Intense Triceps Surae Contraction Increases Lower Extremity Venous Blood Flow.

Objective: Venous thromboembolism can be prevented by physical prophylaxis, such as active ankle exercise (AAE), in addition to pharmacological treatment. However, the relationship between the intensity of triceps surae (TS) exercise and venous flow is unclear, and physical thromboprophylaxis has not been established for patients with leg cast immobilization. The goals of the current study were to clarify the degree of intensity of TS isotonic contraction required to increase peak blood velocity (PV) in the superficial femoral vein to higher than that at no resistance and to determine if TS isometric contraction can increase PV.

Methods: A prospective, nonrandomized, controlled trial was performed in 20 healthy young adult men. PVs at rest and during one TS isotonic or isometric contraction were measured using Doppler ultrasonography. Isotonic contraction intensity was defined as no resistance with contraction of maximum effort and 25%, 50%, 75%, and 100% of one repetition maximum (1RM). Isometric contraction intensity was defined as 15-35%, 40-60%, 65-85%, and 90-100% of the maximal voluntary contraction.

Results: Isotonic contraction at 75% 1RM (51.4 cm/s [95% CI, 40.1-62.6]) and 100% 1RM (54.9 cm/s [95% CI, 43.1-66.7]) significantly increased PV compared to that with no resistance (41.0 cm/s [95% CI, 32.2-49.8]) (P=0.005, 0.001, respectively). Isometric contraction increased PV significantly at all intensities (all P≤0.002).

Conclusions: Applying resistance at ≥75% 1RM increases venous flow and enhances the effect of AAE with TS isotonic contraction. TS isometric contraction may serve as thromboprophylaxis for patients undergoing leg cast immobilization.