The effect of the speed and range of motion of movement on the hyperemic response to passive leg movement

Abstract

Passive leg movement (PLM)-induced hyperemia is used to assess the function of the vascular endothelium. This study sought to determine the impact of movement speed and range of motion (ROM) on the hyperemic response to PLM and determine if the currently recommended protocol of moving the leg through a 90° ROM at 180°/sec provides a peak hyperemic response to PLM. 11 healthy adults underwent multiple bouts of PLM, in which either movement speed (60-240°/sec) or ROM (30-120° knee flexion) were varied. Femoral artery blood flow (Doppler Ultrasound) and mean arterial pressure (MAP; photoplethysmography) were measured throughout. Movement speed generally exhibited positive linear relationships with the hyperemic response to PLM, eliciting ~15-20% increase in hyperemia and conductance for each 30°/sec increase in speed (P < 0.05). However, increasing the movement speed above 180°/sec was physically difficult and seemingly impractical to implement. ROM exhibited curvilinear relationships (P<0.05) with hyperemia and conductance, which peaked at 90°, such that a 30° increase or decrease in ROM from 90° resulted in a 10-40% attenuation (P < 0.05) in the hyperemic response. Alterations in the balance of antegrade and retrograde flow appear to play a role in this attenuation. Movement speed and ROM have a profound impact on PLM-induced hyperemia. When using PLM to assess vascular endothelial function, it is recommended to perform the test at the traditional 180°/sec with 90° ROM, which offers a near peak hyperemic response, while maintaining test feasibility.

Keywords: Endothelial function; exercise blood flow; movement speed; passive leg movement; range of motion.

Figure 1

Effect of the speed of passive leg movement (PLM) on the hyperemic response to PLM. (A) Average leg blood flow response to PLM at different movement speeds. Error bars were not included for clarity. (B) Relationship between movement speed and peak change (ΔPeak) responses in blood flow elicited by PLM. (C) Relationship between movement speed and area under the curve during 60 sec (AUC _60sec) of PLM representing the total hyperemic response during 60 sec of PLM. (D) Relationship between movement speed and area under the curve during 60 cycles (AUC _60cycles) of PLM, representing the total hyperemic response during 60 cycles of PLM. “a”: significantly different than 60°/sec. “b”: significantly different than 120°/sec. “c”: significantly different than 180°/sec. “d”: significantly different than 240°/sec. “‐”: not significantly different. CPM: cycles per minute. In panels B–D the thick black line represents the curve of best fit between the individual hyperemic responses and movement speed.

Figure 2

Effect of the speed of passive leg movement (PLM) on antegrade and retrograde blood flow during PLM. (A) Relationship between movement speed and peak change (ΔPeak) in antegrade and retrograde blood flow elicited by PLM. (B) Relationship between movement speed and area under the curve during 60 sec (AUC _{60 sec}) of PLM for antegrade and retrograde flow. (C) Relationship between movement speed and area under the curve during 60 cycles (AUC _{60 cycles}) of PLM. Note that the thick black line represents the curve of best fit between the individual hyperemic responses and movement speed.

Figure 3

Effect of the speed of passive leg movement (PLM) on mean arterial pressure (MAP) heart rate (HR) and vascular conductance during PLM. (A) Average MAP response to PLM at different movement speeds. (B) Relationship between movement speed and peak increase in MAP during PLM. (C) Average HR response to PLM at different movement speeds. (D) Relationship between peak increase in HR during PLM and movement speed. (E) Relationship between movement speed and peak change (ΔPeak) in conductance during PLM. (F) Relationship between movement speed and area under the curve during 60 sec (AUC _60sec) of PLM. (G) Relationship between movement speed and area under the curve during 60 cycles (AUC _60cycles) of PLM. “a”: significantly different than 60°/sec. “b”: significantly different than 120°/sec. “c”: significantly different than 180°/sec. “d”: significantly different than 240°/sec. “‐”: not significantly different. Note that the thick black line represents the curve of best fit between the individual hyperemic responses and movement speed.

Figure 4

Effect of the range of motion (ROM) of passive leg movement (PLM) on the hyperemic response to PLM. (A) Average leg blood flow response to PLM at different ROM's. Error bars were not included for clarity. (B) Relationship between movement ROM and peak change (ΔPeak) in blood flow elicited by PLM. (C) Relationship between movement ROM and area under the curve during 60 sec (AUC _60sec) of PLM. (D) Relationship between movement ROM and area under the curve during 60 cycles (AUC _60cycles) of PLM. “a”: significantly different than 30°. “b”: significantly different than 60°. “c”: significantly different than 90°. “d”: significantly different than 120°. “–”: not significantly different from any condition. Note that the thick black line in panels B–D represents the curve of best fit between the individual hyperemic responses and movement speed.

Figure 5

Effect of the range of motion (ROM) of passive leg movement (PLM) on antegrade and retrograde blood flow during PLM. (A) Relationship between movement ROM and peak change (ΔPeak) in antegrade and retrograde blood flow elicited by PLM. (B) Relationship between movement ROM and area under the curve during 60 sec (AUC _60sec) of PLM for antegrade and retrograde flow. (C) Relationship between movement ROM and area under the curve during 60 cycles (AUC _60cycles) of PLM. Note that the thick black line represents the curve of best fit between the individual hyperemic responses and movement speed.

Figure 6

Effect of the range of motion (ROM) of passive leg movement (PLM) on mean arterial pressure (MAP) heart rate (HR) and vascular conductance during PLM. (A) Average MAP response to PLM at different movement ROM. (B) Relationship between movement ROM and peak increase in MAP during PLM. (C) Average HR response to PLM at different movement ROM. (D) Relationship between movement ROM and the peak increase in HR during PLM. (E) Relationship between movement ROM and peak change (ΔPeak) in conductance during PLM. (F) Relationship between movement ROM and area under the curve during 60 sec (AUC _60sec) of PLM. (G) Relationship between movement ROM and area under the curve during 60 cycles (AUC _60cycles) of PLM. “a”: significantly different than 30°. “b”: significantly different than 60°. “c”: significantly different than 90°. “d”: significantly different than 120°. “–”: not significantly different from any condition. Note that the thick black line represents the curve of best fit between the individual hyperemic responses and movement ROM.