Effects of different frequencies of ankle pump exercise on lower limb hemodynamics: a systematic review and meta-analysis.

Background: Ankle pump exercise (APE) is commonly used to improve lower-limb circulation, but the hemodynamic effects of different frequencies remain unclear. This study evaluated frequency-specific hemodynamic changes after APE to inform practical exercise protocols. Methods: As of March 2026, six databases-PubMed, Embase, the Cochrane Library, CNKI, Wanfang, and VIP-were systematically searched according to PRISMA guidelines. Eight studies involving 546 participants, including healthy individuals and patients with postoperative immobilization, fractures, hemiplegia, or restricted mobility, were included, of which only one was an RCT. The effects of APE at different frequencies on mean femoral venous blood flow velocity were analyzed using a paired change-score approach. Analyses were conducted at the specific-frequency level to reduce unit-of-analysis error from repeated frequency comparisons and shared baseline measurements. Sensitivity analyses were performed, and methodological quality was assessed using the NHLBI quality assessment tools according to study design. Results: Studies were grouped according to APE frequency, and frequency-specific within-arm analyses showed that mean femoral venous blood flow velocity generally increased from baseline across all evaluated frequencies. Smaller increases were observed at lower frequencies, particularly at 3 cycles/min, whereas more pronounced within-arm increases were generally observed at 10 cycles/min or higher, including at 10 cycles/min (MD = 15.16 cm/s, 95% CI: 11.87 to 18.46). However, this observation was based mainly on indirect comparisons of changes from baseline across studies rather than direct head-to-head comparisons between different frequencies. No consistent pattern indicated that progressively higher frequencies necessarily resulted in additional benefits. Sensitivity analyses using fixed-effect models and leave-one-out procedures showed that the direction and statistical significance of the findings were generally stable. Conclusions: APE may improve lower-limb venous hemodynamics by increasing mean femoral venous blood flow velocity. Frequencies of 10 cycles/min or higher tended to show larger within-arm increases than lower-frequency protocols, but this observation was based mainly on indirect cross-study comparisons rather than direct head-to-head comparisons and should be interpreted cautiously. Given the predominance of non-randomized or quasi-experimental studies and the very low certainty of evidence, the optimal exercise frequency remains uncertain, and further well-designed studies are needed to confirm these findings.