Strength Exercises for Flexibility

At first glance, the link between strength training and flexibility isn't obvious. Some even believe that strength training reduces flexibility. That's not correct. When done properly, strength training can actually improve your flexibility.

Train through the full range of motion

Whether you train with machines or free weights, make sure you always perform the exercise through the full possible range of motion. In terms of the muscle, this means loading it from its most shortened to its most stretched position. Also make sure you hold the weight at the turning point – in other words, in the maximally shortened or maximally stretched position – for 2 seconds each time. If you do the exercise for 6 – 10 reps, you'll spend a total of around 12 – 20 seconds in the maximally stretched position. That should be enough to trigger the corresponding change in muscle length. Through this length training, you'll be able to produce force at a relatively longer muscle length (see also our blog post on the strength curve).

This type of exercise requires strong passive structures (bones, tendons, ligaments and cartilage), because the forces involved must be absorbed even in these extreme positions.

Stretching

Stretching (that is, no force is produced at a long muscle length) doesn't trigger any change in muscle length (assuming you don't stretch for 24 hours straight). You can think of stretching as a form of relaxation. The greater range of motion you get from stretching is more likely due to the muscle spindles reacting later and triggering pain. Stretching also doesn't strengthen these passive structures to the same extent, which can lead to injuries when forces occur.

Definition: muscle spindle (source: Wikipedia)

Muscle spindles are sensory organs within the muscles that detect the stretch state of the skeletal muscle. Muscle spindles consist of five to ten striated muscle fibres – one to three millimetres long in humans – surrounded by a connective tissue sheath. Between the muscle fibres of the leg extensor (quadriceps femoris) in the thigh, five hundred to a thousand muscle spindles are embedded, each up to ten millimetres long. The more muscle spindles a muscle contains, the more finely the movements associated with it can be coordinated.