 days, participants completed a second cycling bout at 30% WRpeak, also matched to 250 kJ of external work.

Behavioral: Higher-Intensity Work-Matched Cycling Exercise; Behavioral: Lower-Intensity Work-Matched Cycling Exercise

Sequence BA: 30% WRpeak Then 70% WRpeak

EXPERIMENTAL

Participants first completed a cycling exercise bout at 30% of individual peak work rate (WRpeak) until 250 kJ of external work was achieved. After a washout period of at least 7 days, participants completed a second cycling bout at 70% WRpeak, also matched to 250 kJ of external work.

Behavioral: Higher-Intensity Work-Matched Cycling Exercise; Behavioral: Lower-Intensity Work-Matched Cycling Exercise

Interventions

Higher-Intensity Work-Matched Cycling Exercise BEHAVIORAL

Participants performed cycle-ergometer exercise at 70% of individual peak work rate (WRpeak) until a total external mechanical work of 250 kJ was completed. Venous blood samples were obtained before exercise, immediately after exercise, and at 15, 30, and 60 minutes of recovery.

Sequence AB: 70% WRpeak Then 30% WRpeak; Sequence BA: 30% WRpeak Then 70% WRpeak

Lower-Intensity Work-Matched Cycling Exercise BEHAVIORAL

Participants performed cycle-ergometer exercise at 30% of individual peak work rate (WRpeak) until a total external mechanical work of 250 kJ was completed. Venous blood samples were obtained before exercise, immediately after exercise, and at 15, 30, and 60 minutes of recovery.

Sequence AB: 70% WRpeak Then 30% WRpeak; Sequence BA: 30% WRpeak Then 70% WRpeak

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

Sponsors & Collaborators

• Samarra University: lead

Study Sites (1)

College of Physical Education and Sports Sciences, University of Samarra

Samarra, Muhafazat Salah ad Din, 34010, Iraq

Location

Study Officials

• SAIF RASHEED GHANIM, PhD

  College of Physical Education and Sports Sciences, University of Samarra

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Masking Details: assays were blinded to exercise condition and intervention sequence. Blood samples were labeled using coded identifiers that did not reveal participant identity, exercise intensity, or sequence assignment. Participants and exercise staff could not be blinded because of the obvious difference between the two exercise intensities.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Model Details: Participants completed two work-matched cycling exercise conditions in a randomized, counterbalanced crossover design. Each participant performed exercise at 70% and 30% of individual peak work rate (WRpeak), with both conditions matched for 250 kJ of external work and separated by a washout period of at least 7 days. Participants were assigned to either sequence AB (70% followed by 30% WRpeak) or sequence BA (30% followed by 70% WRpeak).

Study Record Dates

• First Submitted: September 19, 2026
• First Posted: September 25, 2026
• Study Start: August 3, 2026
• Primary Completion: September 9, 2026
• Study Completion: September 9, 2026
• Last Updated: September 25, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Beginning after publication of the study results and continuing for 5 years thereafter.
• Access Criteria: De-identified individual participant data will be available to qualified researchers upon reasonable request to the corresponding author. Requests should include a scientifically valid research proposal and a description of the intended a

Locations

IR (1)