Flexibility in the body can be determined by range of motion (ROM), which occurs at the joint. This can be affected by a number of issues, including connective tissue structure, activity, age and gender. The range of motion is specific to each of the body’s joints anatomy.
Range of motion can be measured through flexibility, which has two components: static and dynamic. Static flexibility is the amount of movement a joint and its surrounding muscles have during a passive movement e.g. a calf stretch (1,2). You can perform static stretches using a partner, an external force or a machine as they don’t need any voluntary muscle action from the individual.
Dynamic flexibility requires voluntary muscle action and is the available range of motion during active movements e.g. leg swings. The range of motion of a joint is generally greater in dynamic movements than with static positions (3).
Factors Affecting Flexibility
There are certain factors that will affect flexibility. There are anatomical factors, such as joint structure, age and gender, which cannot be altered significantly through training. Then there are activities, related to exercise, such as activity level, resistance exercises, stretching exercises, which can improve flexibility.
The structure of the joint determines range of movement (4). There are different joints in the body e.g. ball and socket (shoulder) and hinge (knee). The type of joint, the joints’ articulating surfaces and soft tissues (muscles, tendons and ligaments) surrounding the joint, all affect range of motion.
Age and Gender
Young people tend to be more flexible than older people (8) and females more flexible than males (5). The difference in flexibility in young men and women could be down to the structural and anatomical differences and the type of activity that is performed and to what extent. Fibrosis is the thickening and scarring of connective tissue and is a process that happens when people get older. This could be down to lack of physical activity, injury and the tendency to use less of the available range of motion during movement.
Tendons, ligaments, fascial sheaths, joint capsules and skin may limit range of motion (2). Elasticity is the when the muscle can return to its original length after a passive stretch. Plasticity is when the muscle can gain new and greater length after passive stretches (7). Elasticity and plasticity of the connective tissue are other factors, which can affect/determine flexibility (7). Performing stretching exercises can take advantage of the plastic potential of the connective tissues.
Resistance Training with Limited Range of Motion
Resistance training may increase flexibility if it done correctly and with proper technique (6). Using heavy resistance and a limited range of motion may decrease range of motion at that particular joint (2). So that range of motion does not get lost, exercises should be done with a full range of motion of all joints involved, maintaining correct technique (9).
Large amounts of muscle may affect range of motion by decreasing joint movement. Someone with large biceps (front of upper arm) and shoulders, may experience difficulty when stretching the triceps (back of upper arm) (2).
Active people tend to be more flexible than inactive people (5). This can be true if a person performs activities such as resistance training using a full range of motion, functional activities and flexibility exercises, both static and dynamic. Activity alone will not improve flexibility; static and dynamic exercises must be implemented if flexibility at a joint is to be maintained or improved.
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