Women have Greater Stretch Tolerance

Anecdotally, we all know men are much stiffer than women. I mean you’re your dad or husband or even your 11-year-old boy bend over and touch their toes…they aren’t going far! Unfortunately, we don’t know why this is! Some think it has to do with muscle fiber distribution or perhaps it is simpler and that men don’t monitor their health as well as women. Nonetheless, women appear to have more extensibility.

Now, many think extensibility is simply a product of muscle length, but other factors, some as simple as stretch tolerance determine extensibility.

So, we think men are stiffer than women, but we aren’t sure what makes them stiff…time to find out!

Research on Hamstrings Extensibilty

A group of ninety participants (M=45, F=45; ~23.4 years) without a history of hamstrings injury underwent a straight leg raise test. Also, hamstrings stiffness and stretch tolerance were tested.

Women had 9.9 degrees more straight leg raise mobility than men. Subjected reported sensation was 16 mm lower in women. Mechanical force was also significantly less in women than men.

So…What is the Difference Between Men and Women?

Overall, the women had

1. Lower passive stiffness through a common range of motion
2. Better stretch tolerance
3. Greater hamstrings extensibility

Also, stretch tolerance, not passive stiffness, was a significant predictor of total hamstrings extensibility for men only.
This is an interesting finding as many report women have higher pain sensitivity (Wiesenfeld-Hallin 2005; Wise 2002; Robinson 2001).

The researcher’s note [watch out science time]:
“Higher pain scores in men may be associated with between sex differences in afferent feedback, particularly of the group III afferents. Group III afferents, also known as Aδ fibers, are thinly myelinated fibers and have free nerve endings within the connective tissue of skeletal muscle. Group III afferents primarily transmit information about mechanical stimuli in muscle, and in combination with group IV afferents are activated by nociceptive stimuli (e.g. bradykinin) and thus are the proposed source of pain in skeletal muscle. Research examining discharge properties of group III afferents in response to constant stretch is equivocal, but responses do increase as tension developed in a muscle increases. It is not clear whether the pain scores reported in this study, particularly those reported by men, are mediated by increased group III afferent discharge rates. Moreover, there is no evidence examining group III afferent discharge properties during a stretching task where mechanical tension within the muscle is gradually increasing, or comparing group III discharge properties between sexes. Concomitant to nociception potentially explaining between sex differences in stretch tolerance is consideration for whether pain is causing a reflex response that impairs hamstrings extensibility in men (Marshall 2014)”.
Simply put, men may have a higher pain tolerance with certain feedback mechanisms, but possibly not during stretching. During stretching, group III afferents (the Aδ fibers) have free nerve endings in the skeletal muscle. These afferents release a substance called bradykinin which may also contribute to the higher pain scores in men. Nonetheless, we need to learn more about the different types of pain during different activities (stretching, lifting, running, etc.).

Practical Implication

Women have a greater stretch tolerance than men in their hamstrings. Unfortunately, we don’t know if having greater hamstrings stretch tolerance is beneficial. If seeking improved hamstrings extensibility, consider the following method of improving your stretch tolerance.