The Acute Effects of Active, Passive, and Proprioceptive Neuromuscular Facilitation and Dynamic Stretching on Lower-Limb Muscle Stiffness and Range of Motion: A Randomized Crossover Study

Objective: This study comprehensively compared the acute effects of active stretching (AC), passive stretching (PA), proprioceptive neuromuscular facilitation (PNF), and dynamic stretching (DS) on lower-limb muscle stiffness and range of motion (ROM). Methods: A randomized crossover repeated-measures design was employed. Data were acquired using MyotonPRO (Myoton AS, Tallinn, Estonia, Software v.5.0.0.257). Twelve physically active male college students participated in the study. Each participant completed all five conditions (CO, AC, PA, PNF, DS) in a randomized order, separated by 48 h washout periods. Muscle stiffness and ROM of the lower-limbs were evaluated before and after each stretching intervention. Muscle stiffness was measured in the following muscles (L = left; R = right): quadriceps: vastus lateralis (Vlt), rectus femoris (RF), vastus medialis (Vm); hamstrings: semitendinosus (Sem), biceps femoris (Bic); gluteus maximus (GM); gastrocnemius: medial (Gcm)/lateral (Gclt). A two-factor repeated-measures analysis of variance (ANOVA) with Bonferroni correction was employed to examine ROM and muscle stiffness under different stretching methods. Results: 1. All methods improved ROM (PA 95% CI [2.15, 4.66], η2 = 0.35; PNF 95% CI [1.80, 4.32], η2 = 0.30; AC 95% CI [1.92, 4.43], η2 = 0.32; DS 95% CI [3.50, 6.01], η2 = 0.51; p < 0.05); 2. PA significantly reduced muscle stiffness in Gcm-L (95% CI [−28.00, −8.74], η2 = 0.210), Gclt-L (95% CI [−16.52, −2.18], η2 = 0.110)/R (95% CI [−32.75, −8.10], η2 = 0.167), and Vm-L (95% CI [−15.73, −6.33], η2 = 0.079), but increased RF-L (95% CI [6.16, 21.58], η2 = 0.191) stiffness; PNF significantly increased Sem-L (95% CI [2.46, 16.51], η2 = 0.117) and Vm-R (95% CI [4.83, 16.21], η2 = 0.200) stiffness; AC significantly reduced Sem-R (95% CI [−20.59, −0.83], η2 = 0.079) stiffness while increasing GM-R (95% CI [6.34, 17.29], η2 = 0.254) stiffness; DS significantly decreased muscle stiffness in Vlt-L (95% CI [−21.23, −5.90], η2 = 0.186) and Sem-R (95% CI [−23.09, −3.33], η2 = 0.115) (p < 0.05). Conclusions: DS significantly improved lower limb flexibility and reduced muscle stiffness in selected muscles. AC improved anterior thigh muscle stiffness. PA reduced stiffness in posterior chain muscles. PNF increased stiffness in specific muscles, suggesting caution before explosive activities.