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BPK 143 Lecture Notes - Stretching, Stretch Reflex, Lumbar Vertebrae

Biomedical Physio & Kines
Course Code
BPK 143
Tony Leyland

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- Flexibility is the range of motion (ROM) around a joint
- Stretching is a component of exercise programs
- The 120-minute run test is also known as the Copper Test
- Dr.Cooper suggests that, by the time you are 50 years old, 50% of your training should be resistance
- Benefits of stretching include
1) Joint health
2) Reduction of low-back pain and injuries
3) Reduction of DOMS
4) Pain relief
5) Athletic performance
6) Improve posture
7) Relaxation
- ROM must be adequate for daily activities
- Some people have a greater ROM because of the way their bones are shaped
- Different joint structures allow different ranges of motion
- Normal activity and exercises through full ROM reduce the likelihood of a muscle shortening, and a well
designed stretching program can actually lengthen the muscles
- With a stretching program, sarcomeres are laid down in series, increasing muscle length
- The nervous system plays a role in what range of motion you can achieve by regulating muscle
- Reciprocal innervations: takes place when a muscle contracts, inhibiting contraction of antagonist
muscles; for example, when hip flexors contract, hip extensors relax
- Muscle spindles: these are sensory nerve endings in the muscle that detect muscle length change and
rate of change. Force applied to a muscle stimulates muscle spindles, which activate protective reflexes
and result in muscle contraction (such as the knee jerk response to neurological testing procedures)
- Golgi tendon organ: a tendon organ that is located at the insertion where the muscle fibres insert into
the tendon. When the muscle generates force, the sensory terminals are compressed and a signal is
sent to the spinal cord which signals the stretch reflex

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- When contracting hip flexors in a hamstring stretch, initially the muscle spindles in the hamstring fire
and the muscle contracts to protect it from an excessive stretch
- If the stretch is hold long enough, the stretch reflex diminishes and a subject can stretch the muscle out
- Reason why in order to get the full benefit from static strength, you must hold it for more than 20
Static stretching
- This method encompasses various techniques that lengthen a muscle to an elongated position (to the
point of discomfort), where it is held in position statically for 20-40 seconds
- During the holding period, participants may feel a mild discomfort in the muscles
- When performed properly, static stretching lessens the sensitivity of tension receptors, which allows
the muscle to relax and be stretched to greater lengths
- Passive stretching: an external force, such as gravity or push from a partner, moves the limb into the
new position
- The more force exerted on the limb, the less time it will take to get a substantial stretch
- As long as the stretch force is applied gradually, the risk of injury is low
- Active stretching: occurs when you move your limb into position by contracting the antagonist muscle:
no external force is used.
- Reduce the potential for injury
- Ballistic stretching: momentum from body parts propels the muscle into an extended range of motion,
exceeding an individuals static, passive stretching ability. These types of stretches are usually initiated
by quite vigorous movements
- Dynamic stretching: the movement into the stretch position is more controlled and the fully stretched
position is often held for one or two seconds. Dynamic stretching involves lower limb belocities than
ballistic stretching.
- Dynamic stretching is important during warm-up for sports involving dynamic activity
Benefits of ballistic stretching include:
1) It develops dynamic flexibility better. Ballistic stretching adheres to the principle of specificity by
stressing muscle and connective tissues in manners in which they will be used

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2) It has been shown to be effective, although more research is definitely needed
3) It can be performed in unison during team warm-ups, which can help to promote team camaraderie
4) It can be less boring than static stretching
- More is not always the best
- The ideal advice lies somewhere in the middle if flexibility is viewed on a continuum
- No flexibility ( anklosis, a stiffness or fixation of a joint through surgery or disease) is highly undesirable
- Extreme flexibility or instability can lead to dislocations, poor coordination, and increased risk of joint,
muscle and connective tissue injury
- Evident that support the notion that stretching can prevent injury is lacking
- Those possessing high flexibility and low flexibility, have been shown to be a higher risk of injury
- Low flexibility may increase the risk of muscle and tendon injury
- High flexibility may increase the risk of ligament and cartilage injury
- Warming-up prior to activity is essential, but static stretching should not be part of that warm-up
- Five reasons why stretching before exercise would not prevent injuries
1) In animals, immobilization or heating-induced increases in muscle compliance (stretch-ability)
causes tissues to rupture more easily
2) Stretching before exercise should have no effect for activities in which excessive muscle length is
not an issue , such as jogging
3) Stretching wont affect compliance during eccentric activity, when most strained are believed to
4) Stretching can produce damage to the structures within the muscle fibre
5) Stretching appears to mask muscle pain in humans, and this may increase chances of excessive
exercise effort
- Caution must be used when doing static stretching perior to hard training as it may weaken the muscle
leaving it prone to injury
- Warm-up is designed to prepare for the activity to come, reduce the chance of injury, and improve
performance, NOT improve flexibility
- The warm-up is not about training any particular component of fitness
- Increased compliance (stretch-ability) in the tendon (due to static stretching) increases the time
required to transmit force from muscle to bone
- Static stretching slows you down
- Other studies found that static stretching decreases muscle strength by as much as 30%
- Stretching the muscle in one leg can reduce strength in the other leg, probably because the central
nervous system inhibits input due to the duration of the static stretch
- Stretching is most effective when the muscle is warm
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