Increasing Strength and Power Through Flexibility and Stretching

By: Matt Sleeper

Yes, stretching.

Athletes can, and often do, possess more potential for strength than they are currently able to realize. Muscular strength is effected by three main factors:

1) Muscle cross-section area (size); This is how much the muscle fibers overlap each other during relaxation, the more fibers overlapping, the greater potential for force production.

2) Type of muscle fibers; There are 2 main types of fibers, type I and type II. Type I fibers are long and lean, capable of repeating motion for long periods of time without fatigue, but only able to produce small amounts of force. Type II are just the opposite, shorter and bulkier, not able to contract for long periods of time but able to produce large amounts of force quickly. These muscle types are developed based on the types of stimulus they are exposed to (types of workouts an athlete does).

And 3) Neuromuscular efficiency; This is essentially the ability for an athlete’s nerves to tell the muscles to contract efficiently.

For this blog post I am going to focus on the third aspect, because it is something that can be changed fairly quickly within an athlete. While true muscular adaptations (hypertrophy and fiber growth) take 3-5 weeks to attain, neuromuscular adaptations occur within days.

The key concept here is something called “length tension relationships” within an athlete’s muscles. Think of your muscles as ropes and your joint (where the movement happens) as a pully. If you pull on one side of a rope on a pully, the other side moves, but if there is tension on the other side of the pully like a piano, the rope requires a lot more force to move.

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This applies to muscular anatomy because major muscle groups have an agonist (the muscle you are trying to move) and an antagonist (the muscle opposite of said muscle). If you extend your arm, and actively flex your bicep (the agonist), your arm will only flex if you relax your triceps (the antagonist). If you actively flex both biceps and triceps simultaneously, your arm wont flex or extend, it will stay in place. You are probably thinking “no duh, obviously” but the crux here is that muscles in our bodies are being contracted with different intensities all the time without us realizing it. This is obvious when we think about our heart that beats to pump blood and diaphragm that helps us breath, but less so when we think about skeletal muscle. The decision to flex a muscle is taken away from us by what is called “stretch reflex”. These little organs in our muscles send constant signals through our nerves through our spinal cord, which, never make it to our brains. Think of it as a toy race car track, the signals (or cars) go around in a path from our flexed muscles to the spinal cord then right back, because our brains don’t need to be told that a muscle is flexed constantly.


You might say, “I’m not flexing any muscles right now, I’m sitting, chillin”. Just because you are not constantly flexing a muscle, doesn’t mean it isn’t flexed. If you are sitting, your hip is flexed, thus your hip flexors (ilio-psoas and rectus femoris) are flexed. It is not just muscular contraction that sends signals between muscles, it is also the position of our muscle fibers. If muscle fibers are close together (usually this occurs in a flexed position) then those little organs are circling through our spine to the antagonist muscle to tell it to relax without us telling them to do that! This is what causes “altered reciprocal inhibition”, one muscle is flexed, causing the other muscle to relax, because of these neural signals that don’t even reach our brain.

That’s the science of it, how does it affect you? Well, think about how long you sit each day, each second you sit that signal from the little organs in your hip flexors get sent through your spinal cord to your hamstrings and glutes telling them to relax, so they are in a constant state of relaxation. Those signals don’t stop once you stand up, they don’t even stop once you start consciously engaging those hamstrings and glutes. Ever tried to squat with relaxed glutes and hamstrings? Me neither, we would just crumple to the ground. But, similar to when you were flexing and extending your arm earlier (don’t lie, I know you were) there are various degrees to which you can consciously flex one muscle and relax the other. Same principle applies, though the tension on your hip flexors isn’t so great that it prevents complete hamstring and glute contraction, it is still great enough to prevent maximal contraction, thus reducing the ability to produce force. (Beachle & Earle, 2008)

So how do we fix it? By stretching. Chronic flexion gets an athlete in to this situation, chronic extension can get them out. What I mean by that is even if you do spend all day sitting, that’s ok, you can spend a good amount of time stretching those muscles that are in a flexed position all day to combat these altered muscular relationships. Stretching the muscles in question each day 10-15 minutes is enough to prevent and even reverse these effects, but I recommend you split it up in to multiple stretch sessions (Cherry, 1980). Once the antagonists become lengthened again (in this case the psoas and rectus femoris), those inhibitory signals will slow down and allow the agonists (hamstrings and glutes) to be able to contract more efficiently.

Try it out! Spend 3-5 minutes in an active stretch of your hip flexors before squatting. Take a knee and execute that Samson stretch while simultaneously flexing your glute and hamstring. You will feel the difference immediately. A few minutes spent stretching before a workout will not return the length tension relationships to normal, but will have a positive, yet temporary, effect on slowing down the inhibitory signals being sent to your hip extensors. A constantly pursued flexibility program is the best approach to correct muscle imbalances. (Cipriani et al, 2003.)


Get out there and get flexible!


(Maybe not that flexible)


Beachle, T.R. Earle, R.W. Essentials of Strength Training and Conditioning, Third Edition. Human Kinetics. 2008.

Cherry, D.B. Review of physical therapy alternatives for reducing muscle contracture. Phys Ther 60: 877-881. 1980.

Cipriani, D.B. Abel, and D. Pirrwitz. A comparison of two stretching protocols on hip range of motion: Implications for total daily stretch duration. J Strength Cond Res 17(2): 274-278. (2003)

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