ORIGINAL ARTICLE Andrew Cornwell ® Arnold G. Nelson ® Ben Sidaway Acute effects of stretching on the neuromechanical properties of the triceps surae muscle complex Accepted: 12 November 2001 / Published online: 5 February 2002 Ó Springer-Verlag 2002 Abstract Previous research has shown that an acute bout of passive muscle stretching can diminish perfor- mance in certain movements where success is a function of maximal force and/or power output. Two possible mechanisms that might account for such findings are a change in active musculotendinous stiffness and a de- pression of muscle activation. To investigate the likeli- hood of these two mechanisms contributing to a post- stretch reduction in performance, we examined the acute effects of stretching on the active stiffness and muscle activation of the triceps surae muscle group during maximal single-joint jumps with movement restricted to the ankle joint. Ten males performed both static (SJ) and countermovement (CMJ) jumps before and after pas- sively stretching the triceps surae. Electrical activity of the triceps surae during each jump was determined by integrating electromyographic recordings (IEMG) over the course of the movement. Triceps surae musculoten- dinous stiffness was calculated before and after stretch- ing using a technique developed by Cavagna (1970). Following stretching, a significant decrease [mean (SD) 7.4 (1.9)%; P<0.05] in jump height for the CMJ oc- curred, but for the SJ, no significant (P>0.05) change in jump height was found. A small but significant decrease [2.8 (1.24)%; P<0.05] in stiffness was noted, but the magnitude of this change was probably not sufficient for it to have been a major factor underlying the decline in CMJ performance. Paradoxically, after stretching, the SJ exhibited a significant (P<0.05) decrease in IEMG, but the IEMG for the CMJ remained unchanged (P>0.05). It appears that an acute bout of stretching can impact negatively upon the performance of a single- joint CMJ, but it is unlikely that the mechanism re- sponsible is a depression of muscle activation or a change in musculotendinous stiffness. Keywords Stretch-shortening ® Stiffness ® Stretching ® Jumping ® Elastic energy Introduction Recent investigations have suggested that an acute bout of passive muscle stretching might diminish performance where maximal force and/or power output is critical (Cornwell et al. 2001; Hennig and Podzielny 1994; Kokkonen et al. 1998; Nelson et al. 2001). Both Corn- well et al. (2001) and Hennig and Podzielny (1994) have shown the height of maximum effort jumps to be re- duced after stretching the muscles of the lower extrem- ity. Similarly, Kokkonen et al. (1998) demonstrated that an acute stretching bout had a deleterious effect on maximum lifting capability in both a knee-extension and knee-flexion weight-training exercise. Although these studies failed to explicate the underlying mechanism(s) responsible for such findings, it has been speculated that a decrease in active musculotendinous stiffness (stiffness under stimulated conditions) and/or a depression of muscle activation as a result of the stretching procedure might have been contributing factors (Cornwell et al. 2001; Kokkonen et al. 1998). After examining the relationship between active musclotendinous stiffness and performance in a bench- press-type movement, Wilson et al. (1994) suggested that for isometric and concentric contractions, a stiff mus- culotendinous unit allows the force generated by the contractile component to be transmitted to the skeletal Eur J Appl Physiol (2002) 86: 428–434 DOI 10.1007/s00421-001-0565-1 A. Cornwell (&) Department of Kinesiology and Physical Education, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA 90032, USA E-mail: acornwe@calstatela.edu Tel.: +1-323-3434648 Fax: +1-323-3436482 A.G. Nelson Louisiana State University, Department of Kinesiology, Long Field House, Baton Rouge, LA 70803, USA B. Sidaway Husson College, Department of Physical Therapy, 1 College Circle, Bangor, MN 04401, USA