Mobility is the amount of motion available at a joint or series of joints. Range of Motion (ROM) is the degree of rotation available at a joint. In contrast, Flexibility is the extensibility of periarticular structure (ie: muscle, fascia, tendon, joint structures). Flexibility is only one factor that contributes to ROM and mobility. (NSCA 2012)
A degree of mobility is required to accomplish any physical task, whether a daily activity or sport. Specific inflexibilities (hypomobility) may contribute to increased risk of injury (NSCA 2012). Also see Common Flexibility Insufficiencies. However, greater mobility may impair performance in sports that do not require a high degree of flexibility such as running. Runners with less flexibility are actually more efficient at running (Jones 2002). Conversely, too much mobility (hypermobility) may decrease joint integrity (NSCA 2012) particularly if the accompanying muscular and/or join structures are not strong enough to compensate for the joint’s laxity under stress.
Optimal mobility spans within an idea range depending upon a particular performance task. Altering mobility within this range will not affect performance or the potential for injury. (NSCA 2012)
Intense static stretching may also temporarily reduce maximum force production. The loss of voluntary strength and muscular power may last up to one hour after the static stretch (Evetovich 2003, Young 2003). However, performers who participate in activities that require more than average flexibility (eg: gymnasts, dancers, figure skaters) may still find particular stretch exercises to be beneficial to their overall performance despite the temporary loss of strength and power..
With the exception of those with genetic joint hypermobility syndromes, flexibility is not a general characteristic in normal people, but rather join specific. Therefore, no one test assess general flexibility. In addition, joints typically do not act in isolation. Rather they function as part of a kinetic chain (NSCA 2012). Therefore, a joint may have different range of motion depending upon either an adjacent joints positioning (hip flexion with knee extended or flexed) or its own alternative positioning (eg hip flexion while internally or externally rotated).
Range of Motion (ROM) can be assessed actively (AROM) or passively (PROM). AROM involves the subject moving their own joint typically using antagonist musculature, whereas PROM involves and an evaluator or outside force moving the subjects joint. since a ROM requires the muscles to generate sufficient torque, it may not be possible to differentiate between limited ROM due to insufficient flexibility versus weakness or pain. This is why the American Medical Association recommends testing both a ROM & PROM in patients suspected of physical impairment. (NSCA 2012)
For these reasons, flexibility assessments and the resultant mobility programming should be customized to an individual’s needs and their objectives. An assessment can be conducted to determine which muscles/joints should and should not be stretched, as well as how they should be stretched.
A composite flexibility test measures multiple joint movements in a non-functional patterns pattern. The most popular composite test is the sit and reach test. Other composite tests include shoulder lift test, fingertip-to floor test, and the Apley scratch test. The limitation of these tests are that they do not distinguish the contributions each join makes toward the movement.
Sit & Reach
The Sit & Reach Flexibility Test is easy to administer and is an indirect measurement of flexibility as it is recorded as distance rather than degrees. It is a composite test (measuring multiple joints movements) and has low test validity (NSCA 2012). Although it appears to be more valid for hamstring flexibility, both spine and hamstring flexibility are assessed (Minkler & Patterson 1994). This means that someone with poor hamstrings flexibility may not be assessed correctly if they can compensate their reach through greater than average spine or shoulder mobility.
The higher scores of the Sit & Reach tests can be misinterpreted as being adequate or ideal, particularly if the subject exhibits hypermobility through the spine and/or shoulder girdle. In addition, the Sit & Reach test cannot assess for bilateral flexibility asymmetries. Also see Sit & Reach Box.
Functional Movement Screening
Flexibility issues affecting functional movement can be screen for through the Functional Movement Screening (FMS). The FMS will allow for a more comprehensive screening for important flexibility and mobility deficiencies with arguably superior hamstrings flexibility and shoulder mobility assessments.
In addition to testing for flexibility and mobility in various joints and movements, the FMS already includes hamstring and shoulder flexibility tests, arguably superior to the Sit & Reach and Shoulder Flexibility tests.
- Active Straight-Leg Raise
- Hamstring flexibility only
- Shoulder Mobility
- Shoulder extension, flexion, internal rotation, external rotation
- Shoulder girdle upward and downward rotation, protraction, retraction
Once an asymmetry or deficiency is detected through the FMS, more precise measurements can be used. Specific ROM assessments can pinpoint insufficiency. Likewise, particular postural issues may also be scrutinized with corresponding flexibility tests.
Isolated ROM versus Muscle Length Tests
Isolated tests involve assessing a single joint with biarticulate muscles in the shortened position through adjacent joints. For example, when testing hip flexion or hip extensor flexibility, the knee is also flexed not to limit the range of motion via the articulate hamstrings. Isolated ROM testing allows for maximum range of motion for a specific joint. (NSCA 2012)
Muscle length tests involve assessing flexibility of biarticulate muscles. For example, when testing hamstring flexibility, the hamstring is stretched across both joints by extending the knee prior to or after flexing the hip. (NSCA 2012)
Evetovich TK, Nauman NJ, Conley DS, Todd JB (2003). Effect of static stretching of the biceps brachii on torque, electromyography, and mechanomyography during concentric isokinetic muscle actions. J Strength Cond Res. 17(3):484-8.
NSCA (2012). NSCA's guide to tests and assessments, Human Kinetics. pg 275-315.
Jones BH (1997). The role of medical surveillance and research in army injury prevention. American College of Sports Medicine Conference abstract, Denver.
Minkler S & Patterson P (1994). The validity of the modified sit-and-reach test in college-age students. Research Quarterly for Exercise and Sport. 65, 189-192.
Young WB, Behm DG (2003). Effects of running, static stretching and practice jumps on explosive force production and jumping performance. J Sports Med Phys Fitness. 43(1):21-7.