Every morning, without fail, my dog starts the day with a mini yoga session. He does a down dog followed by an up dog and then sits in his doggy version of child’s pose waiting for someone to get his breakfast. Sounds like heaven, doesn’t it? But, it got me thinking about the role of stretching. There’s so much conflicting advice out there. Whilst working as a physio, I wrote an article about exactly this topic, so I thought I’d dig it out and have a re-cap.
The important anatomy/physiology bit
To fully understand if, or more likely, why you need to stretch, it’s important to be aware of some basic human anatomy and physiology.
A skeletal muscle, such as your hamstrings, quadriceps and biceps etc, is made up from individual muscle fibres bundled together and contained by connective tissue. They are usually anchored to a bone at each end by tendons and normally cross at least one joint so that when they contract, your joint moves. For example your hamstrings originate from your ischial tuberosity (the bony bit in your bum that you sit on) and attach just below your knee, meaning that when they contract they will cause your knee joint to bend. All good so far?
Muscles resemble something similar to those Russian dolls. You know, the ones where if you open the biggest one there is a smaller one inside and so on. Each muscle is made up of bundles of muscle fibres which in turn are made up of myofibrils. The contractile element of the muscle is called a sarcomere and these make up the myofibrils. Sarcomere’s consist of thick myofilaments called myosin and thin ones called actin. These thick and thin myofilaments lie end to end and OVERLAP. The overlap is important.
So to quickly recap, the ‘russian doll pecking order’ starting from the biggest, is muscle, muscle fibre, myofibril, sarcomere, myofilament (myosin and actin).
Few!! Almost there….
The Sliding Mechanism
When you stretch a muscle, the myosin and actin slide apart and the area of overlap between the thick and thin myofilaments decreases, improving the overall length of the muscle fibre. This is important. Muscles don’t stretch in the same way that a piece of chewing gum does, they only ‘appear’ to stretch. Humour me, and interlock your fingers in front of you. Now slide them apart slightly so that the finger tips of one hand are in line with the knuckles of your other. That’s how myosin and actin work together to increase muscle length, by sliding NOT stretching. Muscles do have an element of elasticity, but it’s primarily this sliding mechanism that is responsible for the change in length.
This is particularly useful to know when rehabbing a muscle strain or tear. For the sliding mechanism to work effectively, fibres need to line up next to each other. Think of uncooked spaghetti lying neatly in a packet. During recovery from an injury, new muscle fibres will mature and remodel. Prior to this phase though, the new fibres are disorganised and look something akin to cooked spaghetti dropped on the floor, kind of like spaghetti junction, all mismatched and higgledy piggledy. Not much potential for the sliding mechanism to work efficiently. This is why muscles can feel stiff and tight after an injury, like a calf strain for example.
Gradually stretching the muscle is important during this stage in order to tease the fibres into a more uniform pattern. This improved alignment will optimise the sliding mechanism, restoring the muscles ‘length’. Without it, the muscle is prone to tear when forced to lengthen or contract suddenly. For example when you progress from casual jogging to sprinting after a calf injury. Think about pulling the spaghetti apart in that cooked, mesh form, as opposed to the nicely aligned version. Disaster!
I know that was a bit heavy going, but if you understand what’s happening to your muscles when you stretch, it helps you to answer the when and how questions.
Stretching after exercise
When you have used a muscle and it has repeatedly contracted, for example my calfs after a 6x800m track session this morning, then the overlap between the thick and thin myofilaments will have increased over and over again. This shortens the overall length of the muscle and is partly why you can feel tight after training. It stands to reason then, that stretching after exercise to restore normal length makes complete sense. One word of warning though. After an intense session, your muscles may have small microtears from such a high level of exertion. If you stretch hard immediately afterwards then you are in danger of making these small tears bigger. I would therefore only ever stretch lightly after a big session, and maybe separate your stretching sessions to a different time of day.
Stretching before exercise
Prior to exercising however, is a different story. Research shows that static stretching (the type where you hold a particular stretch for a given period of time) causes a muscle to fatigue. Specifically, force plate readings for the amount of power that the muscle can generate can be reduced by up to 20%, and this can last for half an hour. If you are then planning to work a muscle that you have already fatigued by holding a static stretch, then your performance may be reduced as a result. Not ideal.
For this reason, dynamic stretching (leg swings, lunges and spine twists), rather than static stretching is advised prior to training. This warms up the myofilament sliding mechanism, preparing the muscle for exercise without the fatigue.
How much stretching is enough?
To make permanent changes to a muscle length, stretching just before and after exercise is unlikely to be enough. The difficulty here is that the research is so varied it is hard to quantify what is. In an ideal world you would stretch a muscle every day to make the most efficient improvement, but really?? In the real world, if you have a particular problematic area then I would focus on stretching it daily, or even better several times a day until you have restored the full length. Like my dog, little and often is arguably the best approach!
It’s also worth remembering, that whilst this article focusses on muscle length, clearly other things can affect flexibility, such as joint range of movement or restriction in the joint capsule.
As a final point, any changes to your current regime, should also be introduced slowly. One article found that if you took runners who never stretch and make them stretch daily, their injury rate was just as high as the group of runners who stretched daily and were forced to stop. So you can see the problem with making recommendations when it comes to frequency. My best advice here, is to experiment. Don’t be frightened to try new things. Make sure you make any changes gradually, but get to know your own body and find what works for you. The reason for the inconsistencies in the literature is very likely, as always, that every body is different.
To sum up then…
- Technically muscles slide rather than stretch
- Warm up with dynamic rather than static stretching prior to training to avoid potential muscle fatigue.
- Gentle static stretching after training is fine but don’t overdo it, particularly after a hard session.
- To improve muscle length you really need to be stretching daily, though exact amounts is likely to differ between people. Little and often is a good approach.
- Get injuries, or persistent tightness assessed by a Chartered Physiotherapist for more specific individual advice.
So basically, just be more dog! And if you can find someone to willingly make your breakfast while you sit in child’s pose, then please let me know how you’re doing it, because I’m clearly doing something wrong!