Abstract:Recently, there has been a shift from static stretching (SS) or proprioceptive neuromuscular facilitation (PNF) stretching within a warm-up to a greater emphasis on dynamic stretching (DS). The objective of this review was to compare the effects of SS, DS, and PNF on performance, range of motion (ROM), and injury prevention. The data indicated that SS-(-3.7%), DS-(+1.3%), and PNF-(-4.4%) induced performance changes were small to moderate with testing performed immediately after stretching, possibly because of reduced muscle activation after SS and PNF. A dose-response relationship illustrated greater performance deficits with ≥60 s (-4.6%) than with <60 s (-1.1%) SS per muscle group. Conversely, SS demonstrated a moderate (2.2%) performance benefit at longer muscle lengths. Testing was performed on average 3-5 min after stretching, and most studies did not include poststretching dynamic activities; when these activities were included, no clear performance effect was observed. DS produced small-to-moderate performance improvements when completed within minutes of physical activity. SS and PNF stretching had no clear effect on all-cause or overuse injuries; no data are available for DS. All forms of training induced ROM improvements, typically lasting <30 min. Changes may result from acute reductions in muscle and tendon stiffness or from neural adaptations causing an improved stretch tolerance. Considering the small-to-moderate changes immediately after stretching and the study limitations, stretching within a warm-up that includes additional poststretching dynamic activity is recommended for reducing muscle injuries and increasing joint ROM with inconsequential effects on subsequent athletic performance.Key words: static stretch, dynamic stretch, proprioceptive neuromuscular facilitation, ballistic stretch, flexibility, warm-up.Résumé : Depuis peu, on utilise plutôt l'étirement dynamique (« DS ») que l'étirement statique (« SS ») ou la facilitation neuromusculaire proprioceptive (« PNF ») au sein d'une séance d'échauffement. Cette analyse documentaire se propose de comparer les effets de SS, DS et PNF sur la performance, l'amplitude de mouvement (« ROM ») et la prévention de blessures. D'après les données, on observe des modifications de performance faibles à modérées quand l'évaluation est réalisée immédi-atement après la séance d'étirement : SS (-3,7 %), DS (+1,3 %) et PNF (-4,4 %), et ce, possiblement à cause de la diminution de l'activation musculaire consécutive à SS et PNF. La relation dose-réponse révèle une plus grande baisse de performance quand la séance de SS par groupe musculaire ≥60 s (-4,6 %) vs. <60 s (-1,1 %). Par contre, SS suscite un gain modéré de performance (2,2 %) quand le muscle est plus allongé. L'évaluation est réalisée en moyenne 3-5 minutes post-étirement. La plupart des études n'incluent pas des activités dynamiques post-étirement; avec l'inclusion de ces activités, on n'observe pas de modification nette de la performance. DS suscite des gains de performance faibles à modérés...

The detrimental effects of static stretch are mainly limited to longer durations (≥ 60 s), which may not be typically used during preexercise routines in clinical, healthy, or athletic populations. Shorter durations of stretch (<60 s) can be performed in a preexercise routine without compromising maximal muscle performance.

The effects of static stretch on muscle and tendon mechanical properties and muscle activation were studied in fifteen healthy human volunteers. Peak active and passive moment data were recorded during plantar flexion trials on an isokinetic dynamometer. Electromyography (EMG) monitoring of the triceps surae muscles, real-time motion analysis of the lower leg, and ultrasound imaging of the Achilles-medial gastrocnemius muscle-tendon junction were simultaneously conducted. Subjects performed three 60-s static stretches before being retested 2 min and 30 min poststretch. There were three main findings in the present study. First, peak concentric moment was significantly reduced after stretch; 60% of the deficit recovered 30 min poststretch. This was accompanied by, and correlated with (r = 0.81; P < 0.01) reductions in peak triceps surae EMG amplitude, which was fully recovered at 30 min poststretch. Second, Achilles tendon length was significantly shorter during the concentric contraction after stretch and at 30 min poststretch; however, no change in tendon stiffness was detected. Third, passive joint moment was significantly reduced after stretch, and this was accompanied by significant reductions in medial gastrocnemius passive muscle stiffness; both measures fully recovered by 30 min poststretch. These data indicate that the stretching protocol used in this study induced losses in concentric moment that were accompanied by, and related to, reductions in neuromuscular activity, but they were not associated with alterations in tendon stiffness or shorter muscle operating length. Reductions in passive moment were associated with reductions in muscle stiffness, whereas tendon mechanics were unaffected by the stretch. Importantly, the impact on mechanical properties and neuromuscular activity was minimal at 30 min poststretch.

Although similar ROM increases occur after Iso and SS, changes in muscle and tendon stiffness are distinct. Concomitant reductions in muscle and tendon stiffness after CR stretching suggest a broader adaptive response that likely explains its superior efficacy in acutely increasing ROM. Although mechanical changes appear tissue-specific between interventions, similar increases in stretch tolerance after all interventions are strongly correlated with changes in ROM.

Blazevich AJ, Cannavan D, Waugh CM, Miller SC, Thorlund JB, Aagaard P, Kay AD. Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans. 117: 452-462, 2014. First published June 19, 2014 doi:10.1152/japplphysiol.00204.2014.-The neuromuscular adaptations in response to muscle stretch training have not been clearly described. In the present study, changes in muscle (at fascicular and whole muscle levels) and tendon mechanics, muscle activity, and spinal motoneuron excitability were examined during standardized plantar flexor stretches after 3 wk of twice daily stretch training (4 ϫ 30 s). No changes were observed in a nonexercising control group (n ϭ 9), however stretch training elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM (n ϭ 12). Only a trend toward a decrease in passive plantar flexor moment during stretch (Ϫ9.9%; P ϭ 0.15) was observed, and no changes in electromyographic amplitudes during ROM or at end ROM were detected. Decreases in H max:Mmax (tibial nerve stimulation) were observed at plantar flexed (gastrocnemius medialis and soleus) and neutral (soleus only) joint angles, but not with the ankle dorsiflexed. Muscle and fascicle strain increased (12 vs. 23%) along with a decrease in muscle stiffness (Ϫ18%) during stretch to a constant target joint angle. Muscle length at end ROM increased (13%) without a change in fascicle length, fascicle rotation, tendon elongation, or tendon stiffness following training. A lack of change in maximum voluntary contraction moment and rate of force development at any joint angle was taken to indicate a lack of change in series compliance of the muscle-tendon unit. Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance) and both muscle and fascicle elongation rather than changes in volitional muscle activation or motoneuron pool excitability. J Appl Physiol