Acute effects of passive vs. active warm-up associated with stretching on flexibility and neuromuscular function of hamstring muscles in physically active individuals
Authors: Babault Nicolas , Hitier Marion , Paizis Christos , Cometti Carole 
Published: May 2023

The present study aimed to explore the effects of passive vs. active warm-up protocols associated with static or neurodynamic stretching on the hamstring muscles function. We hypothesized 1) passive warm-up would similarly alter the neuromuscular function more particularly while considering flexibility or stiffness indexes and 2) stretching would only produce slight additional effects (independently of the modality). Sixteen physically active individuals participated in four randomized experimental sessions: 1) passive warm-up and static stretching, 2) passive warm-up and neurodynamic stretching, 3) active warm-up and static stretching, and 4) active warm-up and neurodynamic stretching. Passive warm-up was 20 minutes in a 45°C room. Active warm-up was 20 minutes and included cycling, submaximal contractions and athletic drills. Stretching (either passive or neurodynamic) was composed of six series of 30 seconds stretch. Tests were conducted before warm-up (baseline), immediately after the warm-up (post-warm) and immediately after stretching (post-stretch). They included a maximal voluntary contraction and associated electromyographic activity, passive torque during a passive stretch until the maximal discomfort and, a stand and reach flexibility test. The subjective efficiency of all procedures was evaluated.The results of the present study revealed no significant condition effects for all main outcomes (maximal voluntary torque, electromyography, passive torque and flexibility). A time effect was obtained for maximal voluntary torque and revealed a significant decrease post-stretch as compared to post-warm (p=.015). The electromyographic activity of both biceps femoris and semitendinosus muscles significantly decreased between baseline and post-stretch (p=.017 and p=.005, respectively). No significant changes in passive torque were obtained with time (p=.069). Flexibility significantly increased post-warm (p<.001) and further increased post-stretch (p<.001) as compared to baseline. Volunteers reported active warm-up as the most efficient for subsequent muscle performance and neurodynamic stretch as the most efficient for flexibility.The present study confirmed our a priori hypothesis. Passive or active warm-up have similar effects on the neuromuscular function. The likely muscle temperature increase after warm-up, per se, is sufficient enough to improve the lower-limb flexibility. Stretching would additionally increase flexibility with an adverse strength decrease. Stretching should therefore be included in a comprehensive warm-up only when a high degree of flexibility is requested. In contrast, warm-up is sufficient when a reduced degree of flexibility is needed. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.