Does stretch training induce muscle hypertrophy in humans? A review of the literature

Abstract

Stretch training is widely used in a variety of fitness‐related capacities such as increasing joint range of motion, preventing contractures and alleviating injuries. Moreover, some researches indicate that stretch training may induce muscle hypertrophy; however, studies on the topic have been primarily relegated to animal and in vitro models. The purpose of this brief review was to evaluate whether stretch training is a viable strategy to induce muscle hypertrophy in humans. An extensive literature search was performed using PubMed/MEDLINE, SciELO and Scopus databases, using terms related to stretching and muscle hypertrophy. Only human trials that evaluated changes in measures of muscle size or architecture following training protocols that it was performed stretching exercises were selected for inclusion. Of the 10 studies identified, 3 observed some significantly positive effects of stretch training on muscle structure. Intriguingly, in these studies, the stretching was carried out with an apparatus that aided in its performance, or with an external overload. In all studies, the subjects performed stretching at their own self‐determined range of motion, and no effect was observed. Of the 5 available studies that integrated stretching into a resistance training programme, 2 applied the stretching in the interset rest period and were the ones that showed enhanced muscle growth. In conclusion, passive, low‐intensity stretch does not appear to confer beneficial changes in muscle size and architecture; alternatively, albeit limited evidence suggests that when stretching is done with a certain degree of tensile strain (particularly when loaded, or added between active muscle contractions) may elicit muscle hypertrophy.

Effect of a 10-Week Stretching Program of the Triceps Surae Muscle Architecture and Tendon Mechanical Properties

“…These results corroborate the study from Moltubakk, investigated the effect of the stretching after 24 weeks and found no significant differences in FL and PA. It is important to consider that the intensity applied in this study was low and according to a recent review [26], discussed that exercise's intensity it is more important to induce structural adaptations with the stretch training. Thus further studies are needed to verify whether different intensities long-term stretching are efficient to generate adaptations in the FL and PA.…”

“…Based on recent compilation reviews [6,26], only the study [22], analyzed muscle and tendon adaptations to stretching for a long period of stretching stimulation (more than eight weeks). However, no significant changes were observed for tendon stiffness and gastrocnemius medialis FL, suggesting that over a period of time between 3 and 8 weeks, the main contributor to muscle extensibility is a change in the subject's sensation.…”

Placing Greater Torque at Shorter or Longer Muscle Lengths? Effects of Cable vs. Barbell Preacher Curl Training on Muscular Strength and Hypertrophy in Young Adults

“…Moreover, this experiment was carried out in untrained young adults and results cannot be generalized to other populations of different ages, or training statuses, given that responses to training are influenced by such factors [ 1 , 24 ]. Finally, muscle thickness was assessed only at the mid-portion of the biceps, and considering that training-induced hypertrophy may be inhomogeneous [ 1 , 17 , 31 ], the assessment of more muscle sites (e.g., proximal and distal; short and long heads of the biceps separately) might provide greater insights regarding the hypertrophy responses.…”

“…This seems to most likely occur by altering joint moment arm, providing greater mechanical tension [13,16], which has been shown to be important for muscle growth [1]. Given that muscle tends to grow where it experiences the highest levels of tension, and more sarcomerogenesis may occur to adapt the muscle to receive high torques when stretched [16,17], greater hypertrophy in training with elongated muscle would be plausible.…”

Pre-stretching of the Hamstrings Before Squatting Acutely Increases Biceps Femoris Thickness Without Impairing Exercise Performance

“…Although the concentric phase of the squat involves hip extension, squatting does not result in significant hypertrophy of the hamstrings (Bloomquist et al, 2013;Kubo et al, 2019), conceivably due to the relative absence of change in the muscle's length-tension curve during the movement (Sugisaki et al, 2014). It is speculated that interset stretching to a certain level of mechanical tension results in muscle hypertrophy (Nunes et al, 2020), while acute, passive stretching could decrease performance during maximal contractions (Magnusson and Renström, 2006).…”