You might hear that stretching and being flexible can prevent you from injury. There is a great amount of information on the net about stretching exercises and how to increase flexibility.
However, did you know that being too flexible, especially at the joints, can cause you trouble?
This article will discuss about….
1. joint range of motion and the relationship with flexibility.
2. how excessive flexibility do harm to your body.
Facts about range of motion
Range of motion (ROM) refers to the range of mobility your muscle or joint can move, how far can you stretch it. There are two categories of ROMs.
- Active range of motion(AROM)
The amount of mobility you can actively move your body parts. For example, raising your hands above your head to the maximal angle.
This mainly includes the flexibility of muscles and tendons.
- Passive range of motion(PROM)
The amount of mobility you can passively be stretched by someone else. For example, when you are doing the splits, your coach is there to help you split further.
This mainly includes the flexibility of muscles, tendons, joints and ligaments.
It is good to have fine muscle/tendon flexibility and can be improved by stretching exercise. On the flip side, excessive joint range of motion (passive range of motion) can make the joints unstable and vulnerable.
Joint laxity test
Test to see if you have unstable joints.
- Bend your little finger backwards.
You get 1 point if your little finger can be bent 90 degrees, 2 points for both hands. (Figure 1)
- Bend your thumb toward your wrist.
You get 1 point if your thumb can touch your forearm, 2 points for both hands. (Figure 2)
3. Straighten your elbow to the maximum degree, you can add pressure with the other hand.
You get 1 point if your elbows have a 10 degree of hyperextension, 2 points for both sides. (Figure 3)
4. Straighten your knees to the maximal degree.
You get 1 point if your knees have a 10 degree of hyperextension, 2 points for both sides. (Figure 4)
5. Bent forward with your knees fully extended so that the palms of the hands rest flat on the floor.
You get 1 point if your palm can fully touch the ground, 2 points for both.
A score of over 4 (including 4) represents ligament laxity and joint hyper-mobility.
What can go wrong if I have a score over 4?
There are two circumstances:
- You have joint and ligament laxity but have strong muscle and tendon to hold the joints in place. The chance of injury is small.
- You have joint and ligament laxity and weak muscles to provide stability. You may have higher chance of injuring yourself during daily and sport activities.
I. Anterior cruciate injury (ACL injury): The chances of injury in females compare with males are 2–6 times.
II. Ankle sprain
III. Shoulder joint instability: It can cause damage to tissues around the shoulder girdle.
IV. Wrist joint degeneration/ spur formation: Excessive movement occurs in the wrist bone, distal radius and ulna, causing unwanted pressure in the bones.
V. Scoliosis: Joint laxity occurs at the spine and can be deformed by poor posture.
What affects the passive range of motion?
Sex is the main factor! Flexibility in females are mainly greater than males.
Factors between sex that make differences in flexibility:
- Ligamant circumference:
The ligament circumference is greater in male compared with females, making the joints stronger and firmer.
- Collagen composition:
The composition of type III collagen in females is greater than males, providing more elasticity in the ligaments and joints.
- Estrogen hormones：
When female grows into puberty, the ovary secretes estrogen.
A previous research reported that joint elasticity between gender is the same during childhood, however joint elasticity increases in females after puberty. Estrogen makes the ligament soft and more elastic, therefore increase the passive range of motion. Estrogen peaks during ovulation and corpus luteum, the chance of sport injury is higher.
Relaxin is a pregnancy hormone, it helps the pelvic to create space for the fetus. The hormone maintains at a concentration even after 6 month postpartum.
Men has more concentration of progesterone than women. Studies reported that the anterior cruciate ligament in men is stiffer than women. This hormone inhibits the performance of relaxin, decreasing the passive range of motion.
Be sure to check out the next article about exercising with ligament laxity and what should you do to prevent injury.